We have developed broadband sum-frequency generation (BB-SFG) spectroscopy. It enables us to obtain information on in situ electrochemical systems. One of the electrochemical processes is the CO2 reduction on a polycrystalline copper and polycrystalline gold electrode. The antisymmetric C−H stretching modes of methyl group and antisymmetric C−H stretching modes of methylene group were observed on copper electrode surface, no adsorbed CO intermediate was observed. As for the process on gold electrode surface, the adsorbed CO was the main intermediate detected, and CO was observed at a relative high potential (-0.5V vs SCE). In addition, we present some other examples that investigate the electrochemical interface with SFG techniques, such as the potential-dependent nonresonant (NR) SFG.
Figure 1 (a)(b) Potential-dependent BB-SFG spectra of 0.1M CO2-saturated NaHCO3 solution at poly-Cu electrode (C-H region) and poly-Au electrode (CO region). (c) Variations of the wavenumbers (black) and intensities (red) of the CO peak in (b) from the fitting data.
Acknowledgement: This work was financially supported by NSFC (21327901 and 21621091).