物理化学学报 >> 2019, Vol. 35 >> Issue (2): 215-222.doi: 10.3866/PKU.WHXB201803061

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表面缺陷与钯的沉积对硫化镉纳米晶粒的光催化制氢性能的影响

刘志明,刘国亮*(),洪昕林*()   

  • 收稿日期:2018-01-24 发布日期:2018-07-10
  • 通讯作者: 刘国亮,洪昕林 E-mail:liugl@whu.edu.cn;hongxl@whu.edu.cn
  • 基金资助:
    国家自然科学基金(21373153)

Influence of Surface Defects and Palladium Deposition on the Activity of CdS Nanocrystals for Photocatalytic Hydrogen Production

Zhiming LIU,Guoliang LIU*(),Xinlin HONG*()   

  • Received:2018-01-24 Published:2018-07-10
  • Contact: Guoliang LIU,Xinlin HONG E-mail:liugl@whu.edu.cn;hongxl@whu.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(21373153)

摘要:

近年来,光解水制氢的发展引起了人们的高度关注。CdS是一种具有可见光响应的很有潜力光催化剂,但由于光生电子/空穴对的快速复合和表面上的析氢反应速率低,所以它仅表现出有限的光解水制氢活性。对CdS表面结构和性能的影响的研究仍然非常有限。在本工作中,我们制备了三种具有不同形貌的CdS纳米晶体(长棒状,短棒状和三角片状)用于光解水制氢。随着纵横比的增加,非极性表面暴露面积增大,表面缺陷程度也随之增加,而表面缺陷可以捕获光生电子/空穴,从而降低其复合机会。我们发现氢的生产率可能与表面缺陷的程度有关。另外,这些缺陷可以用来固定Pd粒子形成异质结结构,有利于光生电荷的分离。在1% (w,质量分数) Pd的协助下,所有CdS催化剂的氢气产率都大大提高。值得注意的是,sr-CdS/Pd的制氢产率达到了7884 μmol·h-1·g-1,与文献报道的最高值相当。希望本文能够为了解晶体结构和性能对光催化的影响提供认识。

关键词: CdS纳米晶体, 光催化制氢, 表面缺陷, 异质结, Pd促进作用

Abstract:

The development of the photocatalytic production of hydrogen from water splitting has attracted immense attention in recent years. CdS is a potential photocatalyst with a visible light response, though it still suffers from a limited activity for hydrogen production due to the fast recombination of photo-induced electron/hole pairs and the low reaction rate of hydrogen evolution on the surface. Studies on the effect of CdS surface structure and properties on hydrogen production are still very limited. In this work, we prepared three CdS nanocrystals with different morphologies: long rod, short rod, and triangular plate. The prepared samples were well characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) specific surface area analysis, X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy, and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS). From the results of TEM, XRD and XPS, we find that the three CdS nanocrystals with different morphologies were successfully synthesized. From the PL spectra, we conclude that the area of exposed nonpolar surface and degree of surface defects increase with an increase in aspect ratio. We also performed the photocatalytic hydrogen production reaction using the three CdS crystals. Long rod-like CdS (lr-CdS) exhibits the highest photocatalytic activity, with a hydrogen production rate of 482 μmol·h-1·g-1, which is 2.6 times that of short rod-like CdS (sr-CdS) (183 μmol·h-1·g-1) and 8.8 times that of triangular plate-like CdS (tp-CdS, 55 μmol h-1·g-1). It is found that lr-CdS shows a higher hydrogen production rate than sr-CdS and tp-CdS. We find that the hydrogen production rate is related to the degree of surface defects. Surface defects can trap the photo-induced electrons/holes, thus decreasing their probability of recombination. In addition, these defects can be used to anchor Pd particles to form a heterojunction structure that facilitates the separation of photo-induced charges. Therefore, we also compared three CdS/Pd nanocrystals synthesized with the three abovementioned morphologies with respect to hydrogen production. With 1% (w, mass fraction) Pd, the hydrogen production rate was greatly enhanced compared to all the CdS catalysts. Compared to the unpromoted CdS, the reaction rate is enhanced 43.1, 10.7 and 6.0 times over those of sr-CdS, lr-CdS and tp-CdS, respectively. Notably, the hydrogen production rate with short rod-like CdS/Pd reaches 7884 μmol·h-1·g-1, which can be favorably compared with the ever-increasing values reported in the literature. Hopefully, this work provides knowledge on the effect of crystal surface structure and properties on photocatalysis.

Key words: CdS nanocrystal, Photocatalytic hydrogen production, Surface defects, Heterojunction structure, Pd promotion

MSC2000: 

  • O643