Characterization of LaFe0.6Co0.4O3 washcoat layer on a monolithic substrate

Abstract

Development of automotive three-way catalysts (TWC) is a critical research topic owing to the increasingly stringent emission regulations together with the price and scarcity of precious metals. Among different materials classes, perovskite-type oxides are known to be valuable alternatives because of their high catalytic activities and thermal stability. The interest in doped lanthanum ferrite perovskite as a catalyst is the concept of regeneration of catalyst nanoparticles, which makes it be used efficiently in automobile exhaust for longer duration in comparison to the conventional TWCs. B-site cation regeneration prevents particle growth and sulfur poisoning; hence, the consumption of precious metals will be reduced without lowering the catalytic performance. The aim of this study is to optimize the characteristics of a LaFe0.6Co0.4O3 (LFC) washcoat layer on a cordierite (2MgO.2Al2O3.5SiO2) monolithic substrate through dip coating of the slurry of amorphous and calcined nano-sized LFC particles. Experiments have been conducted to find the optimum amount of viscosity of the slurry, number of dipping repetitions, and suspension time in order to get the highest specific surface area and adherence to the substrate. Also, differences between a slurry with amorphous and calcined powder, precipitation agent and calcination temperature are investigated. It was found that a slurry with 8% w/w of LFC powder, 2% w/w of PVA, 1% w/w of HNO3, and 7.8% w/w of glycerol in water yields suitable slurry characteristics for the dip-coating purpose. SEM pictures were acquired to find out the morphology of the washcoat layer. By repeating the dip-coating process for two times with the calcined powder, a uniform and porous layer is formed on the monolithic substrate with particle size of around 200 nm after sintering at 900 °C.