Nature and Distribution of Stable Subsurface Oxygen in Copper Electrodes During Electrochemical CO2 Reduction

Filippo Carlo Cavalca, Rafael Ferragut, Stefano Aghion, André Eilert, Oscar Diaz-Morales, Chang Liu, Ai Leen Koh, Thomas Willum Hansen, Lars G.M. Pettersson, Anders Nilsson

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    Abstract

    Oxide-derived copper (OD-Cu) electrodes exhibit higher activity than pristine copper during the carbon dioxide reduction reaction (CO2RR) and higher selectivity towards ethylene. The presence of residual subsurface oxygen in OD-Cu has been proposed to be responsible for such improvements, although its stability under the reductive CO2RR conditions remains unclear. This work sheds light on the nature and stability of subsurface oxygen. Our spectroscopic results show that oxygen is primarily concentrated in an amorphous 1-2 nm thick layer within the Cu subsurface, confirming that subsurface oxygen is stable during CO2RR for up to 1 hour at -1.15 V vs RHE. Besides, it is associated with a high density of defects in the OD-Cu structure. We propose that both low-coordination of the amorphous OD-Cu surface and the presence of subsurface oxygen that withdraws charge from the copper sp- and d-bands might selectively enhance the binding energy of CO.
    Original languageEnglish
    JournalJournal of Physical Chemistry C
    Volume121
    Issue number45
    Pages (from-to)25003-25009
    ISSN1932-7447
    DOIs
    Publication statusPublished - 2017

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