Effectively Increased Efficiency for Electroreduction of Carbon Monoxide Using Supported Polycrystalline Copper Powder Electrocatalysts

Abstract

Many electrocatalysts can efficiently convert CO2 to CO. However, the further conversion of CO to higher-value products was hindered by the low activity of the CO reduction reaction and the consequent lack of mechanistic insights for designing better catalysts. A flow-type reactor could potentially improve the reaction rate of CO reduction. However, the currently available configurations would pose great challenges in reaction mechanism understanding due to their complex nature and/or lack of precise potential control. Here we report, in a standard electrochemical cell with a three-electrode setup, a supported bulk polycrystalline copper powder electrode reduces CO to hydrocarbons and multicarbon oxygenates with dramatically increased activities of more than 100 mA cm–2 and selectivities of more than 80%. The high activity and selectivity that was achieved demonstrates the practical feasibility of electrochemical CO or CO2 (with a tandem strategy) conversion and enables the experimental exploration of the CO reduction mechanism to further reduced products.

Hydroxide Is Not a Promoter of C2+ Product Formation in the Electrochemical Reduction of CO on Copper

“…While these results seem to suggest a quite feasible way to promote CO 2 electroreduction towards more valuable products, that is, to increase the electrolyte pH, major inconsistencies exist between this hypothesis and the current mechanistic understanding of the formation of C 2+ products . As revealed by recent experimental and computational investigations, the rate determining step (RDS) of C 2+ product formation is the dimerization of two CO ads through Langmuir–Hinshelwood process which does not include proton transfer . Thus, the C 2+ product formation rate is not expected to show such a strong dependence on the electrolyte pH.…”

Sustainable Membrane‐Coated Electrodes for CO2 Electroreduction to Methanol in Alkaline Media

“…[52] For all the electrodes tested in this work, the current densities increased with increasing potential, although the lower potentials (À 0.5 V and À 0.3 V vs Ag/AgCl) are not included in Table 2 because the current densities generated in those conditions were too low to make the calculations reliable. [17,51] The uncoated GDE prepared in this work generated higher current densities and increased methanol production than the pure CS : PVA MCE, with a FE for methanol of 40.11 % and 19.71 %, respectively. [17,51] The uncoated GDE prepared in this work generated higher current densities and increased methanol production than the pure CS : PVA MCE, with a FE for methanol of 40.11 % and 19.71 %, respectively.…”

“…The decreasing FE to methanol with increasing potential and current density at higher overpotentials can be allocated to the HER as the dominating reaction. [17,51] The uncoated GDE prepared in this work generated higher current densities and increased methanol production than the pure CS : PVA MCE, with a FE for methanol of 40.11 % and 19.71 %, respectively. These results are attributed to the higher accessibility of CO 2 to the catalyst in the uncoated GDE, and confirmed that the membrane over-layer was posing an additional resistance to transport.…”

“…The pH of the KOH 1 M electrolyte solution was 14.07 as-prepared and after aeration with N 2 , while this value descended to 10.5 after saturation with CO 2 due to partial carbonation of KOH, but this was constant along the voltammetry electrolysis experiment as was the pH. [17,51] In the CO 2 saturated electrolyte, a reduction peak appeared at 0.25 V vs RHE, attributed to CO 2 RR. In Figure 2, the reduction activity observed in the red voltammograms (no CO 2 ) can be only be attributed to the electrode or H 2 O reduction (HER) contributions.…”

“…[43] For all the electrodes tested, notorious current reductions were observed at overpotentials higher than À 0.5 V vs RHE, where HER is the predominant reaction. [17,51] In the CO 2 saturated electrolyte, a reduction peak appeared at 0.25 V vs RHE, attributed to CO 2 RR. This reduction activity was more significant for the MCEs with Cu-UZAR-S3/CS : PVA and Cu-Y/CS : PVA MMMs as membrane over-layers, whose voltammograms are represented in Figures 2e and 2f, respectively.…”