SnO2/TiO2纳米管复合光催化剂的性能及失活再生

基于微波水热法和微乳液法合成SnO₂/TiO₂纳米管复合光催化剂. 通过X射线衍射（XRD）、配有能量色散X射线光谱仪（EDX）的透射电镜（TEM）和电化学手段对光催化剂进行表征. 以甲苯为模型污染物，考察光催化剂在紫外光（UV）和真空远紫外光（VUV）下的性能及失活再生. 结果表明，SnO₂/TiO₂纳米管复合光催化剂形成三元异质结（锐钛矿相TiO₂（A-TiO₂）/金红石相TiO₂（R-TiO₂）、A-TiO₂/SnO₂和R-TiO₂/SnO₂异质结），促使光生电子-空穴对的有效分离，提高光催化活性. SnO₂/TiO₂表现出最佳的光催化性能，UV和VUV条件下的甲苯降解率均达100%，CO₂生成速率（k₂）均为P25的3倍左右. 但由于UV光照矿化能力不足，中间产物易在催化剂表面累积. 随着UV光照时间的增加，SnO₂/TiO₂逐渐失活，20 h 后k₂由138.5 mg·m^-3·h^-1下降到76.1 mg·m^-3·h^-1. 利用VUV再生失活的SnO₂/TiO₂，过程中产生的·OH、O₂^-·、O（¹D）、O（³P）、O₃等活性物质可氧化吸附于催化剂活性位的难降解中间产物，使催化剂得以再生，12 h后k₂恢复到143.6 mg·m^-3·h^-1. UV和VUV的协同效应使UV降解耦合VUV再生成为一种可持续的光催化降解污染物模式.

Performance,Deactivation and Regeneration of SnO2/TiO2 Nanotube Composite Photocatalysts

SnO₂/TiO₂ nanotube composite photocatalysts were synthesized by microwave-assisted hydrothermal and micro-emulsion methods. The photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy with energy-dispersive X-ray spectroscopy (TEM/EDX), and electrochemical techniques. Toluene was chosen as a model pollutant to evaluate the performance, deactivation, and regeneration behavior of the photocatalysts under ultraviolet (UV) and vacuum ultraviolet (VUV) irradiation. The results show that ternary heterojunctions of SnO₂/TiO₂ nanotube composite photocatalysts including anatase TiO₂ (A-TiO₂)/rutile TiO₂ (R-TiO₂), A-TiO₂/SnO₂, and R-TiO₂/SnO₂ were successfully created. They were able to separate photogenerated electron-hole pairs efficiently, and promote photocatalytic activity accordingly. SnO₂/TiO₂ showed the best photocatalytic performance. Under UV or VUV irradiation, the toluene degradation rate of SnO₂/TiO₂ was 100%, and the CO₂ formation rate (k₂) of SnO₂/TiO₂ was approximately 3 times higher than that of P25. Because of the low mineralization rate under UV irradiation, the refractory intermediates generated can occupy active photocatalytic sites on the photocatalyst surface, which hinders the photocatalytic oxidation rate. After 20 h of UV irradiation, the k₂ of SnO₂/TiO₂ decreased from 138.5 to 76.1 mg·m^-3·h^-1, implying that the photocatalysts can be deactivated quickly. VUV irradiation was employed to regenerate the deactivated SnO₂/SnO₂/TiO₂ nanotube composite photocatalysts were synthesized by microwave-assisted hydrothermal and micro-emulsion methods. The photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy with energy-dispersive X-ray spectroscopy (TEM/EDX), and electrochemical techniques. Toluene was chosen as a model pollutant to evaluate the performance, deactivation, and regeneration behavior of the photocatalysts under ultraviolet (UV) and vacuum ultraviolet (VUV) irradiation. The results show that ternary heterojunctions of SnO₂/TiO₂ nanotube composite photocatalysts including anatase TiO₂ (A-TiO₂)/rutile TiO₂ (R-TiO₂), A-TiO₂/SnO₂, and R-TiO₂/SnO₂ were successfully created. They were able to separate photogenerated electron-hole pairs efficiently, and promote photocatalytic activity accordingly. SnO₂/TiO₂ showed the best photocatalytic performance. Under UV or VUV irradiation, the toluene degradation rate of SnO₂/TiO₂ was 100%, and the CO₂ formation rate (k₂) of SnO₂/TiO₂ was approximately 3 times higher than that of P25. Because of the low mineralization rate under UV irradiation, the refractory intermediates generated can occupy active photocatalytic sites on the photocatalyst surface, which hinders the photocatalytic oxidation rate. After 20 h of UV irradiation, the k₂ of SnO₂/TiO₂ decreased from 138.5 to 76.1 mg·m^-3·h^-1, implying that the photocatalysts can be deactivated quickly. VUV irradiation was employed to regenerate the deactivated SnO₂/TiO₂ because reactive species such as ·OH, O₂^-·, O(¹D), O(³P), and O₃ can be generated. These play an important role in the oxidation of refractory intermediates on the photocatalyst surface, and k₂ increased to 143.6 mg·m^-3·h^-1 accordingly. Therefore, UV photodegradation combined with VUV regeneration could be a feasible photocatalytic process because of a synergistic effect between UV and VUV.