Operando high-temperature near-ambient pressure X-ray photoelectron spectroscopy and impedance spectroscopy study of Ni−Ce0.9Gd0.1O2−δ solid oxide fuel cell anode

• DOI: 10.1016/j.ijhydene.2020.06.228
• Publication Date: 2020-08-08T20:38:23Z
• Authors: Kuno Kooser; Tanel Käämbre; Mihkel Vestli; Urmas Joost; Samuli Urpelainen; Mati Kook; Fabrice Bournel; Jean-Jacques Gallet; Enn Lust; Edwin Kukk; Gunnar Nurk
• Keywords: EIS; NAP-XPS; Ni-GDC; ta114; Solid oxide fuel cell; Operando; 02 engineering and technology; 0210 nano-technology; Surface chemistry; ta116; 7. Clean energy

Abstract In this study we present the results of operando high temperature near-ambient-pressure x-ray photoelectron spectroscopy (HT-NAP-XPS) measurements of a pulsed laser deposited thin film N i − C e 0.9 G d 0.1 O 2 − δ model electrode. In our measurements, we have used the novel three electrode dual-chamber electrochemical cell developed in our previous work at different H 2 pressures and at different electrochemical conditions at around 650 °C. The possible redox reactions on the anode surface ( N i 2 + ↔ N i 0 , C e 4 + ↔ C e 3 + ) were investigated by HT-NAP-XPS technique simultaneously with electrochemical impedance spectroscopy measurements. The oxygen partial pressure in counter and reference electrode compartment was controlled at 0.2 bar. Changes in electronic structure of the C e 3 d and N i 2 p photoelectron spectra caused by electrode potential and H 2 pressure variations were observed and estimated by curve fitting procedure. The O 1 s and valence band photoelectron signals were used for depth probing of the chemical composition and redox changes at Ni-GDC and for studying the influence of the electrochemical polarization on the chemical state of Ni-GDC surface atoms. As a result changes in oxidation state of electrode surface atoms caused by electrode polarization and oxide ion flux through the membrane were detected with simultaneous significant variation of electrochemical impedance.