Ternary chalcogenides XGaS2 (X = Ag or Cu) for photocatalytic hydrogen generation from water splitting under irradiation of visible light

Ternary chalcogenide silver gallium sulfide (AgGaS2), which has an orthorhombic structure, was already synthesized. However, the feasibility of using the crystal for hydrogen production through photocatalytic water splitting has not been explored. Here, we systematically investigated the structural, electronic, optical, and transport properties of XGaS2 (X = Ag or Cu) with orthorhombic structure by using the first principles calculations. The band alignments indicate that all calculated absolute potentials of the valence and conduction band edges met the requirement of photocatalytic water splitting reaction. The presence of 2.64 and 2.56 eV direct band energy gaps and obvious optical absorption within the visible light range imply that XGaS2 can correspond to solar light. Moreover, the large electron mobility and the obvious differences between electron mobility and hole mobility were identified in XGaS2 structures, which is beneficial to the photocatalytic performance of the water splitting reaction. The present findings can provide a helpful reference for developing novel photocatalytic materials with XGaS2 for hydrogen generation from water splitting under irradiation of visible light.