Unique 1D Co3O4 crystallized nanofibers with (220) oriented facets as high-performance lithium ion battery anode material

Conversion of cobalt from spent LIBs to Co3O4 electrode material for application in supercapacitors

The cathode material of lithium-ion batteries (LIBs) is endowed with valuable metals, such as cobalt. The improper treatment of these batteries pollutes the environment and causes enormous resource waste. Therefore, the recovery of valuable metals from spent LIBs has attracted widespread attention. In this study, Co3O4 electrode materials were prepared by a simple homogeneous precipitation method and heat treatment using a leaching solution of spent LIBs-positive electrode material as the cobalt source. The crystal structure and morphology of the products were examined at different annealing temperatures, and their electrochemical performance was analyzed. The results show that low-temperature annealing contributes to grain refinement. The Co3O4 material prepared at 300°C annealing temperature has a rod-like structure with distinct pores and a specific surface area of 58.98 m2 g-1. Furthermore, electrochemical performance testing reveals that Co3O4 prepared at 300°C displays the best electrochemical performance as an electrode material, with a specific capacitance of 97.93 F g-1 and a cycle retention rate of 79.12% after 500 charge-discharge cycles. These findings demonstrate the feasibility of recycling valuable metal cobalt from spent LIBs cathode materials to produce Co3O4 materials for use as supercapacitor electrode materials, opening up new avenues for the recycling and utilisation of spent LIBs.

Enhanced Electrochemical Performance of Carbon-Composited Co3O4 Microspheres as Anode Materials for Lithium-Ion Batteries

Cobalt (II, III) oxide (Co3O4) has recently gained attention as an alternative anode material to commercial graphite in lithium-ion batteries (LIBs) due to its superior safety and large theoretical capacity of about 890 mAh g-1. However, its practical application is limited by poor electrical conductivity and rapid capacity degradation because of significant volume increases and structural strain during repeated lithiation/delithiation cycles. To address these issues, this work presents a novel approach to synthesizing carbon-composited Co3O4 microspheres (Co3O4@C), using abietic acid (AA) as a carbon source to increase conductivity and structural stability. The resulting Co3O4@C anodes show an impressive discharge capacity of 1557.4 mAh g-1 after 200 cycling processes at a current density of 0.1 C, representing a significant improvement over bare Co3O4. This study demonstrates the potential of carbon-compositing as a strategy to mitigate the limitations of Co3O4 and extend its cyclability, making it a viable candidate for next-generation LIB anodes.

Preparation and lithium storage of core-shell honeycomb-like Co3O4@C microspheres

Core-shell honeycomb-like Co₃O₄@C microspheres were synthesized via a facile solvothermal method and subsequent annealing treatment under an argon atmosphere. Owing to the core-shell honeycomb-like structure, a long cycling life was achieved (a high reversible specific capacity of 318.9 mA h g^-1 was maintained at 5C after 1000 cycles). Benefiting from the coated carbon layers, excellent rate capability was realized (a reversible specific capacity as high as 332.6 mA h g^-1 was still retained at 10C). The design of core-shell honeycomb-like microspheres provides a new idea for the development of anode materials for high-performance lithium-ion batteries.

Flame Spray Pyrolysis Co3O4/CoO as Highly-Efficient Nanocatalyst for Oxygen Reduction Reaction

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.

Co3O4/TiO2 hetero-structure for methyl orange dye degradation

Advanced oxidation processes based on sulphate radical generated by peroxymonosulphate (PMS) activation is a promising area for environmental remediation. One of the biggest drawbacks of heterogeneous PMS activation is catalyst instability and metal ion leaching. In this study, a simple organic binder mediated route was explored to substitute Ti⁴⁺ ions into the Co₃O₄ host lattice structure to create a Co-O-Ti bond to minimise cobalt leaching during methyl orange degradation. The catalyst was characterised by X-ray diffraction, and scanning and transmission electron microscopy. The as-prepared catalysts with Co₃O₄:TiO₂ ratio of 70:30 exhibited minimal leaching (0.9 mg/L) compared to other ratios studied. However, the pristine Co₃O₄ exhibited highest catalytic activity (rate constant = 0.41 min^-1) and leaching (26.7 mg/L) compared to composite material (70:30 Co₃O₄:TiO₂). Interestingly, the morphology of the composite and leaching of Co²⁺ ions were found to be temperature dependent, as an optimum temperature ensured strong Co-O-Ti bond for prevention of Co²⁺ leaching. The classical quenching test was utilised to determine the presence and role of radical species on methyl orange degradation. The fabricated catalyst also exhibited good catalytic activity in degrading mixed dyes and good recyclability, making it a potential candidate for commercial application.

