High-temperature long-term stable ordered mesoporous Ni–CGO as an anode for solid oxidefuel cells

Abstract

High temperature stable ordered mesoporous nickel–gadolinium-doped ceria cermets were prepared from a silica hard template (KIT-6), by a multistep impregnation process. The resulting cermet consists of an intimately mixed composite at the nanoscale with highly connected nickel and ceria percolation networks that ensure good electronic conductivity and strong penetration of the active area inside the material. The mesoporous cermets were implemented and evaluated as anodes for intermediate-temperature solid oxide fuel cells using gadolinia-doped ceria as the electrolyte. Targeted values of anode/electrolyte area specific resistance were obtained in the intermediate range of temperatures (ASR = 0.25 Ω cm² at 675 °C). Virtually no degradation of the microstructure and the electrochemical performance was observed for the cermet after more than 200 h of testing at 800 °C in a water vapor saturated 5% H₂ in argon atmosphere. This confirmed the stability of the mesostructure under SOFC operating conditions. Finally, fuel cell tests were carried out using an electrolyte-supported SOFC consisting of a double mesoporous layer (NiO–CGO 50 : 50 wt% and NiO–CGO 65 : 35 wt%) working as the anode and La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) as the cathode. A maximum value of the power density of 435 mW cm⁻² was achieved at 800 °C in water vapor saturated pure H₂. The here-presented mesoporous approach gives rise to a new class of high-temperature stable nanostructured composites, electrochemically analogous to a mixed ionic electronic conductor, for intermediate temperature solid oxide fuel cells.