Synergy between palladium single atoms and small nanoparticles co-anchored on carbon atom self-doped graphitic carbon nitride boosting photocatalytic H2 generation

Supramolecule self-assembly of dicyandiamide and uracil followed by thermal polymerization route is designed to prepare carbon atom self-doped g-C₃N₄ (CCN_x), and then wet reduction is applied to fabricate Pd single atoms (Pd₁) and nanoparticles (Pd_NPs) co-anchored CCN_x heterojunctions (Pd_1+NPs/CCN_x). In Pd_1+NPs/CCN_x structure, interlayer Pd−N₄ coordination is the most favorable for chemically stabilizing Pd₁, while Pd_NPs accumulate on the in-plane of CCN_x. Pd_1+NPs/CCN_x heterojunctions exhibit remarkably enhanced photocatalytic H₂ evolution reaction (HER) activity, and HER rate and AQY value reach up to 24.1 mmol g⁻¹ h⁻¹ and 17.1% (400 nm) over the optimized Pd_1+NPs/CCN_x catalyst. Mechanism studies unveil that synergy of as-built interlayer N−Pd−N electron transfer channels at the atomic-scale and surface Mott–Schottky effect of small Pd nanoparticles notably accelerates migration of photogenerated electrons, which leads to plentiful electrons accumulation around Pd single atoms and small nanoparticles to decrease the energy barrier of H* activation and boost HER photodynamics significantly.