g-C3N4@Ag的光催化性能及原位热动力学研究

采用硼氢化钠作还原剂将吸附于石墨相氮化碳(g-C₃N₄)表面的硝酸银还原成纳米银(Ag)颗粒，通过调控在氮化碳上原位沉积时硝酸银的用量，制备了不同Ag负载量的g-C₃N₄@Ag复合催化剂.使用场发射扫描电子显微镜(FE-SEM)观察、X射线粉末衍射(XRD)分析、N₂吸附-脱附等温曲线(BET)分析、X射线光电子能谱(XPS)分析等方法对制备的材料进行了表征.由紫外-可见吸收光谱(UV-Vis)分析和光微量热-荧光光谱联用分析研究了复合催化剂对罗丹明B降解的原位热动力学性质.结果表明:当Ag纳米颗粒的质量分数为4%时其降解罗丹明B的反应速率常数为1.55×10-2 min-1，其催化性能是未修饰g-C₃N₄的1.9倍；在光密度为10、20、32 W/m2条件下，反应均在120 s左右达到表观吸热最大值，随后放热，最终恒定放热速率依次为7.293×10-8、1.316×10-7和1.162×10-7 mJ/s.文中的研究结果对研究光催化原位过程的热力学、动力学及光谱性质具有重要意义和潜在应用价值.

Photocatalytic Properties and in-situ Thermokinetics of g-C3N4@Ag

Silver nitrate adsorbed on the surface of graphite-phase carbon nitride (g-C₃N₄) was reduced to nano-silver (Ag) particles with sodium borohydride as the reducing agent. g-C₃N₄@Ag composite catalysts with different Ag loads were in-situ deposited on carbon nitride by adjusting the ratio of silver nitrate to carbon nitride. The prepared materials were characterized with the field emission scanning electron microscopy (FE-SEM), the X-ray powder diffraction (XRD), the N₂ adsorption-desorption isotherm (BET), the X-ray photoelectron spectroscopy (XPS) and so on. The in-situ thermokinetic properties of Rhodamine B degradation over composite catalysts were studied with UV-Vis absorption spectroscopy and photo-microcalorimetry-fluorescence spectroscopy. The results showed that when the mass fraction of Ag nanoparticles was 4%, the reaction rate constant of Rhodamine B degradation was 1.55×10-2 min-1, and the catalytic activity of Rhodamine B was 1.9 times higher than that of unmodified g-C₃N₄. Under the conditions of 10, 20 and 32 W/m2, the reaction reached the maximum apparent heat absorption at about 120 s, followed by exothermic reaction, and the final apparent exothermic rate was 7.293×10-8, 1.316×10-7 and 1.162×10-7 mJ/s respectively. The results are of great significance and potential applicative value to the study of thermodynamics, kinetics and spectral properties of in-situ photocatalysis.