Chongqing Key Laboratory of Catalysis and Functional Organic Molecules, College of Environmental and Biological Engineering, Chongqing Technology and Business University , Chongqing 400067, China.
ACS Appl Mater Interfaces. 2013 Nov 13;5(21):11392-401. doi: 10.1021/am403653a. Epub 2013 Nov 1.
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.
光催化剂 g-C3N4 的光催化性能受到快速电荷复合的限制，效率较低。本工作开发了一种简便的原位方法，用具有分子复合前体的方法构建 g-C3N4/g-C3N4 无金属本征异质结，旨在极大地促进电荷分离。考虑到分别由尿素和硫脲制备的 g-C3N4 样品具有不同的能带结构，将尿素和硫脲的分子复合前体在相同的热条件下同时处理，原位形成新型层状 g-C3N4/g-C3N4 无金属异质结（g-g CN 异质结）。这种合成方法使用易得的丰富绿色前体，简便、经济且环境友好。同质 g-g CN 异质结的确认基于 XRD、HRTEM、价带 XPS、ns 级 PL、光电流和 EIS 测量。在可见光照射下，光生电子从 g-C3N4（硫脲）转移到 g-C3N4（尿素），驱动力是导带偏移 0.10 eV，而光生空穴从 g-C3N4（尿素）转移到 g-C3N4（硫脲），驱动力是价带偏移 0.40 eV。异质结中两个 g-C3N4 组件之间的电位差是有效电荷分离和转移的主要驱动力。对于空气中的 NO 去除，g-g CN 异质结表现出比单独的 g-C3N4 和 g-C3N4 样品的物理混合物更显著的可见光光催化活性。g-g CN 同质异质结增强的光催化性能可直接归因于异质结界面的有效电荷分离和转移以及载流子寿命的延长。这项工作表明，合理设计和构建同质异质结可以为开发新的高效可见光光催化剂开辟新途径。
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