Small ZnIn<sub>2</sub>S<sub>4</sub> Nanosheets with\nAbundant Edge-Active Sites Modified with MoS<sub>2</sub> Nanosheets\nfor Hydrogen Evolution

Due to their unique optical properties and large specific\nsurface\nareas, two-dimensional (2D) layered materials hold great promise for\na wide range of applications in photocatalysis. A one-step, low-temperature\nreflow method was employed to synthesize 2D small-sized ZnIn<sub>2</sub>S<sub>4</sub> (S-ZIS) nanosheets with the assistance of CH<sub>3</sub>NO and C<sub>6</sub>H<sub>5</sub>Na<sub>3</sub>O<sub>7</sub> as surfactants.\nThe synthesized S-ZIS, consisting of preferentially exposed edge facet\n(102) with an average size of approximately 200 nm, exhibited a larger\nspecific surface area and shortened carrier lifetime compared to traditional\nZnIn<sub>2</sub>S<sub>4</sub> (ZIS). Furthermore, the separation and\nmigration of photogenerated electron–hole pairs in MoS<sub>2</sub>-modified S-ZIS (S-ZIS/MoS<sub>2</sub>) were effectively promoted\ndue to the intimate contact between MoS<sub>2</sub> and the S-ZIS\ninterface. Under simulated solar light irradiation, the optimum hydrogen\nevolution rate was achieved for the binary S-ZIS/MoS<sub>2</sub>-3\nheterostructure, reaching 21.66 mmol·g<sup>–1</sup>·h<sup>–1</sup>, which was 3 and 21 times higher than that of S-ZIS\nand ZIS, respectively. Additionally, an apparent quantum yield (AQY)\nof 76% was achieved at 400 nm. This study provides valuable insights\ninto the reasonable design and optimization of 2D heterostructures\nwith preferably exposed edge-active sites and offers an innovative\nstrategy for the development of efficient composite photocatalytic\nsystems.