Anatomy of Adsorption in Open-End and Closed-End Slit Mesopores: Adsorption, Desorption, and Equilibrium Branches of Hysteresis Loop

We present a detailed analysis, using simulated data, of the adsorption and desorption in two finite length slit mesopores, one with both ends open to the surroundings and the other with one end closed, to investigate the microscopic behavior of an adsorbate in a confined space. The mesoscopic analysis of the interface separating the gas-like phase and the condensed phase reveals the mechanisms that lead to hysteresis in these two types of pore. The effects of pore width, temperature, and surface strength on these mechanisms are also studied to probe the detailed behavior of the system just before condensation and just after evaporation. In particular, for closed-end pores, we observe the development of a meniscus and the subsequent movement of the developed meniscus in adsorption and desorption. From these observations we are able to explain why adsorption and desorption branches have two distinct sections, slow and fast variations with pressure (corresponding to the two stages (1) developing meniscus and (2) developed meniscus), which have not been recognized in earlier literature