The electrochemical properties of Co3O4 as a lithium-ion battery electrode: a first-principles study

Extensive first principles calculations were performed to study the structural and electrochemical features of Co3O4 during its lithiation process as an anode material for lithium-ion batteries (LIBs). We found that with up to 8 mol Li in Co3O4, the formed LinCo3O4 structures are stable for low Li concentrations of n ≤ 1, but obvious structure distortions and volume expansions occur for LinCo3O4 with n > 1. This may be the reason why Co3O4 has a high Li capability but low cycling life as a LIB anode. The ab initio molecular dynamics simulations for LinCo3O4 (n = 2, 4, 8) further suggest a two-step electrochemistry process of Co3O4 → CoO → Co upon the lithiation process. We detected a distorted surface structure as Li atoms react with the Co3O4(110) surface, which also reduces the rate capability of the Co3O4 anode.

Pseudocapacitive behavior of the Fe2O3 anode and its contribution to high reversible capacity in lithium ion batteries

Pseudocapacitance, which is the storage of charge based on continuous and fast reversible redox reactions at the surface of electrode materials, is commonly observed for electrodes in lithium ion batteries, especially for transition metal oxide anodes. In this report, bare Fe2O3 of granular morphology (∼30 nm in diameter) with high purity and decent crystallinity as well as recommendable electrochemical performances is fabricated hydrothermally and employed as the subject to clarify pseudocapacitive behavior in transition metal oxide anodes. Electrochemical technologies such as galvanostatic charging/discharging, differential capacity analysis (dQ/dV) and the power law relationship (i = aνb), which can distinguish pseudocapacitive behaviors of an electrode reaction were employed to analyze the electrodes. Reversible capacities of ∼120 mA h g-1 (0.117 F cm-2) for Fe2O3 were found within particular electrochemical windows (2.3-3.0 V, 0.3-0.8 V for discharging and 2.2-3.0 V, 0.3-1.3 V for charging). A new direction of optimizing the capacities, rate and cycling performances for lithium ion batteries is pointed out with connections between the pseudocapacitive behavior and morphologies of surfaces as well as structures of the electrodes.

Preparation of 3D hierarchical porous Co3O4 nanostructures with enhanced performance in lithium-ion batteries

Three-dimensional hierarchical Co₃O₄ microspheres assembled by well-aligned 1D porous nanorods were successfully fabricated. The sample exhibited excellent electrochemical properties as anode materials for LIBs.

Enhanced photoelectrochemical water splitting by oxides heterojunction photocathode coupled with Ag

A novel one-dimensional Co₃O₄/CuO/Ag composite structure film was directly grown on indium tin oxide glass substrate by a simple hydrothermal method and electrodeposition method. The film was employed for the first time as a photocathode for photoelectrochemical (PEC) water splitting to generate hydrogen. The photocurrent density of the Co₃O₄/CuO/Ag composite structure achieved -5.13 mA cm^-2 at -0.2 V vs. RHE, which is roughly 12.8 times that of 1D Co₃O₄ nanowires and 3.31 times Co₃O₄/CuO heterojunction photocathodes. The enhanced PEC performance of this Co₃O₄/CuO/Ag composite structure ascribes increased light-harvesting and light-absorption, distensible photoresponse range, decreased interface charge transfer resistance, and improved photogenerated electron-hole pairs transfer and separation.

Fabrication of Co3O4 nanoparticles in thin porous carbon shells from metal–organic frameworks for enhanced electrochemical performance

Ultrasmall Co₃O₄ nanoparticle with thin porous carbon shell is reported by employing metal–organic framework as precursor and CO₂ as oxidizing atmosphere, which exhibits a long cycling stability and high rate performance for Li-ion battery.