Structure-Tailored Surface Oxide on Cu-Ga Intermetallics Enhances CO 2 Reduction Selectivity to Methanol at Ultralow Potential

• Published in: Advanced materials (Weinheim) Vol. 34; no. 19; p. e2109426
• Main Authors: Bagchi, Debabrata, Raj, Jithu, Singh, Ashutosh Kumar, Cherevotan, Arjun, Roy, Soumyabrata, Manoj, Kaja Sai, Vinod, C P, Peter, Sebastian C
• Format: Journal Article
• Language: English
• Published: Germany 01.05.2022
• Subjects: electrochemistry; methanol; CO 2 reduction
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202109426

Electrochemical CO reduction reaction (eCO RR) is performed on two intermetallic compounds formed by copper and gallium metals (CuGa and Cu Ga ). Among them, CuGa selectively converts CO to methanol with remarkable Faradaic efficiency of 77.26% at an extremely low potential of -0.3 V vs RHE. The high performance of CuGa compared to Cu Ga is driven by its unique 2D structure, which retains surface and subsurface oxide species (Ga O ) even in the reduction atmosphere. The Ga O species is mapped by X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) techniques and electrochemical measurements. The eCO RR selectivity to methanol are decreased at higher potential due to the lattice expansion caused by the reduction of the Ga O , which is probed by in situ XAFS, quasi in situ powder X-ray diffraction, and ex situ XPS measurements. The mechanism of the formation of methanol is visualized by in situ infrared (IR) spectroscopy and the source of the carbon of methanol at the molecular level is confirmed from the isotope-labeling experiments in presence of CO . Finally, to minimize the mass transport limitations and improve the overall eCO RR performance, a poly(tetrafluoroethylene)-based gas diffusion electrode is used in the flow cell configuration.