Electrochemically Activated NiFeO_xH_y for Enhanced Oxygen Evolution

To minimize the utilization of fossil fuels, the demand for H2 production through water electrolysis has considerably increased. NiFeOxHy-based electrocatalysts have attracted extensive attention owing to their excellent electrocatalytic activity in the oxygen evolution reaction (OER). To realize their commercialization, NiFeOxHy-based catalysts are being ameliorated for better performance in the OER. Here, we present a simple and scalable approach for fabricating NiFeOxHy by preparing a Ni–Fe master alloy plate followed by electrochemical activation including cyclized oxidation and reduction of metal ions. During the activation, the amorphous layer evolved only on the catalyst surface by circulating the oxidation states of Ni and Fe. The activated NiFeOxHy required only 250 mV of overpotential for 10 mA cm–2 and 30 mV dec–1 of Tafel slope, which is much better than the electrodeposited NiFeOxHy. The enhanced OER activity originates from the amorphous surface layer which contains partially oxidized Ni ions. This study suggests valuable possibilities for the design of better OER electrocatalysts using simple electrochemical methods.