C/N自掺杂提高g-C3N4光响应的理论研究

依托半导体的光催化性能对环境中的污染物进行降解是解决环境污染的一种有效途径.类石墨烯相C_3N_4(g-C_3N_4)具有稳定的化学性能和独特的电子结构,在光催化领域展现出巨大的应用潜力.采用第一性原理,本文对不同比例的C/N自掺杂g-C_3N_4的晶体结构和电子结构进行了探究.通过不同掺杂位形成能的比较,探究了单原子替位掺杂和多原子表面转移掺杂的最优化结构.通过电子结构的比较发现:C原子自掺杂较N原子自掺杂形成能更低,易于在实验中实现;随N掺杂比例的增加, g-C_3N_4的吸收光谱向红外移动; C掺杂比例为1/12时对可见光的响应最强.该理论结果除获得掺杂的微观机理解释,亦利于对后续实验的合成提供理论依据和指导.

Theoretical study on optical response improving of g-C3N4 by C/N self-doping

It becomes an effective way to solve environmental pollution by using photocatalysis of semiconductors. For the reasons of chemical stabilization and unique electronic structure, polymeric graphitic carbon nitride (g-C3N4) has been used extensively in the field of photocatalysis. Using the first principle calculations, optimized crystal structures and electronic structures are calculated for the doped cases. From comparisons of formation energies, the most stable crystal structures are obtained for monatomic substitutional doping cases and polyatomic surface transfer doping ones. The results reveal that C/g-C3N4 can be easier synthetized than N/g-C3N4 because of its lower formation energy. The results show that the best doping ratio of C is 1/12 for the reason of high visible light response. The calculated results are helpful to provide theoretical basis and instruction for subsequent synthesis in addition to the microscopic mechanism of doping.