Deciphering the surface electrochemical reconstruction of ruthenium-cobalt-nickel phosphide for efficient high-current hydrogen evolution and overall water splitting

RuCoNiP rapidly reconfigures to RuCoNiP@α-Ni(OH)2 and RuCoNiP@Co/Ni(OH)x during HER and OER, which can be used as efficient catalysts for HER, OER and overall water splitting. [Display omitted] •RuCoNiP was rapidly prepared and RuCoNiP@M(OH)x reconstructions was revealed.•RuCoNiP@α-Ni(OH)2 exhibits excellent activity and stability for HER.•DFT reveals RuCoNiP@α-Ni(OH)2 attenuates the competitive adsorption of OH* and H*.•RuCoNiP@Co/Ni(OH)x achieves both high activity and stability of OER.•RuCoNiP@α-Ni(OH)2//RuCoNiP@Co/Ni(OH)x achieved alkaline water splitting. Development of efficient and stable bifunctional transition metal phosphide catalysts is critical for advancing hydrogen production technologies. Herein, RuCo co-doped Ni8P3 (RuCoNiP) was designed and synthesized by one-step electrodeposition for Ni electronic structure modulation, and evolved to RuCoNiP@α-Ni(OH)2 and RuCoNiP@Co/Ni(OH)x heterointerfaces by self-assembled reconstruction during HER and OER processes, respectively. RuCoNiP@α-Ni(OH)2 enhances HER activity (305.8 mV@−1000 mA cm−2) and stability (100 h@−1000 mA cm−2) by weakening OH* and H* competitive adsorption. Density functional theory (DFT) calculations revel that the ΔGH* of Ni site (RuCoNiP) is reduced by the assignment of a large number of Ni d-states at the Fermi level by RuCo doping, which synergistically interacts with the enhanced adsorption of α-Ni(OH)2 to OH*, resulting in a lower energy barrier for hydrogen adsorption–desorption. Moreover, RuCoNiP@Co/Ni(OH)x relies on M(OH)x to enhance the activity (351.4 mV@1000 mA cm−2) and stability (100 h@1000 mA cm−2) of OER. Dual-electrode system RuCoNiP@α-Ni(OH)2//RuCoNiP@Co/Ni(OH)x demonstrates an ultra-low battery voltage (1.95 V@1000 mA cm−2) and excellent stability (50 h@1000 mA cm−2). This efficient synthetic strategy and the self-assembled heterojunction structure offer a promising path for developing efficient overall water-splitting catalysts.