Journal articles: 'Cobalt oxide (Co3O4)'

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Eliseeva, E. A., S. L. Berezina, I. G. Gorichev, L. E. Slynko, and V. N. Goryacheva. "The Initial Surface Structure of Co3O4 as a Factor of Influence on Kinetic Features of the Dissolution of the Solid Phase." Herald of the Bauman Moscow State Technical University. Series Natural Sciences, no. 4 (91) (August 2020): 138–44. http://dx.doi.org/10.18698/1812-3368-2020-4-138-144.

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Due to the depletion of natural reserves of cobalt-containing ores, it is urgent to optimize the processes of cobalt replenishment, based on the leaching of its compounds, processing of industrial waste, regeneration of cobalt compounds from catalysts. The kinetic characteristics of the dissolution of metal oxides are influenced by the initial state of their surface structure, which requires the accumulation of experimental material and individual targeted studies. The paper presents the results of an experimental study of the surface structure of industrial Co3O4 cobalt oxide samples. The studies were carried out by electron microscopy and X-ray phase analysis and revealed the size and shape of the Co3O4 particles and the nature of their surface distribution. The correspondence of experimental and theoretical data has been established, Co3O4 cobalt oxide has been identified as an α-form of the cubic crystal system. The data obtained are of interest in the study of the effect of the surface characteristics of the solid phase of Co3O4 cobalt oxide on the dissolution kinetics under the chemical and electrochemical influence

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Lendzion-Bieluń, Zofia, Roman Jędrzejewski, and Walerian Arabczyk. "The effect of aluminium oxide on the reduction of cobalt oxide and thermostabillity of cobalt and cobalt oxide." Open Chemistry 9, no. 5 (October 1, 2011): 834–39. http://dx.doi.org/10.2478/s11532-011-0059-x.

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AbstractDuring precipitation and calcination at 200°C nanocrystalline Co3O4 was obtained with average size crystallites of 13 nm and a well developed specific surface area of 44 m2 g−1. A small addition of a structural promoter, e.g. Al2O3, increases the specific surface area of the cobalt oxide (54 m2 g−1) and decreases the average size of crystallites (7 nm). Al2O3 inhibits the reduction process of Co3O4 by hydrogen. Reduction of cobalt oxide with aluminium oxide addition runs by equilibrium state at all the respective temperatures. The apparent activation energy of the recrystallization process of the nanocrystalline cobalt promoted by the aluminium oxide is 85 kJ mol−1. Aluminium oxide improves the thermostability of both cobalt oxide and the cobalt obtained as a result of oxide phase reduction.

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Абдуллин, Х. А., С. К. Жумагулов, Г. А. Исмаилова, Ж. К. Калкозова, В. В. Кудряшов, and А. С. Серикканов. "Синтез гетерогенных наноструктур ZnO/Co-=SUB=-3-=/SUB=-O-=SUB=-4-=/SUB=- методом химического осаждения из растворов." Журнал технической физики 90, no. 7 (2020): 1184. http://dx.doi.org/10.21883/jtf.2020.07.49454.317-19.

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Nanocrystalline cobalt oxide Co3O4 and the ZnO / Co3O4 composite were obtained by the chemical bath deposition method followed by thermal annealing. It has been shown that the growth mechanism of cobalt carbonates changes dramatically in the presence of zinc oxide particles during synthesis, as a result, the phase composition, morphology, and material properties change. The conductive layers formed from the ZnO / Co3O4 composite have an electrical resistance at room temperature that is more than three orders of magnitude lower than the resistance of the Co3O4 layers, and ZnO / Co3O4 composite gas sensors showed significantly higher gas sensitivity at room temperature than that of control cobalt oxide sensors.

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Zeng, H. C., J. Lin, and K. L. Tan. "Memory effect of ZrO2 matrix on surface Co3O4–CoO transition." Journal of Materials Research 10, no. 12 (December 1995): 3096–105. http://dx.doi.org/10.1557/jmr.1995.3096.

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Cobalt oxide system Co3O4-CoO has been studied on the ZrO2 matrix surfaces with FTIR and XPS. The tetragonal and monoclinic ZrO2 matrix materials have been synthesized from the Zr-n-propoxide-acetylacetone-water-isopropanol system. The study shows that the ZrO2 matrix is able to retain the relative Co3O4:CoO population at elevated temperatures. The thermodynamically stable oxide population (Co3O4:CoO) at room temperature for ZrO2-supported Co3O4-CoO is about 50:50 (Co2+ :Co3+ = 2:1), which is markedly different from the 100:0 case (Co2+ :Co3+ = 1:2) for an unsupported Co3O4-CoO surface oxide system. The relative Co3O4 :CoO ratio in the surface region of the ZrO2 is temperature dependent but matrix-polymorph independent. The composition of an oxide solid solution formed by the Co3O4-CoO and matrices of ZrO2 is determined to have a cobalt molar percentage of 4.5%. Diffusion thermodynamic quantities are investigated, and the measured diffusion activation energy for a cobalt ion in the ZrO2 matrices is 0.21 eV. The mechanism of the ZrO2 memory effect on surface Co3O4-CoO transition will also be addressed.

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Zhang, Weidong, Paola Anguita, Javier Díez-Ramírez, Claude Descorme, Jose Luis Valverde, and Anne Giroir-Fendler. "Comparison of Different Metal Doping Effects on Co3O4 Catalysts for the Total Oxidation of Toluene and Propane." Catalysts 10, no. 8 (August 3, 2020): 865. http://dx.doi.org/10.3390/catal10080865.

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Metal-doped (Mn, Cu, Ni, and Fe) cobalt oxides were prepared by a coprecipitation method and were used as catalysts for the total oxidation of toluene and propane. The metal-doped catalysts displayed the same cubic spinel Co3O4 structure as the pure cobalt oxide did; the variation of cell parameter demonstrated the incorporation of dopants into the cobalt oxide lattice. FTIR spectra revealed the segregation of manganese oxide and iron oxide. The addition of dopant greatly influenced the crystallite size, strain, specific surface area, reducibility, and subsequently the catalytic performance of cobalt oxides. The catalytic activity of new materials was closely related to the nature of the dopant and the type of hydrocarbons. The doping of Mn, Ni, and Cu favored the combustion of toluene, with the Mn-doped one being the most active (14.6 × 10−8 mol gCo−1 s−1 at 210 °C; T50 = 224 °C), while the presence of Fe in Co3O4 inhibited its toluene activity. Regarding the combustion of propane, the introduction of Cu, Ni, and Fe had a negative effect on propane oxidation, while the presence of Mn in Co3O4 maintained its propane activity (6.1 × 10−8 mol gCo−1 s−1 at 160 °C; T50 = 201 °C). The excellent performance of Mn-doped Co3O4 could be attributed to the small grain size, high degree of strain, high surface area, and strong interaction between Mn and Co. Moreover, the presence of 4.4 vol.% H2O badly suppressed the activity of metal-doped catalysts for propane oxidation, among them, Fe-doped Co3O4 showed the best durability for wet propane combustion.

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Gorimbo, Joshua, Ralph Muvhiiwa, Ephraim Llane, and Diane Hildebrandt. "Cobalt Catalyst Reduction Thermodynamics in Fischer Tropsch: An Attainable Region Approach." Reactions 1, no. 2 (November 17, 2020): 115–29. http://dx.doi.org/10.3390/reactions1020010.

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A fundamental understanding of the precise reduction reaction pathway of cobalt-based catalysts is a crucial piece of knowledge in terms of the Fischer–Tropsch Synthesis (FTS) reaction. The use of hydrogen (H2) as the reduction agent results in a two-stage reduction of cobalt tetraoxide (Co3O4) to cobalt oxide (CoO) and then to metallic Co. The objective of the present work is to apply the Thermodynamic Attainable Region (TAR) to cobalt catalyst reduction using H2 so as to gain better insight regarding the thermodynamics of reduction reaction. TAR space diagrams suggest that complete Co3O4 reduction is feasible through two reaction pathways. Thus, the observed AR results suggest that the temperature programmed reduction’s (TPR) first reaction peak may be attributed to direct reduction of Co3O4 → Co and/or reduction to an intermediate compound Co3O4 → CoO. The second peak is a result of the reduction of either of the cobalt oxides to Co (Co3O4 → Co or CoO → Co).

