The catalytic activity of Au25 NCs in CO2RR was obtained using an electrochemical workstation (CHI 600E) with a three-electrode system coupled to a CO2 flow cell. The electrolyte solution was 1 M KOH, and the reference electrode was an Ag/AgCl electrode immersed in saturated KCl solution. An anion-exchange membrane and a platinum plate were used as the ion mobility channel and counter electrode, respectively. The working electrode was prepared by dissolving 1 mg of carbon nanotube and 1 mg Au25 NCs in 0.5 mL of CH2Cl2, creating a uniform dispersion ink containing 10 µL of 5 wt% Nafion solution. This solution was sprayed onto a 1 cm 2 gas diffusion layer (GDL) with a mass loading 2 mg/cm 2 . The potentials were converted to RHE using the following equation: 𝐸(RHE) = 𝐸(Ag/AgCl) + 0.197V + 0.0591 × pH Before the electrochemical CO2 reduction reaction, the cathodic electrolyte was saturated with CO2 for 30 minutes. The cathodic and anodic reaction chambers were separated by an anion exchange membrane. During the CO2RR process, each electrolyte cell contained 30 mL of electrolyte circulated at 40 rpm using a peristaltic pump. The gas products were analyzed quantitatively with a gas chromatograph (GC, Huaai 9560). The Faradaic efficiency (FE) of the gas products was calculated using the formula: