Autologous growth of nickel oxyhydroxides with in situ electrochemical iron doping for efficient oxygen evolution reactions

Abstract

Nanostructured Ni and Fe hydroxides and oxides have drawn significant attention for the oxygen evolution reaction (OER) because of their high catalytic efficiency and low cost. Herein, a facile cyclic voltammetry method is reported for the autologous growth of a highly integrated and efficient NiFe–OOH catalyst for the OER by electrochemical roughening of Ni foam substrates in 6 M KOH using an iron rod counter electrode. The electrochemical roughening created a nanostructured Ni surface with low interfacial electrical resistance and 25 times higher surface area, accompanied by in situ doping of Fe. Electrochemical characterization revealed that the formed NiFe–OOH catalysts exhibit an extremely low OER onset overpotential of 190 mV and a Tafel slope merely of 48.1 mV dec⁻¹ in 1 M KOH. Furthermore, a NaBH₄ reductive treatment was applied to create more surface defects on NiFe–OOH leading to further enhanced catalyst conductivity and a further decrease of the Tafel slope to 34.7 mV dec⁻¹. The electrode demonstrated prolonged electrochemical and mechanical stability at high current densities in industrial 30 wt% KOH solutions.