Double integrals of the EPR spectra (normalised to the maximum data point) plotted against potential and fitted with the Nernst equation (apparent number of electrons transferred, n app = 0.3) during the forward (green, E forward (catalytic, FE-EPR) = +859 mV) and reverse (yellow, E reverse(catalytic, FE-EPR) = +902 mV) CV scans. Grey open circles are from all EPR spectra collected (Extended Data Fig. 6 ), and the coloured circles correspond to the EPR data shown in b .
