Comparative study on the mechanism in photocatalytic degradation of different-type organic dyes on SnS2 and CdS

The photocatalytic performances of the SnS2 and the CdS under the irradiation of visible light were investigated by using different organic dyes as reactants. The photodegradation of organic dyes containing N=N double bond on the SnS2 followed a reduction mechanism with photoelectrons via the Sn-IV/Sn-II transition while the photodegradation of organic dyes containing N=N double bond on the CdS and the photodegradation of organic dyes without N=N double bond on either the SnS2 or the CdS followed an oxidation mechanism with center dot O-2 center dot and center dot OH radicals. The SnS2 exhibited much higher activity than the CdS during the photocatalytic degradation of organic dyes containing N=N double bond, since the reduction of reactant molecules on the SnS2 surface was much faster than the migration of either the center dot O-2(-) or the center dot OH radicals. However, the SnS2 displayed even lower activity than the CdS in the photocatalytic degradation of other organic dyes without N=N double bond, since all these reactions followed the oxidation mechanism and the SnS2 displayed a lower efficiency than the CdS in producing center dot O-2(-) or center dot OH radicals due to the presence of the Sn-IV/Sn-II transition. (C) 2012 Elsevier B.V. All rights reserved.