Porous Cu-Mn-O catalysts fabricated by spray pyrolysis method for efficient CO oxidation
Series of “Hopcalite” catalysts for low-temperature CO oxidation are prepared through a facile ultra-sonic spray pyrolysis approach. It has been found that the spray pyrolysis temperature and Cu/Mn atomic ratio in initial precursors show significant impacts on the catalytic activity of Cu-Mn-O catalysts. The catalyst synthesized at 550 °C with Cu/Mn = 1/2 in precursor (Cu1Mn2-550) shows the highest catalytic activity towards CO oxidation (T 100 = 63 °C; E a = 17.04 KJ mol −1 ), owing to the formation of CuMn 2 O 4 phase with poor crystallinity. The synergistic effect of Cu and Mn species in spinel Cu-Mn-O phases attributes to the evaluated catalytic activity compared with those of pure oxides of copper or manganese towards CO oxidation. The results reveal that Cu1Mn2-550 not only provides more defects and vacancies to create more active sites, but also generates more highly active Cu (II) to promote CO oxidation. On the contrary, the decreasing amount of Cu (II) and the higher degree of crystallinity resulting from higher synthesis temperature lead to the deterioration of catalytic activity. Moreover, the phase transformation among the Cu x Mn 3-x O 4 spinels also shows significant effect on CO conversion rate. Finally, the formation mechanism of Cu-Mn-O catalysts and related CO oxidation process are discussed based on series of characterizations.
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