DRIFTS-MS Investigation of Low-Temperature CO Oxidation on Cu-Doped Manganese Oxide Prepared Using Nitrate Aerosol Decomposition.

Cu-doped manganese oxide (Cu-MnO) prepared using aerosol decomposition was used as a CO oxidation catalyst. Cu was successfully doped into MnO due to their nitrate precursors having closed thermal decomposition properties, which ensured the atomic ratio of Cu/(Cu + Mn) in Cu-MnO close to that in their nitrate precursors. The 0.5Cu-MnO catalyst of 0.48 Cu/(Cu + Mn) atomic ratio had the best CO oxidation performance, with and as low as 48 and 69 °C, respectively. The 0.5Cu-MnO catalyst also had (1) a hollow sphere morphology, where the sphere wall was composed of a large number of nanospheres (about 10 nm), (2) the largest specific surface area and defects on the interfacing of the nanospheres, and (3) the highest Mn, Cu, and Oads ratios, which facilitated oxygen vacancy formation, CO adsorption, and CO oxidation, respectively, yielding a synergetic effect on CO oxidation. DRIFTS-MS analysis results showed that terminal-type oxygen (M=O) and bridge-type oxygen (M-O-M) on 0.5Cu-MnO were reactive at a low temperature, resulting in-good low-temperature CO oxidation performance. Water could adsorb on 0.5Cu-MnO and inhibited M=O and M-O-M reaction with CO. Water could not inhibit O decomposition to M=O and M-O-M. The 0.5Cu-MnO catalyst had excellent water resistance at 150 °C, at which the influence of water (up to 5%) on CO oxidation could be completely eliminated.