GaAs quantum dot/TiO2 heterojunction for visible-light photocatalytic hydrogen evolution: promotion of oxygen vacancy

The development of materials with photocatalytic activity in a visible-light region is of great significance for solar energy utilization and clean energy production. In this paper, we designed a GaAs quantum dot (QD)/TiO2 heterojunction with high performance of visible-light photocatalytic hydrogen evolution based on first-principle calculations. The results show that six designed GaAs QDs are thermally stable at 300 K, and they have proper visible-light absorption except GaAs-12 QD. GaAs-20 QD maintains good stability at 350 K. Further investigations indicate that the interface Ga atoms in the GaAs-20/TiO2 heterojunction are active sites for photocatalytic reaction, and the type-II band alignment of the GaAs-20/TiO2 heterojunction can lead to effective separation of photoexcited electron–hole pairs. Moreover, the energy barrier of hydrogen production in GaAs-20/TiO2 is about 56% lower than that in TiO2, and oxygen vacancy in GaAs-20/TiO2 heterojunction could transform the hydrogen production from endothermic reaction into exothermic reaction, which has an obvious promotion effect on photocatalytic hydrogen evolution. In short, our calculations indicate that the GaAs-20/TiO2 heterojunction has high performance in visible-light photocatalytic hydrogen evolution. The GaAs quantum dot (QD)/TiO2 heterojunction with high performance of visible-light photocatalytic hydrogen evolution was designed based on first-principle calculations. The oxygen vacancy in the GaAs-20/TiO2 heterojunction could transform the hydrogen production from endothermic reaction into exothermic reaction.