Electron spin resonance spin-trapping detection of radical intermediates in N-doped TiO2-assisted photodegradation of 4-chlorophenol.
The electron spin resonance (ESR) spin-trapping technique using 5,5-dimethyl-1-pyrroline-N-oxide as the spin-trap reagent has been applied to detect free radical intermediates generated during in situ ultraviolet or visible irradiation of aqueous 4-chlorphenol (4-CP)/N-doped TiO(2) suspensions. ESR measurements gave the first direct evidence that the active species ((*)OH and O(2*-)) are responsible for the photodecomposition of 4-CP over N-doped TiO(2) under visible-light irradiation, strongly suggesting that the photocatalytic reaction of organic compounds in powdered N-doped TiO(2) systems proceed via surface intermediates of oxygen reduction or water oxidation, not via direct reaction with holes trapped at the N-induced midgap level. These results have important implications for the evaluation of the oxidative powder of TiO(2-x)N(x) catalysts.
Fu
Hongbo
H
Department of Chemistry, Tsinghua University, Beijing 100084, China.
Zhang
Liwu
L
Zhang
Shicheng
S
Zhu
Yongfa
Y
Zhao
Jincai
J