Fig. 1: FAD mechanism at metal-gas and metal-solution interfaces.

a Elementary steps of FAD at metal-gas and metal-solution interfaces. b Evans diagram for FAD in 0.2 M FA + 0.2 M NaHCOO(SF) + 0.2 M NaClO4 at pH3.7. c The measured value of FAD reaction rate as compared to the value predicted by the Evans diagram method in b. d A typical schematic plot of the Evans diagram where FAOR is relatively sluggish. e A typical schematic plot of the Evans diagram on FAD with similar reaction rate of FAOR and HER. φ0 refers to the potential when the second term on the right side of Eq. 1 or 2 is zero. Source data are provided as a Source Data file.