Improvement of the photocatalytic hydrogen evolution activity of Sm2Ti2S2O5 under visible light by metal ion additives

Sm2Ti2S2O5 was modified with various metal ions, and the effects on photocatalytic H2 evolution from a Na2S–Na2SO3 solution were investigated. In particular, the catalytic enhancement effects of magnesium and silver additives were focused on, and structural analysis and photoelectrochemical measurements were carried out to investigate the mechanism involved. It was found that their promotion effects were different. The addition of silver ions during the preparation of the photocatalyst resulted in the formation of Ag2S nanoparticles and greatly promoted photooxidation of electron donors. Differently, the addition of magnesium ions significantly inhibited such photooxidation, but led to a reduction in the defect density in Sm2Ti2S2O5. The simultaneous addition of 5% Mg and 1% Ag was found to produce the highest level of catalytic performance. Finally, the optimal H2 evolution rate of the modified photocatalysts reached 630 μmol h−1, seven times that of an unmodified sample.