1. Introduction

Some perovskite oxides, such as doped BaCeO₃ and BaZrO₃ electrolyte-based protonic ceramic fuel cell (PCFC) have received increasing attention as electrolytes of reduced temperature to operate [1,2]. Furthermore, PCFC leads to the production of water vapor at the cathode side, which helps to improve the conversion efficiency of SOFC system. And it is possible to reduce the cost of the stack because inexpensive metal materials can be used for interconnectors in stacks. However most of the previous researches on PCFC are small-sized cell and it is necessary to further improve the power density. In this work, we reported that a cell stack of a new structure was designed and made with large-sized PCFC and porous alloys for anode and cathode current collector to improve power density, and the characteristics were evaluated.

2. Experimental

2.1 Preparation of large-sized PCFC

BaCe_0.8Y_0.2O_3-δ(BCY20) and BaZr_0.8Y_0.2O_3-δ(BZY20) were prepared by solid state reaction method and were mixed with NiO by a ball-mill to prepare an anode powder. The powder was pressed uniaxially under 40 MPa into anode pellet. On anode pellet BCY20 and BZY20 electrolyte layer were deposited by a screen printing and co-sintered at 1450 ºC for 10 hours. LSCF cathode powder was also deposited and sintered at 1000 ºC. Figure 1(A) shows an optical image of a large-sized PCFC.

2.2 Preparation of Ni and Ni-Sn porous metals

A polyurethane foam with interconnected cells was treated to become electrically conductive. This was followed by the application of a predetermined amount of nickel via electrodeposition. The base material, or plastic foam, was removed through heat treatment at 800 ºC. The remaining nickel was reduced in a reducing gas at approximately 1000 ºC to become a nickel porous metal. Next, the Ni porous metal was coated with a predetermined amount of Sn by electrodeposition. Additionally, this was heat-treated in a reducing gas at approximately 1000 ºC to become a Ni-Sn porous alloy by means of Sn diffusion into Ni. Figure 1(B) shows an SEM image of the surface of the Ni-Sn porous alloy [3].

3. Result

The power generating characteristics of a single-PCFC in which Ni-Sn porous alloy and Ni porous metal were applied as a cathode and anode collector was evaluated at the operating temperature of 600 ºC. Peak power densities of 500 mW/cm² and 333 mW/cm² were achieved, respectively, at 600 ºC and 500 ºC operating on hydrogen fuel.

[1] H. Iwahara, et al., Solid State Ionics, 61, 65 (1993)

[2] J. Dailly, et al., Journal of Power Sources, 240, 323 (2013)

[3] C. Hiraiwa, et al., International Journal of Hydrogen Energy, 42, 12567 (2017)