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

Abstract

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 (CuOx) particles into porous nitrogen-doped carbon nanofibers (CuOx@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 CuOx and reactants during eCO2RR. The obtained CuOx@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 CuOx (∼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.