含时密度泛函理论研究非金属掺杂对石墨型氮化碳电荷分离的影响
Influence of Nonmetal Dopants on Charge Separation of Graphitic Carbon Nitride by Time-Dependent Density Functional Theory
摘要：
光催化剂是绿色能源生产和环境净化的重要材料。非金属掺杂的石墨碳氮化物（g-C3 N4）由于具有低成本、高电荷分离效率和宽可见光吸收等优良的光催化性能，近年来引起了人们的广泛关注。在这项研究中，我们使用含时的密度泛函理论和波函数分析来评估的电荷分离特性的磷，氧和硫掺杂的g-C3 N4光子激发的基础上的电子-空穴对距离，电子-空穴对重叠，和电荷转移量。掺杂的七嗪环的最低未占分子轨道向下移动，以促进光子激发时电子从未掺杂到掺杂的七嗪环的转移。通常，与氧和硫掺杂剂相比，磷掺杂剂产生相对高的电荷转移、高的电子-空穴对分离和低的电子-空穴重叠。在低浓度下，硫掺杂剂具有与磷掺杂剂相似的性能。此外，磷掺杂剂吸引光子激发的电子，而氧和硫掺杂剂有助于电子-空穴对分离。在g-C3 N4中，集中在一个七嗪环上的掺杂剂比分布在多个七嗪环上的掺杂剂具有更高的电荷分离性能;模拟结果表明，在非金属掺杂的g-C3 N4中，掺杂构型比掺杂浓度对电荷分离效率更重要。
英文摘要：
Photocatalysts are crucial materials for green energy production and environmental purification. Non-metal doped graphitic carbon nitride (g-C3N4) has attracted much attention in recent years because of low-cost and desired photocatalytic performance characteristics such as high charge separation efficiency and broad visible light absorption. In this study, we used time-dependent density functional theory and wave function analysis to evaluate the charge separation characteristics of phosphorus-, oxygen- and sulfur-doped g-C3N4 upon photon excitation based on electron-hole pair distances, electron-hole pair overlaps, and charge transfer amounts. The lowest unoccupied molecular orbital of doped heptazine rings was shifted downward to facilitate electron transfer from undoped to doped heptazine rings upon photon excitation. Generally, the phosphorus dopant yielded relatively high charge transfer, high electron-hole pair separations, and low electron-hole overlap compared with the oxygen and sulfur dopants. In a low concentration, the sulfur dopant had the similar performance as the phosphorus dopant did. Furthermore, the phosphorus dopant attracted photon excited electrons, whereas the oxygen and sulfur dopants contributed to electron-hole pair separation. The dopants concentrated in one heptazine ring exhibited high charge separation performance than those dopants distributed among multiple heptazine rings in g-C3N4; the simulation results suggested that doping configurations are more crucial than doping concentrations with respect to charge separation efficiency in nonmetal-doped g-C3N4.
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