3DOM Perovskite Enabled Interfacial Microenvironment Regulation With Accelerated Complete Reconstruction to Grain‐Boundary‐Rich Nano‐Copper for High‐Current C 2+ Electrosynthesis

ABSTRACT Electrochemical CO 2 reduction reaction (CO 2 RR) offers a compelling pathway to convert carbon emissions into value‐added chemicals, yet achieving high activity, selectivity, and durability under industrial conditions remains challenging. Though copper oxides could uniquely promote C 2+ electrosynthesis, their performance is dictated by dynamic oxide reconstruction, which is strongly governed by the interfacial microenvironment. Here, we report direct interfacial microenvironment regulation by constructing a 3D ordered macroporous (3DOM) architecture from layered perovskite La 2 CuO 4 . The 3DOM architecture simultaneously strengthens the surface electric field, elevates local pH, and accelerates mass transport at the interface, driving accelerated and complete reconstruction of La 2 CuO 4 into dendritic grain‐boundary‐rich nano‐copper. Consequently, 3DOM‐La 2 CuO 4 delivers a high C 2+ partial current density of 585 mA cm −2 in a flow cell, outperforming bulk counterpart and most reported Cu‐oxide‐based catalysts. In a membrane‐electrode assembly, stable operation is sustained for ∼ 200 h at 600 mA cm −2 with high C 2+ selectivity. Combined experimental and theoretical analysis identify undercoordinated, compressively strained Cu atoms at grain boundaries as the intrinsic active sites for C 2+ formation, by facilitating * COH formation, stabilizing * OCCOH intermediate, and suppressing the competing hydrogen production. This work establishes electrode‐architecture‐driven microenvironment engineering as a general strategy for directing oxide reconstruction and designing high‐performance CO 2 RR catalysts.