Room-temperature synthesis of Zn0.80Cd0.20S solid solution with a high visible-light photocatalytic activity for hydrogen evolution

Abstract

Visible light photocatalytic H₂ production from water splitting is of great significance for its potential applications in converting solar energy into chemical energy. In this study, a series of Zn_1−xCd_xS solid solutions with a nanoporous structure were successfully synthesized via a facile template-free method at room temperature. The obtained solid solutions were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS) and N₂ adsorption–desorption analysis. The solid solutions show efficient photocatalytic activity for H₂ evolution from aqueous solutions containing sacrificial reagents S²⁻ and SO₃²⁻ under visible-light irradiation without a Pt cocatalyst, and loading of the Pt cocatalyst further improves the visible-light photocatalytic activity. The optimal photocatalyst with x = 0.20 prepared at pH = 7.3 displays the highest activity for H₂ evolution. The bare and 0.25 wt% Pt loaded Zn_0.80Cd_0.20S nanoparticles exhibit a high H₂ evolution rate of 193 μmol h⁻¹ and 458 μmol h⁻¹ under visible-light irradiation (λ ≥ 420 nm), respectively. In addition, the bare and 0.25 wt% Pt loaded Zn_0.80Cd_0.20S catalysts show a high H₂ evolution rate of 252 and 640 μmol h⁻¹ under simulated solar light irradiation, respectively. Moreover, the Zn_0.80Cd_0.20S catalyst displays a high photocatalytic stability for H₂ evolution under long-term light irradiation. The incorporation of Cd in the solid solution leads to the visible light absorption, and the high content of Zn in the solid solution results in a relatively negative conduction band, a modulated band gap and a rather wide valence bandwidth, which are responsible for the excellent photocatalytic performance of H₂ production and for the high photostability.