Tracking the evolution of transition metal single atom catalysts for the CO2 electroreduction: an operando HERFD XANES and XES study

Transition metal-nitrogen-doped carbons (TMNCs) are an attractive class of systems that shows promise application for the CO2 electroreduction reaction (CO2RR). However, despite important advances in the field, some open questions remain about the nature, stability and evolution of the possible metal active sites during CO2RR under static and pulsed potential conditions. Herein, we propose, for the first time, an operando combined a HERFD XANES and XES study targeting the CO2RR active species for a series of TMNCs materials (Co, Cu, Fe and Ni TMNCs), relevant for CO2RR research. The unique structure/electronic sensitivity of these spectroscopic techniques will be fundamental to have access the finest spectral features characterizing the CO2RR active centers, their reactive intermediates and possible C/O ligands, allowing us to clarify the main reaction steps and explain the TMNCs catalytic properties.