Stable surface oxygen on nanostructured silver for efficient CO2 electroreduction

- Nanostructured Ag surface exhibited enhanced electrochemical CO2 reduction activity.
- Surface analysis revealed that enhanced nanostructured Ag possess locally stable surface O.
- Surface O is suggested to contribute to COOH and CO intermediate interaction for CO2 reduction.

We investigated properties involved in the enhancement in electrocatalytic carbon dioxide (CO2) reduction to carbon monoxide (CO) in electrochemically treated Ag surfaces with surface sensitive analysis methods such as Auger spectroscopy, atomic force microscopy (AFM) coupled with Kelvin probe force microscopy (KPFM) techniques, and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The absence of Ag M4,5VV Auger signals for the electrochemically treated Ag indicate the presence of localized surface oxygen (O) which survives on the best performing Ag electrocatalysts even in the reductive environment of the CO2 reduction reaction. Higher work functions were located at the nanostructure boundaries observed by KPFM/AFM implying the higher surface O concentrations in these regions. Furthermore, NEXAFS measured the selective prominence of π* states over σ* in the active Ag surfaces which suggests stronger interaction with intermediates of CO2 reduction while minimizing the -OH interaction contributing to increase CO2 reduction activity and selectivity. These results provide direction in engineering surfaces for efficient electrochemical CO2 conversion.

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