Effects of inorganic electron donors in photocatalytic hydrogen production over Ru/(CuAg)0.15In0.3Zn1.4S2 under visible light irradiation

Abstract

Selection of appropriate electron donors is important for charge transfer and photocatalytic hydrogen (H2) production from water. The influence of different inorganic electron donors (i.e., I−, S2−/SO32−, S2−, SO32−, Fe2+, and Ce3+) on H2 production was investigated on the (CuAg)0.15In0.3Zn1.4S2 photocatalyst under visible light. The highest photocatalytic H2 production rates were 1750, 1317, 820, 360, 260, 10 μmol g−1 h−1 with electron donors of 0.2M KI, 0.25M Na2S in combination with 0.35M Na2SO3, 0.25M Na2S, 0.35M Na2SO3, 0.2M FeCl2, and 0.2M Ce2(SO4)3, respectively. I− was determined as the most effective electron donor for (CuAg)0.15In0.3Zn1.4S2 photocatalyst, probably because (1) the redox potential of I3−/I− is relatively more suitable than those of other redox pairs for the charge transfer to valence band and (2) the positive surface charge of the (CuAg)0.15In0.3Zn1.4S2 photocatalyst at the solution pH of 2 facilitates the absorption of I− and subsequent reaction with the valence band holes. The effect of the initial I− concentrations on the H2 production and the potential reaction routes of I− on the photocatalyst were both analyzed to shed light on the reaction mechanisms. This study compared the efficacy of different inorganic electron donors in improving photocatalytic H2 production and provided fundamental insight into the search of appropriate electron donors and the efficient photocatalytic system design.