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Electrochemically Induced Phase Changes in La 2 CuO 4 During Cathodic Electrocatalysis
Author(s) -
Whittingham Alexander W. H.,
Smith Rodney D. L.
Publication year - 2019
Publication title -
chemelectrochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 59
ISSN - 2196-0216
DOI - 10.1002/celc.201901412
Subject(s) - electrocatalyst , ionic bonding , x ray photoelectron spectroscopy , materials science , anode , conductivity , electron transfer , ionic conductivity , electrochemistry , oxygen , phase (matter) , chemistry , inorganic chemistry , chemical engineering , electrode , ion , organic chemistry , engineering , electrolyte
The ability of layered perovskites to accommodate both oxygen vacancies and hyperstoichiometry provides a dimension of tunability that makes them appealing for electrocatalytic applications, but the resulting ionic conductivity enables electron transfer reactions within bulk crystals. We report on the stability of La 2 CuO 4 in the voltage regimes relevant to oxygen reduction, hydrogen evolution and CO 2 reduction. Voltammetric experiments, X‐ray photoelectron spectroscopy and X‐ray diffraction reveal both surface and bulk electron transfer reactions. Application of anodic voltages results in expansion in the crystal c‐axis, while cathodic voltages induce contraction. The ability to catalyze each of the three cathodic reactions is confirmed, but X‐ray diffraction and electron microscopy reveal amorphization of the electrocatalyst at voltages below −0.4 V that affects both the oxygen reduction and CO 2 reduction reactions. While the ionic conductivity of Ruddlesden Popper oxides introduces intriguing properties, it simultaneously introduces the risk of structural instability in catalytically relevant voltages.