Marked CO2 Reduction to Generate C1-C3 Products Using Pt0.9Ru0.1/C-Based Membrane Electrode Assembly at Extremely Low Overpotentials.

The electrochemical CO2 reduction reaction (CO2RR) over Pt electrocatalysts in an aqueous solution system yields mainly H2 and a slight amount of carbon-based products. This limitation can be overcome by using a membrane electrode assembly (MEA) containing a Pt/C electrocatalyst without any overpotential. However, the obtained CO2RR product was only CH4. In this study, we investigated the CO2RR using MEA containing a Pt0.9Ru0.1/C electrocatalyst. Consequently, not only methane as a C1 product but also ethanol as a C2 product and acetone as a C3 product were produced at extremely small overpotentials. This is the first time in the literature that ethanol and acetone were produced from the CO2RR over a Pt-Ru-based electrocatalyst. This fact was confirmed through mass spectrometry, gas chromatography, and isotope labeling experiments. The Faradaic efficiencies of CH4, C2H5OH, and CH3COCH3 were 20.6%, 5.9%, and 5.2%, respectively, and the total Faradaic efficiency was 31.7%. The three products were generated via the Langmuir-Hinshelwood mechanism involving adsorbed CO (COads) and H atoms on the electrocatalyst. The adsorption configuration of COads determines the generation of methane, ethanol, and acetone. The C-C coupling reactions occurred through the formation of COads clusters. Our findings promote the production of valuable C2+ compounds from the CO2RR, which is an important CO2 capture, utilization, and storage technology for realizing carbon neutrality.