The urea oxidation reaction (UOR) is a possible solution to solve the world’s energy crisis. Fuel cells have been used in the UOR to generate hydrogen with a lower potential compared to water splitting, decreasing the costs of energy production. Urea is abundantly present in agricultural waste and in industrial and human wastewater. Besides generating hydrogen, this reaction provides a pathway to eliminate urea, which is a hazard in the environment and to people’s health. In this study, nanosheets of CuCo₂O₄ grown on nickel foam were synthesized as an electrocatalyst for urea oxidation to generate hydrogen as a green fuel. The synthesized electrocatalyst was characterized using X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. The electroactivity of CuCo₂O₄ towards the oxidation of urea in alkaline solution was evaluated using electrochemical measurements. Nanosheets of CuCo₂O₄ grown on nickel foam required the potential of 1.36 V in 1 M KOH with 0.33 M urea to deliver a current density of 10 mA/cm². The CuCo₂O₄ electrode was electrochemically stable for over 15 h of continuous measurements. The high catalytic activities for the hydrogen evolution reaction make the CuCo₂O₄ electrode a bifunctional catalyst and a promising electroactive material for hydrogen production. The two-electrode electrolyzer demanded a potential of 1.45 V, which was 260 mV less than that for the urea-free counterpart. Our study suggests that the CuCo₂O₄ electrode can be a promising material as an efficient UOR catalyst for fuel cells to generate hydrogen at a low cost.

In this project, we present a comparative study of the electrochemical performance for tubular MCo₂O₄ (M = Cr, Mn, Ni) microstructures prepared using cotton fiber as a bio-template. Crystal structure, surface properties, morphology, and electrochemical properties of MCo₂O₄ are characterized using X-ray diffraction (XRD), gas adsorption, scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FTIR), cyclic voltammetry (CV), and galvanostatic charge-discharge cycling (GCD). The electrochemical performance of the electrode made up of tubular MCo₂O₄ structures was evaluated in aqueous 3M KOH electrolytes. The as-obtained templated MCo₂O₄ microstructures inherit the tubular morphology. The large-surface-area of tubular microstructures leads to a noticeable pseudocapacitive property with the excellent electrochemical performance of NiCo₂O₄ with specific capacitance value exceeding 407.2 F/g at 2 mV/s scan rate. In addition, a Coulombic efficiency ~100%, and excellent cycling stability with 100% capacitance retention for MCo₂O₄ was noted even after 5000 cycles. These tubular MCo₂O₄ microstructure display peak power density is exceeding 7000 W/Kg. The superior performance of the tubular MCo₂O₄ microstructure electrode is attributed to their high surface area, adequate pore volume distribution, and active carbon matrix, which allows effective redox reaction and diffusion of hydrated ions.

For electrochemical supercapacitors, nickel cobaltite (NiCo₂O₄) has emerged as a new energy storage material. The electrocapacitive performance of metal oxides is significantly influenced by their morphology and electrical characteristics. The synthesis route can modulate the morphological structure, while their energy band gaps and defects can vary the electrical properties. In addition to modifying the energy band gap, doping can improve crystal stability and refine grain size, providing much-needed surface area for high specific capacitance. This study evaluates the electrochemical performance of aluminum-doped Ni_1−xAl_xCo₂O₄ (0 ≤ x ≤ 0.8) compounds. The Ni_1−xAl_xCo₂O₄ samples were synthesized through a hydrothermal method by varying the Al to Ni molar ratio. The physical, morphological, and electrochemical properties of Ni_1−xAl_xCo₂O₄ are observed to vary with Al³⁺ content. A morphological change from urchin-like spheres to nanoplate-like structures with a concomitant increase in the surface area, reaching up to 189 m²/g for x = 0.8, was observed with increasing Al³⁺ content in Ni_1−xAl_xCo₂O₄. The electrochemical performance of Ni_1−xAl_xCo₂O₄ as an electrode was assessed in a 3M KOH solution. The high specific capacitance of 512 F/g at a 2 mV/s scan rate, 268 F/g at a current density of 0.5 A/g, and energy density of 12.4 Wh/kg was observed for the x = 0.0 sample, which was reduced upon further Al³⁺ substitution. The as-synthesized Ni_1−xAl_xCo₂O₄ electrode exhibited a maximum energy density of 12.4 W h kg⁻¹ with an outstanding high-power density of approximately 6316.6 W h kg⁻¹ for x = 0.0 and an energy density of 8.7 W h kg⁻¹ with an outstanding high-power density of approximately 6670.9 W h kg⁻¹ for x = 0.6. The capacitance retention of 97% and 108.52% and the Coulombic efficiency of 100% and 99.24% were observed for x = 0.0 and x = 0.8, respectively. First-principles density functional theory (DFT) calculations show that the band-gap energy of Ni_1−xAl_xCo₂O₄ remained largely invariant with the Al³⁺ substitution for low Al³⁺ content. Although the capacitance performance is reduced upon Al³⁺ doping, overall, the Al³⁺ doped Ni_1−xAl_xCo₂O₄ displayed good energy, powder density, and retention performance. Thus, Al³⁺ could be a cost-effective alternative in replacing Ni with the performance trade off.