Steering C–C Coupling by Hollow Cu₂O@C/N Nanoreactors for Highly Efficient Electroreduction of CO₂ to C₂₊ Products

Abstract Electrochemical CO₂ reduction reaction offers a promising pathway to transform renewable electricity into value‐added fuels and feedstocks in the form of chemical energy. However, the *CO intermediates tend to obtain protons or electrons to generate C₁ products. The Cu⁺, an active catalytic site for C₂₊ products, is easily reduced to Cu⁰ at cathodic potentials. Herein, a hollow cuprous oxide protected by a thin N‐doped carbon shell (H–Cu₂O@C/N) as an efficient nanoreactor to stabilize the Cu⁺ species and enhance the coverage concentration of *CO on the local catalyst surface under the spatial confinement effect is designed, which efficiently accelerates C–C coupling to generate C₂₊ products. As a result, H–Cu₂O@C/N exhibits an outstanding C₂₊ Faradaic efficiency of 75.9% with a partial current density of 248.8 mA cm⁻² in the membrane electrode assembly (MEA) electrolyzer. Density functional theory combined with operando characterizations confirm that the N‐doped carbon layer protects the Cu⁺ active species from electrochemical reduction, and the high coverage density of *CO from spatial confinement effect lowers the reaction barrier of *CH₂CHO, thereby promoting C–C coupling. This work offers invaluable insights into the spatial confinement effect for boosting the steering C–C coupling in Cu‐based catalysts for efficient electroreduction of CO₂ to C₂₊ products.