Improving Electrocatalysts for Oxygen Evolution Using Ni_xFe_{3- x}O₄/Ni Hybrid Nanostructures Formed by Solvothermal Synthesis

Spinel-type oxides have been found to be active electrocatalysts for OER. However, their semiconductor character severely limits their catalytic performance. Herein, we report a facile solvothermal pathway for the synthesis of spinel-type Ni_xFe_3-xO₄ oxides/Ni metal nanocomposites. The good electrical contact between the metal and semiconductor oxide interface and well-tuned compositions of Ni_xFe_3-xO₄ spinel oxides are crucial to achieve better OER performance. Specifically, the Ni_xFe_3-xO₄/Ni nanocomposite sample prepared from a metal precursor ratio of y = 0.15 [y = Fe/(Fe + Ni)] that results in an x value of about 0.36 exhibits catalytic activity with an overpotential of 225 mV to achieve an electrocatalytic current density of j = 10 mA cm^-2 and a Tafel slope of 44 mV dec^-1 in alkaline electrolyte. This study not only provides new perspectives to designing nanocomposite catalysts for OER but also opens a promising avenue for further enhancing electrocatalytic performance via interface and composition engineering.