Functional Nanostructure Engineering of SOFC Cathode by Solution Infiltration

Abstract

Formation and distribution of infiltrated electrocatalyst were controlled through solution chemistry and correlated cathode performance was investigated for a La 0.6 Sr 0.4 Co 0.9 Pt 0.1 O 3 -infiltrated solid-oxide fuel cell (SOFC). Selection of solvent and polymeric additives constituting the slip dramatically affected the infiltrate particles' spatial configuration, and finally determined cathode activity under cell operational conditions. The results imply that microstructural features such as 3-dimensional distribution and interconnectivity of infiltrated nanoparticles must be considered when evaluating activity and stability of cathodes. A modified infiltration process utilizing a mixed solvent of low surface tension and functionally sequenced infiltration was effectively applied to manipulate cathode microstructure.Introduction of an electrocatalyst by solution infiltration has been widely demonstrated as an efficient method to enhance cathode performance of a solid-oxide fuel cell (SOFC). 1-5 Infiltration permits diversity in selection of active components and in engineering of electrode microstructure, namely by facilitating superior microstructural design relative to that achievable via conventional fabrication processes.Although infiltration is generally observed to result in superior cathode performance, some heretofore inexplicable discrepancies have been observed in performance of the electrocatalyst. 1,3 For example, the majority of noble metal infiltration-related research indicates that a small amount of infiltrated noble metal enhances electrochemical performance of baseline cathodes. 6-11 Conversely, a minority of researchers has reported that infiltrated Pd or Pt had little effect on cathode performance. 12,13 Conflicting results may be explicable once the underappreciated and essentially unexplored relationship of infiltrate/backbone structure is considered.Based on the above postulation, we examined cell performance variation associated with infiltrate-backbone microstructural configuration, manipulated by infiltrate slip chemistry. A few relevant investigations were reported: Y. Huang et al. reported that the cathode properties of Sr-doped LaMnO 3 (LSM)-yttria-stabilized zirconia (YSZ) composites formed by infiltration of porous YSZ with aqueous salt solutions with LSM nanoparticles, and with molten salts were essentially identical, implying that the structures of the composite are similar because of LSM mobility on YSZ, associated with surface interactions between them. 14 X. Lou et al. observed that aqueous solutions containing catalyst precursors wet YSZ better than LSCF (La 1-x Sr x Co 1-y Fe y O 3-d ), and proposed that controlling the wetting of precursor solutions on porous backbones can dramatically improve the catalyst layer's uniformity and cathode performance. 15 We adopted the perovskite oxide Pt-substituted LSCo (La 0.6 Sr 0.4 Co 0.9 Pt 0.1 O 3-δ or LSCoPt) as an infiltrate and applied the electrocatalyst to a commercial cell possessing an intrinsically functional cathode compo...

Comparison of Cu and Pt point-contact electrodes on proton conducting BaZr0.7Ce0.2Y0.1O3−

“…Since the development of the solvent based infiltrations used in this work, there have been other reports of similar solvent based solutions in SOFC literature, showing further precedent for the technique [148,149]. Both of the cited articles describe better infiltration characteristics than aqueous based solutions alone; such as have been the findings in this work.…”

Surface decorations to abrupt change performance, robustness, and stability of electrodes for solid oxide cells

“…In addition to that, citric acid, NH 4 OH, X100, etc. can be used as surfactants 12,16 . The addition of surfactant helps the dissolution process and prevents the precipitation of it.…”

“…The sample is sintered at elevated temperatures so that the infiltrate particles can crystalize and bond to the backbone electrode. In some cases, the temperature for crystallization can be lower compared to its stand‐alone powder synthesis process, depending on the precursor 16–19 . As a common practice, La 1‐ x Sr x Co 1− y Fe y O 3− δ (LSCF) cathode is infiltrated with ceria‐based electrolyte materials.…”

“…can be used as surfactants. 12,16 The addition of surfactant helps the dissolution process and prevents the precipitation of it. Some also promote the wetting of the solution to the electrode inner surface to provide even coverage.…”

“…In some cases, the temperature for crystallization can be lower compared to its stand-alone powder synthesis process, depending on the precursor. [16][17][18][19] As a common practice, La 1-x Sr x Co 1−y Fe y O 3−δ (LSCF) cathode is infiltrated with ceria-based electrolyte materials. SDC nanoparticles phase is formed and uniformly distributed on the surface of an LSCF backbone.…”