Stable surface oxygen on nanostructured silver for efficient CO₂ electroreduction

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 M_4,5VV 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.