Tailoring dual-hydrophobic microenvironment for tandem CO2/CO feedstock to enhance CO2 electroreduction on Cu-based catalysts

Achieving high selectivity for value-added products in the electrochemical reduction of CO2 remains challenging due to 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 concentration of CO2 and enhances the dimerization of *CO-*CO. Comprehensive investigation using X-ray absorption spectroscopy, in situ infrared spectroscopy and molecular dynamics simulations indicates 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 of 60.54% for C2+ products, 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.