摘要
CdS nanosheets(NSs)photocatalysts modified with dual earth‐abundant co‐catalysts of metallic carbon black(CB)and NiS2were synthesized by a two‐step solvothermal/impregnation method.Allthe experiment results demonstrated that the co‐loading of CB and NiS2could significantly enhance the photocatalytic H2‐evolution activity of CdS NSs.The photocatalytic performance of the as‐prepared CdS/CB/NiS2samples was tested under visible light(λ≥420nm)by using an aqueous solution containing0.25mol L–1Na2S‐Na2SO3as the sacrifice agent.The CdS‐0.5%CB‐1.0%NiS2composite photocatalysts exhibited the highest H2‐evolution rate of166.7μmol h?1,which was approximately5.16and1.87times higher than those of pure CdS NSs and CdS‐1.0%NiS2,respectively.The possible mechanism for the enhanced H2‐evolution activity of CdS/CB/NiS2composite photocatalysts was proposed.The results showed that the enhanced photocatalytic H2‐evolution activities could be ascribed to the co‐loading of metallic CB and NiS2as co‐catalysts onto the surface of CdS NSs.The excellent synergetic effect between the CB and NiS2could obviously improve visible light absorption,promote separation of photogenerated electron‐hole pairs and boost the H2‐evolution kinetics,thus leading to an enhanced activity for H2evolution.More interestingly,the metallic CB could not only act as a cocatalyst for H2evolution,but also serve as a conductive electron bridge to promote the charge migration.This work not only demonstrates that loading CB as a co‐catalyst is a promising strategy to further boost the photocatalytic activity of CdS/NiS2composites,but also offers a new mechanistic insight into the construction of highly efficient and stable CdS NSs‐based hybrid photocatalysts with dual earth‐abundant co‐catalysts for photocatalytic applications.
光催化产氢技术是目前解决能源和环境问题的最有潜力的方法之一,因此制备安全高效的光催化剂已成为目前的研究热点.在目前研究的各种光催化剂中,CdS光催化剂因为具有较窄的带隙(2.4 eV)和合适的导带位置,所以在可见光催化产氢领域受到广泛关注.然而,光生电子/空穴对易复合和光腐蚀作用极大地限制了CdS光催化剂的放大应用.因此,人们采用众多改性策略以提高CdS光催化剂的可见光产氢活性,其中构建CdS纳米结构和负载助催化剂被认为是最有效的方式.构建CdS纳米结构既可以缩短载流子的迁移路径,也可以减少CdS晶体中的缺陷.很多不同纳米结构的CdS光催化剂已经被开发,例如纳米线、纳米颗粒和纳米棒等.因为制备过程极为复杂繁琐,所以CdS纳米片的研究鲜见报道.本文采用乙酸鎘和硫脲为原材料,通过简单的溶剂热法合成了CdS纳米片.在CdS的各类助催化剂中,由于常用的Pt,Ag和Au等贵金属的高成本和低储量等问题严重限制了它们的实际应用,所以近年来众多非贵金属助催化剂(例如MoS_2,WS2,NiS,NiO和WC等)得到了广泛关注.由于非贵金属助催化剂存在弱电导率和低功函数等问题,影响了对光生电子的收集和利用.纳米碳材料具有极高的电导率、强可见光吸收、有效的载流子分离和较多的反应位点等优点,因此组合纳米碳材料和非贵金属助催化剂被认为是一种有效的解决方案.本文首次采用炭黑和NiS_2作为双助催化剂改性CdS纳米片,通过简单的溶剂热/沉淀两步法成功合成了廉价高效的CdS/CB/NiS_2三元光催化体系.光催化产氢性能测试表明,CdS-0.5%CB-1%NiS_2展现出最高的光催化效率(166.7μmol h^(-1)),分别是CdS NSs和CdS-1.0%NiS_2的5.16和1.87倍.X射线衍射、高分辨电子显微镜和X射线光电子能谱结果证实了CdS催化剂的片状结构,且炭黑和NiS_2成功负载在CdS纳米片表面.紫外-可见漫反�
基金
supported by the National Natural Science Foundation of China(51672089)
the Science and Technology Planning Project of Guangdong Province(2015B020215011)
the State Key Laboratory of Advanced Technology for Material Synthesis and Processing(Wuhan University of Technology)(2015-KF-7)~~
