An intermediate temperature fuel cell based on composite electrolyte of carbonate and doped barium cerate with SrFe0.7Mn0.2Mo0.1O3−δ cathode

Abstract

BaCeO3-based proton conductor BaCe0.5Zr0.3Y0.16Zn0.04O3-δ (BCZYZn) was adopted as a part of the oxide-carbonate composite electrolyte. The total ionic conductivity of BCZYZn-carbonate composite is 0.28 S cm-1 at 500 °C. Perovskite oxide SrFe0.7Mn0.2Mo0.1O3-δ was developed and used as cathode. It was found that SrFe0.7Mn0.2Mo0.1O3-δ exhibits a primitive cubic structure with space group) 221 (m 3 Pm  ; a = 3.8790(1) Å, V = 58.364(1) Å 3. The electrical conductivity of SrFe0.7Mn0.2Mo0.1O3-δ is 15-26 S cm-1 in the temperature range 400-700 °C measured by d.c. method. Single cell with BCZYZn-carbonate composite electrolyte and SrFe0.7Mn0.2Mo0.1O3-δ cathode was fabricated and tested with humidified H2 (~3 vol% H2O) as fuel and air as oxidant. A similar configuration cell with lithiated NiO cathode was also constructed for comparison. It was found that neither BaCe0.5Zr0.3Y0.16Zn0.04O3-δ nor SrFe0.7Mn0.2Mo0.1O3-δ is chemically compatible with (Li,Na)2CO3. The fuel cell performance is not as good as those based on doped ceria-carbonate electrolytes.

Synthesis of Ba 0.3 Ca 0.7 Co 0.8 Fe 0.2 O 3-δ composite material as novel catalytic cathode for ceria-carbonate electrolyte fuel cells

“…The analysis indicates that as-prepared BCCF37 is actually the composite-type material due to cobalt and calcium oxides present as secondary phases. The presence of the secondary phases additional to the perovskite phase turns the material into its composite nature, which enhances the properties of the BCCF37 material with higher conductivity and cell performance which is in agreement with the composite type materials for intermediate temperatures fuel cells [12][13][14]. Since the observed cobalt oxide and calcium oxides peaks co-exist with the perovskite phase, therefore the enhancement may be due to the composite effect.…”

“…Replacement of Sr by the cheaper Calcium (Ca) being an A-site dopant has been reported as a possible solution [9]. Recently, use of composite materials for electrolytes and perovskite cathode materials has been demonstrated as a practical approach to address the faced challenges for LT and IT (400-700 C) fuel cells and has attracted huge efforts to develop high performance devices [12][13][14].…”

Carbon Deposition and Sulfur Poisoning in SrFe0.75Mo0.25O3-δand SrFe0.5Mn0.25Mo0.25O3-δElectrode Materials for Symmetrical SOFCs

“…The same cubic structure was also reported for a similar chemical composition, SrFe 0.7 Mn 0.2 Mo 0.1 O 3-δ . 20 As evidenced, partial substitution of iron by manganese does not change the crystal symmetry for SrFe 0.5 Mn 0.25 Mo 0.25 O 3-δ , but leads to a slight decrease in the unit cell parameter. Taking into account the smiliar ionic radii of the Fe and Mn cations (in the expected high spin configuration: 8,21,22 r Fe3+ = 0.645 Å and r Mn3+ = 0.645 Å, r Fe2+ = 0.78 Å and r Mn2+ = 0.83 Å), it is reasonable to assume that the materials differ in oxygen nonstoichiometry δ, with the Mn-containing sample having a smaller value of δ.…”

Screening of electrode materials and cell concepts for composite ceria + salt electrolytes

“…Amphoteric electrode metal oxides easily dissolve in acidic or basic environments. Strategies to circumvent the poor stability of metal oxide electrodes involve control of the melt oxobasicity with admixtures (eg, rare earth or alkaline carbonates/oxides), but also formation of solid solutions based on conventional NiO with other metals . The state‐of‐the art solutions show some efficacy, but alternative materials with high conductivity and chemically stable are still needed.…”

“…Within a significant list of tested electrode materials, the best area specific resistance (ASR) values are in the order of 0.1 Ω.cm 2 at 550°C, using a standard LiNiO 2 cathode. A few complex chemical compositions show ASR values about twice to three times higher in the 500°C to 550°C range.…”