Amorphous MoS2 decorated on uniform Cd0.8Zn0.2S microspheres with dramatically improved photocatalytic hydrogen evolution performance

Abstract

A series of Cd_1−xZn_xS solid solutions and samples of amorphous MoS₂ decorated on Cd_1−xZn_xS microspheres were successfully prepared. The crystal phases, morphologies, elemental distribution, chemical compositions, optical properties, and specific surface areas of the as-fabricated samples were investigated by the corresponding measurement techniques. The photocatalytic H₂ evolution activities of the MoS₂/Cd_1−xZn_xS composites were explored and compared using lactic acid as a sacrificial reagent. The results manifested that 5 wt% MoS₂ loaded on the surface of the Cd_0.8Zn_0.2S solid solution could attain the highest photocatalytic H₂ evolution rate of 12.39 mmol g⁻¹ h⁻¹, corresponding to an apparent quantum efficiency (AQE) of about 16.5% under 420 nm monochromatic light. The electrochemical impedance spectroscopy (EIS), transient photocurrent response and photoluminescence (PL) spectroscopy experiments confirmed that MoS₂ as a cocatalyst could promote the transfer and separation of photogenerated charge carriers on the Cd_0.8Zn_0.2S solid solution. In addition, amorphous MoS₂ decorated on the Cd_0.8Zn_0.2S sample showed a much better performance than that of crystalline MoS₂. This could be because amorphous MoS₂ possessed more abundant active sites than its crystalline counterpart. Based on the energy band positions of Cd_0.8Zn_0.2S and MoS₂, a tentative mechanism for the enhanced photocatalytic H₂ evolution activity was proposed.