双功能复合材料g-C₃N₄/CdS/Ni催化光解水产氢和5-羟甲基糠醛氧化性能

The bifunctional photocatalyst g-C₃N₄/CdS/Ni was synthesized by high temperature calcination, in situ growth method and photoreduction method in three steps. The introduction of CdS in this composite can enhance the separation rate of photogenerated holes and electrons. And the loading of Ni can further improve the photoinduced hydrogen production rate. In addition, the photocatalytic hydrogen evolution reaction was carried out in triethanolamine(TEOA, hole sacrificial agent) aqueous solution and the optimal CdS content of the composite was determined. Experiments showed that the composite with 25%(mass fraction) CdS exhibited the best photocatalytic activity and the Ni was a good cocatalyst for hydrogen production. The highest H₂ gene- ration rate catalyzed by g-C₃N₄/25CdS/Ni composite was 4134.5 μmol·g^-1·h^-1, which was 115 times higher than that of g-C₃N₄/Ni composite. Subsequently, the TEOA in this system was replaced by 5-hydroxymethylfurfural(HMF). HMF can be selectively oxidized to the value-added chemical 2, 5-diformylfuran(DFF). When the conversion of HMF was 82.3% and the selectivity of DFF was 69.4%, the yield of DFF was up to the highest(57.2%). At the same time, the yield of H₂ in this system was 51.8 μmol/g. In summary, g-C₃N₄/CdS/Ni composite can catalyze photoinduced H₂ evolution and HMF selective oxidation in the same system.