A general method for type I and type II g-C3N4/g-C3N4 metal-free isotype heterostructures with enhanced visible light photocatalysis
A general method for type I and type II g-C3N4/g-C3N4 metal-free isotype heterostructures with enhanced visible light photocatalysis
复制标题
具有增强可见光催化作用的 I 型和 II 型 g-C3N4/g-C3N4 无金属同型异质结构的通用方法
DOI：
10.1039/c5nj00351b
复制
发表时间：
2015-01-01
影响因子：
3.3
通讯作者：
Wu, Zhongbiao
中科院分区：
文献类型：
--
作者：
Dong, Fan;Ni, Zilin;Wu, Zhongbiao
为了解决原始g-C3N4的快速电荷重组问题，使用了容易获得的复合前体，如双氰胺（三聚氰胺）和尿素，并进行了原位热处理，形成了I型和II型g-C3N4/g-C3N4无金属同型异质结构。这些异质结构的构建基于不同的带向模式（交错带向和跨带带向）。采用x射线衍射、光致发光、透射电镜和价带x射线光电子能谱等方法对g-C3N4/g-C3N4异质结构进行了确证。对于双氰胺和尿素的g-C3N4/g-C3N4异质结构（II型，交错带位），在可见光下，CN-D的导带（g-C3N4来自双氰胺）中的光生电子在0.04 eV的驱动下可以转移到CN-U的导带（g-C3N4来自尿素）中，而光生空穴在0.36 eV的价带偏移驱动下可以从CN-U转移到CN-D中，从而实现了光电子和空穴的有效分离。对于由三聚氰胺和尿素制成的g-C3N4/g-C3N4异质结构（I型，跨带取向），在0.17 eV的导带偏移驱动下，光致电子可以从CN-U转移到CN-M（由三聚氰胺制成的g-C3N4），而光致空穴不能从一侧转移到另一侧，也促进了光致电子和空穴的分离。通过形成I型和II型g-C3N4/g-C3N4异质结构，克服了原始g-C3N4快速电荷重组的固有缺陷。对于空气中ppb级NO的去除，I型和II型g-C3N4基异质结构的光催化活性和稳定性比单独g-C3N4的光催化活性和稳定性都有显著提高，这可以直接归因于促进了电荷分离。I型和II型同型异质结的合理设计和构建对于开发具有大规模环境和能源应用潜力的高效可见光催化剂具有普遍和有力的意义。本研究还丰富了新型可见光异质结构光催化剂的种类，在其他领域具有广泛的应用前景。
In order to address the fast charge recombination of pristine g-C3N4, easily available composite precursors such as dicyandiamide (melamine) and urea were used and thermally treated in situ creating type I and type II g-C3N4/g-C3N4 metal-free isotype heterostructures. The construction of these heterostructures was based on different band-alignment patterns (staggered and straddled band alignments). The confirmation of isotype g-C3N4/g-C3N4 heterostructures was based on X-ray diffraction, photoluminescence, transmission electron microscopy, and valence band X-ray photoelectron spectroscopy. For g-C3N4/g-C3N4 heterostructures from dicyandiamide and urea (type II, staggered band alignments) under visible light, the photogenerated electrons in the conduction band of CN-D (g-C3N4 from dicyandiamide) could transfer to the conduction band of CN-U (g-C3N4 from urea) driven by an offset of 0.04 eV, whereas the photogenerated holes could transfer from CN-U to CN-D driven by a valence band offset of 0.36 eV, thus photogenerated electrons and holes could be separated effectively. For g-C3N4/g-C3N4 heterostructures from melamine and urea (type I, straddled band alignments), the photo-induced electrons could transfer from CN-U to CN-M (g-C3N4 from melamine) driven by a conduction band offset of 0.17 eV, while photogenerated holes could not be transported from one side to another side, also promoting the separation of photo-induced electrons and holes. The intrinsic drawback of fast charge recombination of pristine g-C3N4 was overcome by formation of type I and type II g-C3N4/g-C3N4 heterostructures. For the removal of ppb-level NO in air, the type I and type II g-C3N4 based heterostructures demonstrated highly enhanced photocatalytic activity and stability in comparison with g-C3N4 alone, which could be directly ascribed to the promoted charge separation. The rational design and construction of type I and type II isotype heterojunctions was general and powerful for the development of efficient visible-light photocatalysts with potential large scale environmental and energetic applications. The present work could also enrich new types of visible-light heterostructured photocatalysts, which may find wide application in other areas.