Stochastic desorption of water molecules adsorbed inside single-wall carbon nanotube through nanowindows

Abstract

Understanding water adsorption/desorption process through nanowindows provides new insights into membrane applications, supercapacitors and elucidation of biological ion separation mechanism. This study evidenced a new stochastic desorption mechanism of water molecules adsorbed inside highly pure single-wall carbon nanotube (SWCNT) through nanowindows, which evidently differs from conventional water desorption mechanism from carbon micropores. This new mechanism was clarified by the comparative analysis of water adsorption/desorption behaviors on endcap-closed SWCNT having nanowindows and endcap-open SWCNT without nanowindows. The water desorption for both open SWCNT samples was deeply associated with unique adsorbed water structures consisting of an ice-like adlayer akin to the graphene wall of SWCNT and core liquid-like water. Nanowindows destabilize the ice-like adlayer, leading to stochastic desorption of water molecules, followed by single-step desorption of adsorbed water through nanowindows of endcap-closed SWCNT having nanowindows. In contrast, water molecules are desorbed from ice-like adlayer and core liquid-like water separately for the endcap-open SWCNT without nanowindows.