The bicarbonate/carbonate (HCO3 -/CO3 2-) equilibrium was studied using operando SERS to quantif y the induced local alkalization which occurs under CO2 electrolysis conditions. The HCO3 -/CO3 2-equilibrium shifts towards CO3 2-with the increase of pH, resulting in a decrease of the intensity of HCO3 -Raman bands (at 1018 cm -1 and 1365 cm -1 ) and simultaneous increase of CO3 2-band (at 1066 cm -1 ). As shown in Figure , the intensity of this CO3 2-band grew with the applying more negative potentials, especially f or pure Cu f oam. For instance, Cu f oam local pH shifted from 6.8 at OCP into ~11 at -0.7 V, while the local pH of CO-selective bimetallic f oams rose to 9.0 at same potential, providing direct evidence of the local alkalization developed under CO2 electrolysis. Furthermore, HCOO -selective bimetallic foams also showed a local alkalization under CO2 electrolysis, especially at higher applied potentials. Based on these observations, we were curious why these Cu hydroxide/carbonate surface species did not appear in our quasi in-situ glovebox-assisted XPS and XAS analyses. The main dif ference here is that the Raman spectra are acquired during continuous applied bias. Thus, we investigated the effects of bias removal on these detected Cu hydroxide/carbonate peaks to evaluate the possibility of surface transformation at open circuit in the electrolyte. We f ollowed the induced changes in the obtained Raman spectra of our synthesized bimetallic foams over time following the bias removal, while either keeping them inside the same electrolyte or exposing them to air. As seen in Figure , the typical Cu2O/CuO mixture peaks were observed along with a ) b )