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Co3O4 was synthesized on carbon paper (CP) using a facile method to improve electrochemical nitrate-to-ammonia conversion efficiency. The resulting Co3O4-CP electrode demonstrated an exceptional Faradaic efficiency of almost 100% across a broad range of application conditions, with a peak NH3 yield of 3.43 mmol h−1 cm−2 (2.25 mol gCo−1 h−1).

Abstract As promising energy storage equipment, Zn-air battery exhibits the advantage of high energy density, lightweight and compact structure over other rechargeable batteries, which is an ideal choice for electric vehicles. For Zn-air battery, the activity of air cathode plays an important role in its performance. Here, we report the fabrication of Co 3 O 4 based bulky electrode with three-dimensional mesoporous carbon as matrix, which originates from cheap filter paper precursor. This electrode exhibits excellent activity and durability in oxygen reduction (ORR) and oxygen evolution reaction (OER) process, which possesses small half-wave potential (ORR 1/2 = 0.811 V) and low overpotential (OER 10 = 1.518 V) for ORR and OER, respectively. With this electrode as air cathode directly, a rechargeable Zn-air battery is assembled successfully. During discharge process, the maximum power density of this Zn-air battery achieves 71 mW cm−2. Furthermore, it also exhibits high specific capacity (828 mAh g−1 at 20 mA cm−2, 544 mAh g−1 at 50 mA cm−2) and small voltage gap (0.91 V at 10 mA cm−2) in charge and discharge process. As a rechargeable battery, it also shows promising stability after long time charge-discharge experiments. Thus, we find out a simple and convenient method to fabricate cheap and effective bi-functional air cathode for rechargeable Zn-air battery. Graphical abstract A Co 3 O 4 electrode was fabricated with Co(NO 3) 2 ·6H 2 O and filter paper as precursors, which exhibits excellent ORR and OER activities. It was employed as air cathode in Zn-air battery. fx1 Highlights • Filter paper was employed as precursor to fabricate Co 3 O 4 electrode. • 3D mesoporous electrode with N-doped carbon as matrix is obtained. • The electrode exhibits excellent ORR and OER activities. • The electrode is employed as air cathode in Zn-air battery directly. [ABSTRACT FROM AUTHOR]

Co3O4 was synthesized on carbon paper (CP) using a facile method to improve electrochemical nitrate-toammonia conversion efficiency. The resulting Co3O4-CP electrode demonstrated an exceptional Faradaic efficiency of almost 100% across a broad range of application conditions, with a peak NH3 yield of 3.43 mmol h-1 cm-2 (2.25 mol gCo-1 h-1). [ABSTRACT FROM AUTHOR]

Cobalt oxide (Co3O4) serves as a promising electrocatalyst for oxygen evolution reactions (OER) in water-electrolytic hydrogen production. For more practical applications, advances in dry-deposition processes for the high-throughput fabrication of such Co3O4 electrocatalysts are needed. In this work, a thermal metal–organic deposition (MOD) technique is developed to form Co3O4 deposits on microscale-diameter carbon fibers constituting a carbon fiber paper (CFP) substrate for high-efficiency OER electrocatalyst applications. The Co3O4 electrocatalysts are deposited while uniformly covering the surface of individual carbon fibers in the reaction temperature range from 400 to 800 °C under an ambient Ar atmosphere. It is found that the microstructure of deposits is dependent on the reaction temperature. The Co3O4 electrocatalysts prepared at 500 °C and over exhibit values of 355–384 mV in overpotential (η10) required to reach a current density of 10 mA cm−2 and 70–79 mV dec−1 in Tafel slope, measured in 1 M KOH aqueous solution. As a result, it is highlighted that the improved crystallinity of the Co3O4 electrocatalyst with the increased reaction temperature leads to an enhancement in electrode-level OER activity with the high electrochemically active surface area (ECSA), low charge transfer resistance (Rct), and low η10, due to the enhanced electrical conductivity. On the other hand, it is found that the inherent catalytic activity of the surface sites of the Co3O4, represented by the turnover frequency (TOF), decreases with reaction temperature due to the high-temperature sintering effect. This work provides the groundwork for the high-throughput fabrication and rational design of high-performance electrocatalysts. [ABSTRACT FROM AUTHOR]

