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

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 La_0.8Sr_1.2Fe_0.9Co_0.1O_4±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 La_0.8Sr_1.2FeO_4±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 La_0.8Sr_1.2FeO_4±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-Gd_0.1Ce_0.9O_2-δ (CGO) composite as an electrode for IT-SSOFCs.