Investigation into the Enhancement of Property and the Difference of Mechanism on Visible Light Degradation of Gaseous Toluene Catalyzed by ZnAl Layered Double Hydroxides before and after Au Support

In this paper, Au-supported ZnAl layered double hydroxides (Au/LDHs) were synthesized and used as visible light photocatalyst for gaseous toluene degradation. The differences of physical structure and photocatalytic property of ZnAl-LDHs before and after Au modification were investigated. The factors of Au mass percent, initial concentration of toluene, catalyst dosage [A], irradiation intensity [B], relative humidity [C], and reaction temperature [T] onto gaseous toluene photodegradation by Au/LDHs are discussed, and a rate equation based on these parameters was determined, i.e, ln(C/C-0) = -904.1 e(-11.15x103/RT) x [A](0)(0.6201) x [B](0)(0.5840) x [C](0)(0.7960) x t. With the addition of gold support, the efficiency of LDHs increased from 23.3 to 85.6% of 175 mg/m(3) gaseous toluene after 3 h of irradiation, along with an enhancement of reaction rate and 50% reduction in activation energy. The enhancement of catalytic activity of visible light degradation of gaseous toluene catalyzed by Au/LDHs is mainly from a change in mechanistic pathway introduced by Au support, which is discussed and supported based on the investigation of different wavelength contribution, active species, electrochemical impedance spectra, intermediates, and degradation pathway.