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Shi, Peng Hui, Shao Bo Zhu, Rui Jing Su, Jin Tao Ren, Deng Xin Li, and Shi Hong Xu. "Synthesis of Co₃O₄/RGO as Catalyst for Degradation of Orange II in Water by Advanced Oxidation Processes Based on Sulfate Radicals." Advanced Materials Research 534 (June 2012): 269–72. http://dx.doi.org/10.4028/www.scientific.net/amr.534.269.

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One step synthesis reduced graphene oxide and cobalt oxides nanocomposites (Co3O4/RGO) in ethylene glycol as heterogeneous catalyst. The Co3O4/RGO was conﬁrmed by X-ray diffraction (XRD). And Co3O4/RGO exhibits an unexpected, surprisingly high catalytic activity in degradation of Orange II in water by advanced oxidation processes based on sulfate radicals and 100% decomposition could be achieved in 16 min.

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Abudayyak, Mahmoud, Tuba Altincekic Gurkaynak, and Gül Özhan. "In vitro evaluation of cobalt oxide nanoparticle-induced toxicity." Toxicology and Industrial Health 33, no. 8 (June 9, 2017): 646–54. http://dx.doi.org/10.1177/0748233717706633.

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Cobalt oxide (Co3O4) nanoparticles have applications in nanomedicine and nanotechnology; therefore, any possible adverse effects require thorough investigation. The present study investigated the effects of Co3O4 nanoparticles on four different cell lines: liver, HepG2 hepatocellular carcinoma cells; lung, A549 lung carcinoma cells; gastrointestinal, Caco-2 colorectal adenocarcinoma cells; and nervous system, SH-SY5Y neuroblastoma cells. A difference was observed in cell sensitivity toward Co3O4 nanoparticles. Co3O4 nanoparticles were taken up by all the cell types. However, no cell death was observed in HepG2, Caco-2, or SH-SY5Y cells; only A549 cells showed cytotoxicity at relatively high exposure concentrations. Co3O4 nanoparticles did not induce DNA damage or apoptosis in the cell lines tested except in A549. Interestingly, Co3O4 nanoparticles induced cellular oxidative damage in all cell types except Caco-2, resulting in increased malondialdehyde and 8-hydroxydeoxyguanosine levels and decreased glutathione levels. According to our results, it could be indicated that high concentrations of Co3O4 nanoparticles affected the pulmonary system but were unlikely to affect the liver, nervous system, or gastrointestinal system. Co3O4 nanoparticles might be safely used for industrial, commercial, and nanomedical applications if dose rates are adjusted depending on the route of exposure. However, further in vivo and in vitro studies are required to confirm the safety of Co3O4 nanoparticles.

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Lusiana, Lusiana, and Sigit Dwi Yudanto. "Pembentukan Fasa Co3O4 Dengan Metoda Dekomposisi CoCO3 Menggunakan Sinar Diffraksi." Jurnal Teknik Mesin 12, no. 2 (December 31, 2019): 46–49. http://dx.doi.org/10.30630/jtm.12.2.262.

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Experiments have been carried out to obtain the decomposition of cobalt carbonate cobalt oxide to be used as raw material for the manufacture of calcium cobalt oxide thermoelectric materials. The experiments were performed by heating cobalt carbonate powder material (CoCO3) from Kanto Chemical with a temperature of 1000°C. Heating aims to obtain Co3O4 phase. Co3O4 phase is what will be used in the manufacture of thermoelectric materials based on the phase diagram of the system Ca-Co-O. The results of X-ray diffraction CoCO3 materials are heated to 1000°C showed that Co3O4 phase has been formed. Analysis quantitative diffraction pattern shows the diffraction peaks are the property throughout the Co3O4 phase. The crystal structure of Co3O4 is Face Centered Cubic (FCC) with space group F d -3 m. Lattice parameters of the diffraction pattern is the result of smoothing a = 8.0838 Å.

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Wang, Hong Juan, Dong Zhou, Feng Peng, and Hao Yu. "Facile Synthesis and Performance of Reduced Graphene Oxide/Cobalt Oxide Composite for Supercapacitor." Advanced Materials Research 785-786 (September 2013): 779–82. http://dx.doi.org/10.4028/www.scientific.net/amr.785-786.779.

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A series of reduced graphene oxide/cobalt oxide composites (Co3O4/rGO)were fabricated via a chemical precipitation approach and subsequent calcination in Ar atmosphere. Experimental results show that Co3O4/rGO composite with 86 wt% of Co3O4 loading exhibits the optimum specific capacitance of 240 F g-1 in 6.0 M KOH electrolyte at the current density of 0.8 A g-1, excellent quick charge-discharge performance and outstanding cyclic stability with 2.3% of its specific capacitance increase after 2400 cycles at the current density of 8 A g-1 in GCD test, exhibiting significant potential of Co3O4 /rGO composite in the application of supercapacitors.

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11

Judson, GJ, TR Woonton, JD McFarlane, and A. Mitsioulis. "Evaluation of cobalt pellets for sheep." Australian Journal of Experimental Agriculture 35, no. 1 (1995): 41. http://dx.doi.org/10.1071/ea9950041.

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Vitamin B12 concentrations were measured in plasma and liver, and cobalt (Co) concentrations determined in faeces, of sheep given intraruminal Co pellets with or without steel grub screws (grinders). The Co pellets contained 30 or 60% by weight Co oxide (Co3O4). Sheep were maintained on pasture at 2 sites in the South East of South Australia in an area where sheep have been shown to respond to Co supplementation. All pellets, apart from one given without a grinder, maintained above-adequate vitamin B12 concentrations in liver (>200 nmol/kg wet weight) and plasma (>400 �mol/L) for 1 year. In the second year, some pellets containing 30% Co3O4 failed to maintain adequate vitamin B12 concentrations in the liver of sheep at 1 site when untreated sheep were at risk of seasonal Co deficiency (liver vitamin B12 concentrations <100 nmol/kg wet weight). Under these circumstances, a more recently formulated pellet containing 30% Co3O4, when given with a grinder, maintained adequate vitamin B,? status of sheep for 3 years. The 'traditional' pellet containing 60% Co3O4 increased vitamin B12 concentrations to high normal values (in plasma >I500 pmol/L, in liver >200 nmol/kg wet weight) for at least 3 years. Pellets containing 30% Co3P4 may only prevent Co deficiency for 1 year, depending on the source of the pellets.

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Moridon, Siti Nurul Falaein, Mohd Nur Ikhmal Salehmin, Khuzaimah Arifin, Lorna Jeffery Minggu, and Mohammad B. Kassim. "Synthesis of Cobalt Oxide on FTO by Hydrothermal Method for Photoelectrochemical Water Splitting Application." Applied Sciences 11, no. 7 (March 29, 2021): 3031. http://dx.doi.org/10.3390/app11073031.

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Cobalt oxide thin films were successfully grown directly on fluorine-doped tin oxide glass substrates through a simple, green, and low-cost hydrothermal method. An investigation into the physicochemical characteristics and photoelectrochemical (PEC) properties of the developed cobalt oxide thin film was comprehensively performed. At various annealing temperatures, different morphologies and crystal phases of cobalt oxide were observed. Microflowers (Co3O4) and microflowers with nanowire petals (Co3O4/CoO) were produced at 450 °C and 550 °C, respectively. Evaluation of the PEC performance of the samples in KOH (pH 13), Na2SO4 (pH 6.7), and H2SO4 (pH 1) revealed that the highest photocurrent −2.3 mA cm−2 generated at −0.5 V vs. reversible hydrogen electrode (RHE) was produced by Co3O4 (450 °C) in H2SO4 (pH 1). This photocurrent corresponded to an 8-fold enhancement compared with that achieved in neutral and basic electrolytes and was higher than the results reported by other studies. This promising photocurrent generation was due to the abundant source of protons, which was favorable for the hydrogen evolution reaction (HER) in H2SO4 (pH 1). The present study showed that Co3O4 is photoactive under acidic conditions, which is encouraging for HER compared with the mixed-phase Co3O4/CoO.

