Porous Cu/C nanofibers promote electrochemical CO-to-ethylene conversion high CO availability

In the CO 2 reduction reaction (CO 2 RR), efficient CO 2 mass transport is important to facilitate CO 2 -to-ethylene (C 2 H 4 ) conversion which requires *CO dimerization. Here, we report carbon (C) shell-augmented Cu-embedded porous C nanofibers (CNFs) to elucidate the effects of mesoporous C on CO 2 -to-C 2 H 4 conversion. The mesoporous C structures were controlled by harnessing blended polymers (PAN + PMMA) which have distinct thermal decomposition behaviors and by inducing selective C oxidation during calcination. Furthermore, we found that selective C oxidation can induce the C precipitation from the CO (g) and CO 2 (g) by the Boudouard reaction. This enabled the formation of C shells on the surface of Cu active sites. C shell-augmented Cu/CNFs having the highest surface area of mesopores enhanced the CO 2 mass transport and CO 2 adsorption for high CO 2 availability. Porous Cu/CNFs, fabricated by the calcination of electrospun Cu-precursor + blended polymer nanofibers (NFs) with the 60% PMMA ratio and selective C oxidation, induced an efficient C 2 H 4 faradaic efficiency (FE) of 39.5% at −1.27 V ( vs. RHE), 1.7-fold improvement from the C 2 H 4 FE of 23.2% at −1.25 V ( vs. RHE) in Cu/CNFs, fabricated by full reduction without PMMA (the lowest surface area of mesopores). Investigating the CO 2 RR under CO 2 deficient conditions and analyzing the in situ Raman spectra reveal that enhanced CO 2 mass transport and CO 2 adsorption can facilitate CO 2 availability with high *CO coverage for efficient C 2 H 4 production. C-shell-augmented porous Cu/CNFs can enhance CO 2 availability for efficient C 2 H 4 production via promoted CO 2 mass transport and CO 2 adsorption.