摘要
MoS2/ZnIn2S4composites with MoS2anchored on the surface of ZnIn2S4microspheres were synthesized by a two‐step hydrothermal process.The obtained samples were characterized by X‐ray diffraction,field emission scanning electron microscopy,energy dispersive X‐ray spectroscopy,high‐resolution transmission electron microscopy,X‐ray photoelectron spectroscopy,Raman spectroscopy,ultraviolet–visible diffuse reflectance absorption spectroscopy,nitrogen adsorption–desorption measurements,photoluminescence spectroscopy,and photoelectrochemical tests.The influence of the loading of MoS2on the photocatalytic H2evolution activity was investigated using lactic acid as a sacrificial reagent.A H2evolution rate of343μmol/h was achieved under visible light irradiation over the1wt%MoS2/ZnIn2S4composite,corresponding to an apparent quantum efficiency of about3.85%at420nm monochromatic light.The marked improvement of the photocatalytic H2evolution activity compared with ZnIn2S4can be ascribed to efficient transfer and separation of photogenerated charge carriers and facilitation of the photocatalytic H2evolution reaction at the MoS2active sites.
开发高效、稳定的半导体光催化材料是太阳能光催化制氢领域的研究热点,ZnIn_2S_4因其合适的能隙、带边电势位置以及稳定、低毒等优点而受到广泛关注.但在实际应用中,单纯的ZnIn_2S_4光催化制氢活性仍较低,主要原因是ZnIn_2S_4受激产生光生电子-空穴对后,载流子的传输、分离效果不理想,易在体相或表面复合;再者是单一的ZnIn_2S_4表面缺少催化反应产氢的活性位点.为提高催化活性,通常在催化剂的表面负载一定量的贵金属作为助催化剂,但由于贵金属成本高和稀缺性,限制了其实际的应用.因此,开发低成本、储量丰富、高效的非贵金属助催化剂来增强ZnIn_2S_4的光催化制氢活性具有显著意义.最近研究表明,具有层状结构的MoS_2可被作为一种非贵金属助催化剂应用于光催化制氢,且已取得了优异的光催化制氢效果.理论计算得出,暴露在MoS_2边缘的不饱和S原子具有与质子H+很强的键合作用,从而使其能够作为活性位点便利地产生氢气.因而将MoS_2负载于ZnIn_2S_4的表面,可进一步提高ZnIn_2S_4的光催化制氢活性.本文采用二步水热法制备了MoS_2负载于ZnIn_2S_4微球表面的MoS_2/ZnIn_2S_4复合光催化剂.采用X-射线衍射、场发射扫描电子显微镜、透射电子显微镜、X射线光电子能谱、Raman光谱、紫外-可见漫反射吸收光谱、氮气吸附-脱附测试和荧光光谱等技术对所得样品进行了表征.以乳酸作为牺牲试剂考察了MoS_2负载量对光催化制氢活性的影响.结果显示,当MoS_2含量为1 wt%时,MoS_2/ZnIn_2S_4复合光催化剂的光催化产氢活性最高,达343μmol/h,是单纯ZnIn_2S_4的14.9倍.此外,对1 wt%MoS_2/ZnIn_2S_4样品进行光催化制氢的长效循环测试表明,该样品在可见光下能够保持稳定、有效的光催化制氢性能.据此提出一个可能的增强光催化制氢活性机理:适量的MoS_2可以促进ZnIn_2S_4表面光生载流子的有效传输
基金
supported by the National Natural Science Foundation of China(51302200)~~
