A Comparative Study of Oxygen Reduction Reaction on Bi- and La-Doped SrFeO[sub 3−δ] Perovskite Cathodes

Abstract

In this work the oxygen reduction reaction on Bi 0.5 Sr 0.5 FeO 3−␦ ͑BSF͒ and La 0.5 Sr 0.5 FeO 3−␦ ͑LSF͒ as cathodes for intermediate temperature solid oxide fuel cells ͑600-750°C͒ is compared in detail. Partial substitution of Sr in SrFeO 3−␦ with 50 mole % of Bi or La results in the distinct structural features which strongly impact its electrochemical characteristics due to the presence of a lone electron pair in Bi 3+ , which is not available in La 3+ . Cubic structure for BSF favours higher ionic conductivity and enhanced formation of oxygen vacancies relative to rhombohedral structure for LSF. Large oxygen nonstoichiometry for BSF, nevertheless, leads to the dominance of Fe 3+ and subsequent low electronic conductivity relative to LSF. It was found that upon cathodic polarization, the oxygen vacancies are created on LSF which helps reducing its interfacial resistance afterward, which is not the case for BSF. Overall, BSF demonstrates good electrochemical performance which can be further optimized by enhancing its electronic conductivity.

Preparation and electrochemical performance of cobalt-free cathode material Ba0.5Sr0.5Fe0.9Nb0.1O3−δ for intermediate-temperature solid oxide fuel cells

“…The decrease of the conductivity is mainly due to the increasing concentration of oxygen vacancies in BSFN at temperatures above 425 °C [19] . Similar conduction behavior has also been observed for the Bi 0.5 Sr 0.5 FeO 3−δ [9] , [11] , SrFe 0.9 Nb 0.1 O 3−δ [12] , SrFe 1−x Ti x O 3−δ [14] and LaBaCuFeO 5+x [19] cathode materials. The electrical conductivity of the BSFN sample sintered at 1250 °C is higher than that of the sample sintered at 1300 °C.…”

“…As shown in Fig.4(A), the ASR values decrease markedly with the increasing temperature. The ASR values of the BSFN cathode on the SDC electrolyte are 0.17, 0.078, 0.042 and 0.024 Ω·cm 2 at 650, 700, 750 and 800 °C, respectively, which are significantly lower than those of other cobalt-free cathodes on SDC electrolyte in the previous reports, such as Ba 0.5 Sr 0.5 · Zn 0.2 Fe 0.8 O 3-δ (0.23 Ω·cm 2 at 700 °C) [5] , Ba 0.5 Sr 0.5 Fe 0.8 Cu 0.2 O 3-δ (0.137 Ω·cm 2 at 700 °C) [7] , SrFe 0.9 Nb 0.1 O 3−δ (0.290 Ω·cm 2 at 700 °C) [9] , Bi 0.5 Sr 0.5 FeO 3−δ (0.12 Ω·cm 2 at 700 °C) [11] , La 0.5 Sr 0.5 FeO 3−δ (0.79 Ω·cm 2 at 700 °C) [11] and Sm 0.5 Sr 0.5 Fe 0.8 Cu 0.2 O 3-δ (0.085 Ω·cm 2 at 700 °C) [21] . This indicates that the BSFN cathode has a higher electrochemical catalytic activity for oxygen reduction reaction.…”

“…[8][9][10][11][12][13][14] . Particularly, SrFe 0.9 Nb 0.1 O 3−δ was prepared by us and its good electrochemical performance as an IT-SOFC cathode was demonstrated [9] .…”

One-dimensional porous La0.5Sr0.5CoO2.91 nanotubes as a highly efficient electrocatalyst for rechargeable lithium-oxygen batteries

“…In addition, perovskites, having a general formula of ABO 3 , are interesting oxygen electrode catalysts because of their high oxide ion mobility. By partially substituting a cation A 0 for A, or a cation B 0 for B, with a different valence, ionic defects or changes in the valence states of the catalytically active metal B can be induced in the perovskite thereby influencing its catalytic activity and conductivity [18][19][20]. Among the LaMO 3 (M = Ni, Co,Fe, Mn, and Cr) materials which have been used for modified rotating ring-disk electrodes, LaCoO 3 showed the largest ORR current density and most positive onset potential.…”

Electrode redox properties of Ba1−xLaxFeO3−δ as cobalt free cathode materials for intermediate-temperature SOFCs

“…7. The E a for ASRs of Ba 1Àx La x FeO 3Àd are 116, 106, 104 and 101 kJ/mol, which is relatively low with respect to other cobalt-free cathodes [15,41,42] and even BSCF (116 kJ/ mol) [7]. A low E a implies that the ASR has low temperature dependence.…”