Sustainable and efficient hydrogen evolution over a noble metal-free WP double modified ZnxCd1−xS photocatalyst driven by visible-light

Abstract

In terms of energy acquisition, research on the photocatalytic cracking of water to produce hydrogen has become a hub for us to make a transition from theoretical research to practical applications. Charge separations and surface redox reactions of semiconductors are key factors that affect hydrogen production activity. In this study, we used an n-type semiconductor WP as a cocatalyst to modify the solid solution of Zn_xCd_1−xS and found it to have excellent photocatalytic activity under visible light irradiation. Ultraviolet diffuse reflectance spectroscopy showed the red shift of the absorption band of the composite catalyst and the strong absorption of visible light. Under the action of the matching energy band structure, the fluorescence lifetime of the composite catalyst is shortened (2.33 ns) and the electron injection rate is accelerated (K_et = 0.58 × 10⁹ s⁻¹). Under these favorable conditions, the increased hydrogen production activity of the composite catalyst is finally reflected in the enhanced hydrogen production rate, which reached up to 15 028.6 μmol g⁻¹ h⁻¹. In addition, the yield of hydrogen produced by adding a fresh lactic acid catalyst in the fifth cycle after four cycles of testing was greatly improved. Obviously, the addition of WP turns the composite catalyst into a photocatalyst with high efficiency, stability and is a non-noble metal cocatalyst. Finally, through a series of characterization experiments (SEM, TEM, XPS, BET, Mott–Schottky et al.), we proposed the possible mechanism of WP/Zn_xCd_1−xS that efficiently promotes hydrogen production. This provides new understanding for designing an effective cocatalyst modified semiconductor to improve photocatalytic activity.