ZnO nanowire arrays with in situ sequentially self-assembled vertically oriented CdS nanosheets as superior photoanodes for photoelectrochemical water splitting

Abstract

The performance of photoelectrochemical (PEC) water splitting, a highly promising strategy for solar to hydrogen energy conversion, is greatly restricted by the photoanode reaction. For the first time, high-density CdS nanosheets have been in situ grown on ZnO nanowire arrays with a vertical orientation via a sequential self-assembly approach. The obtained hierarchical and hybrid nanostructured array delivers a photocurrent density of 9.10 mA cm⁻² at 1.23 V (versus the reversible hydrogen electrode) and a maximum photoconversion efficiency of 3.72%, both of which are among the highest reported for ZnO-based photoanodes. The superior PEC performance is primarily due to the CdS nanosheet layer greatly increasing visible light absorption, enhancing charge separation, and facilitating charge transfer and transport. This work not only develops a facile, mild, and economical strategy to in situ self-assemble quantum NSs on ZnO NWAs for application as high-performance photoanodes toward PEC water splitting, but also sheds light on the mechanisms for both the formation and the performance enhancement of ZnO NWAs assembled with vertically oriented CdS NSs.