Fig. 5: Theoretical analysis of the activity and stability of the hybrid active site.
From: Iron atom–cluster interactions increase activity and improve durability in Fe–N–C fuel cells
a Model structure of Fe–N4/Fe4–N6 used for theoretical calculation with a spontaneously formed OH ligand. b Schematic ORR process on the Fe–N4 site of Fe–N4-OH/Fe4–N6. c Free energy diagrams at 1.23 V for ORR over three types of active sites of Fe–N4, Fe–N4/Fe4–N6 and Fe–N4-OH/Fe4–N6. d Fe–N radical distribution function profiles of the Fe–N4 moiety in the models of bare Fe–N4 and Fe–N4/Fe4–N6 at 25 and 80 °C. Wavy arrows are used to indicate the amplitude of Fe–N bond-length fluctuation. e Snapshots of Fe–N4 and Fe–N4/Fe4–N6 obtained from MD simulations at 80 °C. The initial configuration (left) and an intermediate state (right) are provided to show the elongation of the Fe–N bond as marked by the yellow box. Source data are provided as a Source Data file.
