介孔二氧化钛/导电碳毡光电极制备及其苯甲醛降解机理分析

Preparation,photoelectric catalysis performance and degradation mechanism of mesoporous titanium dioxide / conductive carbon felt electrode

基于表面活性剂十六烷基三甲基溴化铵为液晶模板,以四氯化钛为钛源,导电碳毡为载体,通过超声波辅助水热法(ultrasound-assisted hydrothermal method,UH)制备介孔二氧化钛/导电碳毡复合体材料(mesoporous titania/conductive carbon felt,MPT/CCF)(UH-MPT/CCF),为了探讨其结构与光电催化活性,直接采用水热法制备介孔二氧化钛/导电碳毡(H-MPT/CCF)和无孔二氧化钛/导电碳毡(no porous titania/conductive carbon felt,NPT/CCF)复合体材料,利用XRD、XPS、SEM、TEM、TG-DTA、N2吸附-脱附等方法对样品结构进行表征,以气相苯甲醛为目标降解物,研究UH-MPT/CCF的光电催化性能及其对气相苯甲醛的降解机理。结果表明,UH-MPT/CCF材料通过介孔化增加了活性中心(·OH和Ti3+),通过CCF的负载提高了对目标降解物的吸附富集,通过偏电压促进光生电子-空穴对的分离,在这三方的协同作用下UH-MPT/CCF对苯甲醛在100 min内降解率为83.9%,分别是H-MPT/CCF、NPT/CCF和P25/CCF的1.38、1.75和2.38倍。气相苯甲醛光电催化降解产生的主要中间产物是苯、1,3-己二烯-5-炔,以及少量的3,3,5-三甲基环己烯、2,3-二甲基-1,3-庚二烯、3-甲基-3-环己烯-1-醇等。根据GC/MS分析结果,进一步提出了气相苯甲醛的降解机理。

Based on a liquid crystal template, consisting of cetyltrimethyl ammonium bromide surfactant, titanium tetrachloride and conductive carbon felt were used as a titanium source and carrier, respectively. Meso- porous titanium dioxide/conductive carbon felt （UH-MPT/CCF） composites were prepared by using an ultra- sound-assisted hydrothermal synthesis method. In order to investigate the structure and photoelectrocatalytic per- formance, a hydrothermal method was applied to synthesize mesoporous titanium dioxide/conductive carbon felt （H-MPT/CCF） and non-porous titania/conductive carbon felt （NPT/CCF）. The structures of obtained samples were examined via X-ray diffraction （XRD） , X-ray photoelectron spectroscopy （XPS） , scanning electron mi- croscopy （SEM） , transmission electron microscopy （TEM） , thermogravimetry （TG） -differential thermal analy- sis （DTA） , and nitrogen adsorption-desorption. By choosing benzaldehyde as the target degradation product, the photoelectrocatalytic performance of UH-MPT/CCF under ultraviolet light irradiation was discussed. The results showed that UH-MPT/CCF increased active center （ ~ OH and Ti3~ ） through a mesoporous effect, enhanced the adsorption of the target objects through the CCF support, and led to separation of photogenerated electron-hole pairs via the bias voltage. As a result of the synergy of these three effects, degradation rate of gaseous benzaldehyde by UH-MPT/CCF after 100 min was 83.9% , which were 1.38, 1.75, and 2.38 times as high as those of H-MPT/ CCF, NPT/CCF, and P25/CCF, respectively. Photoelectroeatalytic products of gaseous benzaldehyde included the main intermediates of benzene, 1,3-hexadien-5-yne and a small amount of 3,5,5-trimethylcyclohexene, 2,3-dime- thyl-1,3-heptadiene, and 3-methyl-3-cyclohexen-l-alcohol. According to the results of gas chromatography/mass spectrometry （GC/MS） analysis, the mechanism of the degradation process of gaseous benzaldehyde was proposed.