Asymmetric Bridging Multi‐Active Sites in a‐NiSeS Cocatalyst for Upgrading Photocatalytic H₂ Evolution

Abstract Cocatalyst‐coupled photocatalytic system offers an attractive tactic to produce eco‐friendly H₂ fuel from renewable water and sunlight. However, the efficiency of single homologous active site in current cocatalysts is seriously restricted by the opposite binding‐energy requirement for hydrogen adsorption and desorption. Herein, an asymmetric strategy of bridging multi‐active sites is validated to break the strong relevancy of H adsorption–desorption rate on the designed amorphous NiSeS (a‐NiSeS) cocatalyst. It is found that the S–Ni–Se modules with self‐optimized electron‐rich S^(2+δ)− and electron‐deficient Se^(2‐δ)− atoms can induce the transfer of hydrogen from S^(2+δ)− to Se^(2‐δ)− sites for synchronously realizing the fast H adsorption and desorption. Consequently, the TiO₂/a‐NiSeS photocatalyst delivers a significantly enhanced H₂‐evolution activity of 8216 µmol h⁻¹ g⁻¹, which is 2.5 and 3.3 times higher than that of TiO₂/a‐NiS and TiO₂/a‐NiSe, respectively. The improved activity is ascribed to the unique synergistic mechanism of asymmetric bridging multi‐active sites, namely, S^(2+δ)− site works as the hydrogen‐rich center, thermodynamically neutral bridge site of S–Ni–Se functions as the mediator for rapidly transferring H from S^(2+δ)− to Se^(2‐δ)−, while the Se^(2‐δ)− site expedites the desorption of hydrogen to free H₂. This work provides atomic‐level insight into the underlying cocatalytic mechanism of H adsorption and desorption.