Adsorption in nanopores with finite pore walls from truncated graphene

Abstract

Adsorption mechanism depends on adsorbent geometry. The most important factors defined by geometry are: the surface accessible for adsorption and the distribution of energy of adsorption. In a particular type of pores with walls built from graphene layer fragments, we observe a competition between these two factors: an increase of adsorption due to the additional adsorption surface introduced by the walls' edges and a decrease of adsorption uptake due to smaller adsorption energy near the edges. We present the results of Monte Carlo simulations of N2 and H2 adsorption in model, finite size carbon slit pores. This model mimics real carbon samples better than usually used infinite pore models, whatever is the assumed pore shape (slit-like, tubular, curved etc). In particular, it allows us to account for the adsorption at the pore edges, totally neglected in infinite models. We show that the contribution of edges to the total adsorption is not negligible: in smallest pores, with the diameters comparable with the pore width, the edge contribu-tion can be even equally or more important than that of the pore inside. We discuss and compare Monte Carlo simulations and DFT approach in similar pore geometries