Highly enhanced electrochemical property by Mg-doping La2Ni1-xMgxO4+δ (x = 0.0, 0.02, 0.05 and 0.10) cathodes for intermediate-temperature solid oxide fuel cells

Abstract

From the view point of compatibility of both crystalline and element with the prototypical perovskite-type electrolyte of La0.9Sr0.1Ga0.8Mg0.2O3-δ, a series of micro-Mg-doped La2NiO4+δ compounds with compositions of La2Ni1-xMgxO4+δ (x = 0.0, 0.02, 0.05 and 0.10) were successfully synthesized via a traditional sol-gel process and evaluated as cathode for intermediate-temperature solid oxide fuel cells (IT-SOFC). The effects of Mg-doping on crystal structures, bond properties and covalent states were analyzed by X-Ray Diffraction (XRD), Infrared spectra (IR) and X-ray photoelectron spectroscopy (XPS) techniques, respectively. It is found that Mg-doping is benefit for the migration of the interstitial oxygen by weakening the Ni(Mg)O bond. More importantly, we found that Mg doped at the subsurface under the Ni of (001) surface will promote both the O2 adsorption and decomposition process from the analysis of the oxygen migration dynamics. Considering the balance of electronic conductivity, it was indicated that La2Ni0.98Mg0.02O4+δ (LNM0.02) manifested the optimal electrochemical property with the lowest area specific resistance of 0.05 Ω cm2 at 800 °C, and along with a maximum power density of 528 mW cm−2 for an electrolyte supported single cell LNM0.02|LSGM|NiO-SDC at 800 °C with approximately 20% higher than that of the La2NiO4+δ (LN) (∼429 mW cm−2) cathode. The results indicate that introducing micro-dose of Mg into Ni-site in La2NiO4+δ compound is an efficient way to obtain an excellent cathode material for IT-SOFCs.