催化学报

催化学报 ›› 2017, Vol. 38 ›› Issue (2): 296-304.DOI: 10.1016/S1872-2067(16)62554-8

• 论文 • 上一篇    下一篇

NiS2助剂修饰g-C3N4光催化剂的简易合成及光催化制氢性能增强研究

陈峰a, 杨慧a, 王雪飞a, 余火根a,b   

  1. a 武汉理工大学化学, 化工与生命科学学院, 湖北武汉 430070;
    b 武汉理工大学硅酸盐国家重点实验室, 湖北武汉 430070
  • 收稿日期:2016-08-30 修回日期:2016-09-28 出版日期:2017-02-18 发布日期:2017-03-14
  • 通讯作者: Xuefei Wang,Tel:+86-13387570017;Fax:+86-27-87879468;E-mail:xuefei@whut.edu.cn;Huogen Yu,Tel:+86-27-87871029;Fax:+86-27-87879468;E-mail:yuhuogen@whut.edu.cn
  • 基金资助:

    国家自然科学基金（21277107，21477094，51672203，51472192）；新世纪优秀人才计划（NCET-13-0944）；中央高校基础研究基金（WUT2015IB002）.

Facile synthesis and enhanced photocatalytic H2-evolution performance of NiS2-modified g-C3N4 photocatalysts

Feng Chena, Hui Yanga, Xuefei Wanga, Huogen Yua,b   

  1. a School of Chemistry, Chemical Engineering and Life Sciences, Wuhan University of Technology, Wuhan 430070, Hubei, China;
    b State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, Hubei, China
  • Received:2016-08-30 Revised:2016-09-28 Online:2017-02-18 Published:2017-03-14
  • Contact: 10.1016/S1872-2067(16)62554-8
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21277107, 21477094, 51672203, 51472192), the Program for New Century Excellent Talents in University (NCET-13-0944), and the Fundamental Research Funds for the Central Universities (WUT 2015IB002).

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摘要：

g-C3N4是一种新型的稳定的半导体光催化材料，它可以通过热缩聚法、固相反应法、电化学沉积法和溶剂热法等制备.g-C3N4禁带宽度约为2.7 eV，吸收边在460 nm左右，具有合适的导带位置，可用作可见光响应制氢的光催化材料，但在实际应用中g-C3N4光催化性能较低，其原因可归纳为：（1）g-C3N4在吸收光子产生电子和空穴对后，光生载流子的传输速率较慢，容易在体相或表面复合，致使g-C3N4的量子效率较低；（2）材料在合成过程中易于结块，使g-C3N4的比表面积远小于理论值，严重削弱了g-C3N4光催化材料的制氢性能.目前已有很多关于g-C3N4改性的报道，但一些方法对材料的处理过程耗时较长或者合成过程较难控制.用助剂改性是提高光催化制氢活性的半导体材料的主要策略之一.合适的助剂可改进电荷分离和加速表面催化反应，从而提高光催化剂的制氢活性.虽然稀有金属或贵金属，如铂、金和银可大大提高g-C3N4的制氢速率，但由于其昂贵和稀缺性，因而应用严重受限.因此，开发成本低、储量丰富、高性能助剂来进一步提高制氢性能具有重要意义.
NiS2来源丰富、价格低廉.它可在酸性和碱性的环境保持相对较高的稳定性，且其表面电子结构表现出类金属特性.但它较难与半导体光催化剂形成强耦合和界面，通常需要水热等条件下合成.实验表明，g-C3N4表面存在着大量的含氧官能团及未缩合的氨基基团，为表面接枝提供了丰富的反应活性位点，因而可利用g-C3N4表面均匀分布的含氧官能团等和Ni2+结合，再原位与S2-反应，从而在g-C3N4上负载耦合紧密的NiS2助剂，进一步提高复合材料的光催化制氢活性.
本文采用低温浸渍法制备了NiS2/g-C3N4光催化剂.NiS2助剂在温和的反应条件下与g-C3N4光催化剂复合，可以防止催化剂结构的破坏，同时使得助剂均匀地分散，并紧密结合在催化剂表面，从而大大提高光催化剂的制氢性能.该样品制备过程为：（1）通过水热处理制备含氧官能团和较大比表面积的g-C3N4；（2）添加Ni（NO3）2前驱体后，Ni2+离子由于静电作用紧密吸附在g-C3N4表面；（3）在80℃加入硫代乙酰胺（TAA），可在g-C3N4的表面紧密和均匀形成助剂NiS2.表征结果证实成功制备NiS2纳米粒子修饰的g-C3N4光催化剂.当Ni含量为3 wt%，样品表现出最大的制氢速率（116 μmol h-1 g-1），明显高于纯g-C3N4.此外，对NiS2/g-C3N4（3 wt%）的样品进行光催化性能的循环测试结果表明：该样品在可见光照射下可以保持一个稳定的、有效的光催化制氢性能.根据实验结果，我们提出一个可能的光催化机理：即NiS2促进了物质表面快速转移光生电子，使g-C3N4光生电荷有效分离.基于NiS2具有成本低和效率高的优点，因而有望广泛应用于制备高性能的光催化材料.

关键词: 光催化, NiS2, 石墨化氮化碳, 助剂, 可见光催化制氢

Abstract:

NiS2 is a promising cocatalyst to improve the photocatalytic performance of g-C3N4 for the production of H2. However, the synthesis of the NiS2 cocatalyst usually requires harsh conditions, which risks destroying the microstructures of the g-C3N4 photocatalysts. In this study, a facile and low-temperature (80℃) impregnation method was developed to prepare NiS2/g-C3N4 photocatalysts. First, the g-C3N4 powders were processed by the hydrothermal method in order to introduce oxygen-containing functional groups (such as -OH and -CONH-) to the surface of g-C3N4. Then, the Ni2+ ions could be adsorbed near the g-C3N4 via strong electrostatic interaction between g-C3N4 and Ni2+ ions upon the addition of Ni(NO3)2 solution. Finally, NiS2 nanoparticles were formed on the surface of g-C3N4 upon the addition of TAA. It was found that the NiS2 nanoparticles were solidly and homogeneously grafted on the surface of g-C3N4, resulting in greatly improved photocatalytic H2 production. When the amount of NiS2 was 3 wt%, the resultant NiS2/g-C3N4 photocatalyst showed the highest H2 evolution rate (116.343 μmol h-1 g-1), which is significantly higher than that of the pure g-C3N4 (3 μmol h-1 g-1). Moreover, the results of a recycling test for the NiS2/g-C3N4(3 wt%) sample showed that this sample could maintain a stable and effective photocatalytic H2-evolution performance under visible-light irradiation. Based on the above results, a possible mechanism of the improved photocatalytic performance was proposed for the presented NiS2/g-C3N4 photocatalysts, in which the photogenerated electrons of g-C3N4 can be rapidly transferred to the NiS2 nanoparticles via the close and continuous contact between them; then, the photogenerated electrons rapidly react with H2O adsorbed on the surface of NiS2, which has a surficial metallic character and high catalytic activity, to produce H2. Considering the mild and facile synthesis method, the presented low-cost and highly efficient NiS2-modified g-C3N4 photocatalysts would have great potential for practical use in photocatalytic H2 production.

Key words: Photocatalysis, NiS2, Graphite-like carbon-nitride, Cocatalyst, Visible-light photocatalytic hydrogen evolution