Figure 4.

High‐resolution XPS spectra of a FeSi sample after 24 h OER at 10 mA cm⁻². a) Fe 2p spectrum revealing the presence of Fe^III (* denotes the satellite speaks). b) Deconvoluted Si 2p spectrum showing Si^II and Si^IV with a minute amount of residue Si⁰. c) O 1s spectrum with previously observed binding energies of various oxygen species (dotted lines; see Figure S63, Supporting Information, for the direct comparison of the O 1s spectra before and after OER).^{[ 50} , ⁵¹ , ^{52 ]}