Deep sulfur doping induces the rapid electrochemical self-reconstruction of Ni–Fe hydroxide to drive water oxidation

Abstract

A desirable electrochemical reconstruction of oxygen-evolution-reaction (OER) electrocatalysts is crucial to practical water electrolysis. However, it is an extremely complex dynamic process, and ways to accelerate the natural self-activation process via reconstruction toward producing more desired active products remain unclear. Here, a beneficial and rapid reconstruction of Ni–Fe hydroxide with low crystallinity and deep sulfur doping is achieved using a chemical etching and co-precipitation strategy at room temperature. Advantageous electrochemical self-reconstruction could be accomplished within 10 CV cycles, and the generated catalyst presents a superior OER performance with an overpotential of 233 mV at 10 mA cm⁻² and a Tafel slope of 21.9 mV dec⁻¹. The stepped-up self-activation indicates that a low crystallinity can powerfully reduce the resistance to electrochemical reconstruction and sulfur leaching vigorously facilitates the phase transformation into more oxyhydroxides with a high intrinsic activity. This work highlights the exact role of crystallinity and defect structures in electrochemical reconstruction under OER conditions.