CO2 electrolysis – Complementary operando XRD, XAS and Raman spectroscopy study on the stability of CuxO foam catalysts

• Published in: Journal of catalysis Vol. 389; pp. 592 - 603
• Main Authors: Dutta, Abhijit, Rahaman, Motiar, Hecker, Burkhard, Drnec, Jakub, Kiran, Kiran, Zelocualtecatl Montiel, Ivan, Jochen Weber, Daniel, Zanetti, Alberto, Cedeño López, Alena, Martens, Isaac, Broekmann, Peter, Oezaslan, Mehtap
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.09.2020
• Subjects: CO2 electro-reduction; Cu foam; Operando Raman spectroscopy; Operando X-ray absorption spectroscopy; Operando X-ray diffraction; Operando X-ray absorption spectroscopy; Cu foam; Operando Raman spectroscopy; CO2 electro-reduction; Operando X-ray diffraction
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2020.06.024

[Display omitted] •A set of highly complementary operando techniques (Advanced operando X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD) and Raman spectroscopy) sensitive to potential-dependent alteration of highly porous oxidic precursor materials used for the electrochemical reduction of CO2 into value-added products such as hydrocarbons and higher alcohols.•This complementary and holistic approach of ‘bulk’- and surface-sensitive techniques demonstrates that the electro-reduction of porous CuxO foams into metallic Cu is completed before CO2RR products formation sets in.•There are substantial differences in the particular potential dependence of the oxide reduction when comparing the ‘bulk’ with the respective ‘surface’ processes.•It is valuable in comparison with the bulk-sensitive XAS and XRD techniques which both indicate oxide-metal transitions that are ‘delayed’ on the potential scale with respect to what is observed in the surface-sensitive Raman spectroscopy. Copper oxides have recently emerged as promising precursor catalyst materials demonstrating enhanced reactivity and selectivity towards C2 and C3 products like ethylene, ethanol, and n-propanol generated from the direct electro-reduction reaction of CO2 (denoted as CO2RR). Advanced operando X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD) and Raman spectroscopy were employed to probe the potential-dependent changes of the chemical states of Cu species in the Cu oxide foams (referred to as CuxO) before and during the CO2RR. This complementary and holistic approach of ‘bulk’- and surface-sensitive techniques demonstrates that the electro-reduction of CuxO foams into metallic Cu is completed before hydrocarbon (e.g., ethylene, ethane) and alcohol (e.g., ethanol, n-propanol) formation sets in. There are, however, substantial differences in the potential dependence of the oxide reduction when comparing the ‘bulk’ with the respective ‘surface’ processes. Only in the very initial stage of the CO2RR, the reduction of the Cu oxide precursor species is temporarily superimposed on the production of CO and H2. Complementary identical location (IL) SEM analysis of the CuxO foams prior to and after the CO2RR reveals a significant alteration in the surface morphology caused by the appearance of smaller Cu nanoparticles formed by the reduction process of CuxO species.