Electron delocalization-modulated hydroxyl binding for enhanced hydrogen evolution reaction activity

The introduction of foreign metals with a higher oxophilicity represents a promising strategy to promote water dissociation and in turn kinetics of alkaline hydrogen evolution reaction (HER). However, the further improvement of HER activity is limited by the unfavorable interaction of hydroxyl generated by the dissociation of water with active sites. Herein, we propose a strategy of alkaline earth metal cations-driven electron delocalization to elaborately tailor the binding of hydroxyl with the active sites. Taking FeNiMg-layered double hydroxides (FeNiMg-LDH) as a prototypical example, the combined operando spectroscopy analysis and theoretical calculations show that the introduction of Mg cations in solid- solution phase can create a local electronic field and delocalize the electron between Fe and adsorbed hydroxyl, resulting in an optimization of hydroxyl binding strength. Accordingly, FeNiMg-LDH lowers the overpotentials to deliver 10 mA cm^-2 in alkaline electrolyte by 39 and 64 mV, compared to FeNi-LDH and Ni-LDH catalysts, respectively. This work sheds new light on the rational design of advanced HER electrocatalyst for alkaline water electrolysis.