Optimization of anode structure for intermediate temperature solid oxide fuel cell via phase‐inversion cotape casting

Abstract

A functional layer and a porous support that together constitute an anode for a solid oxide fuel cell were simultaneously formed by the phase-inversion tape casting method. Two slurries, one composed of NiO and yttria-stabilized zirconia (YSZ) powders and the other of NiO, YSZ, and graphite were cocasted and solidified by immersion in a water bath via the phase-inversion mechanism. The asformed green tape consisted of a sponge-like thin layer and a fingerlike thick porous layer, derived from the first slurry and the second slurry, respectively. The former acted as the anode functional layer (AFL), while the latter was used as the anode substrate. The AFL thickness was varied between 20 and 60 lm by adjusting the blade gap for the tape casting. Single cells based on such NiO-YSZ anodes were prepared with thin YSZ electrolytes and YSZ-(La 0.8 Sr 0.2 ) 0.95 MnO 3Àd (LSM) cathodes, and their electrochemical performance was measured using air as oxidant and hydrogen as fuel. The maximum power densities obtained at 750°C were 720, 821, and 988 mW cm À2 with the AFL thickness at 60, 40, and 20 lm, respectively. The satisfactory electrochemical performance was attributed to the dual-layer structure of the anode, where the sponge-like AFL layer provided plenty of triple-phase boundaries for hydrogen oxidation, and the fingerlike thick porous substrate allowed for facile fuel transport. The phase-inversion tape casting developed in this study is applicable to the preparation of other planar ceramic electrodes with dual-layer asymmetric structure. K E Y W O R D Sanode functional layers, NiO and yttria-stabilized zirconia anodes, phase-inversion tape casting, solid oxide fuel cells

Review of anodic reactions in hydrocarbon fueled solid oxide fuel cells and strategies to improve anode performance and stability

“…The results of electrochemical impedance spectroscopy indicated that low-frequency resistance, which corresponds to gas diffusion, decreased slightly after adding Ni to the anode, indicating such anode configuration should accelerate electrochemical performance. Detailed studies were conducted by the group of Chusheng Chen, which proved that the gas penetration performance was higher for the electrode with straight open pores [90][91][92]. Nano-catalysts used as a catalyst layer for anodes also proved helpful with increasing the anode performance.…”

Tuning the Microstructure and Thickness of Ceramic Layers with Advanced Coating Technologies Using Zirconia as an Example

“…Both freeze casting and phase-inversion-assisted tape casting have been utilized to fabricate gas separation membranes [155][156][157] as well as supports for SOFCs and SOECs. [158][159][160][161][162] The basic principle of freeze casting is the formation of a very specific pore morphology through the directional freezing of the liquid phase in the slurry, and its subsequent sublimation. The main application of freeze casting using tape-cast ceramic powder suspensions is unidirectional freezing, where the tape is brought into contact with a cold surface on one side that removes sufficient heat from the tape to freeze the solvent.…”

“…Both freeze casting and phase‐inversion‐assisted tape casting have been utilized to fabricate gas separation membranes [ 155–157 ] as well as supports for SOFCs and SOECs. [ 158–162 ]…”

Tubular solid oxide fuel cells fabricated by a novel freeze casting method

“…Two methods, phase inversion and freeze casting, have received significant attention in this regard. Different research groups have reported the application of phase inversion method to fabricate SOFC anode supports with a gradient porous microstructure . The phase inversion method produces finger‐like pore channels across the gas diffusion layer and a sponge‐like porous structure close to the anode‐electrolyte interface.…”

“…Different research groups have reported the application of phase inversion method to fabricate SOFC anode supports with a gradient porous microstructure. [15][16][17][18] The phase inversion method produces finger-like pore channels across the gas diffusion layer and a sponge-like porous structure close to the anode-electrolyte interface. This leads to fast gaseous diffusion through the anode without reduction in the electrochemical active sites, that is three-phase boundary (TPB) regions.…”