Favorable surface etching of NiRuFe(OH)_x in neutral hydrogen evolution reaction

Surface transformation of the catalyst during electrocatalysis bring great challenge towards catalyst development and application. In this work, we report an interesting phenomenon that the NiRuFe(OH)_x will experience a favorable surface etching during the initial period when electrocatalytic hydrogen evolution reaction (HER) takes place in a neutral medium. The etched surface of NiRuFe(OH)_x can improve the catalytic performance in neutral HER with only 49 mV to drive the 10 mA cm⁻². The materials characterizations and electrochemical measurements confirm the unique surface information before and after etching. We attribute the improved HER performance to the induced crystal defects, which are likely to bring higher intrinsic catalytic activity. The stability measurements evidence this functional surface can effectively catalyze HER in a neutral medium over 200 h, prove its robust feature. This work, we believe, can serve as a model for the exploration of neutral HER catalysts and the identification of true active sites during electrocatalysis.