Microstructure and Performance of Anode for Microtubular Solid Oxide Fuel Cells

doi:10.15541/jim20140185

Abstract

Abstract:

NiO-YSZ hollow fibers were fabricated via a phase-inversion spinning technique. An YSZ electrolyte film was dip-coated on the outer surface of the fiber and then co-sintered at 1450℃ to form electrolyte/anode hollow fiber half cell. The microstructure of the NiO-YSZ anode was modulated by controlling NMP/ethanol ratio of the inner coagulant during spinning process. Experimental results showed that, with the 1-Methy 1-2-Pyrrolidinone (NMP) content increase from 0 to 30wt%, 50wt%, 70wt% and 100wt%, the microscopy of the anode hollow fibers evolved from a sandwiched structure, i.e. finger-like pore/sponge voids/finger-like pore morphology, to a finger-pore-penetrating structure, leading to porosity increase of the anode. Meanwhile, gas tightness of YSZ electrolyte film, mechanical strength of the reduced dual-layer hollow fibers, and conductivity of anode could decrease. Microtubular fuel cells were fabricated by coating a porous Ag cathode onto the dense YSZ electrolyte film. The concentration polarization in the H₂/air cell decreased with increasing the length of the finger-like pores. The microtubular SOFC made from the anode hollow fibers with 70wt% of NMP-ethanol as the inner coagulant demonstrated the minimum polarization resistance and the highest output performance with 662 mW/cm²power density.

Key words: microtubular solid oxide fuel cell, hollow fiber, anode microstructure, concentration polarization

CLC Number:

O646
TQ174

YANG Nai-Tao, SHEN Yi-Chi, YAN Wei, MENG Xiu-Xia, TAN Xiao-Yao, MA Zi-Feng. Microstructure and Performance of Anode for Microtubular Solid Oxide Fuel Cells[J]. Journal of Inorganic Materials, 2014, 29(12): 1246-1252.

Figures/Tables 9

Fig. 1 Microstructures of YSZ/NiO-YSZ dual-layer hollow fibers (1450℃) Internal coagulant was (a) pure ethanol, (b) 70wt% ehanol/30 wt% NMP, (c) 50wt% ehanol/50 wt% NMP, (d) 30wt% ehanol/70wt% NMP and (e) pure NMP; 1-cross-section, 2-inner surface, 3-outer surface

Table 1 Solubility parameters of the solvent and non-solvent

Substance/mixtures	δ	δ_d	δ_p	δ_h
PESf	21.9	17.6	10.4	7.8
NMP	22.9	18	12.3	7.2
H₂O	47.9	15.5	16.0	42.3
Ethanol(EtOH)	26.0	15.8	8.8	19.4
EtOH/NMP=7: 3	24.8	16.46	9.85	15.74
EtOH/NMP=5: 5	24.0	16.9	10.55	13.3
EtOH/NMP=3: 7	23.3	17.34	11.25	10.86

Fig. 2 Conductivities of Ni-YSZ anode hollow fiber vs ratio of NMP/ethanol

Fig. 3 Porosities of NiO-YSZ and reduced Ni-YSZ hollow fiber vs ratio of NMP/ethanol

Fig. 4 Mechanical strength of NiO-YSZ and reduced Ni-YSZ hollow fiber vs. ratio of NMP/ethanol

Fig. 5 Gas-tightness of electrolyte membrane vs ratio of NMP/ethanol

Fig. 6 Potential and power density vs current density of MT- SOFC based the asymmetric anode at 800℃

Fig. 7 EIS of MT-SOFC based asymmetric anode at OCV (800℃) (a) Ratio of NMP/ethanol; (b) Total resistance(Rt), polarization resistance, activation resistance(Ra), and diffusion resistance (Rd)

Table 2 Resistance vs internal coagulants for MT-SOFC

NMP	R_o/Ω	R_a/Ω	R_t/Ω	R_p/Ω	R_d/Ω	(R_a/R_p)×100	(R_d/R_p)×100
0	0.16	0.37	1.22	1.06	0.69	34.91	65.09
30wt%	0.16	0.23	0.86	0.70	0.47	32.86	67.14
50wt%	0.16	0.22	0.76	0.60	0.38	36.67	63.33
70wt%	0.16	0.21	0.50	0.34	0.13	61.76	38.24
100wt%	0.16	0.26	0.56	0.40	0.14	65.00	35.00

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