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Mirzaeian, Mojtaba, Nazym Akhanova, Maratbek Gabdullin, Zhanar Kalkozova, Aida Tulegenova, Shyryn Nurbolat, and Khabibulla Abdullin. "Improvement of the Pseudocapacitive Performance of Cobalt Oxide-Based Electrodes for Electrochemical Capacitors." Energies 13, no. 19 (October 8, 2020): 5228. http://dx.doi.org/10.3390/en13195228.

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Cobalt oxide nanopowders are synthesized by the pyrolysis of aerosol particles of water solution of cobalt acetate. Cobalt nanopowder is obtained by subsequent reduction of obtained cobalt oxide by annealing under a hydrogen atmosphere. The average crystallite size of the synthesized porous particles ranged from 7 to 30 nm, depending on the synthesis temperature. The electrochemical characteristics of electrodes based on synthesized cobalt oxide and reduced cobalt oxide are investigated in an electrochemical cell using a 3.5 M KOH solution as the electrolyte. The results of electrochemical measurements show that the electrode based on reduced cobalt oxide (Re-Co3O4) exhibits significantly higher capacity, and lower Faradaic charge–transfer and ion diffusion resistances when compared to the electrodes based on the initial cobalt oxide Co3O4. This observed effect is mainly due to a wide range of reversible redox transitions such as Co(II) ↔ Co(III) and Co(III) ↔ Co(IV) associated with different cobalt oxide/hydroxide species formed on the surface of metal particles during the cell operation; the small thickness of the oxide/hydroxide layer providing a high reaction rate, and also the presence of a metal skeleton leading to a low series resistance of the electrode.

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Grzesik, Zbigniew, and Anna Kaczmarska. "Defect structure of CO3O4 cobalt oxide." Annales de chimie Science des Matériaux 40, no. 1-2 (June 28, 2016): 103–9. http://dx.doi.org/10.3166/acsm.40.103-109.

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A. Hamdan, Suhad, Iftikhar M. Ali, and Isam M.Ibrahim. "Toxic Gas Response for Nanostructured Cobalt Oxide Thin Films." Iraqi Journal of Physics (IJP) 19, no. 50 (September 1, 2021): 20–30. http://dx.doi.org/10.30723/ijp.v19i50.629.

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The gas sensing properties of undoped Co3O4 and doped with Y2O3 nanostructures were investigated. The films were synthesized using the hydrothermal method on a seeded layer. The XRD, SEM analysis and gas sensing properties were investigated for the prepared thin films. XRD analysis showed that all films were polycrystalline, of a cubic structure with crystallite size of (12.6) nm for cobalt oxide and (12.3) nm for the Co3O4:6% Y2O3. The SEM analysis of thin films indicated that all films undoped Co3O4 and doped possessed a nanosphere-like structure. The sensitivity, response time and recovery time to H2S reducing and NO2 oxidizing gases were tested at different operating temperatures. The resistance changed with exposure to the test gas. The results revealed that the Co3O4:6%Y2O3 possessed the highest sensitivity around 90% (at room temperature) and 62.5% (at 150 oC) when exposed to the reducing gas H2S and oxidizing gas NO2, respectively with 0.8sec for both recovery and response times.

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Azzi, Hajer, I. Rekkab-Hammoumraoui, L. Chérif-Aouali, and A. Choukchou-Braham. "Mesoporous Co3O4 as a New Catalyst for Allylic Oxidation of Cyclohexene." Bulletin of Chemical Reaction Engineering & Catalysis 14, no. 1 (April 15, 2019): 112. http://dx.doi.org/10.9767/bcrec.14.1.2467.112-123.

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Mesoporous cobalt oxide was investigated for the liquid phase oxidation of cyclohexene using tertiobutylhydroperoxide (TBHP) as an oxidant. The results were compared with several series of supported cobalt catalysts to study the influence of the cobalt loading and solvents on the overall conversion and selectivity. Mesoporous cobalt was synthesized through the nanocasting route using siliceous SBA-15 mesoporous material as a hard template and cobalt nitrate as the cobalt oxide precursor. Supported cobalt oxide catalysts (Co/MxOy) were synthesized by the impregnation method using two loadings (1 and 5 wt.%) and Al2O3, TiO2, and ZrO2 as supports. Samples were characterised by means: elemental analysis, X-ray powder Diffraction (XRD), BET (surface area), UV-Vis DR Spectroscopy, and MET. The results obtained showed that the cobalt oxide retains the mesoporous structure of SBA-15, and in all Co/MxOy, crystalline Co3O4 and CoO phases are observed. The mesoporous cobalt oxide is more active than the supported cobalt catalysts in the allylic oxidation of cyclohexene, with a conversion of 78 % of cyclohexene and 43.3 % selectivity toward 2-cyclohexene-1-ol. The highest activity of mesoporous cobalt oxide could be ascribed to its largest surface area. Furthermore, Co3O4 has both Lewis and Brönsted acidic sites whereas Co/MxOy has only Lewis acidic sites, which could also explain its superior catalytic activity. Moreover, mesoporous cobalt oxide was more stable than supported cobalt catalysts. Therefore, this catalyst is promising for allylic oxidation of alkenes. Copyright © 2018 BCREC Group. All rights reservedReceived: 30th March 2018; Revised: 24th September 2018; Accepted: 8th Oktober 2018; Available online: 25th January 2019; Published regularly: April 2019How to Cite: Azzi, H., Rekkab-Hammoumraoui, I., Chérif-Aouali1, L., Choukchou-Braham, A. (2019). Mesoporous Co3O4 as a New Catalyst for Allylic Oxidation of Cyclohexene. Bulletin of Chemical Reaction Engineering & Catalysis, 14 (1): 112-123 (doi:10.9767/bcrec.14.1.2467.112-123)Permalink/DOI: https://doi.org/10.9767/bcrec.14.1.2467.112-123

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Shahid, Mehmood, Yiqiang Zhan, Waqar Ahmed, and Suresh Sagadevan. "Cobalt oxide-based nanomaterial for electrochemical sensor applications." Malaysian NANO-An International Journal 1, no. 1 (August 25, 2021): 47–63. http://dx.doi.org/10.22452/mnij.vol1no1.4.

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Amongst the extended list of metal oxides, Co3O4 has gained envisioned attention in various technological fields. It has a proven record of promising material in optical, optoelectronics, sciences, engineering, medicines and biological fields of studies. Co3O4 is a promising candidate due to its large surface-to-volume ratio, simple preparation methods, higher well-defined electrochemical redox activity, high theoretical capacity, low cost, and stable chemical states. Co3O4 has been used in various applications such as fuel cells, photoelectrochemical water splitting, solar cells, supercapacitors, batteries and electrochemical sensors due to its applicability in various fields. It has shown promising outcomes as an electrochemical sensor in various areas such as in the detection of water contamination, as physiological molecule detectors etc. this mini-review summarizes the fields of contaminated water, as fuel and also in the physiological system.

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Ramamurthy, Sundar, Stuart McKernan, and C. Barry Carter. "Study of cobalt oxide films deposited on single-crystal yttria-stabilized zirconia by pulsed-laser ablation." Proceedings, annual meeting, Electron Microscopy Society of America 51 (August 1, 1993): 1154–55. http://dx.doi.org/10.1017/s042482010015160x.

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One of the most common applications of pulsed-laser ablation (PLA) is the production of oxide films of almost any stoichiometry. In this work, thin films of cobalt oxide were grown onto single-crystal yttria-stabilized zirconia (YSZ) substrates of (100) orientation. Film morphology during the early stages of growth has been studied.Cobalt oxide films grown on suitable substrates have potential applications in electronic and magnetic devices. Like most transition metal oxides, cobalt oxide exists in more than one form, depending on the valence of the cations and their distribution . The transition from CoO to Co3O4 occurs at about 900°C in air, CoO being the high-temperature phase. However, by lowering the partial pressure of oxygen, the CoO stability region shifts down to much lower temperatures.The laser system used for the depositions was a Lambda Physik model 210i with KrF excimer laser (λ=248 nm) operating at an energy of 200 mJ per pulse. A Co3O4 pellet (96% dense) was fabricated as the target material.

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Flores-Lasluisa, Jhony Xavier, Javier Quílez-Bermejo, Ana Cristina Ramírez-Pérez, Francisco Huerta, Diego Cazorla-Amorós, and Emilia Morallón. "Copper-Doped Cobalt Spinel Electrocatalysts Supported on Activated Carbon for Hydrogen Evolution Reaction." Materials 12, no. 8 (April 20, 2019): 1302. http://dx.doi.org/10.3390/ma12081302.

