Stability of solid oxide fuel cell anodes based on YST–SDC composite with Ni catalyst (original) (raw)
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Solid State Ionics, 2007
A functional composite powder, in which nano-sized NiO (40 vol.%) was crystallized on YSZ particles, was synthesized by the Pechini-type polymerizable complex method in an effort to improve the performance and durability of SOFC anodes. The pore-structure (e.g. porosity, pore size) and mechanical properties (e.g. strength, density) of the electrode were optimized by a combination of two different species of YSZ powder (Tosoh 0.3 μm and Millennium 10 μm). A single cell made from the composite powder exhibited high power density of 1.1 W cm − 2 and high durability under a load of 1.0 A cm − 2 during 530 h of operating time at 800°C. It could be concluded that this functional composite would enhance the single cell performance and durability at elevated temperature.
Journal of Power Sources, 2012
Y-doped SrTiO 3 (YST) is currently used as an effective anode component to solve the shortcomings of conventional Ni-based cermet anodes. In this study, YST-based composite with a different ceramic oxide including samaria-doped ceria (SDC) or yttria-stabilized zirconia (YSZ) was developed as an anode material to evaluate the electrocatalytic performance in hydrogen and methane fuels. The composites showed a good potential in electrical conductivity and compatibility with YSZ electrolyte in the anodic condition. The cell with YST-SDC anode attained the better performance than that with YST-YSZ anode, which was ascribable to the high electrical conductivity and electrocatalytic activity of SDC towards the oxidation of fuels. Addition of nickel remarkably enhanced the electrochemical performance and the stability of the anodes. With 10 wt% of nickel oxide loading, the performance was significantly increased under the operation in humidified hydrogen and methane. Note that in methane fuel, the performance deterioration has not been observed over the short-term operation for 20 h.
Ni-SDC cermet anode for medium-temperature solid oxide fuel cell with lanthanum gallate electrolyte
Journal of Power Sources, 1999
The polarization properties and microstructure of Ni-SDC samaria-doped ceria cermet anodes prepared from spray pyrolysis SP Ž. composite powder, and element interface diffusion between the anode and a La Sr Ga Mg O LSGM electrolyte are 0.9 0.1 0.8 0.2 3yd Ž investigated as a function of anode sintering temperature. The anode sintered at 12508C displays minimum anode polarization with anode. y2 ohmic loss , while the anode prepared at 13008C has the best electrochemical overpotential, viz., 27 mV at 300 mA cm operating at 8008C. The anode ohmic loss gradually increases with increase in the sintering temperature at levels below 13008C, and sharply increases at 13508C. Electron micrographs show a clear grain growth at sintering temperatures higher than 13008C. The anode microstructure appears to be optimized at 13008C, in which nickel particles form a network with well-connected SDC particles finely distributed over the surfaces of the nickel particles. The anode sintered at 13508C has severe grain growth and an apparent interface diffusion of nickel from the anode to the electrolyte. The nickel interface diffusion is assumed to be the main reason for the increment in ohmic loss, and the resulting loss in anode performance. The findings suggest that sintering Ni-SDC composite powder near 12508C is the best method to prepare the anode on a LSGM electrolyte.
Performance and stability of SOFC anode fabricated from NiO–YSZ composite particles
Journal of Power Sources, 2002
Ni-YSZ cermet anodes for solid oxide fuel cells (SOFCs) were fabricated at various sintering temperatures from NiO-YSZ composite particles made by spray pyrolysis (SP) technique. NiO particles covered with fine YSZ (Y 2 O 3 stabilized ZrO 2) particles were used as the composite particles, and the initial ratio of Ni and YSZ was set at 75:25 (mol%). As a result, the cermet anode sintered at 1350 8C showed the morphology in which fine YSZ grains were uniformly dispersed on the surface of Ni grain network. Electrical performance such as electrochemical activity and internal resistance of a Ni-YSZ cermet anode changed with sintering temperature. The anode fabricated at 1350 8C showed the highest electrical performance. Especially, a single cell voltage with the Ni-YSZ cermet anode kept very stable for 8000 h at 1000 8C in the SOFC operation condition of H 2-3% H 2 O and air. The cermet anode after a long-term test had its initial morphology. It indicates that the Ni-YSZ cermet anode fabricated from NiO-YSZ composite particles is a very promising material for its practical use as SOFCs.
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.