CH3O·引发的溴酸盐还原机制探究

The bromate reduction induced by CH_3O·

针对溴酸盐(BrO-3)污染,本研究以三聚氰胺为前驱体制备石墨相氮化碳(g-C3N4)为自由基诱导催化材料.通过XRD、TEM、UV/Vis-DRS对其物相组成和光催化性能进行表征发现,制备的层状g-C3N4有稳定片层结构及可见光响应的禁带宽度(~2.70 e V).可见光照射下,g-C3N4表面产生的光生载流子不能直接还原溴酸盐.然而,若有有机小分子(如甲醇)存在,光催化还原效率迅速增大.通过原位电子顺磁共振谱(EPR)及对材料表面的光电化学测试分析,我们探索了该体系的光催化还原Br O-3的机制.结果表明,g-C3N4带隙较窄其空穴氧化能力较弱,在光催化过程中空穴只能将甲醇分子转化为CH3O·自由基,因而甲醇分子的存在提升了光生载流子的分离效率,加剧了自由基的累积.该自由基具有较高的还原活性,可迅速将水相中的溴酸根还原至溴离子.

we herein prepared the graphitic-C3 N4（ g-C3 N4） materials using melamine as precursors by a pyrolysis approach. Based on characterization XRD,TEM and UV/Vis-DRS,it was found that the layered ha stable laminar structure the gap width of visible light response ~ 2.70 e V. Under visible light,the g-C3 N4 photocatalyst exhibited the inferior photocatalytic reduction of bromate（ Br O-3）,while the reduction efficiency increased rapidly after the addition of organic（ methanol）. in-situ electron paramagnetic resonance（ EPR） and photoelectrochemical analysis The results demonstrate that the narrow g-C3 N4 band gap weaken the hole oxidation ability,thereby only transfer the methanol into methanol free radicals（ CH3 O·） in the process of photocatalysishus the presence of methanol the separation efficiency of the photogenerated electron-hole pairs,the accumulation of free radicals. In viewing of the superior reduction ability,the in-situ generated CH3 O·with high concentration the high Br O-3 removal performance.