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The development of electrocatalysts based on the doping of copper over cobalt spinel supported on a microporous activated carbon has been studied. Both copper–cobalt and cobalt spinel nanoparticles were synthesized using a silica-template method. Hybrid materials consisting of an activated carbon (AC), cobalt oxide (Co3O4), and copper-doped cobalt oxide (CuCo2O4) nanoparticles, were obtained by dry mixing technique and evaluated as electrocatalysts in alkaline media for hydrogen evolution reaction. Physical mixtures containing 5, 10, and 20 wt.% of Co3O4 or CuCo2O4 with a highly microporous activated carbon were prepared and characterized by XRD, TEM, XPS, physical adsorption of gases, and electrochemical techniques. The electrochemical tests revealed that the electrodes containing copper as the dopant cation result in a lower overpotential and higher current density for the hydrogen evolution reaction.

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Sokolov, Ilya E., Valery V. Fomichev, Ruslan M. Zakalyukin, Elena V. Kopylova, Andrey S. Kumskov, Rais N. Mozhchil, and Andrey M. Ionov. "SYNTHESIS OF NANOSIZED ZIRCONIUM DIOXIDE, COBALT OXIDE AND RELATED PHASES IN SUPERCRITICAL CO2 FLUID." IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 64, no. 5 (May 13, 2021): 35–43. http://dx.doi.org/10.6060/ivkkt.20216405.6060.

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This study is devoted to obtaining nanoscale zirconium dioxide, cobalt oxide and related phases by SAS method in supercritical carbon dioxide. The synthesized compounds were characterized by a complex of physico-chemical analytical methods: infrared spectroscopy, differential scanning calorimetry, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy. The experimental parameters for obtaining the nanoparticles were: pressure 10 MPa, temperature 40 °C, carbon dioxide supply rate 35 g/min, the initial solution supply rate 0.5 ml/min. Individual phases containing zirconium and cobalt, and also samples with zirconium to cobalt molar ratios 3:1, 2:1, 1:1, 2:1 and 1:3 were obtained. The use of zirconium and cobalt acetylacetonates as initial components leads to formation of stable products – nanoparticles of acetates of the corresponding metals in the X-ray amorphous state. When heated to 340-350 °C, the destruction of organometallic complexes to oxides occurs with formation of a continuous series of X-ray amorphous solid solutions in the ZrO2-CoO system. At temperatures above 600 °C, the phases crystallize with the decomposition of solid solutions into ZrO2 and Co3O4. When temperature is above 900 °C, further oxidation of cobalt occurs. Thus, cobalt oxide oxidation into Co3O4 proceeds in two steps, at 600 and 900 °C. For samples of zirconium dioxide with cobalt oxide admixture at a temperature of 700 °C stabilization of the cubic modification is observed which is probably due to the entry of cobalt into the cubic structure of zirconium oxide, which prevents transition to tetragonal and monoclinic modifications.

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Lee, Chuan-Pei, Bayu-Tri Murti, Po-Kang Yang, Francesca Rossi, Carlo Carraro, and Roya Maboudian. "Cobalt Oxide-Decorated Silicon Carbide Nano-Tree Array Electrode for Micro-Supercapacitor Application." Materials 14, no. 16 (August 11, 2021): 4514. http://dx.doi.org/10.3390/ma14164514.

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A cobalt oxide (Co3O4)-decorated silicon carbide (SiC) nano-tree array (denoted as Co3O4/SiC NTA) electrode is synthesized, and it is investigated for use in micro-supercapacitor applications. Firstly, the well-standing SiC nanowires (NWs) are prepared by nickel (Ni)-catalyzed chemical vapor deposition (CVD) method, and then the thin layer of Co3O4 and the hierarchical Co3O4 nano-flower-clusters are, respectively, fabricated on the side-walls and the top side of the SiC NWs via electrodeposition. The deposition of Co3O4 on the SiC NWs benefits the charge transfer at the electrode/aqueous electrolyte interface due to its extremely hydrophilic surface characteristic after Co3O4 decoration. Furthermore, the Co3O4/SiC NTA electrode provides a directional charge transport route along the length of SiC nanowires owing to their well-standing architecture. By using the Co3O4/SiC NTA electrode for micro-supercapacitor application, the areal capacitance obtained from cyclic voltammetry measurement reaches 845 mF cm−2 at a 10 mV s−1 scan rate. Finally, the capacitance durability is also evaluated by the cycling test of cyclic voltammetry at a high scan rate of 150 mV s−1 for 2000 cycles, exhibiting excellent stability.

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Gupta, Vijayta, Vinay Kant, and Meena Sharma. "Evaluation of Biological Activities of Chemically Synthesized Cobalt Oxide Nanoparticles in Concentration and Time Dependent Manner." International Journal of Pharmaceutical Sciences and Nanotechnology 13, no. 6 (November 16, 2020): 5243–49. http://dx.doi.org/10.37285/ijpsn.2020.13.6.9.

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The promising results of metal oxides nanoparticles in different areas including the biological system lead us to investigate the antioxidant and antimicrobial actions of chemically synthesized cobalt oxide (Co3O4) nanoparticles. The different concentrations of synthesized Co3O4 nanoparticles were prepared and evaluated for different parameters at different time intervals i.e. on day 1, 30 and 60 after preparations. Co3O4 nanoparticles synthesized in this study were of 52.2 nm average size with a polydispersity index of 0.465. We observed that Co3O4 nanoparticles scavenge different in vitro free radicals (DPPH, ABTS, superoxide anion and hydrogen peroxide radicals) in concentration dependent manner. The percentage of inhibitions of free radicals by Co3O4 nanoparticles was markedly more on day 1 as compared to day 30 and 60. The IC50 values of Co3O4 nanoparticles for these free radicals were also on day 1 as compared to day 30 and 60. The Co3O4 nanoparticles showed the antibacterial actions against both the bacterial strains i.e. S. aureus and E. coli. The MIC and MBC values revealed that action of Co3O4 nanoparticles was more against E. coli than S. aureus. The MIC and MBC values were lower on day 1 as compared to day 30 and 60 with respective to specific bacteria. In conclusions, the Co3O4 nanoparticles synthesized in this study showed potent antioxidant and antibacterial properties due to which it may serve as promising candidate for the combat the biological problems humans, animals and plants associated with reactive oxygen species and bacteria.

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Walsh, Dominic, Yi Yeoun Kim, and Carolina Neudeck. "Synthesis of a Range of Functional Oxide and Sulphide Nanoparticles by Biopolymer Stabilization and Enzymatic Treatment." Advanced Materials Research 123-125 (August 2010): 783–86. http://dx.doi.org/10.4028/www.scientific.net/amr.123-125.783.

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Nanoparticles of the metal oxides magnetite (Fe3O4), cobalt oxide (Co3O4), manganese oxide (Mn3O4) and the metal sulfides CuS, Cu1.96S, Ag2S and CdS were prepared using the biopolymer dextran as a stablising agent. The corresponding enzyme dextranase could then used remove the biopolymer coat to give nanoparticles stabilized by a remnant oligomer. A green and aqueous general route to functional nanoparticles is described.

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Bedair, Tarek M., Il Jae Min, Wooram Park, Yoon Ki Joung, and Dong Keun Han. "Sustained drug release using cobalt oxide nanowires for the preparation of polymer-free drug-eluting stents." Journal of Biomaterials Applications 33, no. 3 (September 2018): 352–62. http://dx.doi.org/10.1177/0885328218792141.

