Establishment of Gas-Liquid-Solid Interface on Multilevel Porous CuO for Potential-Driven Selective CO Electroreduction toward C or C Products.

Copper-based catalysts demonstrate distinctive multicarbon product activity in the CO electroreduction reaction (CORR); however, their low selectivity presents significant challenges for practical applications. Herein, we have developed a multilevel porous spherical CuO 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 CH. At a low current density of 100 mA cm, the faradaic efficiency (FE) for CO reaches an impressive 96.97%. When the current density increases to 1000 mA cm, FE attains 53.05%. Experiments and theoretical calculations indicate that at lower potentials, the pure CuO phase diminishes the adsorption of *CO intermediates, while weak protonation inhibits hydrogen evolution reactions, thereby promoting CO production. Conversely, at more negative potentials, the Cu/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 C products. This study provides novel insights into the rational design of copper-based catalysts for customizable CO electroreduction products.