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Abstract

Operando nuclear resonant inelastic X‐ray scattering (NRIXS) and X‐ray absorption fine‐structure spectroscopy (XAFS) measurements have been used to gain insight into the structure and surface composition of FeCu and FeAg nanoparticles (NPs) during the CO 2 electrochemical reduction (CO 2 RR) and to extract correlations with their catalytic activity and selectivity. The formation of a core‐shell structure during CO 2 RR for FeAg NPs was inferred from the analysis of the operando NRIXS data (phonon density of states, PDOS) and XAFS measurements. Electrochemical analysis of the FeAg NPs revealed a faradaic selectivity of ~ 36 % for CO in 0.1 M KHCO 3 at ‐1.1 V vs RHE, similar to that of pure Ag NPs. In contrast, a predominant selectivity towards H 2 evolution is obtained in the case of the FeCu NPs, analogous to the results obtained for pure Fe NPs, although small Cu NPs have also been shown to favor H 2 production. These results, together with the findings from NRIXS and XAFS, revealed that Ag is preferentially present on the surface of the FeAg NPs during CO 2 RR, while Cu is also likely to be mainly distributed on the surface of the FeCu NPs but with a larger degree of intermixing with Fe.