g-C3N4/CQDs光催化材料的制备及性能

采用高温热解法制备了石墨相氮化碳(g-C_3N_4),将其与碳量子点(CQDs)进行水热复合,得到g-C_3N_4/CQDs复合光催化剂。采用SEM、TEM、FTIR、XRD、UV-Vis/DRS、XPS、N2吸附-脱附等温线手段对制备的复合光催化剂进行了表征,以罗丹明B(Rh B)为模拟污染物,考察了g-C_3N_4/CQDs的可见光催化活性及稳定性。结果表明:与g-C_3N_4相比,g-C_3N_4/CQDs对可见光吸收强度增加,同时其吸收波长向可见光区发生红移;当CQDs含量为1.5%(以g-C_3N_4质量为基准)时,所得g-C_3N_4/CQDs光催化材料的催化活性最佳,其对Rh B的光催化降解率是54.5%,是g-C_3N_4光催化降解率的1.38倍,化学反应动力学拟合相关系数R2=0.9982。且g-C_3N_4/CQDs循环使用3次后,其催化降解率仍保持在50%以上。光催化机理研究表明,空穴(h+)、超氧阴离子自由基(·O2–)、过氧化氢分子(H2O2)和羟基自由基(·OH)都是光催化过程中的主要活性物种,四者氧化作用大小依次为:h+·O2– H2O2·OH。

Preparation and properties of g-C3N4/CQDs photocatalyst materials

The graphite-like carbon nitride (g-C3N4) was prepared by pyrolyzation at high temperature, and then composited with CQDs by hydrothermal method to obtain the g-C3N4/CQDs photo-catalyst. The as-prepared g-C3N4/CQDs was characterized by SEM, TEM, FT-IR, XRD, UV-Vis/DRS, XPS and N2 adsorption and desorption isotherms. Using Rhodamine B (Rh B) as simulated pollutant, the photo-catalytic activity and stability of g-C3N4/CQDs have been investigated under visible light. The results show that the absorption wavelength of g-C3N4/CQDs shifts to the visible light region. When the content of CQDs in composite is 1.5%, the obtained g-C3N4/CQDs photocatalyst has the best catalytic activity. The photocatalytic degradation rate of Rh B by g-C3N4/CQDs is 54.5%, and the correlation coefficient of chemical reaction kinetics is R2=0.9982. The degradation rate of g-C3N4/CQDs is 1.38 times higher than that (39.5%) of pure g-C3N4. After 4 cycles of use, the catalytic degradation rate remained above 50%. The photocatalytic mechanism of catalyst on Rh B was studied. The results show that h+, ·O2-, H2O2 and ·OH were the main active species in the photocatalytic process. The order of oxidation of the four species from strong to weak was: h+ > ·O2- > H2O2 > ·OH.