SrTi1−XMnXO3 and MnOX/SrTiO3 with dendritic morphology: A comparison of physico-chemical properties and soot catalytic combustion

Abstract

Abstract In this work, a comparative study of the physico-chemical and catalytic properties of doped and impregnated Mn-SrTiO3 for the catalytic combustion of soot has been reported. Results show that SrTiO3 demonstrated dendritic morphology that is attributed to SrTiO3 with perovskite structure. XPS analysis confirmed the successful incorporation of Mn4+ species in Ti4+ lattice sites for doped samples, whereas different MnOX species were formed on the surface of SrTiO3 in the case of impregnated catalysts with different Mn loadings. Among all catalysts tested in this work, samples doped with 1 wt% Mn showed the best catalytic behavior, decreasing the combustion temperature well above 100 °C compared with the uncatalyzed reaction and a Mn-turnover number of 5.77 which is comparable with previous perovskite reports. During the soot catalytic combustion process, accelerated oxidation rates were observed at high temperatures. This may be attributed to the mobility of the bulk oxygen reaching the catalyst surface, promoted by the high redox capacity of Mn-doped perovskites. Despite a reduction in the Mn species observed for MnOx impregnated samples, they showed much less catalytic activity when compared with the doped samples because of the strong contribution of bulk oxygen in the perovskite structure. These doped catalysts also displayed low catalytic activity at temperatures below 500 °C, which is possibly due to the presence of surface carbonates. This work contributes to the idea that bulk oxygen plays an important role in perovskites as a catalyst that provides enhanced catalytic activity for soot combustion.