Establishment of Gas-Liquid-Solid Interface on Multilevel Porous Cu₂O for Potential-Driven Selective CO₂ Electroreduction toward C₁ or C₂ Products

Copper-based catalysts demonstrate distinctive multicarbon product activity in the CO₂ electroreduction reaction (CO₂RR); however, their low selectivity presents significant challenges for practical applications. Herein, we have developed a multilevel porous spherical Cu₂O structure, wherein the mesopores are enriched with catalytic active sites and effectively stabilize Cu⁺, while the macropores facilitate the formation of a "gas-liquid-solid" three-phase interface, thereby creating a microenvironment with an increasing water concentration gradient from the interior to the exterior. Potential-driven phase engineering and protonation synergistically optimize the reaction pathway, facilitating a switch between CO and C₂H₄. At a low current density of 100 mA cm^-2, the faradaic efficiency (FE) for CO reaches an impressive 96.97%. When the current density increases to 1000 mA cm^-2, FE_C2H4 attains 53.05%. Experiments and theoretical calculations indicate that at lower potentials, the pure Cu₂O phase diminishes the adsorption of *CO intermediates, while weak protonation inhibits hydrogen evolution reactions, thereby promoting CO production. Conversely, at more negative potentials, the Cu⁰/Cu⁺ interface and strong protonation generate locally elevated concentrations of *CO and *COOH intermediates, which enhance C-C coupling and deep hydrogenation, ultimately improving selectivity toward C₂₊ products. This study provides novel insights into the rational design of copper-based catalysts for customizable CO₂ electroreduction products.