Rationalized carrier confinement significantly enhances overall photocatalytic water splitting in branched CdS/C3N5

Abstract

An efficient way to achieve photo-generated carrier utilization is by heterojunction engineering of photocatalysts. However, to realize the overall water splitting seems to be particularly difficult by virtue of the traditional modification pathway. In this work, the thin layered C3N5 is coupled on branched CdS to accomplish efficient overall water splitting and provide some profound knowledge about heterojunction engineering and the ways in which the interface interaction improves the water splitting properties of photocatalysis. For the cause of overall water splitting, a suitable combination of theoretical calculations and experimental investigations was conducted. The findings show that the photo-generated electrons in CdS/C3N5 could be strongly secured by the thin C3N5 component, significantly increasing the HER rate. The CdS/C3N5 shows photocatalytic hydrogen production of up to 1.28 mmol·g−1, which is 640 % higher than its counterpart. The branched CdS component could balance the free energy barrier in OER reaction steps by enriching holes in Cd atoms, thereby significantly increasing the OER reaction rate. The C3N5 interface essentially protects the S atoms in the CdS component that are vulnerable to photo-corrosion because the small hole is limited to the S atoms in the interface. And theoretically, it has been confirmed that the interface electric field perpendicular to the interface direction is the intrinsic driving force for reducing the probability of carrier recombination. This investigation offers unique insights into the carrier transfer mechanism of CdS/C3N5 and opens up the possibility of utilizing the CdS-based photocatalyst for overall water splitting.