Electrochemical Performance of Ni-CGO Nano-Grained Thin Film Anodes for Micro SOFCs (original) (raw)
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Ni-Based SOFC Anodes: Microstructure and Electrochemistry
The electrochemical behavior of Ni-based SOFC anodes with different microstructures was studied. The anodes consisted either of a Ni gauze, a Ni pattern, a Ni paste, or a Ni-YSZ cermet. According to electrochemical impedance spectroscopy (EIS) measurements, the anodes are dominated by two main processes. The high frequency process decreases exponentially with an applied overpotential and is thermally activated with an activation energy of around 1 e V. The process could be attributed to the adsorption of hydrogen including charge transfer. The low frequency impedance arc arises only under a high overpotential applied between the working and the reference anode. The impedance of this process increases the higher the overpotential and is thermally activated with an activation energy of 0.5 e V. This process is assigned to the desorption of water.
Mesoporous NiO-CGO Obtained by Hard Template as High Surface Area Anode for IT-SOFC
2000
Mesoporous nickel-ceria cermets were synthesized and electrically characterized as anodes for intermediate-temperature solid oxide fuel cells using Ce 0.8 Gd 0.2 O 1.9 as the material for the electrolyte. Mesoporous nickel-ceria cermets were prepared from silica hard templates, with KIT-6 structure, and a multistep impregnation process. A comprehensive (micro)structural analysis was carried out in order to determine the stability of the replicated mesoporous cermet at the typical processing temperatures employed in solid oxide fuel cells fabrication, i.e. from 900ºC to 1100ºC. Electrical characterization of the mesoporous cermets in symmetrical cells was carried out in humidified 5%H 2 in N 2 atmosphere. Targeted values of electrode/electrolyte area specific resistance were achieved in the intermediate temperature range showing the suitability of the here-presented mesoporous approach for developing a new class of high performance anodes for IT-SOFC.
Highly dispersed nano-crystalline NiO-Ce 0.8 Gd 0.2 O 1.9 (GDC) anode powders were synthesized through a novel water-in-oil (W/O) microemulsion route, that has not been previously reported. The spherical-shaped NiO-Ce 0.8 Gd 0.2 O 1.9 nano-powders exhibited a high degree of dispersion, and the morphology of the NiO-Ce 0.8 Gd 0.2 O 1.9 particles was controlled by varying the aqueous to oil phase ratio. The polarization resistance at 800 1C with humidified H 2 fuel and the activation energy of ME10 anode synthesized by the micro-emulsion method with the aqueous to oil phase volume ratios of 1:12 were 0.02 Ω cm 2 and 0.55 eV, respectively, which were significantly lower than those of other Niceria-based anodes. These properties contributed to a smaller particle size and better dispersion compared to conventional anode materials, leading to an increased number of reaction sites. In accordance with the polarization resistance results, single cells containing ME10 anodes exhibited a high maximum power density of 0.36 W cm À 2 at 800 1C with humidified H 2 fuel.
NiO-Ce 0.8 Gd 0.2 O 2−δ cermet anode powders with flake-shaped particles have been synthesized using a unique micro-emulsion-mediated solvothermal process. With an increase in the amount of urea used as a precipitation agent, the particles change from plate to flake shape in a morphological transition. Well-developed flake-shaped anode powders can be obtained from 24 h of solvothermal treatment. The polarization resistance at 800 1C in humidified H 2 and the activation energy of the anode synthesized with 1:4 salt to urea ratio and the solvothermal treatment duration of 24 h are 0.01 Ω cm 2 and 0.53 eV, respectively. In accordance with the polarization resistance results, a single cell with the MEST4 anode shows a high maximum-power density of 0.32 W cm −2 , at 800 1C with a humidified H 2 fuel.
Characterisation of Ni-cermets SOFCs with varying anode densities
Journal of Power Sources, 2007
Mechanical reliability is a critical parameter for both the assembling and long-term operation of solid oxide fuel cells (SOFCs). The mechanical robustness of the SOFCs depends critically on the strength of the anode substrate. To enhance the mechanical strength, the density of the anode substrate was increased. Three variations were chosen in addition to the standard-type SOFCs (4.7 g cm −3): +5% (4.9 g cm −3), +10% (5.1 g cm −3) and +15% (5.3 g cm −3). These SOFCs were characterised with respect to their bending strength, transport parameters, and electrochemical performance. The experimental results showed that the mechanical strength of the anodes can be improved. The electrochemical performance was not detrimentally influenced.
Morphology control of Ni–YSZ cermet anode for lower temperature operation of SOFCs
Journal of Power Sources, 2004
A NiO-Y 2 O 3 stabilized ZrO 2 (YSZ) composite particles for solid oxide fuel cell (SOFC) anode was fabricated by advanced mechanical method in dry process. The processed powder achieved better homogeneity of NiO and YSZ particles, where submicron NiO particles were covered with finer YSZ particles. A Ni-YSZ cermet anode fabricated from the NiO-YSZ composite particles showed the porous structure in which Ni and YSZ grains of less than several hundred nano-meter as well as micron-size pores were uniformly dispersed. The cermet anode achieved high electrical performance at low temperature operation (<800 • C). It was led by larger electrochemical area successfully obtained by the excellent structure of the anode.
Electrochemical performance of Ni-based anodes for solid oxide fuel cells
Journal of Applied Electrochemistry, 2009
The catalytic activity of Ni-based anodic materials was investigated in complete solid oxide fuel cells (SOFCs) by electrochemical analysis. Button cells, consisting of supporting yttria-stabilized zirconia (YSZ) electrolyte layer, (La 1-x Sr x ) y MnO 3 (LSM) cathode and (cermet) Ni 0.5 Co 0.5 -YSZ anode were employed. Powders for anodes were obtained by wet impregnation. This procedure allowed easy production of composite electrodes with homogeneous distribution of phases and controlled microstructure. Two electrodes impedance spectroscopy was carried out at different temperatures and partial pressures of reacting gases in order to evaluate contribution of each component to overall cell losses. Current-voltage characteristic curves were also collected. Feeding with CH 4 was tested and compared to H 2 . No deterioration of cell performance due to carbon formation at anode was observed over a test period of 100 h.