Transition-metal dichalcogenides/Mg(OH)2 van der Waals heterostructures as promising water-splitting photocatalysts: a first-principles study

Abstract

We performed first-principles calculations of the structural, electronic, and optical properties of heterostructures which consist of transition metal dichalcogenides MX₂ (M = Mo, W; X = S) stacked with Mg(OH)₂. All the heterostructures are formed by van der Waals forces. The MoS₂/Mg(OH)₂ and WS₂/Mg(OH)₂ vdW heterostructures were found to be semiconductors with indirect bandgaps and possess intrinsic type-II band alignment. In particular, a comparison of the band edge positions with the redox potential of water indicates that the heterostructures are potential photocatalysts for water splitting, enabling water reduction on the MX₂ layer and water oxidation on the Mg(OH)₂ layer. Moreover, the photogenerated charges will be effectively separated in the presence of a large built-in electric field across the interface. In addition, all of the MX₂/Mg(OH)₂ heterostructures show strong optical absorption in the visible and infrared regions, indicating their promise for application in photocatalytic water splitting.