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 NN double bond on the SnS2 followed a reduction mechanism with photoelectrons via the SnIV/SnII transition while the photodegradation of organic dyes containing NN double bond on the CdS and the photodegradation of organic dyes without NN double bond on either the SnS2 or the CdS followed an oxidation mechanism with O2− and OH radicals. The SnS2 exhibited much higher activity than the CdS during the photocatalytic degradation of organic dyes containing NN double bond, since the reduction of reactant molecules on the SnS2 surface was much faster than the migration of either the O2− or the OH radicals. However, the SnS2 displayed even lower activity than the CdS in the photocatalytic degradation of other organic dyes without NN double bond, since all these reactions followed the oxidation mechanism and the SnS2 displayed a lower efficiency than the CdS in producing O2− or OH radicals due to the presence of the SnIV/SnII transition.