Short-Term Strong Cathodic Polarization of Ni/YSZ and Pt/YSZ. Issue 4 (29th April 2021)

• Record Type: Journal Article
• Authors: Hansen, Karin Vels; Kreka, Kosova; Balasubramanian, Vignesh; Jacobsen, Torben
• Is Part Of: Journal of the Electrochemical Society. Volume 168:Issue 4(2021)
• Publication Date: 2021-04-29
• Subjects: Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/1945-7111/abf87e
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : The initial stages of YSZ reduction and formation of intermetallic phases at Ni∣YSZ interfaces on strongly cathodically polarized electrodes were studied by a number of potential sweep and impedance techniques. The measurements were carried out in the potential range −1.0 V to −3.0 V vs E°(O2 ) in H2 /H2 O at 650 and 750 °C. Below −1.7 V the cathodic current increases almost exponentially, mainly due to electronic conductivity in the YSZ. Reduction and oxidation peaks develop below and above −1.9 V, respectively. The peaks reveal a simultaneous reduction of YSZ at the Ni∣YSZ interface and reoxidation of a Ni-Zr phase. Charges calculated from the reoxidation peaks indicate a thickness of 200 nm for the layer formed by conditioning the electrode for 300 s at −2.6 V vs E°(O2 ). Impedance measurements show a suppressed arc decreasing with increasing polarization. Below −2.3 V vs E°(O2 ) a capacitive high frequency arc segment and an inductive low frequency loop develop. Both are ascribed to electronic conductivity. SEM/EDS microscopy on cross sections of samples cooled with and without polarization showed the formation of uniform and homogeneous intermetallic reaction layers which after reoxidation resulted in a two-phased nanostructures.