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.

The CO2 electroreduction (CO2RR) offers a promising way to address CO2 emission and high-value ultilizaiton but it remains challenging to steer the selectivity of products due to complicated reaction pathways....

The electrochemical reduction of carbon dioxide into multi‐carbon products (C2+) using renewably generated electricity provides a promising pathway for energy and environmental sustainability. Various oxide‐derived copper (OD‐Cu) catalysts have been showcased, but still require high overpotential to drive C2+ production owing to sluggish carbon–carbon bond formation and low CO intermediate (*CO) coverage. Here, the dilemma is circumvented by elaborately devising the OD‐Cu morphology. First, computational studies propose a hollow and hierarchical OD‐Cu microstructure that can generate a core–shell microenvironment to inhibit CO evolution and accelerate *CO dimerization via intermediate confinement and electric field enhancement, thereby boosting C2+ generation. Experimentally, the designed nanoarchitectures are synthesized through a heteroseed‐induced approach followed by electrochemical activation. In situ spectroscopic studies further elaborate correlation between *CO dimerization and designed architectures. Remarkably, the hierarchical OD‐Cu manifests morphology‐dependent selectivity of CO2 reduction, giving a C2+ Faradaic efficiency of 75.6% at a considerably positive potential of −0.55 V versus reversible hydrogen electrode.

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