Integrating Cu+/Cu0 sites on porous nitrogen-doped carbon nanofibers for stable and efficient CO2 electroreduction to multicarbon products

The Cu⁺/Cu⁰ sites of copper-based catalysts are crucial for enhancing the production of multicarbon (C₂₊) products from electrochemical CO₂ reduction reaction (eCO₂RR). However, the unstable Cu⁺ and insufficient Cu⁺/Cu⁰ active sites lead to their limited selectivity and stability for C₂₊ production. Herein, we embedded copper oxide (CuO_x) particles into porous nitrogen-doped carbon nanofibers (CuO_x@PCNF) by pyrolysis of the electrospun fiber film containing ZIF-8 and Cu₂O particles. The porous nitrogen-doped carbon nanofibers protected and dispersed Cu⁺ species, and its microporous structure enhanced the interaction between CuO_x and reactants during eCO₂RR. The obtained CuO_x@PCNF created more effective and stable Cu⁺/Cu⁰ active sites. It showed a high Faradaic efficiency of 62.5% for C₂₊ products in H-cell, which was 2 times higher than that of bare CuO_x (∼31.1%). Furthermore, it achieved a maximum Faradaic efficiency of 80.7% for C₂₊ products in flow cell. In situ characterization and density functional theory (DFT) calculation confirmed that the N-doped carbon layer protected Cu⁺ from electrochemical reduction and lowered the energy barrier for the dimerization of *CO. Stable and exposed Cu⁺/Cu⁰ active sites enhanced the enrichment of *CO and promoted the C–C coupling reaction on the catalyst surface, which facilitated the formation of C₂₊ products.