物理化学学报

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羧酸根功能化的PVP-CdS同质结及其高效的光催化析氢性能

赵娜1,2, 彭静2, 王建平1, 翟茂林2   

  1. 1 中国国家博物馆, 北京 100006;
    2 北京大学化学与分子工程学院, 放射化学与辐射化学重点学科实验室, 北京分子科学国家实验室, 北京 100871
  • 收稿日期:2020-04-15 修回日期:2020-05-01 录用日期:2020-05-06 发布日期:2020-05-11
  • 通讯作者: 翟茂林 E-mail:mlzhai@pku.edu.cn
  • 基金资助:
    科学挑战项目(TZ2018004)和国家自然科学基金(11575009,11405168)资助项目

Novel Carboxy-Functionalized PVP-CdS Nanopopcorns with Homojunctions for Enhanced Photocatalytic Hydrogen Evolution

Na Zhao1,2, Jing Peng2, Jianping Wang1, Maolin Zhai2   

  1. 1 The National Museum of China, Beijing 100006, P. R. China;
    2 Beijing National Laboratory for Molecular Sciences, Radiochemistry and Radiation Chemistry Key Laboratory of Fundamental Science, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China
  • Received:2020-04-15 Revised:2020-05-01 Accepted:2020-05-06 Published:2020-05-11
  • Supported by:
    The project was supported by the Science Challenge Project, China (TZ2018004) and the National Natural Science Foundation of China (11575009, 11405168).

摘要: 光催化制氢是一种十分绿色、环保可持续的产氢方式。为了构建高效的光催化体系,对光催化剂进行表面修饰可以提高反应分子的吸附/活化的能力和电荷转移的效率。在本文中,我们通过γ-射线辐射还原法一步合成了聚乙烯吡咯烷酮包裹的硫化镉(P-CdS)同质结纳米粒子,之后通过室温下的碱化后处理,将P-CdS表面的PVP水解成为具有羧酸根和铵根的MPVP,而CdS的WZ-ZB同质结的晶体结构并未受到影响。一方面,由于MPVP在碱性溶液中的溶解度的提高,一部分MPVP溶解于溶液中,最终从MP-CdS表面去除,从而暴露出更多WZ-ZB同质结的活性位点。另一方面,水解后的MPVP保留在CdS表面,其羧酸根离子与CdS的配位作用,会影响到催化剂的价带结构,进而促进光催化析氢过程。在二者的协同作用下,当碱化NaOH浓度为1 mol·L-1时,MP-CdS-3碱化样品的光催化析氢速率达到477 μmol·g-1·h-1,是未碱化样品的2倍。这种碱化后处理的策略简单且廉价,可以引申到合成一些PVP包裹的各类光催化剂的表面修饰当中,有利于促进硫化镉材料的光催化应用。

关键词: PVP, 同质结, 碱化处理, 光催化析氢

Abstract: Photocatalytic hydrogen evolution is a scalable pathway to generate hydrogen fuels while mitigating environmental crisis. Strategies based on modification of the host photocatalyst surface are key to improve the adsorption/activation ability of the reaction molecules and the efficiency of charge transport, so that high-efficiency photocatalytic systems can be realized. Cadmium sulfide (CdS), a visible light-responsive semiconductor material, is widely used in photocatalysis because of its simple synthesis, low cost, abundant raw materials, and appropriate bandgap structure. Many researchers have focused on improving the photocatalytic efficiency of CdS because the rapid charge recombination in this material limits its applications. Among the various strategies proposed in this regard, surface modification is an effective and simple method used to improve the photocatalytic performance of materials. In this work, polyvinyl pyrrolidone (PVP)-capped CdS (denoted as P-CdS) nanopopcorns with hexagonal wurtzite (WZ)-cubic zinc blende (ZB) homojunctions were fabricated via one-step gamma-ray radiation-induced reduction under ambient conditions. Subsequent alkaline treatment under ambient conditions led to a dramatic improvement in the activity of the alkalized PVP-capped CdS (MP-CdS) photocatalyst. The structure and properties of the photocatalyst were determined by X-ray diffraction (XRD) analysis, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) analysis, Brunauer-Emmett-Teller (BET) specific surface area measurements, and photoelectric tests. The photocatalytic performance was evaluated based on the photocatalytic H2 evolution under visible-light irradiation. The mechanism underlying the enhancement of the photocatalytic activity is also discussed. The results showed that after the alkaline treatment, the crystal structure of CdS with WZ-ZB homojunctions was preserved, but PVP on the surface of CdS hydrolyzed to form PVP hydrolysis product (MPVP) with carboxyl and amino groups. Owing to the increased alkaline solubility, a portion of MPVP dissolved into the solution and was removed from the surface of MP-CdS, exposing a greater number of active sites of the WZ-ZB phase junctions with a larger specific surface area. On the other hand, the carboxyl groups in MPVP coordinated with CdS could affect the bandgap and valence band position of CdS to facilitate the photocatalysis. Because of the synergistic effects of the exposure of WZ-ZB phase junctions and band structure engineering, the alkalized samples at a 1 mol·L-1 concentration of NaOH showed a H2 evolution rate of 477 μmol·g-1·h-1 under visible-light illumination, which was twice that obtained for the pristine P-CdS photocatalysts. This simple and low-cost post-synthesis strategy can be extended to the preparation of diverse functional photocatalysts. The present work is expected to contribute to the practical application of sulfide photocatalysts.

Key words: CdS, Homojunctions, Alkaline treatment, Photocatalytic hydrogen evolution

MSC2000: 

  • O644