Electrochemical Reduction of CO₂ at Copper Nanofoams

Abstract

We report the electrochemical reduction of CO2 at copper foams with hierarchical porosity. We show that both the distribution of products formed from this reaction and their faradaic efficiencies differ significantly from those obtained at smooth electropolished copper electrodes. We attribute these differences to be due to high surface roughness, hierarchical porosity, and confinement of reactive species. We provide preliminary evidence in support of these claims.

RETRACTED ARTICLE: An overview of CO2 electroreduction into hydrocarbons and liquid fuels on nanostructured copper catalysts

“…<1% at −1.1 V). This value increases to 37% at −1.5 V, which is the highest value of Faraday efficiency reported to date for HCOOH at a copper electrode (33). Furthermore, the production of propylene has been observed for the first time on a high surface area nanostructured copper foam electrode from CO 2 reduction ( Figure 1).…”

“…Nanostructured copper has been reported as an exclusive novel material for the electrochemical reduction of CO 2 into hydrocarbons with high Faraday efficiency and selectivity (33,34,42,(49)(50)(51)(52)(53). The onset potential for the reduction of CO 2 at porous copper foam was −1.0 V vs. Ag/AgCl with the formation of formic acid (HCOOH) initially ( Figure 1).…”

“…A series of steps (1)(2)(3)(4)(5)(6) are predicted for the electroreduction of CO 2 at the copper electrode (33). The asterisk (*) in any reaction indicates either a surface bound specie or a vacant active site.…”

“…Due to their unique properties, such as enlarged specific surface area and 2-and 3-dimensional interpenetrating structures, nanostructured metals can provide easy diffusion pathways to the substrate to access the electrolyte ions and a large number of active sites for the catalysis, leading to a faster reaction with high efficiency (30)(31)(32). Recently, a very promising nanostructured material, namely, copper foam with hierarchical porosity, was reported for the reduction of CO 2 with high rate and selectivity for hydrocarbons (33). An outstanding discovery along this way, reported by Kanan's group (34), was the use of oxide-derived nanostructured copper for the reduction of carbon monoxide (CO) into hydrocarbons and liquid fuels at low overpotentials with high Faraday efficiencies.…”

“…However, efficient and durable electrocatalysts for the electroreduction of CO 2 and its derivatives into desirable fuels are not available at the present (37)(38)(39). Many catalysts can reduce the CO 2 to carbon monoxide (CO) (33,(40)(41)(42)(43) but the synthesis of liquid fuels requires that CO should be further reduced by using H 2 O as H + ion source. CO is a derivative of CO 2 which acts as an intermediate during the production of hydrocarbons.…”