Theory-Driven Heterojunction Photocatalyst Design with Continuously Adjustable Band Gap Materials

The utilization efficiency of hot carriers in photocatalyst is limited at present by their fast recombination. Heterojunction interface would reduce the recombination rate by effectively facilitating spatial separation of the hot electron and hole. Here, we establish a heterojunction photocatalyst design principle by using continuously adjustable band gap materials. This is demonstrated using first-principles calculations, and is subsequently validated by direct measurements of photocatalytic activity of ZnxCd1-xS-reduced graphene oxide (RGO) heterojunction as a proof-of-concept photocatalyst. Tuning the Zn/Cd ratio and/or the reduction degree of RGO can result in three types of heterojunctions and different conduction and valence band offsets by varying their band gap and positions of band edges. The modulation of efficient electron-hole separation at the interface is manifested by the consistency of calculated and experimental optical absorbance, and enhanced photocatalytical activity of ZnxCd1-xS-RGO heterojunction. This results can also rationalize the available experimental results of RGO-based composites. This design principle is broadly applicable to the development of other heterojunction materials ranging from photocatalysts and solar cells to functional electronic devices through interfacial band alignment engineering.