Co 3 O 4 catalysts supported on paper-like stainless steel fibers (PSSF) were prepared by MOFs-templated (M) method and applied for catalytic combustion of isopropanol. Physicochemical properties of the as-synthesized Co 3 O 4 catalysts were investigated by SEM, EDS mapping, TEM, XRD, BET, XPS and H 2 -TPR, respectively. Characterization results of SEM and TEM shown that Co 3 O 4 (M)-350 and Co 3 O 4 (M)-400 still remained the dodecahedron shape of the ZIF-67 precursor and possessed porous structures. The XPS results shown that the ratio of Co3+/Co2+ and O c /O c ​+ ​O a ​+ ​O l firstly increased and then decreased with the increase of calcination temperature. Among the as-synthesized catalysts, Co 3 O 4 (M)-400 exhibited the highest activity for the catalytic combustion of isopropanol with the T 50 and T 90 values of 258 ​°C and 281 ​°C, respectively, which was associated with high BET surface area, high amount of Co3+ species and abundant surface chemisorbed oxygen. Moreover, Co 3 O 4 (M)-400 was employed as a structured catalyst for isopropanol combustion, the catalytic kinetics were studied based on different feed concentration, bed height and GHSV. The experimental results indicated that the T 50 and T 90 of isopropanol combustion over Co 3 O 4 (M)-400 with the bed height of 2 ​cm were increased slightly as the GHSV and feed concentration of isopropanol increased. Fig. 1 Preparation process and Catalytic performance of Catalysts. [Display omitted] • A novel gradient porous Co 3 O 4 (M)-X catalyst was prepared by MOFs-templated method. • The effect of preparation methods on properties of Co based catalysts were studied. • Co 3 O 4 (M)-400 shown the highest isopropanol catalytic combustion performance. [ABSTRACT FROM AUTHOR]

The combination and structural regulation of physical adsorption and chemisorption carriers for polysulfides play an important role in limiting the shuttle effect of lithium-sulfur batteries (LSBs). So, in this paper, N, Co co-doped moss-like porous biochar (Co–N/CWPC) is synthesized and used as the sulfur host for LSBs. A large number of pores in the "moss" provide space for sulfur storage and volume expansion. And the introduction of N, Co provides plentiful catalytic adsorption sites, which can not only effectively limit the shuttle of polysulfides but also accelerate the conversion rate of polysulfides to the final discharge products. Moreover, Co also promotes graphitization and improves electrical conductivity of the biochar. After sulfur injection, the electrode shows an initial capacity of 787 mAh g−1 at 0.5 C and maintaining a capacity of 500 mAh g−1 after 500 cycles, the capacity decay rate is 0.07%. Even at a discharge rate of 1.0 C, it still maintained a capacity of 373 mAh g−1 after 1000 revolutions, with a capacity decay rate of 0.04%. [ABSTRACT FROM AUTHOR]

Thermochemical heat storage is an important solar-heat-storage technology with a high temperature and high energy density, which has attracted increasing attention and research in recent years. The mono-metallic redox pair Co3O4/CoO realizes heat storage and exothermic process through a reversible redox reaction. Its basic principle is to store energy by heat absorption through a reduction reaction during high-irradiation hours (high temperature) and then release heat through an exothermic-oxidation reaction during low-irradiation hours (low temperature). This paper presents the design of a cobalt-oxide honeycomb structure, which is extruded from pure Co3O4, a porous media with a high heat-storage density and a high conversion rate. Based on the experimental data, a three-dimensional axisymmetric multi-physics numerical model was developed to simulate the flow, heat transfer, mass transfer, and chemical reaction in the thermochemical heat-storage reactor. Unlike the previous treatment approach of equating chemical reactions with surface reactions, the model in this paper considers the consumption and generation of solids and the diffusion and transfer of oxygen in the porous medium during the reaction process, which brings the simulation results closer to the real values. Finally, the influence of the physical parameters of the honeycomb-structured body on the storage and exothermic process is explored in a wide range. The simulation results show that the physical-parameter settings and structural design of the cobalt-oxide honeycomb structure used in this paper are reasonable, and are conducive to improving its charging/discharging performance. [ABSTRACT FROM AUTHOR]

