Tailoring the Catalytic Microenvironment of Cu2O with SiO2 to Enhance C2+ Product Selectivity in CO2 Electroreduction

Achieving high activity and selectivity of multicarbon products in the CO2 reduction reaction (CO2RR) on Cu-based electrocatalysts remains challenging due to the limited concentration of local OH–, sluggish CO2 diffusion, and competitive hydrogen evolution reaction. Herein, we report aerophilic nanocomposites of hydrophobic SiO2 aerosol and Cu2O nanocubes to tailor the microenvironment for enhancing CO2 electroreduction in 0.1 M KHCO3 aqueous electrolyte. Combined in situ infrared analysis, molecular dynamics simulations, and density functional theory calculations reveal that the composite Cu2O/SiO2 enriches the local hydroxyl by blocking the reaction between OH– and HCO3–, accelerates CO2 diffusion coefficient (from 2.67 × 10–10 to 8.46 × 10–10 m2 s–1), and renders a lower dissociation energy of H2O than bicarbonate (0.49 vs 1.24 eV on Cu2O (111)) as compared to neat Cu2O. Consequently, Cu2O/SiO2 promotes the formation of C2+ products (Faradaic efficiency FEC2+ from 52.4 to 75.6%) and suppresses hydrogen generation (FEH2 from 30.0 to 9.6%) at −1.2 V versus reversible hydrogen electrode. The results provide insight into the selectivity improvement of CO2RR electrocatalysis by regulating the local microenvironment of alkalinity, H2O transportation, and CO2 permeability.