Z-scheme transition metal bridge of Co9S8/Cd/CdS tubular heterostructure for enhanced photocatalytic hydrogen evolution

Abstract

Narrow band gap semiconductors heterojunction with superior coupling and composition matching can enhance light absorption, reduce carrier recombination and increase redox activity. Here, we report Co9S8/Cd/CdS Z-scheme type heterojunctions with hierarchical tubular heterostructure and inexpensive transition metallic electronic bridge between two distinct semiconductors by a simultaneous immobilization and in-situ reduction strategy. The designed heterostructure greatly promotes the redox activity owing to high-density catalytic sites, excellent visible light capture by small band gap Co9S8/CdS and hollow framework in conjunction with fast charge separation and smooth transfer through intermediary conductive Cd. The optimized photocatalyst exhibits a hydrogen generation rate up to 10.42 μmol h−1 without obvious drop in performance over multiple cycles. The structural design, matching tandem constituent and continuous phase mediator are the pivotal factors to engender an efficient solid-state Z-scheme photocatalysis. The facile synthetic approach and noble metal free tandem structure of this work provide alternative avenues for the development of heterojunction photocatalysts for efficient solar-to-chemical conversion.