A bio-inspired nanofibrous Co 3 O 4 /TiO 2 /carbon composite was fabricated using natural cellulose substrate (laboratory filter paper) as both the carbon source and the structural scaffold. Employing a surface sol–gel process to form a thin TiO 2 gel layer coating on each cellulose nanofiber of the filter paper, the resulted composite sheet was successively carbonized in inert atmosphere to give a nanofibrous TiO 2 /carbon composite; afterwards, nano-sized Co 3 O 4 particles (10–30 nm) were uniformly deposited onto the yielded composite fibers via a simple hydrothermal method, resulting in the Co 3 O 4 /TiO 2 /carbon hybrid. The ternary composite possessed a unique hierarchically three-dimensional porous structure which inherited precisely from the initial filter paper. This special structure with the internal conductive carbon fiber and the external nano-sized Co 3 O 4 particles offered the nanocomposite with an excellent electrochemical performance as anodic material for lithium-ion batteries. The optimal sample with a Co 3 O 4 mass content of 50.6% delivered an initial discharge capacity of 1239 mAh g−1 at a current density of 100 mA g−1, which was far exceeded the theoretical capacity of Co 3 O 4. The extra capacity is ascribed to the additional lithium storage sites provided by the large specific surface area of the composite, and the formation of the solid electrolyte interface (SEI) layer in the initial discharge process causing a large consumption of Li+ which results in some irreversible capacity. And after 200 discharge/charge cycles, a high reversible capacity of 764 mAh g−1 was maintained, which is higher than most of the Co 3 O 4 /carbon hybrid materials reported. This work provided a simple and efficient strategy for designing and preparing nanoscale metal-oxide/carbon composite material with considerable potential in energy storage and conversion. Nanofibrous Co 3 O 4 /TiO 2 /carbon composite derived from cellulose substance was fabricated, showing enhanced electrochemical performances as an anodic material for lithium-ion batteries. Image 1 • A cellulose derived nanofibrous Co 3 O 4 /TiO 2 /carbon composite was fabricated. • Nanosized Co 3 O 4 particles were coated uniformly on the nanofiber surfaces. • The composite possessed a unique hierarchically porous net work structure. • It exhibited superior electrochemical performances as anodic material for LIBs. [ABSTRACT FROM AUTHOR]

Co3O4 and CoCO3 materials have broad development prospects as zinc ion battery materials in water systems. In this paper, Co3O4@CoCO3 composite material for water zinc ion battery cathode was synthesized by hydrothermal method, and the best raw material was selected by screening the cobalt source. Then the temperature and time of hydrothermal reaction were optimized, as well as the temperature and time of calcination, so as to discover the best experimental route for the synthesis of Co3O4@CoCO3 composite materials. The capacity of the Co3O4@CoCO3 composite material rises to 124.89 mAh/g after 10 cycles of charge and discharge at 50 mA/g current density, indicating its electrochemical performance is good. The XRD analysis of the material shows that the composite is mainly composed of Co3O4@CoCO3 crystal structure, and no obvious impurity is found. As can be seen from the SEM image of synthesized composite material, the main morphology of the material is a round block structure covered with folds, similar to the popcorn shape. The EDS test and element analysis show that all elements are evenly distributed in microscale. Through the analysis of infrared spectra, it can be seen that Co3O4 and CoCO3 are composited together, forming a stable structure, and enhancing the electrochemical performance of the material. In this paper, Co3O4@CoCO3 composite material for water zinc ion battery cathode was synthesized by hydrothermal method. The capacity of the Co3O4@CoCO3 composite material rises to 124.89 mAh/g after 10 cycles of charge and discharge at 50 mA/g current density. As can be seen from the SEM image of Co3O4@CoCO3 composite material, the surface of the material is covered with folds, similar to the popcorn shape, which can well sustain the electrolyte, promote the occurrence of electrochemical reactions, and provide more active sites for the migration of zinc ions. The EDS test and element analysis show that all elements are evenly distributed in microcosmic. [ABSTRACT FROM AUTHOR]

