Selective reduction of CO2 to formate through bicarbonate reduction on metal electrodes: new insights gained from SG/TC mode of SECMElectronic supplementary information (ESI) available: Chemicals, experimental procedures, electrochemical measurements and NMR analysis. See DOI: 10.1039/c4cc03099k

We discovered using SECM of the electro-reduction of CO 2 on a Au substrate in CO 2 -saturated KHCO 3 solutions that (i) formate comes solely from the direct reduction of bicarbonate; and (ii) CO forms only from CO 2 reduction (under low pH conditions) and at higher applied potentials. The results point to the possibility of the selective reduction of CO 2 to the formate product. Using SG/TC mode of SECM it is discovered that HCOO − comes solely from the direct reduction of HCO 3 − and CO from CO 2 at low pH and high applied potentials in CO 2 /HCO 3 − solution on Au and Ag surfaces, pointing to the selective reduction of CO 2 to HCOO − .