Humidity effect on ion behaviors of moisture-driven CO2 sorbents

Xiaoyang SHI, Hang XIAO, Xiangbiao LIAO, Mitchell ARMSTRONG, Xi CHEN*, Klaus S. LACKNER*

*Corresponding author for this work

Research output: Journal PublicationsJournal Article (refereed)peer-review

27 Citations (Scopus)

Abstract

Ion hydration is a fundamental process in many natural phenomena. This paper presents a quantitative analysis, based on atomistic modeling, of the behavior of ions and the impact of hydration in a novel CO2 sorbent. We explore moisture-driven CO2 sorbents focusing on diffusion of ions and the structure of ion hydration complexes forming inside water-laden resin structures. We show that the stability of the carbonate ion is reduced as the water content of the resin is lowered. As the hydration cloud of the carbonate ion shrinks, it becomes energetically favorable to split a remaining water molecule and form a bicarbonate ion plus a hydroxide ion. These two ions bind less water than a single, doubly charged carbonate ion. As a result, under relatively dry conditions, more OH- ions are available to capture CO2 than in the presence of high humidity. Local concentrations of dissolved inorganic carbon and water determine chemical equilibria. Reaction kinetics is then driven to a large extent by diffusion rates that allow water and anions to move through the resin structure. Understanding the basic mechanics of chemical equilibria and transport may help us to rationally design next-generation efficient moisture-driven CO2 sorbents. © 2018 Author(s).
Original languageEnglish
Article number164708
JournalJournal of Chemical Physics
Volume149
Issue number16
Early online date25 Oct 2018
DOIs
Publication statusPublished - 28 Oct 2018
Externally publishedYes

Bibliographical note

This work was partly supported by a grant from the Office of Naval Research (Grant No. ONR BAA 14-001). X.C. acknowledges the support from the National Natural Science Foundation of China (Grant Nos. 11172231 and 11372241), ARPA-E (Grant No. DE-AR0000396), and AFOSR (Grant No. FA9550-12-1-0159).

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