Abstract
The hydration of ions in nanoscale hydrated clusters is ubiquitous and essential in many physical and chemical processes. Here we show that the hydrolysis reaction is strongly affected by relative humidity. The hydrolysis of CO32- with n = 1-8 water molecules is investigated using an ab initio method. For n = 1-5 water molecules, all the reactants follow a stepwise pathway to the transition state. For n = 6-8 water molecules, all the reactants undergo a direct proton transfer to the transition state with overall lower activation free energy. The activation free energy of the reaction is dramatically reduced from 10.4 to 2.4 kcal mol-1 as the number of water molecules increases from 1 to 6. Meanwhile, the degree of hydrolysis of CO32- is significantly increased compared to the bulk water solution scenario. Incomplete hydration shells facilitate the hydrolysis of CO32- with few water molecules to be not only thermodynamically favorable but also kinetically favorable. We showed that the chemical kinetics is not likely to constrain the speed of CO2 air capture driven by the humidity-swing. Instead, the pore-diffusion of ions is expected to be the time-limiting step in the humidity driven CO2 air capture. The effect of humidity on the speed of CO2 air capture was studied by conducting a CO2 absorption experiment using IER with a high ratio of CO32- to H2O molecules. Our result is able to provide valuable insights into designing efficient CO2 air-capture sorbents.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 27435-27441 |
| Number of pages | 7 |
| Journal | Physical Chemistry Chemical Physics |
| Volume | 19 |
| Issue number | 40 |
| DOIs | |
| State | Published - 2017 |
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ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry
Cite this
The catalytic effect of H2O on the hydrolysis of CO32- in hydrated clusters and its implication in the humidity driven CO2 air capture. / Xiao, Hang; Shi, Xiaoyang; Zhang, Yayun; Liao, Xiangbiao; Hao, Feng; Lackner, Klaus; Chen, Xi.
In: Physical Chemistry Chemical Physics, Vol. 19, No. 40, 2017, p. 27435-27441.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - The catalytic effect of H2O on the hydrolysis of CO32- in hydrated clusters and its implication in the humidity driven CO2 air capture
AU - Xiao, Hang
AU - Shi, Xiaoyang
AU - Zhang, Yayun
AU - Liao, Xiangbiao
AU - Hao, Feng
AU - Lackner, Klaus
AU - Chen, Xi
PY - 2017
Y1 - 2017
N2 - The hydration of ions in nanoscale hydrated clusters is ubiquitous and essential in many physical and chemical processes. Here we show that the hydrolysis reaction is strongly affected by relative humidity. The hydrolysis of CO32- with n = 1-8 water molecules is investigated using an ab initio method. For n = 1-5 water molecules, all the reactants follow a stepwise pathway to the transition state. For n = 6-8 water molecules, all the reactants undergo a direct proton transfer to the transition state with overall lower activation free energy. The activation free energy of the reaction is dramatically reduced from 10.4 to 2.4 kcal mol-1 as the number of water molecules increases from 1 to 6. Meanwhile, the degree of hydrolysis of CO32- is significantly increased compared to the bulk water solution scenario. Incomplete hydration shells facilitate the hydrolysis of CO32- with few water molecules to be not only thermodynamically favorable but also kinetically favorable. We showed that the chemical kinetics is not likely to constrain the speed of CO2 air capture driven by the humidity-swing. Instead, the pore-diffusion of ions is expected to be the time-limiting step in the humidity driven CO2 air capture. The effect of humidity on the speed of CO2 air capture was studied by conducting a CO2 absorption experiment using IER with a high ratio of CO32- to H2O molecules. Our result is able to provide valuable insights into designing efficient CO2 air-capture sorbents.
AB - The hydration of ions in nanoscale hydrated clusters is ubiquitous and essential in many physical and chemical processes. Here we show that the hydrolysis reaction is strongly affected by relative humidity. The hydrolysis of CO32- with n = 1-8 water molecules is investigated using an ab initio method. For n = 1-5 water molecules, all the reactants follow a stepwise pathway to the transition state. For n = 6-8 water molecules, all the reactants undergo a direct proton transfer to the transition state with overall lower activation free energy. The activation free energy of the reaction is dramatically reduced from 10.4 to 2.4 kcal mol-1 as the number of water molecules increases from 1 to 6. Meanwhile, the degree of hydrolysis of CO32- is significantly increased compared to the bulk water solution scenario. Incomplete hydration shells facilitate the hydrolysis of CO32- with few water molecules to be not only thermodynamically favorable but also kinetically favorable. We showed that the chemical kinetics is not likely to constrain the speed of CO2 air capture driven by the humidity-swing. Instead, the pore-diffusion of ions is expected to be the time-limiting step in the humidity driven CO2 air capture. The effect of humidity on the speed of CO2 air capture was studied by conducting a CO2 absorption experiment using IER with a high ratio of CO32- to H2O molecules. Our result is able to provide valuable insights into designing efficient CO2 air-capture sorbents.
UR - http://www.scopus.com/inward/record.url?scp=85031413814&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85031413814&partnerID=8YFLogxK
U2 - 10.1039/c7cp04218c
DO - 10.1039/c7cp04218c
M3 - Article
AN - SCOPUS:85031413814
VL - 19
SP - 27435
EP - 27441
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
SN - 1463-9076
IS - 40
ER -