Size Dependent Photocatalytic Activity of Mesoporous ZnIn2S4 Nanocrystal Networks

Understanding of the band-edge electronic structure and charge-transfer dynamics in size-confined nanostructures is vital in designing new materials for energy conversion applications, including green hydrogen production, decomposition of organic pollutants and solar cells. In this study, a series of mesoporous materials comprising continuous networks of linked zinc indium sulfide (ZnIn2S4) nanocrystals with a tunable diameter (ranging from 4 to 12 nm) is reported. These nanomaterials demonstrate intriguing size-dependent electronic properties, charge-transfer kinetics and photocatalytic behaviors. Our extensive characterizations uncover strong size effects on the catalytic activity of constituent ZnIn2S4 nanocrystals in the photochemical hydrogen evolution reaction. As an outcome, the optimized single-component ZnIn2S4 mesostructure produces hydrogen at a 7.8 mmol gcat(-1) h(-1) release rate under ultraviolet (UV)-visible light irradiation associated with an apparent quantum yield (AQY) of 17.2% at 420 +/- 10 nm, far surpassing its microstructured counterpart by a factor of 10.7x. These findings provide a valuable perspective for the rational design of semiconductor nanostructures through synthetic engineering, aiming at the development of high-performance catalysts for zero-carbon energy-related applications.