Stability of solid oxide fuel cell anodes based on YST–SDC composite with Ni catalyst (original) (raw)
International Journal of Applied Ceramic Technology, 2011
Nickel (Ni)-8 mol% yttria stabilized zirconia (YSZ) cermet prepared through novel electroless technique is used as solid oxide fuel cell anode. The developed anode (28 vol% Ni) is used in two different configurations, viz. anode support and anode active layer (AAL). Highest electrochemical performance of 3.2 A/cm 2 with lowest cell area specific resistance (B94 mO cm 2) at 8001C is obtained from anode-supported single cell having an optimized 15 mm electroless AAL. Electrochemical performances are correlated with anode pore-size distributions. Such high performance cells also exhibit significant low degradation rate (B2% 1000 h À1 at a load 0.5 A/cm 2) during long-term testing.
Highly porous Ni-8YSZ anodes supported by a thin and dense electrolyte layer of 8YSZ have been developed for solid oxide fuel cell applications by reducing a NiO-8YSZ anode/electrolye precursor structure in a gas mixture of 5% H 2 -95% Ar at 800°C for selected time periods up to 8 h. It appears that 2 h of exposure to the reducing conditions is enough to reduce ~ 80% of NiO. XRD and SEM analyses in the reduced samples disclose the formation of the Ni-8YSZ cermet structure with desired porosity and microstructure. The porosity in the anode samples, which increases with the increase in the fraction of reduced NiO, severely affects the hardness and elastic moduli of the anode samples. Vickers indentation tests show that a hardness value of 5.5 GPa in the unreduced anode samples (12% porosity) reduces to less than 1 GPa in the 8 h reduced samples (36.68 % porosity). Similarly, a decrease of ∼ 44% in the Young's modulus and ∼ 40% in shear modulus is observed in the 8 h reduced samples through impulse excitation techniques, in comparison to the unreduced anode precursor. Since the elastic properties of fully dense Ni, NiO and YSZ are comparable to each other, the decrease in the magnitude in elastic moduli and hardness is attributed to the colossal increase in porosity as a result of the reduction of NiO in H 2 atmosphere.
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.
MATEC web of conferences, 2017
Carbon deposition on Ni-based anode is well-known as a major barrier for the practical use and commercialization of hydrocarbon-fuelled solid oxide fuel cells (SOFCs). In this work, Co alloying in Ni-YSZ was studied as an alternative anode material for using CH4 as a fuel. The Ni-YSZ and Ni-Co alloyed-YSZ were prepared by the traditional impregnation method without further mixing processes. After sintering and reduction in H2 atmosphere, the introduced Co can completely dissolved into the Ni lattice and changed the morphology with an increase in the Ni-YSZ grain size and showed a better uniform microstructure. The Co alloying also enhanced the electrochemical performance under CH4 fuel by reducing the resistance and anodic overvoltage. Moreover, the Co addition enhanced the stability of the cell with CH4 a constant load current of 80 mA for 60 h. This performance related to the carbon deposition on the anode surface. The Co alloying showed a high efficiency to suppress the carbon deposition and improved the electrochemical performance of an SOFC cell operating under CH4 fuel.
Investigation on microstructures of NiO–YSZ composite and Ni–YSZ cermet for SOFCs
International Journal of Hydrogen Energy, 2010
NiOeYSZ composites and NieYSZ cermets were successfully performed for solid oxide fuel cell applications. These composites must have enough porosity and appropriate microstructure for transferring the fuel gases. In this study, ball-milling was used as a simple, cost-effective method for the purpose of mixing the raw materials. The homogeneity of NiOeYSZ composites was examined by Map mode of SEM. NiOeYSZ composites were reduced at the high temperature under the controlled atmosphere to fabricate NieYSZ cermet. Variations in the anode phases were investigated by XRD and microstructure and porosity of composites were observed by SEM. Effective parameters like temperatures and the amount of pore former were investigated on open porosity, bulk density, electrical conductivity as well as electrochemical impedance of NiOeYSZ composites and NieYSZ cermet. A thin layer of YSZ was deposited by EPD as an electrolyte on NiOeYSZ composites which had various amount of open porosity, to study its effect on the performance of semicells by electrochemical impedance.
International Journal of Hydrogen Energy, 2013
Titania SMSI a b s t r a c t Sintering of Ni particles in Ni infiltrated porous YSZ anodes and decrease in triple phase boundary is the reason for performance loss in SOFC. In the present work, the idea of strong metal support interaction (SMSI) has been used to prevent the sintering of Ni particles by introducing TiO 2 as support with Ni catalyst. Electrical conductivity variation of porous YSZ matrix impregnated with Ni and Ni/TiO 2 have been investigated. Single button cells (anode supported) with and without TiO 2 impregnated NieYSZ anode were fabricated and characterized through currentevoltage measurement at different loads. It is shown that the conductivity of porous NieYSZ anode and the performance of SOFC button cell with the same anode decreased with the increase in temperature and redox cycling at different time intervals. The power density of 12% NieYSZ anode was 116 mW/cm 2 and it increased to 180 mW/cm 2 for 12% Nie4% TiO 2 eYSZ based anodes at 800 C. This increase was interpreted by strong attachment of Ni particles on TiO 2 preventing Ni coarsening during prolonged reduction in H 2 at 800 C as observed by SEM. The power density increased with further increase in Ni loading and it reached to 400 mW/cm 2 for 16% Nie4%
Electrochemistry Communications, 2011
A new high performance ceramic solid oxide fuel cell (SOFC) anode, Ca-and Co-doped yttrium chromite (YCCC)-samaria-doped ceria (SDC) composite, that resists deactivation by sulfur and does not show degradation during multiple reduction-oxidation cycles is developed. The electrocatalytic activity of the YCCC-SDC anodes in yttria-stabilized zirconia (YSZ) electrolyte-supported cells toward hydrogen oxidation is comparable to that of the Ni/YSZ anode. YCCC-SDC exhibits superior sulfur tolerance showing less than 10% increase in electrode resistance, fully reversible, upon exposure to 20 ppm H 2 S. The excellent redox tolerance is attributed to the dimensional and chemical stability of the YCCC exhibiting minimal isothermal "chemical" expansion.
Low-temperature processed anode for solid oxide fuel cells
2005
Abstract A composite Ni-Y doped Formula (YSZ) composite was prepared by depositing a Formula thick coating of YSZ particles from a colloidal suspension (initial YSZ particle size Formula) onto a sapphire substrate followed by impregnation by Ni polymer precursors into the coating and annealing at Formula. The electrical conductivity at Formula of the composite Ni-YSZ was Formula in air and above Formula in reducing atmosphere.