Tuning the electrocatalytic properties in accordance with the intended application is a key challenge in electrochemical reduction of CO2 (CO2R) to value-added chemicals. One of the common strategies to achieve desired electrocatalytic properties is tailoring active sites in an electrocatalyst by introducing another metal to one metal surface. In this study, we investigated electrocatalytic behaviors of various bimetallic electrocatalysts for CO2R, in which tiny amounts of metal atoms were added to Cu(100) surface. A trisource physical vapor deposition system was used to epitaxially deposit a 100-nm Cu(100) film onto Si(100) substrate, followed by introducing 1-Å-equivalent another metal M (M: Ag, Au, In, Mo, etc.) atoms onto the Cu(100) surface in vacuum. Atomic force microscopy and X-ray photoelectron spectroscopy guaranteed that M certainly existed on Cu and the M/Cu electrocatalyst had a smooth surface whose roughness was ±2 nm. The M/Cu electrocatalyst was supplied to a series of 15-min electrolysis in 0.1 mol dm−3 KHCO3 aqueous solution at potentials ranging from −0.6 to −1.1 V with respect to reversible hydrogen electrode at pH 6.8. Gaseous and liquid products were quantified with gas chromatography and nuclear magnetic resonance, respectively. A series of electrocatalytic evaluation indicated that partial current density was suppressed by introducing M atoms onto Cu(100). For activity, the M atoms on Cu(100) might invoke a poisoning effect. This suggests that metal ion impurities in an electrolyte solution should become a cause of deterioration in electrocatalytic activity of Cu. Faradaic efficiency depended on M atoms on Cu(100). Some M elements enhanced hydrogen evolution reaction and other M elements improved the selectivity for C2 oxygenates. For selectivity, the M atoms on Cu(100) might bring an ensemble effect. Details of electrocatlytic properties of various bimetallic electrocatalysts and classification of these electrocatalysts will be explained in the meeting.

Electrochemical reduction of carbon dioxide over bimetallic metal-on-copper electrocatalysts

255th National Meeting (2018)

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