Emiliana Fabbri

Design and fabrication of a chemically-stable proton conductor bilayer electrolyte for intermediate temperature solid oxide fuel cells (IT-SOFCs)

Bilayer electrolytes made of barium cerate covered with a thin film of barium zirconate deposited by pulsed laser deposition show promise for improving chemical stability without greatly affecting electrochemical performance in fuel cell operation.

Composite Ormosil/Nafion Membranes as Electrolytes for Direct Methanol Fuel Cells

Composite Ormosil/Nafion membranes were prepared and characterized for use as electrolytes in direct methanol fuel cells (DMFCs). An organosilane derivative (sulfonated diphenylsilanediol, SDPSD) was selected as a filler of the Nafion matrix. The composite membranes were characterized by electrochemical impedance spectroscopy, differential scanning calorimetry, and solvent uptake measurements. The composite membranes exhibited higher proton conductivity and enhanced stability than the reference unfilled Nafion membrane, due to the occurrence of an effective interaction between the filler and the polar cluster of the polymer matrix. Polarization curves in a DMFC were acquired and the results showed that the performance of the composite membrane was superior to that of unfilled Nafion due to a reduced methanol permeation rate, as well as to enhanced proton conductivity and thermal stability of the membrane. Due to its satisfactory properties, the composite Nafion/SDPSD membrane has a potential use as electrolyte in DMFCs operating at intermediate temperatures.

A novel single chamber solid oxide fuel cell based on chemically stable thin films of Y-doped BaZrO3 proton conducting electrolyte

A novel single chamber solid oxide fuel cell operating at 550 °C was fabricated depositing a fully-dense, 650 nm thick, BaZr0.8Y0.2O3−δ (BZY) films on Ni-BZY anodes by pulsed laser deposition. Using an optimized cathode for proton conductor electrolytes, an open circuit voltage of 0.53 V and a power density output of 36 mW cm−2 were reached in the single chamber operation mode.

Improving the Performance of High Temperature Protonic Conductor (HTPC) Electrolytes for Solid Oxide Fuel Cell (SOFC) Applications

This work investigated the possibility of coupling the high conductivity of cerates and the good chemical stability of zirconates as proton conductor electrolytes for solid oxide fuel cells (SOFCs). Two different approaches are discussed: the synthesis of barium cerate and zirconate solid solutions, and the fabrication of a bilayer electrolyte made of a Y-doped barium cerate pellet covered by a thin protecting layer of Y-doped barium zirconate. The chemical stability of the tailored samples was tested exposing them to 100% CO2 atmosphere at 700°C for 3 h. X-ray diffraction (XRD) analysis was used to investigate the phase composition of the specimens before and after the CO2 treatment. Electrochemical impedance spectroscopy (EIS) measurements were carried out in humidified H2. Hydrogen-air breathing fuel cell experiments were carried out at 700°C.

Synthesis and Characterization of BaZr 0.8 Y 0.2 O 3 Protonic Conductor for Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFCs)

Barium zirconate BaZr 0.8 Y 0.2 O 3-δ , to be used as protonic conductor under hydrogen containing atmosphere in intermediate temperature (500-700°C) solid oxide fuel cells (IT-SOFCs) was prepared using a sol-gel technique to produce materials with controlled chemical structure and microstructural properties. Several synthetic procedures were investigated, dissolving the metal cations in two solvents (water and ethylene glycol) and using different molar ratios of citric acid with respect to the total metal content. A single phase was obtained at temperature as low as 1100°C. To verify the chemical stability, all the sintered oxides were exposed to CO2 and the phase composition of the resulting specimens was investigated using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). Fuel cell polarization curves on symmetric Pt/BZY20/Pt cells of different thickness were measured at intermediate temperatures (500-700°C).

Pulsed Laser Deposition of Superlattices Based on Ceria and Zirconia

Rapidly growing attention is being recently directed towards the ninvestigation of the ionic conducting properties of oxide film nhetero-structures. Experimental evidence has been reported nshowing that interfacial phenomena at hetero-phase interfaces ngive rise to faster ion conduction pathways than the bulk or nhomo-phase interfaces. Nonetheless, a deeper understanding of nthe interface transport properties is still needed to exploit these neffects. In this work, we have investigated the growth mechanism nof different superlattices fabricated by pulsed laser deposition n(PLD) coupling doped and undoped cerium and zirconium noxides. Single crystalline MgO wafers were selected as ndeposition substrates. The superlattice structures were obtained nby means of a thin buffer layer of SrTiO3 (STO). The growth nmechanism was investigated by reflection high energy electron ndiffraction (RHEED) and X-ray diffraction (XRD) analyses.

