In this work,graphitic carbon nitride (g-C3N4) with large surface area and many nitrogen vacancies was synthesized by introducing ionic liquid [Bmim]Br as a solvent into the solvothermal post-treatment.X-ray diffraction (XRD),N2 adsorption,scanning electron microscopy (SEM),UV-Vis spectroscopy,X-ray photoelectron spectroscopy (XPS),electron paramagnetic resonance (EPR),temperature-programmed desorption of N2 (N2TPD),and photoluminescence (PL) spectroscopy were used to characterize the prepared catalysts.The morphology of the as-prepared g-C3N4 was markedly changed from an orderless layered structure to nanoparticles with a uniform size distribution of around 30-40 nm after the introduction of [Bmim]Br,leading an increase in surface area from 8.6 to 37.9 m2·g-1.N2-TPD,photoluminescence spectra,and density functional theory (DFT) simulations indicated that the nitrogen vacancies not only trapped the photogenerated electrons to enhance their separation rate,but also served as active sites for the adsorption and activation of N2 molecules.The increased surface area of the as-prepared g-C3N4 meant that more nitrogen vacancies were exposed on the surface,leading to a markedly promoted nitrogen photofixation ability.The possible reaction mechanism is proposed.%采用离子液体[Bmim]Br为溶剂,溶剂热后处理法制备了具有大比表面积和氮空穴的石墨相氮化碳催化剂.采用X射线衍射(XRD)光谱、扫描电镜(SEM)、氮气吸附、紫外-可见(uv-vis)光谱、X射线光电子能谱(XPS)、荧光光谱(PL)、电子顺磁共振谱(EPR)、程序升温脱附(TPD)等分析手段对制备的催化剂进行了表征.结果表明经过溶剂热后处理的催化剂形貌由无规则的层状结构变为尺寸为30-40 nm的纳米颗粒,导致比表面积从8.6 m2·g-1增加到37.9 m2·g-1.从N2-TPD、荧光光谱及密度泛函理论(DFT)模拟计算的结果得出,氮空穴不仅能捕获光生电子促进电子空穴的有效分离,还能吸附并活化反应物氮气分子.溶剂热处理后,增加的比表面积导致更多的氮空穴作为反应活性位暴露在催化剂表面,是固氮活性显著提高.本文还探讨了可能的反应机理.
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