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以硫脲和碘化钾为原料,采用热聚合法合成了K掺杂g-C_3N_4光催化剂(CN-K),通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线能谱(XPS)、比表面积(BET)、紫外-可见漫反射(UV-vis DRS)和荧光光谱(PL)等对样品进行微结构表征分析,并在优化晶体结构模型基础上,采用第一性原理计算模拟并解析能带结构和态密度分布.结果表明,掺杂K离子与N形成K–N键,并存在于g-C_3N_4层间.在可见光照射下对ppb级NO表现出了显著增强的可见光催化活性和良好的光化学稳定性.CN-K优异的活性可归因于K掺杂作用对g-C_3N_4电子结构的调变.K掺杂作用调节禁带位置,价带与导带的位置均下移,其中导带下移幅度高于价带,使催化剂禁带宽度减小,因此拓宽了光响应范围,使其可见光区域吸光能力增强;K掺杂使光生载流子的分离效率增加;K掺杂g-C_3N_4比纯g-C_3N_4的价带位置更正,K的掺杂作用使其光生空穴的氧化能力增强.本文阐明了K掺杂g-C_3N_4改性作用机理以及其可见光催化净化NO的机理.本文为光催化剂碱金属改性降解污染物提供了新的认识.
Using thiourea and potassium iodide as raw materials, K-doped g-C_3N_4 photocatalysts (CN-K) were synthesized by thermal polymerization. Their structures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy XPS, BET, UV-vis DRS and fluorescence spectroscopy (PL) were used to characterize the microstructure of the samples. Based on the optimized crystal structure model, First-principles calculation and analysis of the energy band structure and density distribution of the states showed that K-doped K ions form N-bonds with N and exist in the layers of g-C_3N_4. Significantly enhanced visible light catalytic activity and good photochemical stability.The excellent activity of CN-K can be attributed to the modulation of the electronic structure of g-C_3N_4 by the doping effect of K.K doping regulates the band gap location, valence band and conduction The position of the tape is down, in which the conduction band down the amplitude higher than the valence band, the catalyst forbidden band width decreases, thus broadening the optical response range, so that its light absorption capacity increases; K doped photoacoustic carrier Separation efficiency increased; K-doped g-C_3N_4 than pure g-C_3N_4 valence band correction, K doping So as to enhance the oxidation ability of photogenerated holes.The mechanism of the modification of K-doped g-C_3N_4 and the mechanism of visible light photocatalytic purification of NO are clarified in this paper.This paper provides a new understanding of photocatalytic alkali metal modification and degradation of pollutants.