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Adsorption of CO2 and Facile Carbonate Formation on BaZrO3 Surfaces C

Polfus, Jonathan M., Yildiz, Bilge, Tuller, Harry L., Bredesen, Rune
Journal of physical chemistry 2018 v.122 no.1 pp. 307-314
adsorption, barium, barium carbonate, carbon dioxide, carbon monoxide, enthalpy, entropy, methane, steam, temperature, vibrational properties
The adsorption of CO₂ and CO on BaZrO₃ (0 0 1) was investigated by first-principles calculations with a focus on the BaO termination. CO₂ was found to strongly chemisorb on the surface by formation of carbonate species with an adsorption enthalpy of up to −2.25 eV at low coverage and −1.05 eV for a full monolayer. An adsorption entropy of −8.8 × 10–⁴ eV K–¹ was obtained from the vibrational properties of the adsorbates. Surface coverages were evaluated as a function of temperature and CO₂ partial pressure, and the obtained coverage under 1 bar CO₂ was more than 0.8 at 1000 K (conditions relevant for steam methane reforming). The fully saturated surface was stable up to about 400 K under ambient atmosphere, i.e., 400 ppm of CO₂. The initial stage of BaCO₃ formation was evaluated according to migration of barium to the carbonate overlayer, which was found to result in a significant stabilization of the system. The barium migration was found to be essentially unobstructed with a barrier of only ∼5 meV. In light of the stability of carbonate adsorbates at the surface, the prospect of bulk dissolution of carbonate species was evaluated but ultimately found to be negligible in acceptor-doped BaZrO₃.