Electroreduction of carbon monoxide to methane and ethylene at a copper electrode in aqueous solutions at ambient temperature and pressure

Abstract

Carbon monoxide is a substance of primary importance from the viewpoint of utilization of carbon resources. Hydrogenation of CO in the gas phase has been widely studied, but only a small number of papers has been published about electrochemical reduction. Electroreduction of CO did not proceed effectively according to the previous papers;1 the cathodic partial currents for electroreduction of CO were very small, not exceeding 5 X 10"5 A cm"2. We briefly describe here an electroreduction of CO at a Cu cathode in aqueous solutions. This procedure allows an effective cathodic reduction of CO to form hydrocarbons and alcohols with appreciable current densities.An electrodeposited copper sheet (purity 99.999%), donated by Sumitomo Metal Mining Co. Ltd., was cut into an electrode (20 X 20 X 1 mm) with a copper lead strip attached. We did not mount the electrode in resin in order to avoid possible contamination of the boundary interface of electrode/resin. The electrode was polished with fine emery paper (no. 1500), electrolytically polished in 85% phosphoric acid for ca. 2 min at ambient temperature, and then rinsed with doubly distilled deionized water. Electrochemical measurements were conducted at 18 °C with a three-compartment cell in which two anode compartments faced each side of the Cu electrode. The cathode compartment (36-mm inner diameter) was separated from the two anodes with sheets of cation exchange membrane (Selemion). The potential of the cathode was measured with respect to an Ag/AgCl reference electrode. The electrode potential was corrected for the IR drop between the Luggin capillary tip and the cathode. The catholyte (60 mL) was prepared from doubly distilled deionized water and reagent grade chemicals. The call) (a)

RETRACTED ARTICLE: An overview of CO2 electroreduction into hydrocarbons and liquid fuels on nanostructured copper catalysts

“…Although the conversion mechanism of CO 2 to liquid fuels is not very clear at present but it is widely accepted that CO 2 is first reduced to CO and then it is further converted to alcohols and other hydrocarbons through multistep electron transfer pathways. Earlier studies have found that CO reduction on Cu results in similar products as obtained from CO 2 reduction, proposing that CO was an intermediate in the reduction of CO 2 (44)(45)(46).…”

“…Polycrystalline Cu foil had shown lower current densities and H 2 was the only detectable product under these similar conditions. Another study has shown 22% total Faraday efficiency for CO reduction at very negative potentials (around −0.7 V vs. RHE) and its Faraday efficiency for oxygenates was only 7% (45). A maximum of 65% Faraday efficiency from CO reduction have been reported for polycrystalline copper foil at −0.9 V vs. RHE but Faraday efficiency of oxygenates was only 10% (70).…”

“…They predicted a little decrease in the Cu-C bonds and an increase in the C-O bonds to around 1.25 Ǻ; hence, they estimated a mostly double bond character (71,72). When Cu is supplied with only CO in the absence of carbon dioxide, hydrocarbons and multi-carbon oxygenates are produced, but much negative potentials are still required to stimulate CO reduction over H 2 evolution (45,70). Energetic efficient electrolysis is impeded by large overpotentials and favor the production of hydrocarbons over multi-carbon oxygenates.…”

“…Currently, many reports have been presented for each of the CO 2 reduction products, exhibiting a high Faraday efficiency, high energetic efficiency or high current density, but combining all these figures of merit has been a challenge (45,47,48,70).…”

Atomistic Mechanisms Underlying Selectivities in C1 and C2 Products from Electrochemical Reduction of CO on Cu(111)

“…8,9 Thus, CORR determines the overpotentials and selectivities for additionally reduced products from CO 2 RR, so we focus here on CORR. Cu(111) serves as a model electrocatalyst that delivers the essential chemistry of CORR, 10 and it has been confirmed to be stable under electrochemical working conditions, 11 so we focus here on CORR on Cu(111).…”