In Situ Construction of g-C3N4/g-C3N4 Metal-Free Heterojunction for Enhanced Visible-Light Photocatalysis
In Situ Construction of g-C3N4/g-C3N4 Metal-Free Heterojunction for Enhanced Visible-Light Photocatalysis
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DOI：
10.1021/am403653a
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发表时间：
2013-11-13
影响因子：
9.5
通讯作者：
Ho, Wing-Kei
中科院分区：
文献类型：
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作者：
Dong, Fan;Zhao, Zaiwang;Ho, Wing-Kei
星星型光催化剂g-C3 N4的光催化性能受到限制，主要是由于快速的电荷复合而导致光催化效率低。本工作发展了一种简单的原位方法，以分子复合物为前驱体构建g-C3 N4/g-C3 N4无金属同型异质结，目的是大大促进电荷分离。考虑到由尿素和硫脲分别制备的g-C3 N4样品具有不同的能带结构，在相同的热处理条件下同时处理尿素和硫脲的分子复合前驱体，原位生成了一种新型的层状g-C3 N4/g-C3 N4无金属异质结（g-gCN异质结）。该合成方法使用容易获得的地球上丰富的绿色前体，是简便、经济和环境友好的。通过XRD、HRTEM、价带XPS、ns能级PL、光电流和EIS测试证实了g-gCN异质结的存在。在可见光照射下，光生电子从g-C3 N4（硫脲）转移到g-C3 N4（脲）的导带偏移驱动的0.10 eV，而光生空穴从g-C3 N4（脲）转移到g-C3 N4（硫脲）的价带偏移驱动的0.40 eV。异质结中两个g-C3 N4组分之间的电势差是有效电荷分离和转移的主要驱动力。对于空气中的NO的去除，g-g CN异质结表现出显着增强的可见光催化活性比g-C3 N4单独和g-C3 N4样品的物理混合物。g-g CN异质结的光催化性能的提高可以直接归因于异质结界面上有效的电荷分离和转移以及载流子寿命的延长。本工作表明，合理设计和构建同型异质结可以为新型高效可见光催化剂的开发开辟一条新的途径。
The photocatalytic performance of the star photocatalyst g-C3N4 was restricted by the low efficiency because of the fast charge recombination. The present work developed a facile in situ method to construct g-C3N4/g-C3N4 metal-free isotype heterojunction with molecular composite precursors with the aim to greatly promote the charge separation. Considering the fact that g-C3N4 samples prepared from urea and thiourea separately have different band structure, the molecular composite precursors of urea and thiourea were treated simultaneously under the same thermal conditions, in situ creating a novel layered g-C3N4/g-C3N4 metal-free heterojunction (g-g CN heterojunction). This synthesis method is facile, economic, and environmentally benign using easily available earth-abundant green precursors. The confirmation of isotype g-g CN heterojunction was based on XRD, HRTEM, valence band XPS, ns-level PL, photocurrent, and EIS measurement. Upon visible-light irradiation, the photogenerated electrons transfer from g-C3N4 (thiourea) to g-C3N4 (urea) driven by the conduction band offset of 0.10 eV, whereas the photogenerated holes transfer from g-C3N4 (urea) to g-C3N4 (thiourea) driven by the valence band offset of 0.40 eV. The potential difference between the two g-C3N4 components in the heterojunction is the main driving force for efficient charge separation and transfer. For the removal of NO in air, the g-g CN heterojunction exhibited significantly enhanced visible light photocatalytic activity over g-C3N4 alone and physical mixture of g-C3N4 samples. The enhanced photocatalytic performance of g-g CN isotype heterojunction can be directly ascribed to efficient charge separation and transfer across the heterojunction interface as well as prolonged lifetime of charge carriers. This work demonstrated that rational design and construction of isotype heterojunction could open up a new avenue for the development of new efficient visible-light photocatalysts.