Synergistic Coupling between Nanoconfinement and Grain Boundary Improves Electrocatalytic CO ₂ Reduction to <i>n</i> -Propanol

Cu-based nanomaterials are recognized as the most promising catalysts for electrocatalytic CO2 reduction to produce valuable multicarbon products (C2+). However, the low localized concentration of *C1 and *C2 intermediates and poor availability of active sites limit the CO2 conversion efficiency and selectivity for C2+. Herein, a three-dimensional interconnected self-supporting Cu nanowire array with rich grain boundaries (GB-ICCu) is designed to obtain high production of C2+, especially n-propanol (n-PrOH), due to the synergistic coupling between the nanoconfinement effect and the grain boundary. The finite element simulations and experimental results reveal that the three-dimensional interconnected structure between Cu nanowires, like a nanoscaffolding, induces a pronounced nanoconfinement of *C1 and *C2 intermediates and consequently enhances the selectivity toward n-PrOH. Meanwhile, the rich grain boundaries of the (111) and (200) on the surface of each Cu nanowire also strengthen CO2 activation and intermediate adsorption, thereby reducing the energy barrier for C–C coupling. As a result, a high Faradaic efficiency of 17.47% and a partial current density of 10.44 mA cm–2 for n-PrOH are achieved in the H-type cell, while 12.05% and 77.7 mA cm–2 are achieved in the flow cell, respectively, which present an advance in partial current density of n-PrOH, i.e., the yield rate of n-PrOH. This work provides a strategy and a Cu-based electrocatalyst for C3 synthesis via CO2 reduction.