Co(dmgH)2pyCl as a noble-metal-free co-catalyst for highly efficient photocatalytic hydrogen evolution over hexagonal ZnIn2S4

Abstract

Co(dmgH)₂pyCl/ZnIn₂S₄ composites (dmgH = dimethylglyoxime and py = pyridine) with different amounts of Co(dmgH)₂pyCl loaded were prepared from hexagonal ZnIn₂S₄ and Co(dmgH)₂pyCl via an impregnation method. The photocatalytic activity for hydrogen evolution over the as-prepared Co(dmgH)₂pyCl/ZnIn₂S₄ composites under visible light irradiation was investigated. It was found that the hydrogen evolution over hexagonal ZnIn₂S₄ can be significantly increased by loading Co(dmgH)₂pyCl as a co-catalyst. An optimum activity was achieved over 3.0 wt% Co(dmgH)₂pyCl/ZnIn₂S₄ composite, with 1438.5 μmol hydrogen generated and a turnover number of 387 (based on Co(dmgH)₂pyCl) reached in 8 h visible light irradiation. This value is much higher than that obtained over Pt loaded ZnIn₂S₄ under similar conditions, indicating that Co(dmgH)₂pyCl can be a highly efficient noble-metal-free co-catalyst for photocatalytic hydrogen evolution over hexagonal ZnIn₂S₄. The mechanism for the hydrogen evolution over the Co(dmgH)₂pyCl/ZnIn₂S₄ composite was also proposed. This work paves a way to the development of highly efficient noble-metal-free photocatalytic systems for hydrogen evolution.