Size Dependent\nPhotocatalytic Activity of Mesoporous\nZnIn<sub>2</sub>S<sub>4</sub> Nanocrystal Networks

Understanding of the band-edge electronic structure and\ncharge-transfer\ndynamics in size-confined nanostructures is vital in designing new\nmaterials for energy conversion applications, including green hydrogen\nproduction, decomposition of organic pollutants and solar cells. In\nthis study, a series of mesoporous materials comprising continuous\nnetworks of linked zinc indium sulfide (ZnIn<sub>2</sub>S<sub>4</sub>) nanocrystals with a tunable diameter (ranging from 4 to 12 nm)\nis reported. These nanomaterials demonstrate intriguing size-dependent\nelectronic properties, charge-transfer kinetics and photocatalytic\nbehaviors. Our extensive characterizations uncover strong size effects\non the catalytic activity of constituent ZnIn<sub>2</sub>S<sub>4</sub> nanocrystals in the photochemical hydrogen evolution reaction. As\nan outcome, the optimized single-component ZnIn<sub>2</sub>S<sub>4</sub> mesostructure produces hydrogen at a 7.8 mmol g<sub>cat</sub><sup>–1</sup> h<sup>–1</sup> release rate under ultraviolet\n(UV)–visible light irradiation associated with an apparent\nquantum yield (AQY) of 17.2% at 420 ± 10 nm, far surpassing its\nmicrostructured counterpart by a factor of 10.7×. These findings\nprovide a valuable perspective for the rational design of semiconductor\nnanostructures through synthetic engineering, aiming at the development\nof high-performance catalysts for zero-carbon energy-related applications.