Achieving high selectivity for value-added products in the electrochemical reduction of CO2 remains challenging due to the severe hydrogen evolution, sluggish CO2 mass transport and low *CO coverage. Herein, we integrate aerophilic SiO2 and polymer functionalized copper nanoparticles (Cu-poly) to construct a hierarchical-hydrophobic Cu-poly/SiO2 composite, which limits the accessibility of H2O, improves the local CO2 concentration and enhances the dimerization of *CO-*CO. Comprehensive investigations by X-ray absorption spectroscopy, in-situ infrared spectroscopy and molecular dynamics simulations indicate that the polymer and SiO2 elevate the oxidation state of Cu species, enhance the CO2 diffusion coefficients (from 5.27 × 10−7 on Cu to 8.81 × 10−7 cm2 s−1 on Cu-poly/SiO2) and enrich the local *CO concentration. The Cu-poly/SiO2 electrode delivers an enhanced Faradaic efficiency (FE) of 60.54% for C2+ products as compared to 46.1% of Cu at 600 mA cm−2. Notably, a high FE of 36.91% and partial current density of 221.46 mA cm−2 are achieved for C2H4 generation in membrane electrode assembly devices adopting an aqueous bicarbonate electrolyte. This work provides a valuable insight into designing catalytic microenvironments of electrocatalysts for enhancing carbonaceous products by facilitating the co-electrolysis of CO2 and in-situ generated *CO.