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Polymer-based drug-eluting stents (DESs) represented attractive application for the treatment of cardiovascular diseases; however, polymer coating has caused serious adverse responses to tissues such as chronic inflammation due to acidic by-products. Therefore, polymer-free DESs have recently emerged as promising candidates for the treatment; however, burst release of drug(s) from the surface limited its applications. In this study, we focused on delivery of therapeutic drug from polymer-free (or -less) DESs through surface modification using cobalt oxide nanowires (Co3O4 NWs) to improve and control the drug release. The results demonstrated that Co3O4 NWs could be simply fabricated on cobalt–chromium substrate by ammonia-evaporation-induced method. The Co3O4 NWs were uniformly arrayed with diameters of 50–100 nm and lengths of 10 µm. It was found that Co3O4 NWs were comparatively stable without any delamination or change of the morphology under in vitro long-term stability using circulating system. Sirolimus was used as a model drug for studying in vitro release behavior under physiological conditions. The sirolimus release behavior from flat cobalt–chromium showed an initial burst (over 90%) after one day. On the other hand, Co3O4 NWs presented a sustained sirolimus release rate for up to seven days. Similarly, the polymer-less specimens on Co3O4 NWs substrates sustained sirolimus release for a longer-period of time when compared to flat Co–Cr substrates. In summary, the current approach of using Co3O4 NWs-based substrates might have a great potential to sustain drug release for drug-eluting implants and medical devices including stents.

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Makhlouf, M. Th, B. M. Abu-Zied, and T. H. Mansoure. "Direct Fabrication of Cobalt Oxide Nanoparticles Employing Sucrose as a Combustion Fuel." Journal of Nanoparticles 2013 (March 6, 2013): 1–7. http://dx.doi.org/10.1155/2013/384350.

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Combustion method has been used as a fast and facile method to prepare nanocrystalline Co3O4 spinel employing sucrose as a combustion fuel. The products were characterized by thermal analyses (TGA and DTA), X-ray diffraction technique (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. Experimental results revealed that the molar ratio of fuel/oxidizer (F/O) plays an important role in controlling the crystallite size of Co3O4 nanoparticles. Transmission electron microscopy indicated that the crystallite size of Co3O4 nanocrystals was in the range of 13–32 nm. X-ray diffraction confirmed the formation of CoO phase with spinel Co3O4. The effect of calcination temperature on crystallite size and morphology has been, also, discussed.

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Anuradha, C. T., and P. Raji. "Synthesis, Characterization and Anti-Microbial Activity of Oxalate-Assisted CO3O4 Nanoparticles Derived from Homogeneous Co-Precipitation Method." International Journal of Nanoscience 18, no. 05 (July 24, 2019): 1950002. http://dx.doi.org/10.1142/s0219581x19500029.

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Nano-sized cobalt oxide particles exhibit unique and fascinating physical, chemical and anti-microbial activity owing to their large surface to volume ratio. The study of metal oxide nanoparticles interaction with pathogenic microorganisms is great importance for various biomedical applications. The main purpose of this work is to study the anti-bacterial and anti-fungal behavior of cobalt oxide (CO3O4) nanoparticles against gram-positive and gram-negative bacterial strains and different fungi. The structure and morphology of CO3O4 nanoparticles were characterized by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and UV-Visible Spectroscopy, respectively. The CO3O4 nanoparticles showed a significant anti-bacterial activity against two gram-positive bacteria, Staphylococcusaureus (G[Formula: see text]), Streptococcus mutans (G[Formula: see text]), and two gram-negative bacteria, Klebsilla pneumonia (G[Formula: see text]), E. coli (G[Formula: see text]), and it shows a good anti-fungal activity against the two different fungal i.e., Aspergillus flavus (F) and Aspergillus niger (F), at different solvents. It was noted that synthesized CO3O4 nanoparticles exhibited the solvent-dependent anti-bacterial activity against all tested bacterial strains. CO3O4 NPs could be employed effectively for anti-microbial applications.

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Custodio, Cyron L., John Lemuel G. Untalasco, and Menandro C. Marquez. "Preparation of Cuprous Oxide/Cobaltous Oxide Nanostructured Composite with the Aid of Polyethylene Glycol and Ultrasonic Sound." Materials Science Forum 916 (March 2018): 50–54. http://dx.doi.org/10.4028/www.scientific.net/msf.916.50.

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Metal oxide semiconductors such as cobaltous oxide (Co3O4) and cuprous oxide (Cu2O) have caught the attention of many researchers due to their wide variety of applications. The attachment of Cu2O to Co3O4 was assisted by polyethylene glycol and the nanostructuring by ultrasonic sound. X-ray Diffraction (XRD) analysis of the fabricated composite reported characteristic peaks for crystalline Co3O4 and Cu2O. Results from Energy Dispersive X-ray (EDX) Spectroscopy showed the presence of cobalt, copper, and oxygen atoms which supports the result obtained in XRD. Cauliflower to nearly spherical shaped Cu2O - Co3O4 nanostructures were formed as observed in the Scanning Electron Micrographs (SEM) with a mean diameter of 0.5-1.0 μm. the shape of the composite and its surface morphology was altered with the use of different precursor materials for the synthesis of the Co3O4 seed. A blue shift in the UV-vis was observed upon the use of nitrate based precursor indicating the presence of smaller and finer particles in the composite. Overall results prove that Cu2O and Co3O4 can be synthesized using a facile solution approach with the aid of PEG and ultrasonic sound its application in the field of photocatalysis is probable.

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Girardi, Leonardo, Luca Bardini, Niccolò Michieli, Boris Kalinic, Chiara Maurizio, Gian Rizzi, and Giovanni Mattei. "Co3O4 Nanopetals on Si as Photoanodes for the Oxidation of Organics." Surfaces 2, no. 1 (January 11, 2019): 41–53. http://dx.doi.org/10.3390/surfaces2010004.

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Cobalt oxide nanopetals were grown on silicon electrodes by heat-treating metallic cobalt films deposited by DC magnetron sputtering. We show that cobalt oxide, with this peculiar nanostructure, is active towards the photo-electrochemical oxidation of water as well as of organic molecules, and that its electrochemical properties are directly linked to the structure of its surface. The formation of Co3O4 nanopetals, induced by oxidizing annealing at 300 °C, considerably improves the performance of the material with respect to simple cobalt oxide films. Photocurrent measurements and electrochemical impedance are used to explain the behavior of the different structures and to highlight their potential application in water remediation technologies.

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JAHANI, Malihe, Ramazan Ali KHAVARI-NEJAD, Homa MAHMOODZADEH, and Sara SAADATMAND. "Effects of cobalt oxide nanoparticles (Co3O4 NPs) on ion leakage, total phenol, antioxidant enzymes activities and cobalt accumulation in Brassica napus L." Notulae Botanicae Horti Agrobotanici Cluj-Napoca 48, no. 3 (August 17, 2020): 1260–75. http://dx.doi.org/10.15835/nbha48311766.

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Interaction of nanoparticles (NPs) as a significant threat to ecosystems with biological processes of plants is very important. Here, the effects of cobalt oxide (Co3O4) NPs on some physio-biochemical characteristics of Brassica napus L. were investigated. The two-weeks seedlings were sprayed with different concentrations of Co3O4 NPs (0, 50, 100, 250, 500, 1000, 2000, and 4000 mg L-1). The results showed that this treatment significantly affected the fresh and dry weights, area, relative water content (RWC) and relative chlorophyll value (SPAD) of leaves. The highest reduction of growth and biomass indexes occurred at 4000 mg L-1 NPs. The content of H2O2 and electrolyte leakage (EL) increased respectively, after 100 and 250 mg L-1 of Co3O4 NPs and showed a maximum level at 4000 mg L-1. The activities of phenylalanine ammonia lyase (PAL), ascorbate peroxidase (APX) and superoxide dismutase (SOD) increased after 100 mg L-1 of Co3O4 NPs. However, tyrosine ammonia lyase (TAL) activity enhanced after 500 mg L-1. The catalase (CAT) activity and protein content decreased after 1000 mg L-1 of Co3O4 NPs. Application of concentrations higher than 500 mg L-1 of Co3O4 NPs induced polyphenol oxidase (PPO) activity but reduced glutathione reductase (GR). The activities of guaiacol peroxidase (GPX) and glutathione S-transferase (GST) increased at 250-1000 mg L-1 of Co3O4 NPs and then decreased. These results suggested that low concentrations of Co3O4 NPs induced a positive effect on growth parameters but high levels caused extensive oxidative damage and mediated defense responses by organization of phenolic compounds and antioxidative system.

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Anantharamaiah, P. N., and Sweta Giri. "Enhancement of SO2 Gas Sensing Performance of Co3O4 Spinel by Cu Substitution." Sensor Letters 18, no. 2 (February 1, 2020): 83–88. http://dx.doi.org/10.1166/sl.2020.4199.