Due to its excellent performance, Co3O4 are redeemed as a promising supercapacitor material. However, problems like its low ion diffusion speed limit its application. In this paper, by preparing composite materials of Co3O4 and Zn(OH)F, the ion diffusion path of Co3O4 material is extended and the electrochemical performance of the material is enhanced. The composite material grown in situ on nickel foam was synthesized by hydrothermal method, and the optimum experimental route was determined through the selection of zinc and cobalt sources and the optimization of hydrothermal conditions and calcination conditions. When the current density is 1 mA/cm2, the capacity of Co3O4@Zn(OH)F composite material is as high as 5.68 F/cm2, showing relatively stable electrochemical performance, this is because the addition of Zn(OH)F material extends the diffusion path of ions. Subsequently, the physical properties of the composite material with good performance were characterized. The XRD tests showed that the synthesized material was composed of Co3O4 and Zn(OH)F, with high crystallinity and no other impurity peaks. Through SEM analysis, there are nanowire and spheroidal structures that can be found in the micro scale, and the nanowires are interwoven with each other to form snowflake shape, which can provide more transfer paths for charge transfer. The EDS test and element analysis show that all elements are evenly distributed. According to the result of the XPS test, the valence states of each element in the material coincide with those of Co3O4 and Zn(OH)F. The FT-IR test showed that the presence of Zn(OH)F did not affect the structure of Co3O4 material. In conclusion, by adopting the synthesis method described in the text, the ion diffusion performance of Co3O4 is improved, which also proves the possibility of its industrial application as supercapacitor material. [ABSTRACT FROM AUTHOR]

Magnesium-based materials are favored by researchers because of their high hydrogen storage capacity, but they cannot be put to daily use because of their more demanding reaction conditions. Recently, the method to improve the hydrogen storage performance of MgH 2 by catalyst doping has been widely investigated. In this paper, Co 3 O 4 catalysts were prepared by homogeneous precipitation method. It was demonstrated that the Co 3 O 4 catalyst could effectively improve the hydrogen storage performance of MgH 2. According to the experimental results, the dehydrogenation onset temperature of the MgH 2 +15 wt% Co 3 O 4 composite was about 200 °C, which was about 130 °C lower than that of pure MgH 2 , and the amount of dehydrogenation was 6.26 wt%. The dehydrogenation activation energy of the MgH 2 +15 wt% Co 3 O 4 composite was reduced to 89.13 kJ/mol, which was about 45.7% lower than that of pure MgH 2. After complete dehydrogenation, the composites started to absorb hydrogen at 50 °C with 6.2 wt%, while the activation energy of reabsorption was also reduced to 47.97 kJ/mol. After 10 cycles of MgH 2 +15 wt% Co 3 O 4 composites, the hydrogen storage capacity of MgH 2 could still be maintained at 99%, which indicated that it had good cycling stability. It was confirmed by various characterizations that Co 3 O 4 was uniformly distributed on the MgH 2 matrix after ball milling. After the first reaction, Co 3 O 4 was converted to CoO, which was uniformly attached to the Mg/MgH 2 surface and stabilized during the cycling process, continuing to provide active sites for hydrogen. The hydrogen storage composite MgH 2 +Co 3 O 4 was prepared in this study, and Co 3 O 4 was uniformly distributed on the MgH 2 matrix. In the first hydrogen release process, Co 3 O 4 is gradually converted to CoO, and then in the hydrogen absorption process, hydrogen enters Mg. During the cycle, the CoO is in a stable state and evenly dispersed on the Mg/MgH 2 surface, continuing to provide an active site for hydrogen. [Display omitted] • Co 3 O 4 with good air adaptation performance is applied to MgH 2 system. • Composites started to release H 2 at 200 °C and could start to absorb H 2 at 50 °C. • The activation energy of de/hydrogenation was significantly reduced for composites. [ABSTRACT FROM AUTHOR]

