Actualizing Anion–Cation Dual Active Sites in a Single Substance for Hydrogen Evolution

For a single-substance catalyst, due to the different adsorption/desorption kinetics of metallic (cationic) and nonmetallic (anionic) sites, it typically catalyzes hydrogen evolution in a single-active-site manner, which greatly limits the activity of catalysts. Thus, herein, we simultaneously activate the anion (P) and cation (Ni) sites in nickel phosphide (Ni2P) and generate highly active P(Ni) dual sites through the substrate effect of NiS2–NiS heterogeneous structures. Theoretical calculation results combined with in situ Raman spectroscopy unveil that the NiS2–NiS substrate effectively regulates the charge distribution to concentrate around the P atom, therefore resulting in Ni and P synergistic dual active sites for water adsorption, water dissociation, and H* adsorption. Accordingly, the dual active site formed enables the Ni2P/NiS2–NiS electrocatalyst to only require an overpotential of 75 mV to achieve a current density of 10 mA cm–2 in alkaline media, very close to the Pt-group noble metal catalyst. This work highlights the critical regulatory role of substrates in activating the anion–cation dual active site in the single metal/intermetallic compound (such as metal phosphides, sulfides, nitrides, carbides, borides, and silicides) that promotes catalytic performance.