Donor‐Acceptor‐Donor Organic Small Molecules as Hole Transfer Vehicle Covalently Coupled Znln2S4 Nanosheets for Efficient Photocatalytic Hydrogen Evolution

Abstract

AbstractSluggish kinetics of photoexcited charge carriers in photocatalysts, slow hole transfer in oxidation half‐reaction, and consequent fast charge recombination on photocatalyst surface are the Achilles' heel limiting the efficiency of photocatalytic hydrogen evolution (PHE). Herein, the effectiveness of covalent binding alternating D‐A‐D organic small molecules (triphenylamine as the donor unit and benzothiadiazole as the acceptor unit) to Znln2S4 (ZIS) nanosheets in the design and development of highly efficient PHE photocatalysts is demonstrated. The covalent grafting of D‐A‐D molecules broadens the photo‐responsive range of ZIS nanosheets, significantly increasing the density of photogenerated charge carriers. More importantly, D‐A‐D organic small molecules can efficiently extract surface photogenerated holes and suppress the recombination of surface photogenerated electron‐hole pairs, thus facilitating the rapid consumption of retained photogenerated electrons for proton reduction to generate H2 with fast kinetics. Consequently, the optimized PHE rate of the ZIS@DAD hybrid catalyst reaches 28.25 mmol g−1 h−1, a 4.2‐fold improvement over that of ZnIn2S4 nanosheets. The covalent integration of D‐A‐D molecules onto inorganic semiconductor photocatalysts represents a novel and highly efficient strategy for optimizing the overall PHE process. This approach provides a fertile new ground for creating efficient solar‐to‐hydrogen systems.