The doping of B in ZnO/CdS for enhanced visible-light H2 production

Abstract

The visible-light water splitting enhancement of B in ZnO/CdS was systematically studied and the B-doped ZnO/CdS rods (B-ZnO/CdS) showed an excellent H₂ generation rate of 13 100 μmol h⁻¹ g⁻¹, mostly 2 times higher than that of ZnO/CdS (ca. 5249 μmol h⁻¹ g⁻¹, λ > 420 nm), indicating that due to the introduction of the B element, the electron separation efficiency in ZnO/CdS was improved significantly. Through various characterization methods (e.g., PL spectroscopy, UV-Diffuse reflection spectroscopy and photoelectric response), the enhanced electron separation efficiency in the B-ZnO/CdS system was directly demonstrated. In addition, according to the density functional theory (DFT) calculation results, B-ZnO/CdS exhibited a negative adsorption energy of water (E_H2O* = −1.22 eV), and the d-band center of the Cd atom had a positive shift from −8.46 to −8.45 eV, which was favorable for water absorption and dissociation. From the charge density difference and density of states, it could be found that electrons tend to transfer from ZnO to H₂O at the Cd active sites. The accumulated electrons in H₂O could extend the H–OH bond length from 0.975 Å to 0.983 Å, thereby facilitating the dissociation of H₂O.