It was recently demonstrated that the sequential or seriatim application of electrochemical scanning tunneling microscopy (ECSTM) and differential electrochemical mass spectrometry (DEMS) enables the correlation, under actual reaction conditions, of a specific structure on a Cu electrode surface with the generation of a particular CO-reduction product. As an extension of the operando hyphenated-technique approach, we paired ECSTM with electrochemical polarization-modulation IR reflection-absorption spectroscopy (ECPMIRS) to identify a delineating potential that affected the coverage, the molecular orientation, and the adlattice structure of CO adsorbed on Cu(100) in 0.1 M KOH under CO2-reduction conditions. The results may have significant ramifications on the theory-based reaction mechanism for the formation of C2 compounds, as well as insights into the mode of coordination between CO and zerovalent Cu. Keywords: Seriatim ECSTM-ECPMIRS, Operando electrode-surface nanoscopy, Operando molecular vibrational spectroscopy, Potential-dependent CO adsorption on Cu(100), Electrochemical reduction of CO2 in alkaline solution
