MoS₂/Graphene Cocatalyst for Efficient Photocatalytic H₂ Evolution under Visible Light Irradiation

Abstract

Exploiting noble-metal-free cocatalysts is of huge interest for photocatalytic water splitting using solar energy. Here we report a composite material consisting of CdS nanocrystals grown on the suface of a nanosized MoS₂/graphene hybrid as a high-performance noble-metal-free photocatalyst for H₂ evolution under visible light irradiation. Through the optimizing of each component proportion, the MoS₂/G-CdS composite showed the highest photocatalytic H₂ production activity when the content of the MoS₂/graphene cocatalyst is 2.0 wt % and the molar ratio of MoS₂ to graphene is 1:2. The photocatalytic H₂ evolution activity of the proposed MoS₂/G-CdS composite was tested and compared in Na₂S–Na₂SO₃ solution and lactic acid solution. A 1.8 mmol/h H₂ evolution rate in lactic acid solution corresponding to an AQE of 28.1% at 420 nm is not only higher than the case in Na₂S–Na₂SO₃ solution of 1.2 mmol/h but also much higher than that of Pt/CdS in lactic acid solution. The relative mechanism has been investigated. It is believed that this kind of MoS₂/G-CdS composite would have great potential as a promising photocatalyst with high efficiency and low cost for photocatalytic H₂ evolution reaction.