H-cell, catalyst ink was prepared by dispersing 2 mg of catalyst in 1 mL of ethanol with 20 μL 5 wt.% Nafion solution (Sigma Aldrich, Nafion 117, 5 wt.%) and sonicated for 1 h. Then 200 μL of the ink was drop-casted on the glassy carbon working electrode and subsequently dried naturally. The loading was 0.4 mg/cm 2 . The electrochemical performance was carried out in a customized glass H-cell. A platinum and Ag/AgCl were used as the counter and reference electrodes, respectively. The working electrode was separated from the counter electrode by the Nafion-117 membrane (Fuel Cell Store). Before use, the Ag/AgCl reference was calibrated as reported . All potentials in this study were converted to the reversible hydrogen electrode (RHE) according to the Nernst equation (E (vs. RHE) = E (vs. Ag/AgCl) + 0.231+0.0592×pH). The 10 mL of 0.5 M KHCO3 solution electrolyte was added into the working and counter compartment, respectively. The cell was purged with high-purity CO2 gas (Linde, 99.999 %, 20 sccm) for 30 min prior to and throughout the duration of all electrochemical measurements. The electrochemical measurements were controlled and recorded with a CHI 650E potentiostat. The automatic iR (85%) compensation was used. Gas-phase products were quantified by an online gas chromatograph (Ruimin GC 2060, Shanghai) equipped with a methanizer, a Hayesep-D capillary column, a flame ionization detector (FID) for CO, and a thermal conductivity detector (TCD) for H2. The CO2 flow rate was controlled at 3 sccm using a standard series mass flow controller (Alicat Scientific mc-50 sccm). The liquid products were quantified after electrocatalysis using 1 H NMR spectroscopy with solvent (H2O) suppression. 450 μL of electrolyte was mixed with 50 μL of a solution of 10 mM dimethyl sulfoxide (DMSO) in D2O as internal standards for the 1 H NMR analysis. The concentration of MeOH was calculated using the ratio of the area of the MeOH peak (at a chemical shift of 3.32 ppm) to that of the DMSO internal standard. Electrolyte of 13 CO2 in 0.5 M KH 13 CO3 were prepared by bubbling 13 CO2 into 0.5 M KOH for more than 30 minutes.