Electrochemically synthesized Cu–Cu2O composite layers with incorporated carbon nanofibers for artificial light-assisted CO2-based synthesis of hydrocarbons

Composite Cu–Cu 2 O–CNF layers were electrodeposited from an alkaline copper(II) lactate electrolyte containing dispersed carbon nanofibers (CNFs). Synthesized materials were analyzed according to their selectivity, efficiency, and stability in the electrochemical (EC) and photoelectrochemical (PEC) conversion of CO 2 to hydrocarbons. The effect of deposition potential ( E dep. ) on morphology, crystallographic structure, and localization of valence and conduction bands, as well as EC and PEC performance, was investigated. Faradaic efficiencies ( FE ) towards the formation of C 2 H 4 , CH 4 , CO, and H 2 were evaluated both in the dark and under illumination using various conversion potentials in CO 2 -saturated KHCO 3 solution. The maximal FE for the formation of CH 4 and C 2 H 4 , considered as most valuable conversion products, were observed in the presence of light and achieved 9.87% and 17.53%, respectively. Both were observed at conversion potential ( E conv. ) of −0.893 V ( vs . RHE). The highest FE for C 2 H 4 was achieved for the Cu–Cu 2 O–CNF layer electrodeposited at −400 mV ( vs. Ag/AgCl), while for CH 4 for the layer electrodeposited at −375 mV ( vs. Ag/AgCl). The stability of the electrodeposited layer was analysed based on SEM, XPS, and WD-XRF analyses. The obtained results demonstrated that the incorporation of CNFs into the deposited layers had a significant effect on the band structure of the electrodeposited composites. Moreover, it was also observed that the both E dep. and the E conv. significantly affected the EC and PEC performances of the electrodeposited layers. • Cu–Cu 2 O coatings with embedded carbon nanofibers were electrodeposited. • Carbon nanofibers notably altered the band structure of the electrodeposited layers. • Maximal Faradaic efficiency for CH 4 and C 2 H 4 were 9.87 and 17.53 %, respectively. • The presence of carbon nanofibers extended the lifetime of charge carriers.