Abstract
Achieving high selectivity for value-added products in the electrochemical reduction of CO(2) remains challenging due to severe hydrogen evolution, sluggish CO(2) mass transport and low *CO coverage. Herein, we integrate aerophilic SiO(2) and polymer-functionalized copper nanoparticles (Cu-poly) to construct a hierarchical-hydrophobic Cu-poly/SiO(2) composite, which limits the accessibility of H(2)O, improves the local concentration of CO(2) 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 SiO(2) elevate the oxidation state of Cu species, enhance the CO(2) diffusion coefficients (from 5.27 × 10(-7) on Cu to 8.81 × 10(-7) cm(2) s(-1) on Cu-poly/SiO(2)) and enrich the local *CO concentration. The Cu-poly/SiO(2) electrode delivers an enhanced faradaic efficiency of 60.54% for C(2+) 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 C(2)H(4) 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 CO(2) and in situ-generated *CO.