Abstract
Density functional theory (DFT) based first-principles calculations have been employed to explore the hydrogen conversion mechanism on Sr2Fe1.5Mo0.5O6 (SFM) surface. Results show that hydrogen molecule exhibits weak physical adsorption behavior while hydrogen atom strongly chemisorbed on SFM (001) surface. Hydrogen molecule preferably dissociates at surface (Fe)-Fe-(Fe) site with an activation barrier of 0.69 eV. Hydrogen oxidation on SFM (001) surface is favorable both in kinetics and thermodynamics, and the resultant H2O molecule desorption only needs to overcome energy barrier of 0.22–0.24 eV. Oxygen atom diffusion from bulk to surface prefers to follow the path from subsurface (Fe)-O-(Fe) site to outer-surface (Fe)-VO-(Mo) vacancy site, which needs to overcome an energy barrier of 0.49 eV. The rate-limiting step of hydrogen conversion on the SFM surface is determined to be hydrogen dissociation at temperature below 775 °C while it switches to hydrogen adsorption at temperature above 775 °C. The theoretical findings in current study are expected to offer fundamental basis for designing efficient perovskite-based SOFC anodes.
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