Pore size analysis of carbons with heterogeneous kernels from reactive molecular dynamics model and quenched solid density functional theory

Abstract

We presented a new kernel of heterogenous carbon surfaces constructed using the reactive molecular dynamics model (rMD). The rMD model explicitly incorporates edges and corrugations resulting from the oxidative etching of graphene walls. The rMD model eliminates the computational artifacts characteristic to the homogeneous pore wall models. In ultramicropores, early uptake is guided by the competition between central energetic adsorption sites and heterogeneities of the wall. In the larger pores, the central energy diminishes and the preferential adsorption sites are located in the pore wall. Comparisons between the rMD model, which mimics the surface roughness explicitly, and the quenched solid density functional theory (QSDFT) model are performed. The rMD model performs similarly to the QSDFT in the reproduction of the carbon experimental isotherms, indicating that it is a viable alternative to the implicit models for carbon characterization. In calculated PSDs, the rMD model attributes higher volumes to the ultramicropores than the QSDFT model due to enhanced adsorption on the surface defects. Finally, we tested the influence of the N2 molecular probe models on adsorption isotherms. It is found that the discrepancies between the nitrogen probe models on heterogeneous wall surfaces are smaller than those for the homogeneous models.