Adsorption on a Surface with Varying Properties

TL;DR

This paper introduces a self-consistent model for gas adsorption on surfaces with varying properties, revealing bistability, hysteresis, and new dynamic phenomena like self-oscillations.

Contribution

It presents a novel model accounting for surface property variations, predicting bistability, hysteresis, and dynamic behaviors not captured by traditional models.

Findings

Adsorption isotherms differ significantly from Langmuir isotherms.

Bistability occurs when the coupling parameter exceeds a critical value.

Self-oscillations and quasistationary states are observed in the system.

Abstract

We propose a self-consistent model taking into account variations in adsorption properties of the adsorbent surface in the process of adsorption--desorption of molecules of gas on it. We introduce a dimensionless coupling parameter that characterizes the interaction of an adsorbed molecule with polarized medium. It is established that the system can be bistable if the coupling parameter is greater than a critical value and the concentration of gas belongs to a certain interval. We show that the adsorption isotherms obtained within the framework of the proposed model essentially differ from the Langmuir isotherms and establish that the Zeldovich hysteresis is possible. The kinetics of the surface coverage is analyzed in detail. We show that taking account of variations in adsorption properties of the surface in the process of adsorption--desorption leads to new phenomena: a "quasistationary" state in the case of the overdamped approximation and self-oscillations of the system in the general case.