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

The photocatalytic performances of the SnS 2 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 SnS 2 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 SnS 2 or the CdS followed an oxidation mechanism with O 2 − and OH radicals. The SnS 2 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 SnS 2 surface was much faster than the migration of either the O 2 − or the OH radicals. However, the SnS 2 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 SnS 2 displayed a lower efficiency than the CdS in producing O 2 − or OH radicals due to the presence of the Sn IV /Sn II transition.