Photocatalytic nitrogen fixation has attracted much attention due to the fact that it is a way of using solar energy to achieve clean and sustainable conversion of nitrogen to ammonia under mild conditions. In this paper, different proportions of Zn-doped Co3O4 nanopolyhedrons were synthesized using bimetallic ZIFs containing Co2+ and Zn2+ as precursors for the construction of photocatalytic nitrogen fixation semiconductor materials for the first time. The synthesized Co3O4 nano-polyhedron still retains the rhombic dodecahedron shape of ZIF-67 and exhibits a large specific surface area. Moreover, Zn doping results in abundant oxygen vacancies on the surface of Co3O4 polyhedron. These oxygen vacancies not only provide active sites for nitrogen adsorption and activation, but also enhance the separation ability of photocarriers, which can significantly improve the efficiency of photocatalytic nitrogen fixation of the material. When Zn–Co3O4-30 is utilized as the catalyst for photocatalytic nitrogen fixation, the nitrogen fixation rate is 96.8 μmol g−1 h−1, which is much higher than that of pure-Co3O4. In this study, heteroatom-doped Co3O4 polyhedron with rich oxygen vacancy was synthesized by low-temperature oxidation method, which provides a new idea for the design and synthesis of skeleton-based photocatalytic nitrogen fixation materials. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Molecular Science is the property of Journal of Molecular Science Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The negative effects of refractory organic substances in water on the environment and life have aroused worldwide attention. The efficiency of using photoelectrocatalysis (PEC) to degrade refractory organic pollutants depends to a large extent on the properties of the photoanode semiconductor. Therefore, the selection of a satisfactory photoanode semiconductor material to promote the production of intermediate reactive species (hydroxyl radicals and superoxide radicals) has become a key issue in improving the efficiency of PEC. Among the available catalysts, transition metal oxides have received a lot of attention in recent years due to their low price and significant advantages. Due to its outstanding photoelectrocatalytic properties, Co3O4 has emerged as a candidate to serve as a photoelectrocatalyst specifically for the oxidation of water with oxygen in these materials. This paper summarizes in detail the recent advances in Co3O4 materials for PEC, both pure Co3O4 and Co3O4-based composites. In addition, this review discusses the impact of strategies on the performance of photoelectrocatalysts, such as synthesis methods, crystal surface structures, and composites. Finally, this review concludes with a presentation of the challenges and workable solutions for Co3O4-based materials in PEC, along with a discussion of their potential for future research. [ABSTRACT FROM AUTHOR]

In this paper, the effect of alkali metal deposition on the activity of x‐Co3O4 (x=Na, K, Rb, Cs) catalysts for the N2O catalytic decomposition was systematically explored by DFT calculation and various experimental characterization methods. The results demonstrated that the deposition of alkali metal Na improved the activity of the Na‐Co3O4 catalyst for N2O catalytic decomposition at low temperatures. By contrast, the deposition of other alkali metals (K, Rb and Cs) suppressed the catalytic decomposition of N2O perceptibly. Analysis of the results of XRD, FT‐IR, SEM, TEM, XPS, O2‐TPD and H2‐TPR characterization of x‐Co3O4 catalysts showed that the deposition of alkali metals did not affect the morphology and structure of the catalysts. However, it affected the chemical environment around the Co ion in the x‐Co3O4 catalyst, where the deposition of alkali metal Na not only facilitated the reduction of Co3+ to Co2+, but also promoted the surface decomposition step of N2O (i. e. the oxidation of Co2+ to Co3+ by giving electrons) at low temperatures, indicating that alkali metal Na improved the electron donating capability of the catalyst active center and enhanced the performance of the Na‐Co3O4 catalyst for the DCD of N2O at low temperatures. The deposition of other alkali metals did not show the same results as that of alkali metal Na, indicating that the promotion of different alkali metals was different and would directly affect the catalytic effect. At low temperatures, the catalytic activity of catalysts deposited with the alkali metal Na was greater than that of catalysts deposited with other alkali metals. [ABSTRACT FROM AUTHOR]

In this paper, Co3O4/Ce(OH)4/C and Co3O4/CeO2/C cathode materials for sodium‐ion batteries are prepared by electroconversion. The morphology, structure, and electrochemical properties are investigated by X‐ray diffraction, scanning electron microscopy, cyclic voltammetry, charge–discharge test, etc. The results show that Co3O4/Ce(OH)4/C and Co3O4/CeO2/C have the same crystal structure, the diffraction peaks of the samples are sharp, and the material crystallinity is high, and both are of nanospherical porous morphology. In electrochemical performance, the first discharge‐specific capacities of Co3O4/Ce(OH)4/C and Co3O4/CeO2/C are as high as 185.7 and 94.2 mAh g−1 at a rate of 0.1 A g−1. Moreover, the specific capacity of Co3O4/Ce(OH)4/C and Co3O4/CeO2/C increases after 1000 cycles at the 0.5 A g−1 rates, and the coulombic efficiency remains around 100%, showing excellent cycle performance. [ABSTRACT FROM AUTHOR]

