Deciphering the Role of Lattice Selenium in Electrocatalytic Self‐Reconstruction for Boosting Alkaline Hydrogen Evolution

Cathode reconstruction is equally crucial for water electrolysis, yet it has received less attention than anode. Lattice selenium (Se) doping is an effective strategy to improve hydrogen evolution reaction (HER) of metal-based electrocatalysts in cathodes, but many fundamental questions concerning the actual role of Se on the active species as well as catalytic kinetics remain to be clarified, especially in those electrocatalytic self-reconstruction systems. Here, we showcase the accelerated two-stage structural evolution of Se-doped cobalt phosphide (Se-CoP) during alkaline HER by operando X-ray absorption spectroscopy and powder X-ray diffraction, combined with high-resolution transmission electron microscopy (HRTEM) analysis. Further density functional theory (DFT) calculations suggest that the in situ formed dual-component heterostructure of highly crystalline Co(OH)₂ and robust Co nanoclusters, which are decorated with residual Se, is responsible for the high HER performance. The reconstructed Se-CoP on carbon cloth delivers a low overpotential of 79 ± 2 mV at 100 mA · cm^-2 and achieves an impressive charge transfer amount of 6.3 × 10⁵ C cm^-2 operating at 500 mA cm^-2, surpassing the reported electrocatalysts constructed by non-noble metal phosphides. This work provides brand-new perspectives on the self-reconstruction perturbed by heteroatoms for well-designed composite electrocatalysts.