Developing an Automated Tool for Quantitative Analysis of the Deconvoluted Electrochemical Impedance Response of a Solid Oxide Fuel Cell

Despite being commercially available, solid oxide fuel cell (SOFC) technology requires further study to understand its physicochemical processes for diagnostics, prognostics, and quality assurance purposes. Electrochemical impedance spectroscopy (EIS), a widely used characterization technique for SOFCs, is often accompanied by the distribution of relaxation times (DRT) as a method for deconvoluting the contribution of each physicochemical process from the aggregated impedance response spectra. While EIS yields valuable information for the operation of SOFCs, the quantitative analysis of the DRT and its shifts remains cumbersome. To address this issue, and to create a replicable benchmark for the assessment of DRT results, a custom tool was developed in MATLAB to numerically analyze the DRT spectra, identify the DRT peaks, and assess their deviation in terms of peak frequency and DRT amplitude from nominal operating conditions. The preliminary validation of the tool was carried out by applying the tool to an extensive experimental campaign on 23 SOFC button-sized samples from three production batches in which EIS measurements were performed in parametric operating conditions. It was concluded that the results of the automated analysis via the developed tool were in accordance with the qualitative analysis of previous studies. It is capable of providing adequate additional quantitative results in terms of DRT shifts for further analysis and provides the basis for better interoperability of DRT analyses between laboratories.

Plasma-Enhanced Atomic Layer Deposition of Zirconium Oxide Thin Films and Its Application to Solid Oxide Fuel Cells

Zirconium oxides were deposited using plasma-enhanced atomic layer deposition (PEALD) involving (2-(N-methylamino)1-MethylEthyleneCyclopentadienyl)Bis(DiMethylAmino)Zr (abbreviated as CMEN-Zr) and oxygen plasma as zirconium and oxygen sources. The zirconium oxide thin films demonstrate temperature-independent growth rates per cycle of 0.94 A/cycle at 150–215 °C. The deposited ZrO2 thin films were characterized using numerous analytical tools, i.e., X-ray photoelectron spectroscopy for chemical bonding state and composition, X-ray diffraction for crystallinity, atomic force microscopy for surface morphology, field-emission scanning electron microscopy for cross-sectional analysis, spectroscopic ellipsometry and UV–visible spectrophotometry for optical characterization, capacitance–voltage measurements for dielectric constants and atomic defects, and current–voltage characteristics for electrical information. The insulating features of the crystalline and stoichiometric ZrO2 films were implemented in the anode composites to evaluate the influence of ALD-based nano-features on the electrochemical performance of solid oxide fuel cells, with the main emphasis on anode performance. The presence of nanomaterials on Ni/YSZ anode composites is analyzed to determine the negative effects on electrochemical performance and the degradation of cell performance of solid oxide fuel cells (SOFCs). The artificial design was proven to be effective in controlling the cell performance as long as proper material design was adopted in SOFC electrodes.

Nanostructured Double Perovskite Cathode With Low Sintering Temperature For Intermediate Temperature Solid Oxide Fuel Cells

This study focuses on reducing the cathode polarization resistance through the use of mixed ionic electronic conductors and the optimization of cathode microstructure to increase the number of electrochemically active sites. Among the available mixed ionic electronic conductors (MIECs), the layered perovskite GdBa0.5 Sr0.5 CoFeO5+δ (GBSCF) was chosen as a cathode material for intermediate temperature solid oxide fuel cells owing to its excellent electrochemical performance and structural stability. The optimized microstructure of a GBSCF-yttria-stabilized zirconia (YSZ) composite cathode was prepared through an infiltration method with careful control of the sintering temperature to achieve high surface area, adequate porosity, and well-organized connection between nanosized particles to transfer electrons. A symmetric cell shows outstanding results, with the cathode exhibiting an area-specific resistance of 0.006 Ω cm(2) at 700 °C. The maximum power density of a single cell using Ce-Pd anode with a thickness of ∼80 μm electrolyte was ∼0.6 W cm(-2) at 700 °C.

Enhanced oxygen reduction activity and solid oxide fuel cell performance with a nanoparticles-loaded cathode

Reluctant oxygen-reduction-reaction (ORR) activity has been a long-standing challenge limiting cell performance for solid oxide fuel cells (SOFCs) in both centralized and distributed power applications. We report here that this challenge has been tackled with coloading of (La,Sr)MnO3 (LSM) and Y2O3 stabilized zirconia (YSZ) nanoparticles within a porous YSZ framework. This design dramatically improves ORR activity, enhances fuel cell output (200-300% power improvement), and enables superior stability (no observed degradation within 500 h of operation) from 600 to 800 °C. The improved performance is attributed to the intimate contacts between nanoparticulate YSZ and LSM particles in the three-phase boundaries in the cathode.