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Single-phase spinel cobalt oxide (Co3O4) and copper-substituted cobalt oxide (Co2.8Cu0.2O4) nanomaterials were synthesized via a co-precipitation route. To explore the potential applicability of the Co3O4 and Co2.8Cu0.2O4 materials for gas sensor fabrication, their SO2 gas sensing characteristics were studied at three different temperatures using the gas concentration of 3 ppm. Unsubstituted Co3O4 sample exhibits poor response towards SO2 gas whereas the Cu-substituted sample showed superior gas sensing characteristics such as gas response, response time and recovery time at all three temperatures. Among the three studied temperatures, the maximum gas response of 7.5% was found at 200 °C with recovery and response times of 26 sec, indicating an optimal temperature. Our results demonstrate that the nanostructured Co2.8Cu0.2O4 material could be a potential candidate to design SO2 gas sensor for detection of low concentration gas.

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Ibrahim, Buthainah A., Ziad T. Khodiar, and Marwan M. Farhan. "Study of some Physical Properties and the Effect of Gamma Irradiation on Optical Properties of Electrochromic Co₃O₄ Thin Film." Materials Science Forum 1021 (February 2021): 107–14. http://dx.doi.org/10.4028/www.scientific.net/msf.1021.107.

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Cobalt oxide thin film (Co3O4) has been prepared from cobalt chloride with distilled water on conducting glass substrates Fluorine doped Tin Oxide (FTO) at (400ºC) by depositing chemical spray pyrolysis, with thickness (200 nm). The structural properties are studied by XRD. Also, optical properties and electrical properties of Co3O4 thin film are studied by UV spectroscopy and Cyclic voltammetry (CV) respectively. The effects of gamma irradiation on optical properties are also examined. XRD results showed that the film was polycrystalline with cubic structure having preferred orientation (111). The as-prepared Co3O4 film exhibits a noticeable EC behaviour with reversible colour which changes from dark grey to pale yellow with bleaching time (55 s) and colouring time (40 s). After irradiation, the optical properties showed that as the transmittance decrease leads to decrease the direct optical band gap from (3.68eV) to (3.55eV)

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Li, Cai Xia, Hai Fang Xu, Tao Feng, Na Zhang, and Qiang Li. "Synthesis and Characterization of CoO₂ Nanosheets." Advanced Materials Research 177 (December 2010): 5–8. http://dx.doi.org/10.4028/www.scientific.net/amr.177.5.

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The layered sodium cobalt oxide Na0.6CoO2 phase has been synthesized from Na2O2 and Co3O4 by solid-state reaction at 550°C for 12h with the heating rate about 2°C /min. The colloidal suspension of exfoliated, layered cobalt oxide nanosheets was prepared through the intercalation of tetrabutyl ammonium hydroxide ions (TBA) into protonated sodium cobalt oxide. The as-obtained composites were analyzed by powder X-ray diffraction (XRD). They were also cross-confirmed by a range of methods including UV/Vis spectroscopy, and Transmission Electron Microscopy (TEM). The Zeta-potential measurements clearly demonstrated the negative surface charge of cobalt oxide nanosheets.

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Hamdan, Suhad A. "Synthesized pure cobalt oxide nanostructure and doped with yttrium by hydrothermal method for photodetector applications." Iraqi Journal of Physics (IJP) 17, no. 40 (March 1, 2019): 77–87. http://dx.doi.org/10.30723/ijp.v17i40.408.

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In this study, pure Co3O4 nano structure and doping with 4 %, and6 % of Yttrium is successfully synthesized by hydrothermal method.The XRD examination, optical, electrical and photo sensingproperties have been studied for pure and doped Co3O4 thin films.The X-ray diffraction (XRD) analysis shows that all films arepolycrystalline in nature, having cubic structure.The optical properties indication that the optical energy gap followsallowed direct electronic transition calculated using Tauc equationand it increases for doped Co3O4. The photo sensing properties ofthin films are studied as a function of time at different wavelengths tofind the sensitivity for these lights.High photo sensitivity doped Co3O4 with 6% of Yttrium, is a118.774% at wavelength 620 nm, while for pure Co3O4 films nosensitivity at the same wavelength. So, higher sensitivity is found fordoping Co3O4 with fast rise and fall times less than 1s.

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Hussien, Nahed A., and Hanan R. H. Mohamed. "THE PROTECTIVE ROLE OF OMEGA-3 AGAINST GENOTOXICITY AND REPRODUCTIVE TOXICITY OF COBALT OXIDE NANOPARTICLES ACUTE TREATMENT IN MALE MICE." Asian Journal of Pharmaceutical and Clinical Research 11, no. 5 (May 1, 2018): 423. http://dx.doi.org/10.22159/ajpcr.2018.v11i5.25245.

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Objective: Cobalt nanoparticles (NPs), especially cobalt oxide NPs (Co3O4 NPs) are attracting unique shaped NPs that are used in different biomedical applications and medicine. Different in vitro studies report their toxic and carcinogenic effect but limited in vivo studies were present on its genotoxic potential. The present study was aimed to evaluate the genotoxic potential of Co3O4 NPs on bone marrow cells and sperms and the protective role of omega-3 in male albino mice.Methods: Animals were segregated into four groups that were orally treated for 3 consecutive days, Group 1: Negative control; Group 2: Omega-3 (250 mg/kg); Group 3: Co3O4 NPs (20 mg/kg); and Group 4: Combined group (250 mg/kg Omega-3 and Co3O4 NPs 20 mg/kg).Results: The present results show that Co3O4 NPs administration significantly increased number of micronucleated polychromatic erythrocytes (PCEs)/1000 PCEs, sperm abnormalities, and DNA damage, significantly decreased sperm motility and concentration in comparison to negative control group. However, Omega-3 administration in the combined group modulates the genotoxic potential of Co3O4 NPs in comparison to Co3O4 NPs group.Conclusion: The present study reports the genotoxic potential of Co3O4 NPs in vivo and assesses the protective role of Omega-3 administration due to its antioxidant effect.

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Lv, Yinan, Guixia Dong, Lei Li, Jingrui Kang, and Weidan Han. "Cobalt–Nickel Oxides with Three-Dimensional Hexagon Films for High Performance Supercapacitors." Nano 13, no. 03 (March 2018): 1850032. http://dx.doi.org/10.1142/s1793292018500327.

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Cobalt–nickel oxide electrode materials with three-dimensional hexagon films or flower-shaped structures have been synthesized by a chemical precipitation method at different thermal decomposition temperatures. Nickel ions enter into the lattice of Co3O4 by forming solid solution and promote primary nanoparticles partly self-assemble into three-dimensional hexagon films which interlace with each other to form a flower-like structure. Consequently, cobalt–nickel oxide with a Ni/Co mole ratio of 1:6 at 220[Formula: see text]C displays a highest capacitance of 796.16[Formula: see text]F/g at 200[Formula: see text]mA/g and cobalt–nickel oxide with a Ni/Co mole ratio of 1:3 at 200[Formula: see text]C exhibits a highest capacitance of 290[Formula: see text]F/g at 10[Formula: see text]A/g, which significantly improve the electrochemical properties of Co3O4.

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WANG, YAN, JING HUANG, JIANLIANG CAO, GAOJIE LI, and ZHANYING ZHANG. "COBALT OXIDE DECORATED FLOWER-LIKE g-C3N4 HYBRID NANOMATERIALS FOR CARBON MONOXIDE OXIDATION." Surface Review and Letters 24, no. 05 (September 30, 2016): 1750058. http://dx.doi.org/10.1142/s0218625x17500585.

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Co3O4 decorated flower-like g-C3N4 hybrid nanocatalysts were successfully synthesized and prepared via a facial hydrothermal method. The composition and morphology of the as-synthesized Co3O4/g-C3N4 nanocatalysts were characterized by the techniques of XRD, FT-IR, SEM, TEM, XPS and N2-sorption. The analysis results indicated that the as-synthesized samples possess the flower-like structure, which consisted of g-C3N4 nanosheets and Co3O4 nanoparticles with the size about 25[Formula: see text]nm. The as-prepared Co3O4/g-C3N4 catalysts possess high catalytic activity and excellent stability for carbon monoxide (CO) oxidation. The total conversion of Co can be kept for more than 48[Formula: see text]h under the reaction temperature of 120[Formula: see text]C.

