ABSTRACT
Hydrogen generation via semiconductor photocatalysts has gained significant attention as a sustainable fuel generation process. To demonstrate the performance of nanoscale core-shell heterostructure in photocatalytic hydrogen production, we have fabricated CdS nanorods coated with ZnS photocatalyst via wet-chemical reaction followed by deposition of ultrathin MoS2 nanosheets by photo reduction process. The effect of ZnS content and suitable amount of MoS2 loading over the visible-light induced photocatalytic hydrogen evolution was examined in Na2S and Na2SO3 aqueous solutions. Interestingly, it is apparent that a close connection (or heterojunction) between CdS and ZnS is believed to easily tunnel the charge carriers to the surplus surface states, making its electrons and holes energetically favourable to transfer from ZnS to MoS2 for photocatalytic reactions and subsequently, enhances the H2 evolution activity in CdS/ZnS type I core-shell heterostructures. The optimal MoS2 concentration is resolved to be 7 mol% and the subsequent visible-light induced H2 generation rate was 13589 µmol h-1g-1, which is 19 and 158 fold higher than pristine CdS and ZnS respectively. The probable photocatalytic mechanism of CdS/ZnS type I core-shell heterostructure with MoS2 cocatalyst is proposed. Our inexpensive and convenient preparation strategy may offer novel prospects in the engineering of desirable nanoheterostructures with better performance.
ABSTRACT
Ag2CO3/AgBr/graphene oxide (Ag2CO3/AgBr/GO) ternary composites with different percentages of GO were fabricated by a facile co-precipitation strategy. The composites were characterized in the aspect of phase composition, light absorption performance, and micromorphology etc. The activity of the composites was studied by photocatalytic degradation of colored organic dye (rhodamine B, RhB) and colorless organics (phenol) under the shine of visible light. The optimized Ag2CO3/AgBr/GO-7.5 composites revealed the most excellent photocatalytic activity, which exhibited an apparent reaction rate constant exceeding that of pristine AgBr and Ag2CO3 by a factor of 107 and 5.63, respectively. The outstanding performance can be attributed to the effective separation of electrons and holes as well as the strong light absorption ability resulting from the Ag2CO3/AgBr/GO heterostructure. Moreover, it was verified that h+ and â¢O2- were two major active substances responsible for the decomposition of organic pollutants according to the free radical-trapping experiments. Besides, a probable reaction mechanism referring to the charge transfer and separation in the composites was proposed and discussed in detail.