Interface Engineering of Co(OH)2/Ag/FeP Hierarchical Superstructure as Efficient and Robust Electrocatalyst for Overall Water Splitting.

Rational design and preparation of electrocatalyst with optimal component and interfaces, which can work well for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media, are of great importance in practical water splitting. Herein, a multiscale structure surface engineering approach to construct Co(OH)2/Ag/FeP hybrid as efficient electrocatalysis for water splitting in alkaline media is reported. By optimizing the component ratio and engineering interfacial structure, the Co(OH)2/Ag/FeP hybrid eletrocatalyst exhibits promoted HER and OER activity as well as stability in alkaline media, achieving an overpotential of 118 and 236 mV at a current density of 10 mA cm-2, respectively. Further experimental characterizations demonstrate the electron structure changes in Co(OH)2/Ag/FeP hybrid after constructing the interfaces, which is beneficial to generate low-charge state Fe2+ and high-oxidized Co3+/4+. The first-principle calculations reveal that the dissociation of H2O at the interface region is energetically favorable, which is responsible for the enhanced HER and OER activity. Furthermore, two-electrode alkaline water electrolyzer constructed by Co(OH)2/Ag/FeP hybrid electrocatalysts only requires a voltage of 1.56 V to afford a current density of 10 mA cm-2, which is superior to the commercial Pt/C-IrO2 catalytic couple and makes it a promising material to be employed as effective bifunctional catalysts for overall water splitting.