Engineering electron redistribution of bimetallic phosphates with CeO₂ enables high-performance overall water splitting

Transition metal phosphides (TMPs) with Pt-like electronic structures are anticipated to be potential candidates for alkaline hydrogen evolution reaction (HER) electrocatalysis. However, the strong binding strength between metallic active sites in TMPs and intermediates hinders the enhancement of their electrocatalytic activity. Herein, we used surface CeO₂-decorated strategy to regulate surface electron distribution of bimetallic phosphides and achieve the enhanced HER activity. Taking NiCoP nanowire arrays as an example, the surface-modified CeO₂ nanoparticles (CeO₂-NiCoP) make the surface electrons redistribute, promoting the transfer of electrons from NiCoP to CeO₂. As a result, the d-band center of metal active sites in CeO₂-NiCoP is negatively shifted, resulting in the optimized binding strength with H intermediates. Therefore, CeO₂-NiCoP exhibits significantly enhanced HER catalytic activity with low overpotentials of 84, 202 and 242 mV at the current densities of 10, 500 and 1000 mA cm⁻², respectively, much lower than those of NiCoP counterparts (ƞ₁₀ = 142 mV, ƞ₅₀₀ = 349 mV, ƞ₁₀₀₀ = 427 mV). Furthermore, we extend this surface electron redistribution strategy to other bimetallic phosphides and similar trends are observed. Finally, a double-electrode electrolyzer based on CeO₂-NiCoP is assembled to achieve a low cell voltage of 1.80 V at a current density of 1000 mA cm⁻² under simulated industrial conditions, as well as excellent stability. This work provides a feasible method to design highly active and stable electrocatalysts for overall water splitting via regulating electronic structure of TMPs, and enlightens a new mentality in terms of designing surface active sites of catalysts.