In-situ growth of metallic nanoparticles on perovskite parent as a hydrogen electrode for solid oxide cells

Abstract

In this work, in-situ fabricated nano-socketed Fe-Ni particles structured Sr2Fe1.5Mo0.5O6-δ (SFM) electrodes are proposed to simultaneously combine good electrochemical properties of Ni-based materials and good stabilities of SFM-based materials. Preliminary studies on the Ellingham diagram and density functional theory offer certain theoretical basis for realizing the feasibility to extract Fe-Ni alloy from parent Sr2Fe1.3Ni0.2Mo0.5O6-δ in the viewpoint of thermodynamic and minimum energy principle. Experimental results according to X-ray diffraction, scanning electron microscopy-elements mapping, high resolution transmission electron microscopy measurements show that a large amount of uniformly dispersed Fe-Ni nano-catalysts are elegantly exsolved from the perovskite oxide parent. Electrical conductivity relaxation results indicate that surface exchange coefficient of SFM-based material is enhanced from 0.5 × 10−3 to 1.7 × 10−3 cms−1 by the in-situ growth of Fe-Ni alloy at 800 °C. The in-situ fabricated Fe-Ni@SFM combined with Ce0.8Sm0.2O1.9 (SDC) composite electrodes perform a considerably high electrolysis current density of 1257 mA cm−2 at 1.3 V, 850 °C and polarization resistance of 0.20 Ωcm2 at open circuit voltage and 850 °C. Distribution relaxation of time analysis of impedance spectra shows that the gas conversion process is the rate-limiting step in the Fe-Ni@SFM-SDC hydrogen electrode for steam electrolysis.