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 g_cat ^-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 10.7×. 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.