In-situ redox cycling behaviour of Ni–BaZr0.85Y0.15O3−δ cermet anodes for Protonic Ceramic Fuel Cells

Abstract

Abstract:The current work investigates the redox behaviour of peak performing NiBaZr 0.85 Y 0.15 O 3- (Ni-BZY) cermet anodes for protonic ceramic fuel cells (PCFCs) by electrochemical impedance measurements, scanning electron microscopy (SEM) and Xray diffraction (XRD). Peak performing PCFC cermet anodes are documented to require much lower porosity levels than those needed in oxide-ion conducting counterparts. The polarisation behaviour of these optimised PCFC anodes is shown to be drastically impaired by redox cycling, with depletions in performance that correspond to around 80% of the original resistance values noted after the first redox cycle. The ohmic resistance (Rohmic) is also shown to be increased due to delamination at the electrode/electrolyte interface, as confirmed by postmortem microstructural analysis. Insitu measurements by environmental scanning microscopy (ESEM) reveal that degradation proceeds due to volume expansion of the nickel phase during the reoxidation stage of redox cycling. The present study reveals degradation to be very fast for peak performing Ni-BZY cermets of low porosity. Hence, methods to improve redox stability can be considered to be essential before such anodes can be implemented in practical devices.

Thermal and Chemical Expansion in Proton Ceramic Electrolytes and Compatible Electrodes

“…Strategies to alleviate this problem are to increase the porosity of the anode or to use an uneven distribution of the electrolyte grain size. Nasani et al [413] studied the redox behavior of the anode Ni/BZY cermet and showed a similar expansion of NiO upon reoxidation as the one observed for YSZ/NiO. Their microstructural analysis proved that the microcracks and delamination observed were due to the nickel expansion phase upon reoxidation.…”

NiO–Ba0.95Ca0.05Ce0.9Y0.1O3−δ as a Modified Anode Material Fabricated by the Tape Casting Method

“…Accordingly, the corresponding spectra were not analysed using the methods derived for equilibrium or stationary states. In these cases, the intercept of the spectra with the real axis of the Nyquist (Z′, Z″) plot was used to evaluate the resistance [ 46 , 47 ].…”

Co2CrO4 Nanopowders as an Anode Catalyst for Simultaneous Conversion of Ethane to Ethylene and Power in Proton-Conducting Fuel Cell Reactors

“…YSZ needs high temperature, usually 800–1000 °C, to provide sufficiently high ionic conductivity for practical applications. At such high temperatures, the SOFC needs expensive ceramic interconnects and it is not easy to achieve long-term stability, so several efforts have been made to decrease the operating temperature of SOFCs. − Proton-conducting oxides potentially have higher ionic conductivity relative to oxide-conducting membranes at intermediate or low temperature because of the proton’s smaller size and lower transport activation energy. − Hydrogen-fed protonic ceramic membrane fuel cells with a Ni anode have been intensively studied in recent years. − …”