Synthesis of Zn0.2Cd0.8S/MoS2/rGO photocatalyst for efficient solar-driven selective organic conversion

Abstract

ZnxCd(1-x)S solid solution was constructed by introducing zinc ions in the process of hydrothermal synthesis of CdS. To further improve the catalyst activity, Zn0.2Cd0.8S was combined with graphene and MoS2, and then the Zn0.2Cd0.8S/MoS2/rGO ternary composites were obtained. Its photocatalytic reactivity was evaluated by the catalytic oxidative coupling of benzylamine and the photocatalytic semi-dehydrogenation of 1,2,3,4-tetrahydroisoquinoline (THIQ). When Zn0.2Cd0.8S/MoS2/rGO was used in photocatalytic benzylamine oxidative coupling reaction, the conversion reached 95 % after 7 h and the selectivity of N-benzyl-1-phenylmethylimide (BPMI) was 99 %. It was further applied to the photocatalytic semi-dehydrogenation of THIQ, the conversion reached 96 % after 7 h reaction in O2 atmosphere, and the selectivity of 3,4-dihydroisoquinoline (DHIQ) reached 99 %. The heterojunction between Zn0.2Cd0.8S and MoS2 can effectively reduce the recombination efficiency of carrier. The introduction of graphene can increase the active site and promote the transfer of photogenerated electrons. The synergistic effect of MoS2 and graphene makes Zn0.2Cd0.8S have outstanding photocatalytic performance. Cycling experiments show that the ternary composite photocatalyst of Zn0.2Cd0.8S/MoS2/rGO have high stability and recyclability. The possible reaction mechanism of photocatalytic oxidative coupling of benzylamine and semi-dehydrogenation of THIQ was proposed by theoretical calculations and the active species capturing experiments.