Solid oxide cells are electrochemical devices used for the conversion of chemical energy to electrical energy (Solid Oxide Fuel Cells-SOFC) and vice versa (Solid Oxide Electrolysis Cells-SOEC). ...However, long-term performance degradation impedes the widespread commercialization of the technology. To investigate the effects of operation mode on the degradation of Ni/yttria-stabilized zirconia (YSZ) electrodes, two cells from the same production batch are tested for 1000 h at 800 °C; one as SOFC and the other as SOEC. The cells are fed with the same gas composition at the fuel inlet side (p(H2O)/p(H2) = 0.5/0.5) while the direction of the current (±1 A cm−2) is reversed. It is found that Ni coarsening occurs to a similar extent in both operation modes while Ni depletion is only observed in SOEC mode, in the region close to the electrode/electrolyte interface. Here, the Ni/(Ni + Zr + Y) atomic ratio decreases from ~0.49 before operating the cell to ~ 0.28 and the SOEC shows a pronounced decrease in percolating triple phase boundaries (TPBs). The wettability of Ni on YSZ is studied and hypotheses are presented to correlate the phenomena of Ni coarsening and Ni depletion with the cell operation mode.
•The effect of the operation mode (SOEC, SOFC) on SOC degradation was investigated.•Ni coarsening occurs regardless of the SOC operation mode.•Ni depletion at the electrode/electrolyte interface is observed only in SOEC mode.•Ni depletion is a major cause of SOEC performance degradation.•A gradient in Ni/YSZ contact angle as the main driving force for Ni depletion.
Ni coarsening in the Ni/yttria-stabilized zirconia (YSZ) fuel electrode of solid oxide cells (SOCs) is a major cause of long-term performance degradation. Phase-field modeling is a powerful tool for ...studying Ni coarsening in the complex 3D structures of SOC fuel electrodes. In this work, we present a study aimed at validating a phase-field model, comparing simulation results with time-dependent ex-situ tomographic data. Three equilibrium Ni/YSZ contact angles are examined: 97°, 120°, and 150°. Simulated microstructures are characterized through quantities such as the Ni mean radius, triple-phase boundaries, and interface shape distribution. The phase-field model reproduces the improved pore connectivity in the first stage of Ni coarsening observed in the tomography data. This model also indicates that the contact angle plays a key role in the microstructural evolution during Ni coarsening, and the best match to the experiment was obtained with the equilibrium contact angle of 120º, close to a measured value in literature. Finally, the limitations of the model are discussed.
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In early 2015, the Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) provided notification of outbreaks of transmission of carbapenem-resistant ...Enterobacteriaceae (CRE) associated with the use of duodenoscopes in endoscopic retrograde cholangiopancreatograhy (ERCP). In August of 2015, the FDA released supplemental duodenoscope reprocessing measures from an FDA-led expert panel. A multidisciplinary team was established to implement duodenoscope microbiological culturing following duodenoscope reprocessing at our institution, a community based hospital.
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