Fig. 5: Operando Raman spectroscopy.

Spectra were collected for pristine Cu (gray) and Cu-5 (green) during CO2 reduction at two regions, i.e., a low wavenumber range at 200–700 cm−1 and b high wavenumber range at 1700–2250 cm−1 at an applied potential of −0.9 V versus RHE in CO2-saturated 0.1 M KHCO3. Source data are provided as a Source Data file.