Noble-metal-free carbon nanotube-Cd0.1Zn0.9S composites for high visible-light photocatalytic H2-production performance

Abstract

Visible light photocatalytic H₂ production from water splitting using solar light is of great importance from the viewpoint of solar energy conversion and storage. In this study, a novel visible-light-driven photocatalyst multiwalled carbon nanotube modified Cd_0.1Zn_0.9S solid solution (CNT/Cd_0.1Zn_0.9S) was prepared by a simple hydrothermal method. The prepared samples exhibited enhanced photocatalytic H₂-production activity under visible light. CNT content had a great influence on photocatalytic activity and an optimum amount of CNT was determined to be ca. 0.25 wt%, at which the CNT/Cd_0.1Zn_0.9S displayed the highest photocatalytic activity under visible light, giving an H₂-production rate of 78.2 μmol h⁻¹ with an apparent quantum efficiency (QE) of 7.9% at 420 nm, even without any noble metal cocatalysts, exceeding that of pure Cd_0.1Zn_0.9S by more than 3.3 times. The enhanced photocatalytic activity was due to CNT as an excellent electron acceptor and transporter, thus reducing the recombination of charge carriers and enhancing the photocatalytic activity. Furthermore, the prepared sample was photostable and no photocorrosion was observed after photocatalytic recycling. Our findings demonstrated that CNT/Cd_0.1Zn_0.9S composites were a promising candidate for the development of high-performance photocatalysts in photocatalytic H₂ production. This work not only shows a possibility for the utilization of low cost CNT as a substitute for noble metals (such as Pt) in the photocatalytic H₂-production but also for the first time shows a significant enhancement in the H₂-production activity by using metal-free carbon materials as effective co-catalysts.