Fig. 4: The operando and in situ SERS for R-8-Cu-12 and R-Cu-np.

a The operando XANES spectra at the Cu K-edge for R-8-Cu-12 at different potentials during CO2 electrolysis. b The corresponding Fourier transforms FT(k3w(k)) for R-8-Cu-12 at different potentials during CO2 electrolysis. c The in situ SERS spectra over R-8-Cu-12 at different potentials during CO2 electrolysis. d The in situ SERS spectra over R-Cu-np at different potentials during CO2 electrolysis.