Synergistic Management of Interfacial Wettability and Local pH by SiO₂ Carrier Enables Long-Term Stable CO₂ Electrolysis to CO

The zero-gap electrolytic cell with an anion-exchange membrane (AEM) is widely used for electrochemical CO2 reduction reaction (CO2RR) with strong potential for industrialization. However, flooding and salt deposition on the gas diffusion electrode (GDE) represent two critical challenges that impede CO2 mass transfer and constrain the long-term stable operation of the above membrane assembly electrode configuration. In this work, a collaborative management strategy involving interface wettability engineering and dynamic pH regulation is proposed to resolve these two issues simultaneously based on a specially designed Ag/SiO2 catalyst, which produces CO in CO2RR. The uniform SiO2 spheres were decorated with an aminopropyl triethoxysilane modifier to enhance the hydrophobicity of the catalyst-coated GDE, exhibiting an increased contact angle of 151.84°. The Ag/SiO2 catalyst was obtained after loading Ag nanoparticles and coating uniformly on a GDE. By leveraging the amphoteric characteristics of SiO2, the excess OH– at the reaction interface was effectively neutralized, thereby reducing the K+ accumulation (KHCO3) rate by 76%, in comparison with the conventional Ag/C catalyst. This strategy allows the electrolytic cell to operate continuously for over 300 h at a current density of 100 mA cm–2 while maintaining the Faraday efficiency of CO stably above 90%. Through hydrophobic modification of the SiO2 carrier, both issues of flooding and salt deposition were effectively suppressed, thereby offering valuable insights for ensuring long-term stable CO2 electrolysis in the AEM zero-gap electrolytic cell.