The gas products reported were measured by gas chromatography (SRI Model 8610C GC) equipped with a thermal conductivity detector (TCD) and flame ionization detector (FID). The gas flow rate was kept constant at 10 mL/min as measured by a flow meter (Dwyer Instruments, Inc) at the exit of the GDE cell. Ultra-high purity nitrogen gas was used as the carrier gas. The electrochemical cell was directly connected to GC, therefore during reaction the CO2 continuously flowed through the reactor and GC. The gas was sampled from the reaction vessel 30 minutes after applying the reducing potential. Calibration gases at various dilutions were used to establish a calibration curve for accurate product detection.