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1. Measurement of Polarization Resistance of LSM + YSZ Electrodes on YSZ using AC and DC Methods

   Alex Szendrei, Taylor D. (January 2019, Fuel cells)

   Most of the measurements of electrode polarization resistance are conducted using electrochemical impedance spectroscopy (EIS). The electrochemical devices, however, are typically used in a DC mode. The objective of the present work was to measure electrode polarization resistance using both EIS and DC techniques. A solid cylinder of 8YSZ of diameter ~1.17 cm and length ~5.00 cm was made by powder pressing followed by sintering. LSM + YSZ electrodes were applied on the two end surfaces of the cylinder upon which gold mesh was placed. Four Pt electrodes/probes were painted along the circumference. During DC measurements, DC voltage was applied across the end electrodes and potentials were measured at all four probes. The current was also measured. From these measurements electrode polarizations were estimated separately for the two electrodes as a function of current. EIS was conducted across the two end electrodes as well as across electrode-1 and probe-2, and across probe-2 and electrode-2. This allowed the determination of the polarization resistances of the two electrodes separately. Point by point additions of the electrode-1/probe-2 and probe-2/electrode-2 spectra matched the electrode-1/electrode-2 spectra. There was good agreement between the DC and the EIS measurements. 

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2. Three-Dimensional-Printed Composite Structures: The Effect of LSCF Slurry Solid Loading, Binder, and Direct-Write Process Parameters

   https://doi.org/10.3390/ma17122822  

   Yang, Man; Parupelli, Santosh Kumar; Xu, Zhigang; Desai, Salil (June 2024, Materials)

   In this research, a direct-write 3D-printing method was utilized for the fabrication of inter-digitized solid oxide fuel cells (SOFCs) using ceramic materials. The cathode electrode was fabricated using the LSCF (La0.6Sr0.2Fe0.8Co0.2O3-δ) slurry loading and the Polyvinyl butyral (PVB) binder. The rheological parameters of slurries with varying LSCF slurry loading and PVB binder concentration were evaluated to determine their effect on the cathode trace performance in terms of microstructure, size, and resistance. Additionally, the dimensional shrinkage of LSCF lines after sintering was investigated to realize their influence on cathode line width and height. Moreover, the effect of the direct-write process parameters such as pressure, distance between the nozzle and substrate, and speed on the cathode line dimensions and resistance was evaluated. LSCF slurry with 50% solid loading, 12% binder, and 0.2% dispersant concentration was determined to be the optimal value for the fabrication of SOFCs using the direct-write method. The direct-write process parameters, in addition to the binder and LSCF slurry concentration ratios, had a considerable impact on the microstructure of cathode lines. Based on ANOVA findings, pressure and distance had significant effects on the cathode electrode resistance. An increase in the distance between the nozzle and substrate, speed, or extrusion pressure of the direct writing process increased the resistance of the cathode lines. These findings add to the ongoing effort to refine SOFC fabrication techniques, opening the avenues for advanced performance and efficiency of SOFCs in energy applications. 

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3. Operando characterization of metallic and bimetallic electrocatalysts for SOFC fuel electrodes operating under internal methane reforming conditions

   https://doi.org/10.1039/D1TA07299D  

   Drasbæk, Daniel B.; Welander, Märtha M.; Traulsen, Marie L.; Sudireddy, Bhaskar R.; Holtappels, Peter; Walker, Robert A. (March 2022, Journal of Materials Chemistry A)

   Linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and operando Raman spectroscopy were used to study the electrochemical performance and carbon tolerance of SOFCs operating with niobium doped SrTiO 3 (STN) anodes infiltrated with combinations of Ni, Co, and Ce 0.8 Gd 0.2 O 2 (CGO) added to improve catalytic activity. Cell anodes were exposed to fuel feeds of humidified H 2 , pure CH 4 and combinations of CO 2 and CH 4 at an operating temperature of 750 °C. Under pure CH 4 , Raman data show that carbon forms on all anodes containing Ni. In cells with CGO, deposited carbon results in a decreased polarization resistance. This behavior may be due to benefits conferred by CGO to the electrocatalytic activity of triple phase boundaries, presumably through improved oxide ion conductivity and/or due to carbon securing a better electrical connection in the electrodes. Raman spectra from Co-only containing anodes show no sign of carbon deposition. The absence of observable carbon together with low frequency processes observed in the EIS suggest that Co may play a role in oxidizing carbon before measurable amounts accumulate. 

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4. Gold and silver oxide conducting nanocomposite cathode for glucose biofuel cell

   https://doi.org/10.1109/SENSORS47087.2021.9639600  

   Banerjee, Saikat; Nguyen, Mathew; Slaughter, Gymama (October 2021, 2021 IEEE Sensors)

   A glucose biofuel cell on a flexible bacterial nanocellulose film was prepared. The bioelectrodes were printed using gold ink as the conductive material. The anode was modified with colloidal platinum for the oxidation of glucose. The cathode was modified with a nanocomposite comprising gold nanoparticles (AuNPs) and silver oxide (Ag2O) nanoparticles. The cathode was characterized via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and UV spectroscopy techniques. The assembled biofuel cell generated a maximum open circuit voltage (V oc ) of 0.485 V, short circuit current (I sc ) of 0.352 mA/cm 2 , and a maximum peak power density (P max ) of 0.032 mW/cm 2 when operating in 30 mM concentration. This system showed a stable and linear performance with a linear range of 1 mM to 30 mM glucose. The gold printed electrode process is applicable to the development of wearable and implantable abiotic biofuel cell. 

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5. Creating and Preserving Nanoparticles during Co-Sintering of Solid Oxide Electrodes and Its Impact on Electrocatalytic Activity

   https://doi.org/10.3390/catal11091073  

   Muhoza, Sixbert P.; Gross, Michael D. (September 2021, Catalysts)

   A novel processing method that creates and preserves ceramic nanoparticles in solid oxide electrodes during co-sintering at traditional sintering temperatures is introduced. Specifically, carbon templated samarium-doped ceria nanoparticles (nSDC) were successfully integrated with commercial lanthanum strontium cobalt ferrite (LSCF) and commercial SDC powders, producing LSCF-SDC-nSDC cathodes upon processing. The effect of nSDC concentration on cathode electrocatalytic activity was investigated at low operational temperatures, 600 °C–700 °C, with symmetrical cells. Low nSDC loadings, ≤5 wt% nSDC, significantly decreased cell polarization resistance whereas higher loadings increased it. The best electrochemical performance was achieved with 5 wt% nSDC, lowering the polarization resistance by 41% at 600 °C. Fuel cell tests demonstrate that adding 5 wt% nSDC increased the maximum fuel cell power density by 38%. Electrochemical impedance spectra showed substantial improvements in both fuel cell polarization resistance and ohmic resistance, indicating that nSDC increased the electrocatalytically active area of the cathode. This work demonstrates a simple, novel method for effectively increasing electrocatalytic activity of solid oxide electrodes at low operational temperatures. 

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