Active site engineering of Fe- and Ni-sites for highly efficient electrochemical overall water splitting

Cost-effective, highly efficient, and durable catalyst electrodes play a critical role in large-scale water splitting. Although bimetallic phosphides show great potential in electrocatalytic water splitting, the synergistic effect between different active sites has not been investigated to date in detail, which implies lack of an effective strategy to optimize the water splitting performance in a reasonable way. Here we realize robust oxygen evolution (OER) performance with an extremely low overpotential (500 mA cm ⁻² @255 mV), low Tafel slope (29.1 mV dec ⁻¹ ), and superior stability by controlling the Fe sites on the Ni-Fe-P surface. The prepared OER electrode employs non-noble metal catalysts for superior oxygen evolution performance and meets the requirements of commercial water electrolyzers. In addition, remarkable hydrogen evolution (HER) performance with prominent stability is also achieved by reducing the content of Fe dopant. Our theoretical calculations reveal that improved chemisorption of O-containing intermediates induced by Fe doping contributes to the enhanced OER performance and water molecule chemisorption, which is sensitive to the Fe content, is the primary cause affecting alkaline HER performance. This work highlights controllable water splitting performance on the Ni-Fe-P surface by precisely manipulating the surface active Fe-sites.