Doping or Deposition of NiS on Cd_0.3Zn_0.7S Photocatalysts: Optimising Photocatalytic Hydrogen Evolution

The photocatalytic properties of a Cd_0.3Zn_0.7S photocatalyst modified either by NiS doping or by supporting NiS on the catalyst surface were studied. The obtained samples were investigated by different characterization techniques, including X-ray diffraction (XRD), UV/Vis diffuse reflectance spectroscopy (DRS), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity was measured in hydrogen evolution from aqueous solutions of Na₂S/Na₂SO₃ under visible-light irradiation (λ=450 nm). Nickel modifications on the surface and in bulk led to improvements in the photocatalytic activity compared to the pristine sample. The samples modified in bulk underwent changes in composition and an increase of the catalytic activity during illumination was measured. In contrast, the rate of hydrogen photoproduction for the photocatalysts modified by NiS on the surface did not change appreciably. The highest photocatalytic activity values were 11.2 mmol h⁻¹ g⁻¹ and 12.8 mmol h⁻¹ g⁻¹ for the 0.3 % NiS/Cd_0.3Zn_0.7S and Ni_0.001Cd_0.3Zn_0.7S_1.001 photocatalysts, respectively.