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Belles, Loukas, Constantinos Moularas, Szymon Smykała, and Yiannis Deligiannakis. "Flame Spray Pyrolysis Co3O4/CoO as Highly-Efficient Nanocatalyst for Oxygen Reduction Reaction." Nanomaterials 11, no. 4 (April 5, 2021): 925. http://dx.doi.org/10.3390/nano11040925.

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The oxygen reduction reaction (ORR) is the rate-limiting reaction in the cathode side of fuel cells. In the quest for alternatives to Pt-electrodes as cathodes in ORR, appropriate transition metal oxide-based electrocatalysts are needed. In the present work, we have synthesized Co3O4 and CoO/Co3O4 nanostructures using flame spray pyrolysis (FSP), as electrocatalysts for ORR in acidic and alkaline media. A detailed study of the effect of (Co-oxide)/Pt ratio on ORR efficiency shows that the present FSP-made Co-oxides are able to perform ORR at very low-Pt loading, 0.4% of total metal content. In acid medium, an electrode with (5.2% Pt + 4.8% Co3O4), achieved the highest ORR performance (Jmax = 8.31 mA/cm2, E1/2 = 0.66 V). In alkaline medium, superior performance and stability have been achieved by an electrode with (0.4%Pt + 9.6% (CoO/Co3O4)) with ORR activity (Jmax = 3.5 mA/cm2, E1/2 = 0.08 V). Using XRD, XPS, Raman and TEM data, we discuss the structural and electronic aspects of the FSP-made Co-oxide catalysts in relation to the ORR performance. Cyclic voltammetry data indicate that the ORR process involves active sites associated with Co3+ cations at the cobalt oxide surface. Technology-wise, the present work demonstrates that the developed FSP-protocols, constitutes a novel scalable process for production of co-oxides appropriate for oxygen reduction reaction electrodes.

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Shi, Peng Hui, Hon Gai Zheng, Wei Feng Yao, Qiang Wu, Si Yu Tan, and Hong Jian Pang. "Study on the Loadings of Co₃O₄ Supported on rGO as the Catalyst for Degradation of Orange II in Water by AOPs Based on Sulfate Radicals." Advanced Materials Research 955-959 (June 2014): 62–65. http://dx.doi.org/10.4028/www.scientific.net/amr.955-959.62.

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A variety of loadings of Cobalt oxide (Co3O4) was successfully supported on the reduced graphene (Co3O4/rGO) as the catalyst to activate peroxymonosulfate (PMS) to generate sulfate radicals (SO4−•) for degrading Orange II in water. The crystal structure of Co3O4/rGO with different loadings was characterized by X-ray diffraction (XRD), and their catalytic activity was compared in the same conditions. The result showed that the catalyst has an optimum Co3O4 loading. Using the 70.7% loading of Co3O4 in Co3O4/rGO as the catalyst, 100% decomposition could be achieved within 4 min with 1 mM Orange II, 0.05g/L catalyst, and 10 mM PMS.

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Waris, Abdul, Misbahud Din, Asmat Ali, Shakeeb Afridi, Abdul Baset, Atta Ullah Khan, and Muhammad Ali. "Green fabrication of Co and Co3O4 nanoparticles and their biomedical applications: A review." Open Life Sciences 16, no. 1 (January 1, 2021): 14–30. http://dx.doi.org/10.1515/biol-2021-0003.

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Abstract Nanotechnology is the fabrication, characterization, and potential application of various materials at the nanoscale. Over the past few decades, nanomaterials have attracted researchers from different fields because of their high surface-to-volume ratio and other unique and remarkable properties. Cobalt and cobalt oxide nanoparticles (NPs) have various biomedical applications because of their distinctive antioxidant, antimicrobial, antifungal, anticancer, larvicidal, antileishmanial, anticholinergic, wound healing, and antidiabetic properties. In addition to biomedical applications, cobalt and cobalt oxide NPs have been widely used in lithium-ion batteries, pigments and dyes, electronic thin film, capacitors, gas sensors, heterogeneous catalysis, and for environmental remediation purposes. Different chemical and physical approaches have been used to synthesize cobalt and cobalt oxide NPs; however, these methods could be associated with eco-toxicity, cost-effectiveness, high energy, and time consumption. Recently, an eco-friendly, safe, easy, and simple method has been developed by researchers, which uses biotic resources such as plant extract, microorganisms, algae, and other biomolecules such as starch and gelatin. Such biogenic cobalt and cobalt oxide NPs offer more advantages over other physicochemically synthesized methods. In this review, we have summarized the recent literature for the understanding of green synthesis of cobalt and cobalt oxide NPs, their characterization, and various biomedical applications.

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Haiduk, Yulyan S., Alexander A. Khort, Maxim A. Makhavikou, and Alexander A. Savitsky. "Structure and gas sensitivity of WO3–In2O3 and WO3–Co3O4 oxide compositions." Modern Electronic Materials 5, no. 3 (September 12, 2019): 115–25. http://dx.doi.org/10.3897/j.moem.5.3.52308.

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Using oxide compositions is a promising method of increasing the sensitivity and selectivity of semiconductor gas sensors on the basis of SnO2, In2O3, WO3 and other oxides. We have studied nanocrystalline tungsten oxide (WO3), indium oxide (In2O3), cobalt oxide (Co3O4) and mixed oxide compositions with different WO3/In2O3 and WO3/Co3O4 ratios synthesized using the sol-gel method after xerogel annealing at 400–600 °C. The morphology, phase composition and structure of the materials have been studied using X-ray diffraction, infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. We showed that stable structures can be produced in WO3–In2O3 and WO3–Со3O4 nanoheterogeneous compositions. The growth of grain size in WO3 and In2O3, WO3 and Co3O4 during heat treatment of mixed compositions occurs slower than in simple oxides. An increase in the gas sensitivity of the compositions in comparison with simple oxides can be accounted for by smaller grain sizes and hence larger specific surface area, as well as by the dependence of grain surface state on material composition. Both compositions exhibit the greatest nitrogen dioxide response at 130–150 °C and the greatest carbon oxide response at above 230 °C. We have produced low-power nitrogen dioxide sensors with a sensitivity of << 1 ppm and power consumption of ≤ 85 mW.

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SALAVATI-NIASARI, MASOUD, and FATEMEH DAVAR. "SYNTHESIS OF COBALT AND COBALT OXIDE NANOPARTICLES AND THEIR MAGNETIC PROPERTIES." International Journal of Nanoscience 08, no. 03 (June 2009): 273–76. http://dx.doi.org/10.1142/s0219581x09006195.

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Co and Co3O4 nanoparticles are synthesized via a thermal decomposition method in the presence of oleylamine using a new precursor of [Bis(2-hydroxyacetophenato)cobalt(II)]. The products were characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The hysteresis loops of the obtained samples reveal the ferromagnetic behaviors of the enhanced coercivity (Hc) and decreased saturation magnetization (Ms) in contrast to their respective bulk materials.

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Li, Lin Bo, Juan Qin Xue, Tao Hong, Jun Yang, and Xing Wang. "Separation of Cobalt from Zinc Sulfate Solution by Novel Oxidant." Materials Science Forum 695 (July 2011): 145–48. http://dx.doi.org/10.4028/www.scientific.net/msf.695.145.

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The separation of cobalt from zinc sulfate solutions by oxidation-precipitation process using peroxy-monosulfuric acid as oxidant has been presented according to the technological conditions of removal of cobalt from zinc electrolyte. After investigating the important parameters governing the separation of cobalt and their effect on the separation process, the optimal parameters of oxidation precipitation of cobalt were determined, the oxidation precipitation percent of cobalt was up to 90% under the conditions. The XRD analysis results of precipitates demonstrated that the precipitate was cobalt hydroxide oxide (CoOOH) in pure cobalt system while the precipitates were cobaltosic oxide (Co3O4) and basic zinc sulfate (ZnSO4(OH)6.H2O) in zinc-cobalt system.

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Zhang, Ruili, Yuntao Yang, and Ping Yang. "Three-Dimensional Precursor-Derived Synthesis of Co3O4 Towards High Electrochemical Performance." Nanoscience and Nanotechnology Letters 11, no. 10 (October 1, 2019): 1375–86. http://dx.doi.org/10.1166/nnl.2019.3024.

