Porous Cu/C nanofibers promote electrochemical CO2-to-ethylene conversion via high CO2 availability

Abstract

In the CO2 reduction reaction (CO2RR), efficient CO2 mass transport is important to facilitate CO2-to-ethylene (C2H4) 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 CO2-to-C2H4 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 CO2 (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 CO2 mass transport and CO2 adsorption for high CO2 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 C2H4 faradaic efficiency (FE) of 39.5% at −1.27 V (vs. RHE), 1.7-fold improvement from the C2H4 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 CO2RR under CO2 deficient conditions and analyzing the in situ Raman spectra reveal that enhanced CO2 mass transport and CO2 adsorption can facilitate CO2 availability with high *CO coverage for efficient C2H4 production. © 2024 The Royal Society of Chemistry.