Electrochemical Water Oxidation of NiCo2O4 and CoNi2S4 Nanospheres Supported on Ni Foam Substrate

Abstract Electrochemical water splitting is an environment‐friendly technique for producing clean energy. Low‐cost, high performance and robust electro catalysts for electrochemical oxygen evolution reaction (OER) is highly essential for improving the overall efficiency of water splitting. In the present study, NiCo 2 O 4 and CoNi 2 S 4 nanospheres were successfully prepared by employing solvothermal method and optimized at 180°C. XRD result confirmed the formation of cubic structure of both NiCo 2 O 4 and CoNi 2 S 4 nanospheres. SEM images evidently revealed the perfect nanospherical surface morphology of NiCo 2 O 4 and distorted nanospherical morphology of CoNi 2 S 4 . The obtained characteristic Raman active modes of vibrations confirmed the product formation. Photoluminescence study proclaimed the emission behavior of the product. FTIR results confirmed the metal oxygen vibrations such as Ni−O, Co−O and Ni−S of NiCo 2 O 4 and CoNi 2 S 4 nanospheres. UV spectra and Tauc plot revealed the optical band gaps of Ni and Co based oxide and sulfide nanospheres. Electrochemical studies of optimized NiCo 2 O 4 and CoNi 2 S 4 revealed the respective specific capacitance of 767.067 F/g and 648.11 F/g at scan rate of 10 mVs −1 in 1 M KOH electrolyte solution. Furthermore, the current density of 331 and 159 mAg −1 was achieved for the best performed NiCo 2 O 4 and CoNi 2 S 4 electrodes with improved electrical conductivity. The stability over 12 h of highly performed NiCo 2 O 4 nanospheres has been reported. This work suggested a viable and optimized approach to synthesize Ni and Co based oxide and sulfide nanospheres for efficient electrochemical water oxidation.