First-principles study on structural stability of graphene oxide and catalytic activity of nitric acid

Abstract

The stability and electronic structure properties of graphene fumigated by nitric acid are systematically studied by the first-principles method based on ultrasoft pseudopotentials. The model of graphene oxide fumigated by nitric acid is built based on the 2 × 2 supercell model with orthogonal graphene unit cells, which contains 15 carbon and 2 oxygen atoms. The results show that the fumigated graphene containing a carbon atom bonded to an oxygen atom is a stable structure with lower energy, which is consistent with the experimental result. In addition, the mechanical stability analysis shows <inline-formula><tex-math id="Z-20191212071737-1">\begin{document}${ {C_{66}} > 0,\;{C_{11}} > 0,\;{C_{11}}{C_{22}} > C_{12}^2} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20191304_Z-20191212071737-1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="24-20191304_Z-20191212071737-1.png"/></alternatives></inline-formula>, which satisfies the mechanical stability condition. By analyzing the reactant and product, it can be concluded that the nitric acid acts as catalyst. Moreover, the process of graphene oxidation catalyzed by nitric acid is endothermic and the reaction needs heating. By analyzing the electronic properties of the structure, the graphene oxide is determined to be an intrinsic semiconductor with a direct band gap of 1.12 eV and work function of 5.28 eV. These results provide theoretical basis for preparing the graphene oxide and its applications in the field of optoelectronic devices.