In the present paper, simple hydrothermal and solid-state methods are reported for the synthesis of metal chalcogenide (ZnSe), metal oxide (Co3O4) and their nano-heterostructure (ZnSe/Co3O4 3:1, 1:1 and 1:3 ratios by weight), while their photocatalytic efficiencies are also investigated. The X-ray diffraction results corroborate the good crystallinity and purity of all synthesized products, i.e., ZnSe, Co3O4 and their nanocomposites. The scanning electron micro-images of ZnSe show a mixed morphology of nanoparticles (≈16 nm), including spherical and distorted cubes, while Co3O4 has a worm-like morphology (≈20 × 50 nm). The EDX results show that all the elements are present in accordance with their anticipated amounts in the products. The UV/visible absorption spectrum of ZnSe depicts a sharp absorption at around 480 nm, while Co3O4 demonstrates two prominent peaks, 510 nm and 684 nm. The prepared samples were employed for the photocatalytic degradation of Congo red dye and the nano-heterostructure (ZnSe/Co3O4 3:1) shows an exceptional photocatalytic degradation efficiency of 96%. This enhanced photocatalytic activity was due to the synergic effect of ZnSe and Co3O4 that reduced the electron/hole recombination and caused suitable bandgap alignment. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Norfloxacin (NOR) is one of the most widely used antibiotics in animal fanning and hospital. With the mass production and consumption, the large amounts of NOR was discharged into the water environment which caused severe pollution problems. Advanced oxidation processes (AOPs) can decompose, mineralize most organic compounds, including NOR. In this paper, a novel AOPs catalyst based on peroxymonosulfate (PMS), Co3O4/Uio-66-NH2 composites were prepared. The morphology and structure of the composites were shown in this paper. Degradation experimental results show that Co3O4/Uio-66-NH2 composites have better degradation efficiency than Co3O4 nanoparticles, and the leaching concentration of cobalt ions is lower, indicating that the composite material has better stability than Co3O4 alone. Under the conditions of 1.0mM PMS and 0.2g/L Co3O4/Uio-66-NH2 dosage at neutral pH, about 90% ofnorfloxacin (NOR) can be degraded within 30 min. In addition, the mechanism of PMS activation by Co3O4/Uio-66-NH2 composites were studied through the free radical identification by quenching experiments and electron paramagnetic resonance (EPR) technology. In addition, the Co3O4/Uio-66-NH2 composites material has good regeneration efficiency, which has a certain application prospect for the removal of NOR from drinking water, and this work will also provide a potential contribution to the removal of NOR from the environment. [ABSTRACT FROM AUTHOR]

Enhancement of supercapacitors (SCs) with high-energy density and high-power density is still a great challenge. In this paper, a facile strategy for in situ anchoring of Co3O4 particles on N doped carbon cloth (pCoNCC) is reported. Due to the interaction of the doped N and Co3O4, the electrochemical performance improves significantly, reaching 1,940.13 mF·cm−2 at 1 mA·cm−2 and energy density of 172.46 µWh·cm−2 at the power density of 400 µW·cm−2, much larger than that without N doping electrode of 28.5 mF·cm−2. An aqueous symmetric supercapacitor (ASSC) assembled by two pCoNCC electrodes achieves a maximum energy density of 447.42 µWh·cm−2 and a highest power density of 8,000 µW·cm−2. Utilizing such a high-energy storage ASSC, a digital watch and a temperature-humidity detector are powered for nearly 1 and 2 h, respectively. Moreover, the ASSC displays a superb electrochemical stability of 87.7% retention after 10,000 cycles at 40 mA·cm−2. This work would provide a new sight to enhance active materials performance and be beneficial for the future energy storage and supply systems. [ABSTRACT FROM AUTHOR]

