Ag/P-g-C3N4复合材料可见光催化降解双酚AF的机理研究

利用简单的热聚合及原位沉淀法制备了一系列不同质量比(1%～10%)的Ag/P-g-C_3N_4复合材料,采用XRD、SEM、TEM、UV-Vis DRS、FTIR、BET和XPS等表征手段对复合材料的形貌结构、光学特性和化学组成进行了表征.利用合成材料光催化降解双酚AF(BPAF),研究了溶液初始pH、溶解性有机质(DOM)对BPAF降解的影响,并对光催化降解机理进行了探讨.结果表明,在pH=7时,5%Ag/P-g-C_3N_4表现出最强的光催化性能,其在90 min内对BPAF的降解率达到100%.DOM在低浓度(0.5 mg·L~(-1))时促进了BPAF的光降解,而在高浓度时(2～10 mg·L~(-1))抑制了BPAF的光降解.活性基团捕获实验结果表明,在Ag/P-g-C_3N_4降解BPAF过程中,h~+和·OH起主要的作用,直接参与了BPAF的降解.相对于P-g-C_3N_4,Ag/P-g-C_3N_4光催化性能的增强主要是因为Ag的负载促进了e~-和h~+的分离,同时Ag单质的SPR效应提高了复合材料对可见光的吸收率,延长了光生载流子的寿命.

Mechanism of photocatalytic degradation of BPAF by heterojunction Ag/P-g-C3N4 composite under visible light irradiation

A series of Ag/P-g-C₃N₄ composites (1%~10%) were successfully synthesized by thermal polymerization coupled with in-situ precipitation method. The morphology, optical property and chemical states of the synthesized samples were characterized by XRD, SEM, TEM, UV-Vis DRS, FTIR, BET and XPS techniques. The as-prepared samples were applied to degrade BPAF under visible light irradiation. The effect of pH and dissolved organic matter (DOM) was investigated, and the degradation mechanism in photocatalytic process was evaluated. The results indicated that 5% Ag/P-g-C₃N₄ composite exhibited the best photocatalytic performance with the degradation efficiency of 100% in 90 min. The degradation of BPAF was stimulated by DOM at low concentration (0.5 mg·L^-1) but inhibited at high concentrations (2~10 mg·L^-1). The radical trapping experiments revealed that holes (h⁺) and·OH were the dominant active species involved in BPAF degradation, which could degrade BPAF straightforward. Compared with P-g-C₃N₄, the enhanced photocatalytic performance of Ag/P-g-C₃N₄ composite was ascribed to the highly separation rate of e^- and h⁺. In addition, the SPR effect of Ag could strengthen the absorption rate of visible light and lengthen the lifetime of photon-generated carriers.