Al-doped CuS/Znln2S4 forming Schottky junction induced electron trap centers for photocatalytic overall water splitting

Abstract

Synergistically tuning electronic states at the atomic level to facilitate photocatalytic overall water splitting is a challenge. However, elucidation of the role of specific electronic states of Znln2S4 (ZIS) in regulating both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) is still scarce, making it difficult to accurately predict the actual photocatalytic performance. Here, the substitution of Zn sites with Al atoms was found to modulate the potential difference of the ZIS surface domain heterojunction structure, and electrons were further transferred to CuS to form a built-in field that promotes charge separation. When Al doping is present on the ZIS surface, ZIS exhibits p-type semiconductor properties, which leads to the formation of p-n junctions within Al-CuS/ZIS itself. Due to the large work function and metallic properties of CuS, and Al-CuS/ZIS as a whole tends to form a Schottky heterojunction, and the two heterojunction structures synergistically promote the migration of photogenerated carriers. In addition, the Al doping changes the electronic states around the ZIS, allowing the Al ZIS to promote the adsorption of O* and H* during OWS. The solar-driven photocatalytic overall water splitting efficiency of Al-CuS/ZIS is as high as 153.6 (HER) and 73.1 (OER) μmol/h g−1, which is about 10 times that of ZIS. This work opens the possibility to design efficient photocatalytic materials through tunable composition and electronic structure.