NiCo2O4 nanoparticles inlaid on sulphur and nitrogen doped and co-doped rGO sheets as efficient electrocatalysts for the oxygen evolution and methanol oxidation reactions

The present work depicts the fabrication of NiCo2O4 decorated on rGO, and doped and co-doped rGO and its electrocatalytic activity towards the oxygen evolution reaction and methanol oxidation reaction. The NiCo2O4 catalyst with S-doped rGO outperformed the other catalysts, indicating that the sulphur atoms attached on rGO possess low oxophilicity and optimum free energy. This results in facile adsorption of the intermediate products formed during the OER and a rapid release of O2 molecules. The same catalyst requires an overpotential of 1.51 V vs. RHE to attain the benchmark current density value of 10 mA cm-2 and shows a Tafel slope of 57 mV dec-1. It also reveals outstanding stability during its operation for 10 h with a minimum loss in potential. On the other hand, NiCo2O4/S,N-rGO reveals superior activity with high efficiency and stability in catalyzing methanol oxidation. The catalyst delivered a low onset potential of 0.12 V vs. Hg/HgO and high current density of 203.4 mA cm-2 after addition of 0.5 M methanol, revealing the outstanding performance of the electrocatalyst.