Overall water splitting of type-I vdW heterojunction ZnS/Ga2SSe

Abstract

In the domain of photocatalysis, type I heterojunctions have received limited attention, and the quest for effective type I photocatalysts persists. This study introduces a novel type I heterostructure, ZnS/Ga₂SSe, and gives a systematic investigation of its electronic properties, optical properties, and photocatalytic performance by DFT calculations. Electronic properties show that ZnS/Ga₂SSe system has a type I band alignment with a 2.26 eV band gap. Different from traditional type I heterostructure, ZnS/Ga₂SSe has an obvious interfacial electric field and a potential barrier, which promotes spatial charge separation and addresses the drawback of easy recombination of photo-generated carriers in traditional type I heterojunctions. The calculated results of Gibbs free energy show that under the 3.3 eV external potential and pH = 14, water splitting reaction can be achieved spontaneously. Moreover, the heterojunction shows good optical absorption in visible regions and 22.28 % STH efficiency which is higher than the reported type I photocatalysts. The biaxial strain can modulate the electronic structure and maintain type I alignment. Tensile can reduce the bandgap and enhance optical absorption, while compression is the opposite. Under 4 % tensile, STH efficiency can reach 40.3 %, while −4 % compression it will decrease to 10.3 %. These conclusions underline the potential of the ZnS/Ga₂SSe heterojunction as a promising photocatalytic material candidate for water splitting and type I heterojunctions is worth exploring as photocatalysis.