One-pot solvothermal synthesis of MoS2-modified Mn0.2Cd0.8S/MnS heterojunction photocatalysts for highly efficient visible-light-driven H-2 production

摘要

Development of low-cost, highly efficient and stable CdS-based solid solution photocatalysts is of great significance towards photocatalytic H-2 production. Herein, a solvothermal process has been used to fabricate MnxCd1-xS-based products, which can transform into novel heterojunctions consisting of nanorod-like Mn0.2Cd0.8S solid solution and nanoparticle-like alpha-MnS once the x value is higher than 0.20, and the resulted Mn0.2Cd0.8S/MnS heterojunction containing 38 mol% alpha-MnS demonstrates an optimum composition ratio with the best H-2 production activity (335 mu mol h(-1)), which is 1.95 times higher than that (171 mu mol h(-1)) of the single CdS under visible light (lambda = 420 nm) irradiation. After modified with MoS2 cocatalyst via a one-pot solvothermal process, those MoS2-Mn0.2Cd0.8S/MnS composites show significantly improved photocatalytic performance, and the 15 wt% MoS2-Mn0.2Cd0.8S/MnS achieves the best H-2 production activity (995 mu mol h(-1)), which is 2.97 times higher than that (335 mu mol h(-1)) of the pristine Mn0.2Cd0.8S/MnS with the optimum composition ratio and also higher than that (868 mu mol h(-1)) of the 1.0 wt% Pt-Mn0.2Cd0.8S/MnS. The well aligned energy band structures and the intimate contacts among Mno. Mn0.2Cd0.8S, alpha-MnS and MoS2 facilitate the photogenerated electron transferring from the nanoparticle-like alpha-MnS to the nanorod-like Mn0.2Cd0.8S and then to the nanoflake-like MoS2, thus promoting the charge separation and providing more active sites for H-2 production reaction. This study not only presents a rare example of binary Mn0.2Cd0.8S/MnS heterojunction photocatalyst consisting of Mn0.2Cd0.8S solid solution and alpha-MnS, but also paves a new way to explore highly efficient and noble metal-free photocatalytic H-2 production system for solar energy conversion.