Defect Engineered g-C3N4 for Efficient Visible Light Photocatalytic Hydrogen Production
Defect Engineered g-C3N4 for Efficient Visible Light Photocatalytic Hydrogen Production
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DOI：
10.1021/acs.chemmater.5b02344
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发表时间：
2015-07-28
影响因子：
8.6
通讯作者：
Chen, Zhong
中科院分区：
文献类型：
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作者：
Tay, Qiuling;Kanhere, Pushkar;Chen, Zhong
利用可再生能源高效生产氢（H2）是生产清洁燃料的最重要要求。开发具有高活性和良好稳定性的太阳能转换材料体系已成为跨学科科学界最突出和最具挑战性的研究领域之一。近年来，基于三-s-三嗪（七嗪）单元的无金属类石墨类氮化碳（gC 3N4）因其成本低、稳定性好、具有优异的光学和电子性能而成为光催化研究的热点。gC - 3N4的带隙能为2.7 eV。g-C3N4的导电带和价带在阴极上和阳极上分别足够水还原和氧化生成氢和氧。2然而，尽管gC 3N4能够在可见光照射下减少水产生氢气，但氢气产率很低，不能满足工业应用。因此，为了提高gC - 3N4的光催化活性，人们进行了大量的研究。迄今为止，提高gC 3N4光催化活性最常见的方法包括：S掺杂用于缩小带隙；复合结构用于有效电荷分离；单层或几层厚的gC 3N4纳米片用于大长宽比和高表面积；4和介孔gC 3N4用于高表面积和更多的活性位点用于吸附和光催化反应。在此，我们报告了一种通过在gC 3N4中引入缺陷来增强光催化析氢的替代方法，该方法可以将gC 3N4的带隙从2.7 eV减小到2.0 eV。在gC - 3N4的热缩合过程中引入氢气合成了缺陷gC - 3N4。对缺陷工程gC - 3N4的结构和化学性质进行了详细的研究，并进行了基于DFT的电子结构计算，以了解该体系的结构-性能关系。与原始gC 3N4相比，这种缺陷工程gC 3N4在可见光辐射下的产氢量提高了4.8倍。
Efficient hydrogen (H2) production from renewable energy sources is the most important requirement to produce clean fuels. Developing materials systems with high activity and good stability for solar energy conversion has become one of the most prominent and challenging research fields in the interdisciplinary scientific community. Recently, metal-free and graphite-like carbon nitiride (gC 3N4) based on tri-s-triazine (heptazine) units has received much attention in the photocatalysis research due to its low cost, good stability, and excellent optical and electronic properties. 1 gC 3N4 has a band gap energy of 2.7 eV. The conduction and valence bands of g-C3N4 are cathodically and anodically sufficient for water reduction and oxidation respectively to produce hydrogen and oxygen. 2 However, although gC 3N4 is able to reduce water to produce hydrogen under visible light illumination, the hydrogen yield is low and unsatisfactory for industrial applications. Thus, extensive research has been carried out to enhance the photocatalytic activity of gC 3N4. To date, the most common approaches to improve gC 3N4 photocatalytic activity include S doping for band gap narrowing, 1 composite structures for effective charge separation, 3 a single layer or a few atomic layers thick gC 3 N4 nanosheets for large aspect ratios and high surface areas, 4 and mesoporous gC 3N4 for high surface area and more active sites for adsorption and photocatalytic reaction. 5Herein, we report an alternative approach to enhance photocatalytic hydrogen evolution by introducing defects in gC 3N4 which reduces the gC 3N4 band gap from 2.7 to 2.0 eV. This defective gC 3N4 was synthesized by introducing hydrogen gas in the thermal condensation process of gC 3N4. Detailed investigations on the structural and chemical properties of defect engineered gC 3N4 along with DFT based electronic structure calculations were carried out to understand the structure− property relations in this system. With this defect engineered gC 3N4, it shows 4.8 times enhanced hydrogen production under visible light radiation as compared to pristine gC 3N4.