Design of graphene-like gallium nitride and WS_2/WSe_2 nanocomposites for photocatalyst applications

应用于光催化的类石墨烯氮化镓和二硫化钨/二硒化钨纳米复合材料的设计（英文）

The geometric,electronic and optical properties of the graphene-like gallium nitride(GaN) monolayer paired with WS_2 or WSe_2 were studied systematically using the first-principles calculations.GaN interacts with WS2 or WSe_2 via van der Waals interaction and all the most stable configurations of these two nanocomposites exhibit direct band gap characteristics.Meanwhile,the type-Ⅱ heterojunctions are formed because the conduction band minimums and valence band maximums are respectively contributed by WS_2(or WSe_2) and GaN.The imaginary parts of the dielectric function and the absorption spectra of the heterostructures were also calculated and the relatively improved optical properties were observed because of the new interband transitions.In addition,the band offsets as well as the intrinsic electric fields resulting from the interlayer charge transfer indicate that the electron-hole pairs recombination can be effectively inhibited,which is conducive for the photocatalysis process.Moreover,the band gaps of the heterostructures can be modulated by applying biaxial strains and even shift away the conduction band edge potential from the H^+/H_2potential in a certain range,which further enhances the photocatalyst performance.The results indicate that GaN/WS2 or GaN/WSe_2 nanocomposites are good candidate materials for photocatalyst or photoelectronic applications.

本文利用第一性原理对类石墨烯GaN和WS_2/WSe_2构成的复合材料的结构,电学及光学性质进行了系统的研究.氮化镓和WS_2/WSe_2之间通过范德华力进行相互作用,且这两种纳米复合结构中最稳定的构型都显示出直接带隙的特征.同时,由于导带底和价带顶分别由WS_2(或WS e2)和GaN贡献,这两种复合结构形成了第二类异质结.我们对这两种异质结构的介电函数虚部和吸收光谱进行了计算并观察到由带间跃迁所引起的光学性质的增强.此外,能带偏移以及由电荷转移所产生的内建电场能够有效地抑制电荷-空穴对的复合,这对于光催化过程十分有利.通过施加双轴应变能有效地调节这两个异质结的带隙,甚至能在一定程度上使导带边远离H^+/H_2势能,从而进一步地提升异质结构的光催化性能.研究结果表明GaN/WS_2和GaN/WSe_2是优异的光催化和光电应用的候选材料.