Abstract
Manganese oxide OMS-2 material, also known as alpha-MnO<sub>2</sub>, exhibits CO<sub>2</sub> sorption hysteresis at pressures > 7 bar. Our experiments show that the hysteretic behavior strongly depends on time, temperature and pressure. To understand the atomic structures and sorption mechanism we have performed first-principles total energy calculations. The OMS-2 material has the tunnel structure, containing K+ and H<sub>2</sub>O to stabilize the structure. The computed binding energy of H<sub>2</sub>O in the OMS-2 is 0.39eV, smaller than that of K+ by 4eV, and that therefore H<sub>2</sub>O can be easily removed, but K+ remains. K+ behaves as a gate keeper, blocking the diffusion of CO<sub>2</sub> in the OMS-2 due to high energy barrier. Increasing the concentration of CO<sub>2</sub> can dramatically lower the energy barrier for CO<sub>2</sub> to bypass K+. The gate-keeping behavior accounts for the observed hysteresis. Based on the experimental and computational results, a possible CO<sub>2</sub> sorption mechanism by OMS-2 will be discussed.
Original language | American English |
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Journal | American Chemical Society, Division of Fuel Chemistry, Preprints of Symposia |
Volume | 57 |
State | Published - 2012 |
Keywords
- CO2 storage
- adsorption mechanism
- first-principles density functional theory calculations
- manganese oxide OMS-2
EGS Disciplines
- Engineering
- Materials Science and Engineering