The working electrode was prepared as below: 10 mg catalyst was added into the mixture of 100 μL DI water and 300 μL ethanol. After 10 mins ultrasonication, 100 μL homogeneous catalyst ink was dropped onto the carbon cloth (GDL-CT (W1S1009, Fuel Cells Etc.) and dried in air for 1h. 1M KOH with different concentrations of NaSO4 was used as the electrolyte. Linear sweep voltammetry was measured in the range of 0 ~ 1.18 V (vs. RHE), with a sweep rate of 5 mV s -1 . Potentiostatic electrolysis was performed at room temperature and pressure, with a steady CO2 gas flow which is 10 mL min -1 . The GDE cell was sealed and connected with gas chromatography (GC, SRI 8610C) to qualify the gas products in flow mode. A thermal conductivity detector (TCD) was used for analyzing H2, and flame ionization detector (FID) was used for quantifying CO and CH4. After 30 mins reaction, the electrolyte was collected and analyzed by 1 H nuclear magnetic resonance (NMR, Bruker AVII 500) and confirmed by C NMR (NMR, Bruker AVANCE II 700). 400 μL liquid product was mixed with 400 μL D2O, with dimethyl sulfoxide (DMSO) as an internal standard. The yield of gas and liquid products were calculated based on the calibration curves of the standard samples. The Faradaic efficiency (FE) was calculated by the following formula: εFE = where α is electron transfer number, n is the moles of products, F is the Faraday constant (96485 C mol -1 ), Q is all the charge passed during the reaction.