碳点/g-C_(3)N_(4)复合催化剂的制备及其光催化性能

Preparation and photocatalytic performance of carbon dots/g-C_(3)N_(4)composite catalyst

g-C_(3)N_(4)的光吸收和光生载流子的复合问题是限制其高效光催化应用的关键问题,为此本文以煤沥青为前驱体合成碳点(CDs),然后采用超声辅助法制备了CDs/g-C_(3)N_(4)复合催化剂。通过TEM、XRD、UV-Vis漫反射光谱、PL光谱、EIS测试和光电流响应测试等表征了催化剂的结构和光学、光电性能。结果表明,CDs引入后能带结构的调控和界面的形成,拓展了复合光催化剂的光吸收范围,促进了光生电子和空穴的有效分离和迁移,从而有利于光催化反应的进行。以罗丹明B(RhB)为模型反应,在可见光照射下,CDs/gC_(3)N_(4)复合催化剂的光催化活性明显高于纯g-C_(3)N_(4),在40 min内就可以实现98.6%的RhB降解率,其降解速率常数是纯g-C_(3)N_(4)的6.8倍。活性物种捕获实验表明,降解体系中起主要作用的是·O_(2)^(-)。同时CDs/g-C_(3)N_(4)复合催化剂具有良好的稳定性,5次循环反应后,RhB的降解率仍达到97.5%,展示了其在可见光光催化方面较好的应用前景。

The light absorption and photo-induced carrier recombination of g-C_(3)N_(4)are the key problems that limit its efficient photocatalytic applications.Herein,carbon dots(CDs)were synthesized using coal pitch as precursor and then the CDs/g-C_(3)N_(4)composite catalyst was prepared by ultrasonic-assisted method.The structure,optical and photoelectrochemical properties of the catalyst were characterized by TEM,XRD,UV-Vis diffuse reflection spectrum,PL spectrum,EIS test and photocurrent response test.The results show that the regulation of band structure and the formation of interface after the introduction of CDs expand the range of light absorption of the composite photocatalyst,promote the effective separation and migration of photogenerated electrons and holes,and thus facilitate the photocatalytic reaction.Using rhodamine B(RhB)as the model,the photocatalytic activity of CDs/gC_(3)N_(4)composite catalyst is significantly higher than that of pure g-C_(3)N_(4)under visible light irradiation.The degradation rate of RhB can reach 98.6%within 40 min,and the degradation rate constant of CDs/g-C_(3)N_(4)is 6.8 times that of g-C_(3)N_(4).The capture of experiment of active species reveals that•O_(2)^(-)plays a major role in the degradation system.In addition,CDs/g-C_(3)N_(4)composite catalyst exhibit good stability.After 5 cycles,the degradation rate of RhB is still up to 97.5%,which shows a good application prospect in visible light photocatalysis.