Abstract:

Heterogeneous structure building has proven to be an effective strategy for achieving efficient charge separation and improving photocatalytic performance. In this study, based on the synergistic optimization strategy of elemental doping and heterostructure construction, an S-scheme heterojunction photocatalyst (x% NMT/Na-CN) composed of titanium-based metal-organic framework (NH₂-MIL-125, abbreviated as NMT) and sodium-doped carbon nitride (Na-CN) was constructed by a simple impregnation method. The energy band structure of the catalysts was modulated by intra-layer doping of Na, which introduced nitrogen defects and improved the separation efficiency of photogenerated charges. In addition, the composite of Na-CN and NMT formed an S-scheme heterojunction, which further improved the photogenerated charge separation efficiency while retaining the strong redox ability of the composite catalyst. Owing to the synergistic effect of Na doping and NMT composite, the photocatalytic H₂O₂ production rate of 15% NMT/Na-CN in isopropanol solution was as high as 2474.6 μmol g⁻¹ h⁻¹, which was 38 times higher than that of unmodified bulk carbon nitride. This work offers a novel approach to realize the efficient production of H₂O₂ from carbon nitride-based photocatalysts based on the doping-heterojunction synergistic optimization strategy.

Key words: Carbon nitride, MOF, Hydrogen peroxide, S-scheme heterojunction, Doping