Photochemical preparation of Cd/CdS photocatalysts and their efficient photocatalytic hydrogen production under visible light irradiation

Abstract

Metal Cd can serve as an analogue of cocatalysts loaded on CdS to separate electrons and holes to significantly enhance the efficiency of CdS photocatalytic hydrogen production. A series of Cd/CdS photocatalysts were synthesized at various molar ratios of CdSO₄ and Na₂S₂O₃·5H₂O in the presence of simulated solar irradiation. Superior photocatalytic activities relative to that of pure CdS were observed on the Cd/CdS photocatalysts. When the optimal molar ratio R of Na₂S₂O₃·5H₂O to cadmium salt is 7, it results in a high average H₂-production rate of 1753 μmol h⁻¹. Possible mechanisms for both the formation and the enhanced photocatalytic activity of Cd/CdS were proposed on the basis of theoretical speculation and experimental observations. Most of all, this work highlights that (i) Cd/CdS leads to an improvement in the photocatalytic activity for H₂ generation; and (ii) adding Na₂S₂O₃·5H₂O into the solution containing cadmium ions to prepare Cd/CdS can effectively remove cadmium ions.