Abstract:

Modification of graphite phase carbon nitride (g-C₃N₄, CN) is an important means to improve its photocatalytic performance. S-doped carbon nitride (SCN) was prepared by thermal polymerization with thiourea as the precursor, and binary heterojunction composite photocatalysts CN-Ti and SCN-Ti were prepared with graphite phase carbon nitride, S-doped carbon nitride and TiO₂ as the main components. The morphology, structure, optical and electrochemical properties of the photocatalyst were analyzed by X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy, specific surface area, ultraviolet-visible diffuse reflectance and electrochemical test, and their photocatalytic performance were evaluated by degradation of NO. According to the free radical capture experiment, the photocatalytic degradation mechanism was further studied. The results showed that the binary heterojunction composite photocatalyst SCN-Ti had better photocatalytic performance. When the mass ratio of SCN∶TiO₂ was 5∶5, the photocatalytic NO degradation rate was the highest, reaching 84.9% and 57.1% under ultraviolet light and visible light, respectively, which was significantly higher than that of CN (61.7% and 44.2%, respectively), and after five cycles, it still had good photocatalytic activity. The improvement of photocatalytic activity was mainly attributed to the type Ⅱ heterojunction constructed by SCN and TiO₂, which promoted carrier separation and improved the generation efficiency of photogenerated electrons, holes and ·{\mathrm{O}}_{\mathrm{2}}^{-} free radicals that degraded NO active substances. This study provided a reference for broadening the application of g-C₃N₄ in the field of photocatalysis.

Key words: graphite phase carbon nitride, photocatalysis, NO degradation, titanium dioxide heterojunction, S-doped carbon nitride

摘要：

对石墨相氮化碳（g-C₃N₄，CN）进行改性是提高其光催化性能的重要手段。采用热聚合法以硫脲为前体制备了S掺杂氮化碳（SCN），以石墨相氮化碳、S掺杂氮化碳和TiO₂作为光催化剂的主要组分，制备了二元异质结复合光催化剂CN-Ti和SCN-Ti，利用X射线衍射、扫描电子显微镜、X射线光电子能谱、比表面积、紫外可见漫反射、电化学测试等表征手段分析了光催化剂的形貌、结构、光学和电化学性能，通过对NO的降解评价了其光催化性能，根据自由基捕获实验进一步研究了其光催化降解机理。结果表明，二元异质结复合光催化剂SCN-Ti具有更优的光催化性能，SCN和TiO₂质量比为5∶5时所得的光催化剂SCN-Ti-50在紫外光和可见光条件下对NO的降解率最高，分别可达84.9%和57.1%，显著高于CN在紫外光和可见光下对NO的降解率（分别为61.7%和44.2%），且经5次循环后，其仍具有良好的光催化活性。光催化活性的提高主要归因于SCN和TiO₂构建的Ⅱ型异质结促进了载流子分离，提高了降解NO活性物质光生电子、空穴和·{\mathrm{O}}_{\mathrm{2}}^{-}的生成效率。本文为拓宽g-C₃N₄在光催化领域的应用提供了可借鉴的思路。

关键词: 石墨相氮化碳, 光催化, NO降解, 二氧化钛异质结, S掺杂氮化碳