Catalytic Influence of Oxide Component in Ni‐Based Cermet Anodes for Ammonia‐Fueled Solid Oxide Fuel Cells

Yang, Jun; Akagi, Tomoharu; Okanishi, Takeou; Muroyama, Hiroki; Matsui, Toshiaki; Eguchi, Koichi

doi:10.1002/fuce.201400135

Cited by 55 publications

(43 citation statements)

References 22 publications

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“…13 The hydrogen generated from ammonia decomposition over Ni/YSZ cermet anode is consumed as a main fuel, and the influence of residual ammonia on OCV can be neglected. 13 If ammonia decomposed completely, the final compositions of ammonia-containing and hydrogen-containing anode gases would be exactly the same. Otherwise, the hydrogen concentration in the ammoniacontaining fuel was less than that in the hydrogen fuel.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

A Stability Study of Ni/Yttria-Stabilized Zirconia Anode for Direct Ammonia Solid Oxide Fuel Cells

Yang

Molouk

Okanishi

et al. 2015

ACS Appl. Mater. Interfaces

120

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In recent years, solid oxide fuel cells fueled with ammonia have been attracting intensive attention. In this work, ammonia fuel was supplied to the Ni/yttria-stabilized zirconia (YSZ) cermet anode at 600 and 700 °C, and the change of electrochemical performance and microstructure under the open-circuit state was studied in detail. The influence of ammonia exposure on the microstructure of Ni was also investigated by using Ni/YSZ powder and Ni film deposited on a YSZ disk. The obtained results demonstrated that Ni in the cermet anode was partially nitrided under an ammonia atmosphere, which considerably roughened the Ni surface. Moreover, the destruction of the anode support layer was confirmed for the anode-supported cell upon the temperature cycling test between 600 and 700 °C because of the nitriding phenomenon of Ni, resulting in severe performance degradation.

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Section: Resultsmentioning

confidence: 99%

“…13 Ammonia diffuses into the anode chamber and then decomposes to nitrogen and hydrogen. Subsequently, the generated hydrogen is electrochemically oxidized to produce steam and electron.…”

Section: Introductionmentioning

confidence: 99%

A Stability Study of Ni/Yttria-Stabilized Zirconia Anode for Direct Ammonia Solid Oxide Fuel Cells

Yang

Molouk

Okanishi

et al. 2015

ACS Appl. Mater. Interfaces

120

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“…Yang et al have reached the same conclusion for the ammonia utilization over Ni-YSZ anode. 28,29 Thus, the activity for the ammonia decomposition as well as the electrochemical hydrogen oxidation over anode can be considered as one of the key factors for direct ammonia-fuelled SOFCs. However, the superiority of ammonia to methane as a hydrogen carrier for the direct use in SOFCs has not been investigated sufficiently.…”

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confidence: 99%

Electrochemical and Catalytic Behaviors of Ni–YSZ Anode for the Direct Utilization of Ammonia Fuel in Solid Oxide Fuel Cells

