Fig. 1: In situ Co K-edge XAS analysis of [Co-Fe-Pb]O_x.

a–c, XANES data collected for unmodified CFP (a) and [Co–Fe–Pb]O_x-functionalized CFP (b,c) in flowed (1 ml min⁻¹) 0.1 M H₂SO₄ + 5 mM Co²⁺ (a,b) and nominally pure 0.1 M H₂SO₄ (c); black curves show data collected in situ at an open circuit (a) or ex situ for as-deposited catalysts (b,c), whereas coloured curves show in situ spectra at 1.8 (blue), 1.9 (green), 2.0 (orange) and 2.2 V vs RHE (wine). d–f, Rising edge position (d) (at 0.5 normalized intensity; norm. int.)²² vs potential (E) (horizontal ‘OCP’ and ‘as-deposited’ dashed lines correspond to data recorded at open circuit within electrolyte solution and nominally dry samples before analysis, respectively), first derivative (deriv.) of the in situ XANES data collected at 1.9 V vs RHE (e) and FT EXAFS data (f) for [Co-Fe-Pb]O_x in nominally metal-free solution (sky blue), [Co-Fe-Pb]O_x with 5 mM Co²⁺ (wine) and bare CFP with 5 mM Co²⁺ (orange) at 1.9 V vs RHE. [Co-Fe-Pb]O_x was deposited by 1 h galvanostatic (10 mA cm⁻²_geom.) oxidation of quiescent 0.1 M H₂SO₄ containing 5 mM Co²⁺, 1 mM Fe³⁺ and 0.5 mM Pb²⁺ at 23 ± 1 °C. Data for Co(OH)₂ (dashed grey) and CoOOH (dotted grey) references are shown for comparison.

Source data