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Three-dimensional (3D) cobalt oxide (Co3O4) flowers with different shapes were prepared by a facile hydrothermal synthesis. The morphology of Co3O4 precursors has adjusted obviously from acicular shapes to acicular-sheet-like flowers and then to sheet-like flowers by changing reaction temperature and solution concentration. After annealing, as-prepared precursors were converted into 3D flower-like Co3O4 samples and their morphology and sizes were well preserved. The effect of experimental conditions on growth of Co3O4 precursors was explored and the growth mechanism was proposed. Moreover, the electrochemical properties of various Co3O4 with different shapes were tested. The result of electrochemical investigation indicates that 3D flower-like Co3O4 assembled by sheets exhibited high capacitance and excellent cycling performance.

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Iwanek (nee Wilczkowska), Ewa M., Leonarda F. Liotta, Giuseppe Pantaleo, Krzysztof Krawczyk, Ewa Gdyra, Jan Petryk, Janusz W. Sobczak, and Zbigniew Kaszkur. "Investigation of Co3O4 and LaCoO3 Interaction by Performing N2O Decomposition Tests under Co3O4-CoO Transition Temperature." Catalysts 11, no. 3 (March 4, 2021): 325. http://dx.doi.org/10.3390/catal11030325.

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The research presented in this paper addresses the question: How does the addition of a small amount of LaCoO3 impact the activity of a Co3O4 catalyst? By testing such a catalyst in N2O decomposition under conditions at which the thermal decomposition of Co3O4 to CoO is possible, one gains unique insight into how the two phases interact. The activity of such a catalyst increases in the entire studied temperature range, unlike the activity of the undoped cobalt catalyst which is lower at 850 °C than at 800 °C due to the reduction of Co3O4 to CoO. XRD measurements showed that CoO was also the main cobalt oxide present in the Co3.5La catalyst after operating at 850 °C, as did the XPS measurements, but there was no drop of activity associated with this change. The influence of NO, O2 and H2O on the activity of the new catalyst, Co3.5La, was determined. Lack of positive effect of NO, a known oxygen scavenger, on the activity was noticed at all temperatures, showing that the effect of LaCoO3 is probably due to increased oxygen desorption. Temperature programed oxidation (TPO) tests showed that the beneficial effects of the presence of LaCoO3 on the activity of cobalt oxide at 850 °C were probably caused by enhanced diffusion of O2− anions through the entire catalyst, which facilitates desorption of oxygen molecules from the surface.

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Kumar, Rahul, Ankur Soam, and Veena Sahajwalla. "Carbon coated cobalt oxide (CC-CO3O4) as electrode material for supercapacitor applications." Materials Advances 2, no. 9 (2021): 2918–23. http://dx.doi.org/10.1039/d1ma00120e.

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Carbon coated cobalt oxide (CC-Co₃O₄) was synthesized using sucrose and cobalt oxide. CC-Co₃O₄ can be used as electrode material for supercapacitor applications

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Cardenas Flechas, Leydi Julieta, Angela Mercedez Raba Paéz, and Miryam Rincon Joya. "Synthesis and evaluation of nickel doped Co3O4 produced through hydrothermal technique." DYNA 87, no. 213 (April 1, 2020): 184–91. http://dx.doi.org/10.15446/dyna.v87n213.84410.

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The synthesis of undoped cobalt oxide and cobalt oxide with 4%nickel doping is studied in samples obtained through hydrothermal technique. After the final heat treatment at 300°C, X-ray diffraction analysis indicated the formation of cobalt spinel oxide with a complete replacement of nickel in the lattice. An average crystallite size of ~42 nm and ~31nm was found, as well as a particle size of ~ 20 nm and ~30 nm for Co3O4 and Co3-xNixO4, respectively. Structural parameters were established through Rietveld refinement with a good correspondence between the simulated and the experimental pattern with values of x2 = 1.25 and GOF = 0.90 for Co3O4. The energy band gap was found through UV-Vis spectroscopy in two different regions: Eg1 and Eg2 values vary between 1.54 and 2.04eV for samples doped with nickel. The SEM results indicated the formation of nanostructures with semi-cubic shape and irregular rods. Parameters such as crystal size, particle size, surface area, as well as morphology of the final product depend on doping.

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Xu, Jing Li, Ping Liu, Yang Lu, Jia Chang Zhao, Ji Cheng Feng, Yi Wen Song, and Bo He Jin Tang. "Ordered Mesoporous Carbon/Cobalt Oxide Composites as the Electrode Materials for Supercapacitor." Advanced Materials Research 239-242 (May 2011): 1026–29. http://dx.doi.org/10.4028/www.scientific.net/amr.239-242.1026.

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A series of ordered mesoporous carbon/cobalt oxide composites as electrode materials for supercapacitor were prepared via incipient wetness impregnation method. The results show that the structure and electrochemical properties of the composites depend mainly on the cobalt oxide loading amount in the ordered mesoporous carbon. The optimum loading amount of cobalt oxide is found to be 30 wt.%, and the composite derived from which exhibits 283.52 F/g of specific capacitance at the scan rate of 5 mV/s. The specific capacitances of which are higher than that of OMC and pure Co3O4 at every given scan rate, showing good synergetic effect.

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Zhang, Zhen, Jiang Wu, and Dongjing Liu. "Co3O4/g-C3N4 Hybrids for Gas-Phase Hg0 Removal at Low Temperature." Processes 7, no. 5 (May 13, 2019): 279. http://dx.doi.org/10.3390/pr7050279.

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The Co3O4/g-C3N4 hybrids are constructed via the incipient wetness impregnation method by depositing Co3O4 onto the exterior of g-C3N4, and then employed for Hg0 capture within 60–240 °C. The results show that the Co3O4/g-C3N4 hybrid with a Co3O4 content of 12 wt% performs optimally with the highest Hg0 removal efficiency of ~100% at or above 120 °C. The high performances of the Co3O4/g-C3N4 hybrids are probably attributed to the tight interfacial contact between Co3O4 and g-C3N4, with its improved electron transfer, inferring that cobalt oxide and g-C3N4 display a cooperative effect towards Hg0 removal. NO and SO2 shows a significant suppressive influence on the mercury capture performance, plausibly owing to the competing adsorption and side reactions.

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Yu, Shu Ping, Xiao Cong Chang, Zhong Ming Wang, Ke Fei Han, and Hong Zhu. "Preparation and Performance of Co₃O₄/Polyaniline Nano-Composite for Supercapacitor." Advanced Materials Research 239-242 (May 2011): 2042–45. http://dx.doi.org/10.4028/www.scientific.net/amr.239-242.2042.

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Cobalt oxide-Polyaniline (Co3O4/PANI) nanocomposites were prepared via inverted emulsion polymerization. The structure of the obtained composites were characterized by X-ray diffraction (XRD). The electrochemical behavior was studied by cyclic voltammetry(CV) and electrochemical impedance spectrometry(EIS) experiments. The Co3O4/PANI(1:2) composite calcined at 400°C exhibits the highest capacitance value of 357 F/g at the scan rate of 5mV/s.

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Hao, Yalin, and Amyn S. Teja. "Continuous hydrothermal crystallization of α–Fe2O3 and Co3O4 nanoparticles." Journal of Materials Research 18, no. 2 (February 2003): 415–22. http://dx.doi.org/10.1557/jmr.2003.0053.

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Iron oxide (α–Fe2O3) and cobalt oxide (Co3O4) were produced via precipitation reactions carried out in a continuous hydrothermal apparatus. The resulting particles were nanometer-sized because of the high supersaturations generated when metal nitrate solutions are combined with sodium hydroxide or with hot, compressed water. The average particle size increased with the metal nitrate feed concentration and with residence time. A logarithmic relationship was obtained between the particle size and feed concentration and between particle size and residence time in the apparatus. The production of nanoparticles with narrow size distribution was shown to require low metal nitrate feed concentrations and short residence times. In the range of temperatures studied in this work, temperature apparently had no effect on the size except when cobalt nitrate was contacted with supercritical water in the absence of sodium hydroxide. In this case, large cobalt oxide particles were obtained when the temperature was above the critical temperature of water.

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Journal articles on the topic 'Cobalt oxide (Co3O4)'

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