In this paper, the graphene in situ coated Co3O4 core–shell heterogeneous composites have been facilely fabricated via microwave plasma-enhanced chemical vapor deposition method. The graphene thin-shell-layer-covered Co3O4−x particles were revealed by FE-SEM, XRD, XPS and Raman spectra. And the ratio of Co2+/Co3+ is adjusted, and abundant surface oxygen vacancies are created by the microwave plasma etching, which can contribute to the improvement of electrochemical performance for the Co3O4/graphene core–shell composites. Results present that the graphene in situ coated Co3O4−x has a specific capacitance of 192.8 F g−1 under the current density of 0.5 A g−1, which is 4.5 times than that of the original Co3O4 sphere. Meanwhile, the core–shell heterogeneous composite displays excellent cyclic stability with ~ 98.5% specific capacitance retained after 20,000 cycle tests. [ABSTRACT FROM AUTHOR]

Lightweight polyacrylonitrile (PAN)-based carbon fiber can give volume and mass savings, which has been considered as a promising anode material for structural lithium-ion batteries (SLIBs). However, the current issue is the limitation of low capacity. To improve the situation, a novel PAN-based carbon fiber/Co3O4 composite (CF/Co3O4) has been developed through a chemical deposition method. Since combining advantage of high theoretical specific capacity of Co3O4 and great electroconductivity as well as strong mechanical of carbon fiber, the prepared CF/Co3O4 shows excellent performances as an anode material for SLIBs. It presents a coulombic efficiency of over 99% and stable cyclic ability. Even if the number of cycles reaches to 150, a steady discharge reversible capacity up to 625 mAh g−1 can be retained, approximately 2.7 times as much as pure CF (~ 230 mAh g−1). The improved cycling stability of CF/Co3O4 can be owed to the interactions between CF and Co3O4 anchored on the CF. Furthermore, a solid polymer electrolyte was also prepared with the flexibility, which shows a steady discharge reversible capacity of 500 mAh g−1 at 100 mA g−1. The paper provides an affordable method to solve the problem of the limitation of capacity in current SLIBs when using commercial carbon fibers as anode materials. [ABSTRACT FROM AUTHOR]

This paper contains the results of the structural and spectroscopic characterizations of undoped and Cadmium-doped cobalt oxide thin films with different Co/Cd molar ratios (3%, 5%, 7% and 9%). The nanosized undoped and cadmium-doped Co3O4 thin layers were prepared using sol–gel process and deposited on glass substrates by dip coating. The changes caused by the incorporation of cadmium at different levels of doping have been highlighted by the techniques UV–Visible (UV–Vis) spectroscopy, Infrared (IR) spectroscopy, X-ray diffraction (XRD) measurements, SEM coupled EDX and impedance spectroscopy. From the UV–Vis spectroscopy analysis, it was found that all the films are two direct bandgap energies. The optical transmittance and the bandgap energy decrease with increase in Cd concentration. The XRD spectra confirm the films were polycrystalline with a cubic spinel structure. The results of the impedance spectroscopy show that the equivalent circuit of the synthesized samples is an RC parallel circuit. [ABSTRACT FROM AUTHOR]

Thermochemical heat storage is an important solar-heat-storage technology with a high temperature and high energy density, which has attracted increasing attention and research in recent years. The mono-metallic redox pair Co3O4/CoO realizes heat storage and exothermic process through a reversible redox reaction. Its basic principle is to store energy by heat absorption through a reduction reaction during high-irradiation hours (high temperature) and then release heat through an exothermic-oxidation reaction during low-irradiation hours (low temperature). This paper presents the design of a cobalt-oxide honeycomb structure, which is extruded from pure Co3O4, a porous media with a high heat-storage density and a high conversion rate. Based on the experimental data, a three-dimensional axisymmetric multi-physics numerical model was developed to simulate the flow, heat transfer, mass transfer, and chemical reaction in the thermochemical heat-storage reactor. Unlike the previous treatment approach of equating chemical reactions with surface reactions, the model in this paper considers the consumption and generation of solids and the diffusion and transfer of oxygen in the porous medium during the reaction process, which brings the simulation results closer to the real values. Finally, the influence of the physical parameters of the honeycomb-structured body on the storage and exothermic process is explored in a wide range. The simulation results show that the physical-parameter settings and structural design of the cobalt-oxide honeycomb structure used in this paper are reasonable, and are conducive to improving its charging/discharging performance.

