Three kinds of composites were built by nitrogen-doped graphene and phosphomolybdic acid. Based on the density functional theory (DFT), the combined energies, charge populations, orbital distributions and densities of states (DOS) were calculated. The calculated results show that the short-range interactions can be formed by oxygen atoms and nitrogen atoms, and the charge can be transferred from phosphomolybdic acid to graphene. It is found that the conductive bands (CB) of phosphomolybdic acid move to the lower-energy level. At the same time, more valence bands (VB) were found in DOS of three composites. Finally, the reason for the excellent capacitive ability of the composites is revealed. That is, nitrogen-doped graphene can improve the capacitive ability of the material by receiving the excessive electrons on surface of phosphomolybdic acid.

氮掺杂石墨烯和磷钼酸构建了三种复合材料。基于密度泛函理论（DFT），计算了组合能量、电荷数、轨道分布和态密度（DOS）。计算结果表明，氧原子和氮原子可以形成短程相互作用，电荷可以从磷钼酸转移到石墨烯上。发现磷钼酸的导电带（CB）向低能级移动。同时，在三种复合材料的 DOS 中发现了更多的价带 (VB)。最后，揭示了复合材料具有优异电容能力的原因。也就是说，掺氮石墨烯可以通过接收磷钼酸表面多余的电子来提高材料的电容能力。