Hao Qiang, Niu Xiuxiu, Nie Changshun, Hao Simeng, Zou Wei, Ge Jiangman, Chen Daimei, Yao Wenqing
National Laboratory of Mineral Materials, School of Materials Science and Technology, China University of Geosciences, Beijing 100083, China.
Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China.
Phys Chem Chem Phys. 2016 Nov 23;18(46):31410-31418. doi: 10.1039/c6cp06122b.
SiO, an insulator, hardly has any photocatalytic acitivity due to its intrinsic property, and it is generally used as a hard template to increase the surface area of catalysts. However, in this work, we found that the surface state of the insulator SiO can promote the migration of photogenerated charge carriers, leading to the enhancement of the photooxidation ability of graphitic carbon nitride (g-CN). A one-pot calcination method was employed to prepare g-CN/SiO composites using melamine and SiO as precursors. The composites present considerably high photocatalytic degradation activities for 2,4-dichlorophenol (2,4-DCP) and rhodamine B (RhB) under visible light (λ > 420 nm) irradiation, which are about 1.53 and 4.18 times as high as those of bulk g-CN, respectively. The enhancement of the photocatalytic activity is due to the fact that the introduction of the insulator SiO in g-CN/SiO composites can greatly improve the specific surface area of the composites; more importantly, the impurity energy level of SiO can help accelerate the separation and transfer of electron-hole pairs of g-CN. Electron paramagnetic resonance (EPR) spectroscopy and trapping experiments with different radical scavengers show that the main active species of g-CN are superoxide radicals, while holes also play a role in photodegradation. For g-CN/SiO-5, besides superoxide radicals and holes, the effect of hydroxyl radicals was greatly improved. Finally, a possible mechanism for the photogenerated charge carrier migration of the g-CN/SiO photocatalyst was proposed.
二氧化硅（SiO）作为一种绝缘体，由于其固有特性几乎没有任何光催化活性，通常用作硬模板来增加催化剂的表面积。然而，在本研究中，我们发现绝缘体SiO的表面状态可以促进光生电荷载流子的迁移，从而增强石墨相氮化碳（g-CN）的光氧化能力。采用一锅煅烧法，以三聚氰胺和SiO为前驱体制备了g-CN/SiO复合材料。该复合材料在可见光（λ>420nm）照射下对2,4-二氯苯酚（2,4-DCP）和罗丹明B（RhB）具有相当高的光催化降解活性，分别约为块状g-CN的1.53倍和4.18倍。光催化活性的增强是由于在g-CN/SiO复合材料中引入绝缘体SiO可以大大提高复合材料的比表面积；更重要的是，SiO的杂质能级有助于加速g-CN的电子-空穴对的分离和转移。电子顺磁共振（EPR）光谱和使用不同自由基清除剂的捕获实验表明，g-CN的主要活性物种是超氧自由基，而空穴在光降解中也起作用。对于g-CN/SiO-5，除了超氧自由基和空穴外，羟基自由基的作用也大大增强。最后，提出了g-CN/SiO光催化剂光生电荷载流子迁移的可能机制。
