In Situ Growth of Nanoparticles in Layered Perovskite La_0.8Sr_1.2Fe_0.9Co_0.1O_4−δ as an Active and Stable Electrode for Symmetrical Solid Oxide Fuel Cells

Abstract

Compared to traditional deposition techniques, in situ growth of nanoparticles on material surfaces is one of the more time- and cost-effective ways to design new catalysts. The B-site transition-metal cations in perovskite lattice could be partially exsolved as nanoparticles under reducing conditions, greatly enhancing catalytic activity. Here, we demonstrate that growing nanoparticles on the surface of a layered perovskite La0.8Sr1.2Fe0.9Co0.1O4±δ (LSFC), which could be applied as a redox stable and active electrode for intermediate-temperature symmetrical solid oxide fuel cells (IT-SSOFCs). Substitution of a proper amount of Co into the layered perovskite can thus optimize cathode and anode performance simultaneously. For example, the polarization resistances (R p) of LSFC electrode at 800 °C are 0.29 and 1.14 Ω cm2 in air and in 5% H2/N2 respectively, which are much smaller compared with the R p of Co-free La0.8Sr1.2FeO4±δ. The lower polarization resistance for LSFC in air can be mainly attributed to the enhanced electrical conductivity through the partial substitution of iron by cobalt in La0.8Sr1.2FeO4±δ. Meanwhile, the electrocatalytic activity of H2 greatly improved, because of the formation of exsolved homogeneous Co0 nanoparticles on the surface of LSFC, which appears to promote hydrogen oxidation reaction. Lower polarization resistance of 0.21 Ω cm2 in air and 0.93 Ω cm2 in 5% H2/N2 at 800 °C could be obtained further by examining an LSFC–Gd0.1Ce0.9O2−δ (CGO) composite as an electrode for IT-SSOFCs.

Development of High Power Density Metal‐Supported Solid Oxide Fuel Cells

“…It has been noted, however, that nanoscale‐doped ceria can present mixed conduction in air due to the large influence of grain boundaries relative to bulk . Of course, LSM is a much better cathode catalyst than SDCN as clearly seen in Figure c, but a symmetric cell with moderate power density may be interesting for some applications …”

Nickel Exsolution‐Driven Phase Transformation from an n=2 to an n=1 Ruddlesden‐Popper Manganite for Methane Steam Reforming Reaction in SOFC Conditions

“…Then, under reducing atmosphere and high temperature (driven force), nanosized metallic particles can precipitate from the bulk to the surface. This phenomenon is called in situ growth or exsolution and, as is previously presented, it could be considered as the basis for the design and development of more sophisticated oxide materials with advanced functionality . Even though, such mechanism has been applied mainly for perovskite structural oxides and until now few examples of exsolution in RP compounds have been reported…”

High-Performance La0.5Ba0.5Co1/3Mn1/3Fe1/3O3−δ-BaZr1−zYzO3−δ Cathode Composites via an Exsolution Mechanism for Protonic Ceramic Fuel Cells

“…Previous studies employing exsolution methods exploit the stability of the hosting precursor under oxidizing atmosphere while the exsolution occurs under reducing conditions [26]. Hence, this methodology has primarily been used to exsolve metallic nanoparticles [26], an approach which is suitable for anode (fuel electrode) preparation [27][28][29] but not amenable to cathode (air electrode) preparation. In contrast, our approach employs oxidation-driven exsolution from a single phase material that can yield fine, homogeneous, and porous composite cathodes [14].…”