Long-term accumulation of cobalt-containing wastewater may also pollute groundwater and cause a large amount of loss of valuable metals. Therefore, the comprehensive utilization of cobalt-containing wastewater must be realized, especially as cobalt itself is a very important strategic resource. This paper proposes a membrane electroconversion method to separate cobalt ions from cobalt-containing wastewater and prepare cobalt hydroxide. In addition, the electrolysis process was optimized, and single-factor experiments such as the initial concentration, cobalt ions, current density, temperature etc., and economic calculations such as current efficiency were explored. The electrolysis product was calcined as the precursor to obtain the oxide Co3O4, and the calcination experiment was also optimized. In this concentration range, more than 90% of cobalt can be recovered within 2 h. HIGHLIGHTS In this paper, a self-made two-chamber electrolytic cell was used to treat wastewater to prepare cobalt hydroxide, and the electrolysis product was used as a precursor for calcination to produce Co3O4.; A single-factor experiment was used to investigate its influence. Co3O4 calcined products, and their microscopic morphology inherited the nanosheet structure of cobalt hydroxide.;

In this paper, we fabricated p-Co3O4/n-TiO2 heterostructures and investigated their gas sensing properties. The structural and morphological characterization were performed by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy analysis (XPS). The electrical properties of the heterostructure were studied within the temperature range from 293 K to 423 K. Changes in electrical properties and sensing behavior against reducing and oxidizing gases were attributed to the formation of p-n heterojunctions at the Co3O4 and TiO2 interface. In comparison with sensing performed with pristine TiO2 nanotubes (NTs), a significant improvement in H2 sensing at 200 °C was observed, while the sensing response against NO2 decreased for the heterostructures. Additionally, a response against toluene gas, in contrast to pristine TiO2 NTs, appeared in the Co3O4/TiO2 heterostructure samples. [ABSTRACT FROM AUTHOR]

Owing to their multiple mechanisms of bactericidal activity, inorganic metal oxides and hybrid metal oxide nanocomposites may serve as a new class of effective disinfectants. Among metal oxide nanoparticles, iron oxide nanoparticles exhibit minimal or no cytotoxicity to human cells with very efficient bactericidal properties over a wide spectrum of bacteria. This paper presents the very first report on antibacterial properties of novel nanocomposites of iron oxide and cobalt oxide nanoparticles against pathogenic bacterial strains B. subtilis, S. aureus, E.coli and S. typhi. The enhanced bactericidal activity of the Fe/Co oxide nanocomposite was the result of synergistic effect of iron oxide and cobalt oxide nanoparticles. The nanocomposites were synthesized using co-precipitation route with increasing cobalt content in the sample and further characterized using XRD, TEM, Raman and VSM to investigate structural, optical and magnetic properties of the prepared nanocomposites, respectively. Also, the prepared nanocomposites were highly biocompatible and found non-toxic to human cell line MCF7. [ABSTRACT FROM AUTHOR]

Co 3 O 4 is recognized as an advantageous material for harmful VOC abatement. In this paper, three types of Co 3 O 4 catalysts exhibiting either nanosheet morphology or nanosheet tissue structure were synthesized and applied in the combustion of toluene. The characterization results highlight the significance of Co3+ species over surface oxygen. Moreover, the oxygen vacancies of the catalyst formed during the reaction process were found to play a more critical role in influencing the catalytic performance than the oxygen vacancies present in the original catalyst. Through this study, we gained valuable insights into the facets, Co3+ species, and oxygen vacancies, which hold promising potential for enhancing the development of Co 3 O 4 catalytic material for practical applications in toluene degradation. • The catalytic activity of three nanosheet Co 3 O 4 materials for toluene at low temperature was investigated. • The conclusion drawn from the characterizations is that Co3+ is more important than surface adsorbed oxygen. • The content of oxygen vacancies in pristine catalyst is less important than the ability to form oxygen vacancies. • The proportion of different exposed crystal planes greatly influences the catalytic performance of the catalyst. [ABSTRACT FROM AUTHOR]