Composition-Engineered Heavy-Metal-Free Cu–Ga–Zn–S Nanorods for Efficient Photocatalytic Water Splitting

Semiconductor photocatalysts composed of copper-based chalcogenides have emerged as promising candidates for photocatalytic water splitting, enabling the production of hydrogen and oxygen. The incorporation of extra Zn cations into copper chalcogenides is found to significantly alter their optical and electronic properties, such as band gap, charge carrier transfer, and the separation of photo-generated electron and hole couples. In this work, we developed a colloidal approach to synthesizing one-dimensional (1D) quaternary Cu–Ga–Zn–S nanorods (NRs) with enhanced photocatalytic hydrogen evolution performance. The Cu–Ga–Zn–S NRs demonstrate a Zn-dependent growth mechanism, where Zn cations promote the morphological elongation along the [0001] direction. Through the control of the Ga/Zn feeding molar ratios in Cu–Ga–Zn–S NRs, we achieved the maximum photocatalytic hydrogen production rate of 2101 μmol·g–1·h–1, surpassing both of the Zn-free and Zn-rich counterparts. Such improvement can be attributed to the tailored lifetime of photo-generated charge carriers, charge transfer resistance, and separation efficiency of photo-generated electrons and holes, instead of a slight alteration of band gap. Notably, the optimal Cu–Ga–Zn–S NRs also show an anodic photocurrent and photocatalytic oxygen production activity under solar irradiation. Our study presents a facile method for preparing 1D Cu–Ga–Zn–S NRs via composition engineering and offers valuable insights to develop multifunctional photocatalysts for efficient water splitting.