Fig. 3
(001)-SrO terminated surface energy landscape and CoO2(001) terminated surface energy landscape. a The energy landscape for oxygen adsorption, dissociation, and incorporation into the SrO (001) terminated surface and the bulk of the La0.5Sr0.5CoO3 (LSC-50) perovskite. Energy on y-axis is the DFT calculated enthalpy with correction. The initial configuration is O2 molecular and two isolated surface vacancies (2sAO) on the SrO-surface, final configuration is ‘null’ surface, followed by 2-O in the bulk of LSC-50, all three states being common for all mechanisms. The overall change in the enthalpy is denoted by ΔH* = 1.99 eV. Different mechanisms are described in the “Methods” section and the Supplementary Note 1. Only seven kinetically mechanisms are shown. All reaction intermediates are denoted in respective colors and underlined. Transition states are shown as ‘TS’, with the forward reaction barriers (in eV) are written next to the step proceeding through a transition state, or in parenthesis for clarity. b. The energy landscape for O2 adsorption, dissociation and incorporation into the CoO2(001) terminated surface and finally into the bulk of the LaSrCoO3 (LSC-50) perovskite. Energy on y-axis is the DFT calculated enthalpy with correction. The initial configuration is O2 molecular and two isolated surface vacancies (2s, or s + s) on the LSC surface, final configuration is ‘null’ surface (2-O on surface), followed by ‘bulk’ (2-O in bulk), all three states being common for all mechanisms. Overall change in the enthalpy is denoted by ΔH* = 3.48 eV as shown. Different mechanisms are described in “Methods” section and the Supplementary Note 1. Direct dissociative chemisorption mechanisms (Mechanisms B9 through B12) are not included in this figure as they have large chemisorption energy barriers that make the mechanisms orders of magnitude slower than all other mechanisms. All reaction intermediates are denoted in respective colors and underlined. The symbol ‘far’ denotes isolated species whereas ‘near’ denotes species occupying nearest-neighbor surface sites. Transition states are shown as TS. Mechanism B3 (thick purple line) emerges as the fastest ORR mechanism on BO2 termination with O2 adsorption and dissociation as rate-limiting step
