Role of SnS₂ in 2D–2D SnS₂/TiO₂ Nanosheet Heterojunctions for Photocatalytic Hydrogen Evolution

Constructing heterojunctions with face-to-face interface is a new avenue for accelerating the charge separation in semiconductor photocatalysts toward highly efficient solar water splitting systems. Here, a novel SnS2/TiO2 2D–2D ultrathin nanosheet heterostructure was fabricated via a hydrothermal route in two steps. The obtained 2D–2D SnS2/TiO2 nanojunction has not only provided large contact areas but also shortened the charge transport distance, resulting in significantly enhanced photocatalytic H2 evolution property. The H2 generation rate obtained for the optimized sample reaches 652.4 μmol h–1g–1, far exceeding (∼8 times) that of pristine TiO2 and SnS2 ultrathin nanosheets under simulated solar irradiation. Moreover, further analysis reveals a photoinduced carrier transfer from TiO2 to SnS2 at the interface junction, which causes a partial reduction of the SnS2 cocatalyst to SnS in the nanocomposite during the photocatalytic reactions. These results not only demonstrate that the construction of 2D–2D heterojunction is a promising approach to improve the photocatalytic H2 production activity of nanostructured semiconductor photocatalysts but also provide new understanding into the role and evolution of SnS2 nanosheets during the photocatalytic reaction process in heterogeneous photocatalyst systems.