Multilayer Adsorption of Polyatomic Species on Homogeneous and Heterogeneous Surfaces

TL;DR

This paper develops a new analytic model for multilayer adsorption of polyatomic molecules on various surfaces, compares it with simulations, and analyzes how surface and molecule size affect monolayer capacity estimates.

Contribution

Introduces a novel approximate analytic isotherm for polyatomic multilayer adsorption validated by Monte Carlo simulations.

Findings

BET analysis underestimates true monolayer capacity.

Adsorbate size and surface heterogeneity significantly influence monolayer volume estimates.

New model improves understanding of multilayer adsorption behavior.

Abstract

In this work we study the multilayer adsorption of polyatomic species on homogeneous and heterogeneous bivariate surfaces. A new approximate analytic isotherm is obtained and validated by comparing with Monte Carlo simulation. Then, we use the well-known Brunauer-Emmet-Teller's (BET) approach to analyze these isotherms and to estimate the monolayer volume, $v_\mathrm{m}$. The results show that the value of the $v_\mathrm{m}$ obtained in this way depends strongly on adsorbate size and surface topography. In all cases, we find that the use of the BET equation leads to an underestimate of the true monolayer capacity.