中文摘要：

采用平面波超软赝势方法研究了Li、Na、K三种碱金属离子修饰对g-C3N4能带结构和载流子迁移过程的影响。对建立的六种吸附构型分别采用广义梯度近似和局域密度近似进行计算，发现三种碱金属离子均更趋向于吸附在g-C3N4片层内的大空洞中央位置（F位置）。对于碱金属与g-C3N4形成的n型Schottky结，通过能带结构和功函数的计算，发现界面电荷的平衡使g-C3N4的能带电位分别整体下移1.52 V（Li）、1.07 V（Na）、0.86 V（K）。其中K离子的引入一方面将g-C3N4的价带和导带调整到更合适的氧化还原电位，另一方面增大了g-C3N4的最高占据轨道（HOMO）和最低未占据轨道（LOMO）的分布，有利于提高载流子的迁移率，同时出现的HOMO和LOMO轨道非共面特性有利于电子和空穴的分离。

英文摘要：

The effects of Li, Na, and K alkali metal ions on the band structures and carrier transfer of graphitic carbon nitride （g-C3N4） are investigated using the plane-wave ultrasoft pseudopotential method. The generalized gradient approximation and local density approximation are used to calculate total energies of six adsorption configurations. The three alkali ions all tend to adsorb on the large central cavity （F position） in g-C3N4 layers. The calculated band structures and work function values indicate that the interface charge balance of the n-type Schottky junctions formed between the alkali metal ions and g-C3N4 induces the total band edge potential of g-C3N4 to shift down by 1.52 V （Li）, 1.07 V （Na）, and 0.86 V （K）. The incorporation of K ion adjusts the valence and conduction bands to more appropriate redox potentials than those of pure g-C3N4, and increases the distribution of the HOMO and LOMO of g-C3N4, which helps to improve the mobility of carriers. Meanwhile, the non-coplanar HOMO and LOMO favor the separation of electrons and holes.