Structure‐Tailored Surface Oxide on Cu–Ga Intermetallics Enhances CO₂ Reduction Selectivity to Methanol at Ultralow Potential

Abstract

Electrochemical CO2 reduction reaction (eCO2RR) is performed on two intermetallic compounds formed by copper and gallium metals (CuGa2 and Cu9Ga4). Among them, CuGa2 selectively converts CO2 to methanol with remarkable Faradaic efficiency of 77.26% at an extremely low potential of −0.3 V vs RHE. The high performance of CuGa2 compared to Cu9Ga4 is driven by its unique 2D structure, which retains surface and subsurface oxide species (Ga2O3) even in the reduction atmosphere. The Ga2O3 species is mapped by X‐ray photoelectron spectroscopy (XPS) and X‐ray absorption fine structure (XAFS) techniques and electrochemical measurements. The eCO2RR selectivity to methanol are decreased at higher potential due to the lattice expansion caused by the reduction of the Ga2O3, 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 13CO2. Finally, to minimize the mass transport limitations and improve the overall eCO2RR performance, a poly(tetrafluoroethylene)‐based gas diffusion electrode is used in the flow cell configuration.

In Situ Mechanistic Insights for the Oxygen Reduction Reaction in Chemically Modulated Ordered Intermetallic Catalyst Promoting Complete Electron Transfer

“…Figure 4d shows that there is an interesting correlation of bond distances between the experimental real-time observation via extended X-ray absorption fine structure (EXAFS) analysis and computationally optimized structure analysis. 34 Figure 4e shows the data comparison of Pd 3d XPS for Pt 0.2 Pd 1.8 Ge before and after 50,000 ADT cycles of the ORR.…”

Potential- and Time-Dependent Dynamic Nature of an Oxide-Derived PdIn Nanocatalyst during Electrochemical CO2 Reduction

“…55 The real-time in situ XAS study has also been performed at a different time interval to see the electronic structural evolution and charge transfer kinetics between Pd and In in spite of the catalysts. 56,57 The time-dependent XANES spectra of the In K-edge of PdIn@In 2 O 3 sample at −0.9 V potential show that the white line intensity for In decreases, indicating the increase in the electron density on the In site as CO 2 RR progresses (Figure S15a). During the CO 2 RR structure, the bond distance corresponding to In−O bond does not change much, as presented in Figure S15b.…”

Alloying strategies for tuning product selectivity during electrochemical CO2reduction over Cu

“…KCl) in 0.5 M KHCO 3 . Recently, Bagchi et al 192 reported excellent selectivity towards methanol could be achieved with an intermetallic 184 Copyright 2019, the American Chemical Society. Source: https://pubs.acs.org/doi/10.1021/ jacs.9b10709.…”

“…KCl) in 0.5 M KHCO 3 . Recently, Bagchi et al 192 reported excellent selectivity towards methanol could be achieved with an intermetallic CuGa 2 electrocatalyst. An exceptional FE of 77.6% for methanol was achieved at −0.3 V vs .…”