Abstract: A plasma-catalytic system was constructed by coupling multi-needle corona discharge with Ag/TiO2 nanocatalyst. The discharge characteristics of the plasma-catalytic system were diagnosed, and the characterization of the Ag/TiO2 nanocatalyst was also performed. The multi-needle corona discharge coupling Ag/TiO2 nanocatalyst system was applied to remove low-concentration toluene from the air. The secondary pollutant of ozone was monitored during toluene removal. Further, the mechanism of toluene removal and suppressed ozone generation during toluene removal was disclosed. It was found that the plasma diffused in the whole discharge region when the discharge voltage was higher than 7.0 kV. The presence of Ag/TiO2 nanocatalyst showed no obvious influence on the discharge. These features facilitated the high plasma density and intimate interaction between reactants, plasma, and Ag/TiO2 nanocatalysts. Ag particles in the Ag/TiO2 nanocatalyst possessed an average size of 6.5 nm, which created large numbers of highly active Ag-TiO2 interfacial sites and endowed Ag/TiO2 nanocatalyst with strong absorption ability for UV-visible light. At a voltage of 7.5 kV, the multi-needle corona discharge obtained toluene conversion and CO2 selectivity of 21% and 7%, respectively. Coupling of multi-needle corona discharge and Ag/TiO2 nanocatalyst made toluene conversion and CO2 selectivity increased to 83% and 61%, respectively. The concentration of ozone in the plasma-catalytic system was 0.02 mg/m3, which had a remarkable decrease compared with the pure discharge (5.12 mg/m3). The performance of the multi-needle corona discharge coupling Ag/TiO2 nanocatalyst system was attributed to the synergetic effect between the light field, electrical field, and catalytic sites, which could modulate the conversion path of intermediates and extend the avenues of toluene removal. This study would provide an important reference for the application and development of plasma-catalysis techniques in indoor air purification.

Key words: plasma-catalysis, toluene removal, air purification, synergetic effect

摘要： 采用多针电晕放电与Ag/TiO2纳米催化剂的原位耦合构建等离子体催化系统，对系统的放电特性进行诊断，并对催化剂进行表征研究；研究等离子体催化系统对空气中低浓度甲苯的脱除性能，并监测系统脱除甲苯过程中产生的有害副产物臭氧；探讨等离子体催化系统脱除低浓度甲苯及控制副产物臭氧生成的内在机制。研究结果表明，当放电电压高于7.0 kV时，等离子体可弥散于整个放电间隙内，Ag/TiO2纳米催化剂的涂覆未影响放电的正常进行，利于反应气体、等离子体及催化剂间的相互作用；Ag/TiO2纳米催化剂的Ag粒子粒径约为6.5 nm，可以创造大量高活性Ag-TiO2界面位点，并能吸收利用等离子体辐射的紫外-可见光；当放电电压为7.5 kV时，单纯多针电晕放电所得甲苯转化率与CO2选择性分别为21%与7%，等离子体催化系统则使二者分别提升至83%与61%，并将过程中副产物臭氧的浓度由5.12 mg/m3降至0.02 mg/m3以下；多针电晕放电协同Ag/TiO2纳米催化剂系统所展现的优异性能可归因于光、电及界面催化间产生的高效协同作用对反应活性物种转化路径的调控和对甲苯脱除反应路径的拓展。本研究工作可为等离子体催化技术在室内空气净化领域的应用与发展提供重要参考。

关键词: 等离子体催化, 甲苯脱除, 空气净化, 协同作用