Properties evolution of LaCoO₃ Perovskite synthesized by reactive grinding - Application to the toluene oxidation reaction

Perovskites are well known materials that are considered as viable alternative to noble metal-based catalysts in the environmental field. To be competitive, major issues such as unattractive textural properties and lower intrinsic activities than those of noble metal counterparts must be first addressed. On the other hand, reactive grinding is a versatile method to efficiently synthesize materials with improved textural properties, depending on the sequence and parameters. LaCoO3 perovskites were synthesized by a three-step reactive grinding top-down process: (i) solid-state reaction - SSR; (ii) high energy ball milling - HEBM; (iii) low energy ball milling - LEBM. The physicochemical properties evolution of perovskite materials over the reactive grinding process was investigated by XRD, N-2-physisorption, ICP-OES, XPS, H-2-TPR, O-2-TPD and OIE, while their catalytic performances were evaluated for the toluene total oxidation reaction in dry and wet conditions. Each successive reactive grinding step allowed us to optimize the catalysts textural properties, with respectively the obtention of a microcrystalline material, a drastic reduction of crystal size to a nanometric scale along with formation of dense particles and then a significant increase of specific surface area up to 50 m(2).g(-1) by particles deagglomeration. The reactive grinding sequence presented here also deeply impacted the redox properties of LaCoO3 catalysts, leading to increased performances in the toluene total oxidation reaction (SSR < HEBM < LEBM). A special care was paid to the impact of Fe contamination over grinding steps and time, on redox and catalytic properties of LaCoO3 samples.