Fig. 3. DFT-calculated ORR activity on Ag-Pd active site motifs.

a Ag-Pd active site models investigated by DFT for their effect on ORR activity: (i) Ag, (ii) Pd_atom–Ag, (iii) Pd, (iv) Ag₃Pd₁, (v) Ag₂Pd₂, and (vi) Ag₁Pd₃. All the considered surfaces are (111) facets. The identified most active sites are: (i) Ag_top, (ii) Ag–Pd, (iii) Pd–Pd, (iv) Ag–Pd, (v) Pd–Pd, and (vi) Pd–Pd. b Oxygen reduction reaction (ORR) activity map showing overpotentials (vs. the computational hydrogen electrode) for various Ag-Pd structures calculated by DFT. η = 1.23 V − U_L. (The ORR U_L is defined as the highest potential at which all the reaction steps become downhill in energy. Lower η or higher U_L indicate improved theoretical ORR activity). See Supplementary Figs. 15–17 and Supplementary Tables 5 and 6 for more details about strain effects, projected density of states, and the tabulated data.