Noble metal free efficient photocatalytic hydrogen generation by TaON/CdS semiconductor nanocomposites under natural sunlight

Tantalum oxynitride have narrow band gap and its band potentials are suitable for visible light induced hydrogen generation. However, due to fast electron-hole recombination, the efficiency of photocatalytic hydrogen evolution reaction is very low. Herein, we have synthesized semiconductor heterojunction photocatalyst, i.e., TaON/CdS with suitable band positions by a simple precipitation method. Ratio between two semiconductors is optimized to obtain maximum hydrogen evolution. XRD, XPS and TEM analysis demon-strate the formation of heterojunction between these semiconductors. Among the syn-thesized catalysts, 3% TaON/CdS heterostructure exhibits the highest hydrogen evolution activity with H2 production rate of 7.5 mmol h-1 under natural solar light, whereas the rate is 11 mmol h-1 under the visible light generated by xenon (Xe) lamp without the addition of any noble metal as the co-catalyst. The CdS and 3% TaON/CdS nanomaterials show an AQE of 5.1% and 12.2%, respectively. Combination of Mott-Schottky, UPS and DR UV-visible spectroscopy studies revealed the formation of S scheme semiconductor heterojunction between these nanomaterials with valence, conduction band positions, i.e., 1.46,-0.78 eV for CdS and 2.19,-0.66 eV for TaON, respectively. These band positions help in efficient e-h pair separation to produce hydrogen from water. (c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

In this study, a TaON/CdS semiconductor heterojunction photocatalyst was synthesized by a simple precipitation method. The band positions of the two semiconductors were optimized to achieve maximum hydrogen evolution. The formation of a heterojunction between the semiconductors was confirmed by XRD, XPS, and TEM analysis. Among the synthesized catalysts, the 3% TaON/CdS heterostructure showed the highest hydrogen evolution activity under both natural solar light and visible light generated by a xenon lamp without the addition of a noble metal co-catalyst.