Long-Range Confinement-Driven Enrichment of Surface Oxygen-Relevant Species Promotes C−C Electrocoupling in CO₂ Reduction

CO₂ reduction is a highly attractive route to transform CO₂ into useful feedstocks, of which C₂ products are more desired than C₁, yet face high kinetic barriers of C−C electrocoupling. Here, the engineering of pore-enabled local confinement reaction environments is reported for tuning the enrichment of surface-adsorbed oxygen-relevant species and the establishment of their pronounced benefits in promoting C−C coupling over oxide-derived Cu-based catalysts. A new approach of utilizing the microphase separation of a block copolymer is developed to fabricate bicontinuous mesoporous CuO nanofibers (CuO-BPNF). The enhanced confinement from long-range mesochannels enables the adsorption of OH_ad/O_ad on the Cu surface at a wide negative potential range of −0.7 – −1.3 V in CO₂ reduction, which cannot be achieved over conventional deficient and short-range pores. Constant-potential DFT calculations reveal that the surface-bound oxygen species weakens *CO affinity with the Cu (111) surface and lowers the kinetic barriers for both *CO−CO dimerization and *CO hydrogenation to enable *CO−CHO coupling. Accordingly, a CO₂-to-C₂ Faradaic efficiency of 74.7% over CuO-BPNF is shown, significantly larger than counterparts with conventional pores. This work offers a general design principle of confinement engineering to manage the adsorption of reactive species for steering reaction pathways in interfacial catalysis.