Enhancing\nSoot Catalytic Combustion Performance of\nSmMn<sub>2</sub>O<sub>5</sub> via Surface Etching

One of the primary challenges in diesel exhaust treatment\nis the\ndevelopment of catalysts for soot combustion with high catalytic activity.\nIn this work, we investigated the effects of acid etching on the catalytic\ncombustion activity of SmMn<sub>2</sub>O<sub>5</sub> (SMO). The soot\ntemperature-programmed oxidation results showed that the nitric acid-etched\nSMO (ESMO) exhibited better catalytic performance than the raw SMO.\nSpecially, in the presence of NO, the <i>T</i><sub>50</sub> values of ESMO and SMO were 406.5 and 439.7 °C, respectively.\nNO exhibited a significant impact on the catalytic activity of SMO\nand ESMO. Furthermore, ESMO exhibited better soot catalytic combustion\nperformance and higher CO<sub>2</sub> selectivity in the presence\nof SO<sub>2</sub> than those of the raw SMO. Compared with the performance\nof SMO in the absence of SO<sub>2</sub>, the <i>T</i><sub>50</sub> of ESMO just increased by 65.1 °C in the presence of\nSO<sub>2</sub>, and the CO<sub>2</sub> selectivity of ESMO could be\nmaintained as high as 91.1%. After acid etching, the pore structures\nand surface atom distributions were modified. Mn (especially Mn<sup>4+</sup>) and oxygen species were enriched, and amorphous MnOx was\nformed on the catalyst surface, which was the main reason for the\nenhanced catalytic activity. This study suggested that nitric acid\netching is a suitable method for enhancing the combustion activity\nof SMO.