Single Chamber Solid Oxide Fuel Cells (SC-SOFCs) based on a Proton Conducting Electrolyte

Single chamber solid oxide fuel cells (SC-SOFCs) are promising for portable power applications because they are simpler than the conventional dual-chamber cells. SC-SOFCs based on the cell Ni/BaCe0.3Zr0.5Y 0.2O3-δ (BCZY)/Ba0.5Sr 0.5Co0.8Fe0.2O3-δ (BSCF) were investigated under gas mixtures of propane (C3H8), oxygen (O2), and helium (He) with different compositions. To enhance the fuel partial oxidation at low temperatures, a porous layer of Ru was added onto the anode surface. Two configurations, finger (with parallel electrodes) and sandwich (with electrodes on opposite sides of the pellets), were analyzed. ©The Electrochemical Society.

Soft Chemistry Routes for the Synthesis of Sr0.02La0.98Nb0.6Ta0.4O4 Proton Conductor

Niobates and tantalates of rare-earth compounds are high ntemperature proton conductor (HTCP) oxides that are gaining nattention as possible stable electrolyte materials for application in nintermediate temperature solid oxide fuel cells (IT-SOFCs). nSr0.02La0.98Nb0.6Ta0.4O4 was synthesized by auto-combustion and nco-precipitation routes, and by solid state reaction for sake of ncomparison, expecting an improvement in conductivity for the wet nchemistry routes over the conventional solid state reaction method. nSingle phase materials were obtained at 1100°C by autocombustion nand by co-precipitation. The synthesized powders were ncharacterized by X-ray diffraction (XRD) and dilatometric nanalyses. Dense electrolytes were obtained by pressing the ncalcined powders into cylindrical pellets and then sintering at n1600°C for 10 h. The pellets were observed by scanning electron nmicroscopy (SEM). Electrical conductivity of the sintered pellets nwas measured as a function of the temperature by electrochemical nimpedance spectroscopy (EIS) measurements. Proton conductivity nof 2.2×10-4 S cm-1 was obtained in wet argon atmosphere at 800°C nfor the sample produced via auto-combustion.

Performance of Solid Oxide Fuel Cells with In-Doped BaZrO3 Electrolyte Films on Different Anode Substrates

High temperature proton conductors received broad interests because they show high ionic conductivities and low activation energies, and provide an alternative solution for SOFC electrolyte materials compared with oxygen-ion conductors. Although many oxides have been found to show certain protonic conductivity at high temperatures, the most widely studies high temperature proton conductors are still doped BaCeO3 and doped BaZrO3 systems. In the view of practical applications, the poor chemical of BaCeO3 limits its application, whereas BaZrO3 is regarded as a good electrolyte candidate because of its excellent chemical stability and high bulk conductivity. 4 However, the poor sinteractivity and low grain boundary conductivity of BaZrO3 hinder its applications. In addition, current reports for the fuel cells based on BaZrO3 electrolyte usually shows undesirable performance because of its refractory nature.

Soft Chemistry Routes for the Synthesis of Sr

Niobates and tantalates of rare-earth compounds are high ntemperature proton conductor (HTCP) oxides that are gaining nattention as possible stable electrolyte materials for application in nintermediate temperature solid oxide fuel cells (IT-SOFCs). nSr0.02La0.98Nb0.6Ta0.4O4 was synthesized by auto-combustion and nco-precipitation routes, and by solid state reaction for sake of ncomparison, expecting an improvement in conductivity for the wet nchemistry routes over the conventional solid state reaction method. nSingle phase materials were obtained at 1100°C by autocombustion nand by co-precipitation. The synthesized powders were ncharacterized by X-ray diffraction (XRD) and dilatometric nanalyses. Dense electrolytes were obtained by pressing the ncalcined powders into cylindrical pellets and then sintering at n1600°C for 10 h. The pellets were observed by scanning electron nmicroscopy (SEM). Electrical conductivity of the sintered pellets nwas measured as a function of the temperature by electrochemical nimpedance spectroscopy (EIS) measurements. Proton conductivity nof 2.2×10-4 S cm-1 was obtained in wet argon atmosphere at 800°C nfor the sample produced via auto-combustion.