Hierarchically CdS–Ag₂S nanocomposites for efficient photocatalytic H₂ production

Hierarchically nanostructured CdS composed of 4.7 nm-thick self-assembled ultrathin nanosheets was synthesised through a microwave-assisted solvothermal method. Ag₂S nanoparticles (NPs) were deposited at the edge of the CdS nanosheets by an in situ ion exchange strategy. The hierarchically CdS–Ag₂S nanocomposites exhibited a high visible light photocatalytic H₂ evolution rate of 375.6 μmol h⁻¹ g⁻¹, which was 11.5 times higher than that of pure CdS. Given the difference in work functions between CdS and Ag₂S, electrons diffused from the CdS side to the Ag₂S side until the Fermi levels align after their contact. When the CdS–Ag₂S was illuminated, the photogenerated electrons on the conduction band of the CdS further migrated to Ag₂S. Considering the lower overpotential of Ag₂S, the electrons more easily participated in the reduction of protons. Meanwhile, the holes on the valence band of CdS reacted with the hole sacrificial agent (triethanolamine). In this process, the photogenerated electron–hole pairs realised effective separation. The introduction of Ag₂S also enhanced the utilisation of infrared light and increased the temperature of CdS surface. Copyright © 2018 Elsevier B.V. All rights reserved.