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

Achieving high activity and selectivity of multi-carbon 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 simu-lations, 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 x 10-10 to 8.46 x 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.