title: In situ DRIFT and kinetic studies of photocatalytic degradation on benzene vapor with visible-light-driven silver vanadates.
abstract: The visible-light active silver vanadates with different types of crystallines (Ag(4)V(2)O(7) and Ag(3)VO(4) phases) were synthesized by an environmentally friendly aqueous process. The parameters of hydrothermal temperature and hydrothermal time were tuned to maximize the photocatalytic efficiency for the decomposition of benzene vapor under visible-light irradiation. The quantum efficiencies of the photocatalysts are compared on the basis of the crystalline phases, surface area, intensity of surface hydroxyl groups, and Brönsted acid sites. From the results of DRIFTS studies, the photocatalytic activities strongly depend on the intensities of the Brönsted acidity and hydroxyl groups presented on the silver vanadates. The sample synthesized at 140 degrees C and 4h (HM140) exhibits the best photocatalytic activity; it has a reaction rate constant (k(app)) of 1.42 min(-1), much higher than that of P25 (k(app)=0.13 min(-1)). For an irradiation time of 720 min, the mineralization yields of benzene were 48% and 11% for HM140 and P25, respectively. Based on the short-term decrease of benzene concentration and the long-term increase of CO(2) concentration, the photocatalytic ability of the HM140 sample is significantly superior to that of P25. The highest activity can be attributed to the synergetic effects of the richest Brönsted acid sites, and a favorable crystalline phase combined with abundant surface hydroxyl groups.
authors.affiliation: Department of Polymer Materials, Kun Shan University, Yung Kang City, Tainan, Taiwan.
authors.forename: Lung-Chuan
authors.initials: LC
authors.lastname: Chen
authors.forename: Guan-Ting
authors.initials: GT
authors.lastname: Pan
authors.forename: Thomas C-K
authors.initials: TC
authors.lastname: Yang
authors.forename: Tsair-Wang
authors.initials: TW
authors.lastname: Chung
authors.forename: Chao-Ming
authors.initials: CM
authors.lastname: Huang
mesh_terms: D001554:Benzene / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry; D002384:Catalysis; D008401:Gas Chromatography-Mass Spectrometry; D005740:Gases; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical / Q000737:chemistry; D007700:Kinetics; D008027:Light; D010084:Oxidation-Reduction; D019800:Phenol / Q000737:chemistry; D010777:Photochemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D018030:Silver Compounds / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014638:Vanadates / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D005740:Gases; D000644:Quaternary Ammonium Compounds; D018030:Silver Compounds; D002245:Carbon Dioxide; D017665:Hydroxyl Radical; D019800:Phenol; D014638:Vanadates; D001554:Benzene