The pH effects on H2 evolution kinetics for visible light water splitting over the Ru/(CuAg)0.15In0.3Zn1.4S2 photocatalyst

• The solution pH significantly impacted the H2 production rate and quantum yield.
• The stability of the photocatalyst was significantly affected by the solution pH.
• The overall reaction pathways showed the strong dependence on the solution pH.
• The photocatalytic H2 evolution must be sustained by enough H+ and electron donor.

Much progress has been made in the development of novel visible light photocatalysts that split water into hydrogen (H2) and oxygen (O2). In this study, we examine the impact of initial solution pH on H2 production using an Ru/(CuAg)0.15In0.3Zn1.4S2 photocatalyst under visible light irradiation. In addition, the reaction mechanism was analyzed by examining the oxidation products of the electron donor (I‾) at different solution pH values. The results show that the initial pH significantly influenced the rate of H2 production and quantum yield (QY). In particular, the photocatalyst yielded the highest apparent QY (∼12.8%) at 420 ± 5 nm and highest H2 production rate (∼525 μmol h−1) at pH 2; with increasing pH, the H2 production and QY decreased significantly. The oxidation product of I‾ at pH < 6 was mainly I3‾, whereas at pH > 6 water splitting did not occur at all, so no IO3‾ or I2 were observed.

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