Figure 3.

The DFT-calculated free energy of forming oxygen vacancies at a metal oxide surface versus the experimental²² free energy (G_{f,bulk oxide}) and enthalpy (H_{f,bulk oxide}) of formation of the bulk oxide at 25 °C and 1 bar. A linear regression is marked with a solid line. ΔG_v,surface for the highly oxidized MoO₃ was taken as the average of ΔG_v,surface in the range of −0.69–1.59 eV. The mixed metal oxides, i.e., BSCF, LSCF, LSM, and YSZ, are approximations (shown with diamonds), as described in Supporting Information.