Electrochemical Reduction of CO2 to CH3OH at Copper Oxide Surfaces

TLDR

The direct reduction of CO₂ to CH₃OH is known to occur on oxidized Cu electrodes. The study investigates the yield behavior of an electrodeposited cuprous oxide thin film and its relationship to surface chemistry compared to air‑oxidized and anodized Cu electrodes. The authors compare the cuprous oxide thin film to air‑oxidized and anodized Cu electrodes to assess how surface chemistry influences CO₂ reduction to CH₃OH. Cu(I) species in the electrodeposited cuprous oxide film yield higher CH₃OH production (43 µmol cm⁻² h⁻¹, 38 % Faradaic efficiency) than air‑oxidized or anodized Cu, and the yields are dynamic as the oxides reduce to metallic Cu during operation, suggesting Cu(I) stability enables continuous CH₃OH generation comparable to photoelectrochemical and hydrogenation processes.

Abstract

The direct reduction of CO2 to CH3OH is known to occur at several types of electrocatalysts including oxidized Cu electrodes. In this work, we examine the yield behavior of an electrodeposited cuprous oxide thin film and explore relationships between surface chemistry and reaction behavior relative to air-oxidized and anodized Cu electrodes. CH3OH yields (43 μmol cm−2 h−1) and Faradaic efficiencies (38%) observed at cuprous oxide electrodes were remarkably higher than air-oxidized or anodized Cu electrodes suggesting Cu(I) species may play a critical role in selectivity to CH3OH. Experimental results also show CH3OH yields are dynamic and the copper oxides are reduced to metallic Cu in a simultaneous process. Yield behavior is discussed in comparison with photoelectrochemical and hydrogenation reactions where the improved stability of Cu(I) species may allow continuous CH3OH generation.