Molouk

Okanishi

Muroyama

et al. 2015

J. Electrochem. Soc.

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In this study the electrochemical performances of Ni-YSZ anode in humidified H 2 , NH 3 and CH 4 fuels were compared under almost the same partial pressure of oxygen at 500-800 • C. The cell performance was significantly affected by fuel species and operating temperature. The single cell exhibited higher performance in wet NH 3 as compared with that in CH 4 , which was caused by the difference in the catalytic activity of anode for the hydrogen production in wet NH 3 and CH 4 . Thus, it was clarified that NH 3 is a preferable fuel rather than CH 4 for the direct use in SOFCs. Furthermore, the kinetics study on ammonia decomposition over Ni-YSZ anode was conducted at 600 • C. Although the ammonia decomposition increased with increasing ammonia concentration, the decomposition reduced in the presence of hydrogen in the reactant gas. Such a behavior was not confirmed at 850 • C. These results indicated the inhibition effect of hydrogen for ammonia decomposition, which will be the key factor for the design of anode and the operating condition setting. Nowadays one of the most important challenges is producing energy from clean, renewable, durable, efficient and economically feasible sources. Solid oxide fuel cells (SOFCs) meet these goals. Variety of fuels can be used without the external reforming process because of high operating temperature of SOFCs. [1][2][3] Hydrogen is an ideal energy carrier and water is the only product of its combustion. For the massive utilization of hydrogen, however, there are still some difficulties in production, transportation, storage, and safety control. 4,5 Therefore, it is important to use hydrogen containing chemicals such as methane, ethanol and ammonia as alternative fuels.Methane has been studied extensively as a fuel for direct internal reforming SOFCs due to higher energy density compared to hydrogen. In SOFCs, Ni-based cermet anodes such as Ni-YSZ are widely used because nickel is a good catalyst for methane steam reforming as well as electrochemical hydrogen oxidation. However, the low tolerance to carbon deposition of Ni-based cermets is the main obstacle for the direct use of methane. In most of cases, the excess amount of steam is added to the fuel gas to prevent the coke formation, leading to the reduction in the energy conversion efficiency. The development of alternative anodes such as copper-based and perovskite-based materials will be a fundamental solution to this matter. 6,7 At the current state, however, the catalytic activity of these anodes for methane steam reforming is not sufficiently high. [8][9][10] The cell performance is also insufficient for the practical application since this catalytic activity significantly affects the hydrogen concentration in the vicinity of anode. 11,12 Recently ammonia was proven as one of the promising hydrogen carriers for SOFCs because of following reasons; high energy density comparable to that of methane, 4 carbon free, ease in liquefaction at ambient temperature, low production cost, and ease in leakage detection. [13][14]...

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“…Among the various types of fuel cells, solid oxide fuel cells (SOFCs) are expected to have better compatibility with ammonia fuel because of the following reasons: (i) Their zirconia‐based solid electrolyte is stable in the ammonia atmosphere; (ii) ammonia can be catalytically decomposed into hydrogen and nitrogen on the conventional Ni‐based anodes; and (iii) the excess heat released from the electrochemical oxidation of hydrogen in an SOFC stack can be efficiently used for the endothermic ammonia decomposition reaction, which can improve the overall energy and exergy efficiency of the systems. When ammonia is supplied directly to the SOFCs, the utilization of ammonia is described by the following two steps , with the enthalpy change of 42 kJ mol −1 at 25 °C for the Eq. .…”

Section: Introductionmentioning

confidence: 91%

Development of 1 kW‐class Ammonia‐fueled Solid Oxide Fuel Cell Stack

et al. 2020

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Power generation performance and long‐term durability of ammonia‐fueled solid oxide fuel cell (SOFC) systems are investigated with SOFC stacks consisting of 30 planar anode‐supported cells. SOFC systems with three different operation modes are employed: direct ammonia, external decomposition and autothermal decomposition. A novel BaO/Ni/Sm2O3/MgO catalyst is newly developed for the external ammonia cracker, whereas a Co‐Ce‐Zr composite oxide catalyst is used for the autothermal ammonia cracker. Initial performance measurement and 1,000 h long‐term durability test of the stacks are conducted. The stack fueled with direct ammonia achieves 1 kW power output with 52% direct current (DC) electrical efficiency; a slight decrease in its performance compared with the stack with the mixture fuel of hydrogen and nitrogen is attributed to the decrease in the stack temperature caused by the endothermic ammonia decomposition reaction. The external ammonia cracker helps to maintain the stack temperature, improving the initial performance of the stack. The stack performance with the autothermal ammonia cracker is also comparable to those with the other operation modes. It is also demonstrated that the stacks fueled with ammonia have excellent stability during the long‐term tests and 57% energy conversion efficiency at ca. 700 W electrical output is achieved with the external ammonia cracker.

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Catalytic Influence of Oxide Component in Ni‐Based Cermet Anodes for Ammonia‐Fueled Solid Oxide Fuel Cells

Cited by 55 publications

References 22 publications

A Stability Study of Ni/Yttria-Stabilized Zirconia Anode for Direct Ammonia Solid Oxide Fuel Cells

A Stability Study of Ni/Yttria-Stabilized Zirconia Anode for Direct Ammonia Solid Oxide Fuel Cells

Electrochemical and Catalytic Behaviors of Ni–YSZ Anode for the Direct Utilization of Ammonia Fuel in Solid Oxide Fuel Cells

Development of 1 kW‐class Ammonia‐fueled Solid Oxide Fuel Cell Stack

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