Enhancing Soot Catalytic Combustion Performance of SmMn₂O₅ via Surface Etching

One of the primary challenges in diesel exhaust treatment is the development of catalysts for soot combustion with high catalytic activity. In this work, we investigated the effects of acid etching on the catalytic combustion activity of SmMn2O5 (SMO). The soot temperature-programmed oxidation results showed that the nitric acid-etched SMO (ESMO) exhibited better catalytic performance than the raw SMO. Specially, in the presence of NO, the T50 values of ESMO and SMO were 406.5 and 439.7 °C, respectively. NO exhibited a significant impact on the catalytic activity of SMO and ESMO. Furthermore, ESMO exhibited better soot catalytic combustion performance and higher CO2 selectivity in the presence of SO2 than those of the raw SMO. Compared with the performance of SMO in the absence of SO2, the T50 of ESMO just increased by 65.1 °C in the presence of SO2, and the CO2 selectivity of ESMO could be maintained as high as 91.1%. After acid etching, the pore structures and surface atom distributions were modified. Mn (especially Mn4+) and oxygen species were enriched, and amorphous MnOx was formed on the catalyst surface, which was the main reason for the enhanced catalytic activity. This study suggested that nitric acid etching is a suitable method for enhancing the combustion activity of SMO.