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

Abstract

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.