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

Abstract

Cu-doped manganese oxide (Cu–Mn2O4) prepared using aerosol decomposition was used as a CO oxidation catalyst. Cu was successfully doped into Mn2O4 due to their nitrate precursors having closed thermal decomposition properties, which ensured the atomic ratio of Cu/(Cu + Mn) in Cu–Mn2O4 close to that in their nitrate precursors. The 0.5Cu–Mn2O4 catalyst of 0.48 Cu/(Cu + Mn) atomic ratio had the best CO oxidation performance, with T50 and T90 as low as 48 and 69 °C, respectively. The 0.5Cu–Mn2O4 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 Mn3+, 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–Mn2O4 were reactive at a low temperature, resulting in-good low-temperature CO oxidation performance. Water could adsorb on 0.5Cu–Mn2O4 and inhibited M=O and M-O-M reaction with CO. Water could not inhibit O2 decomposition to M=O and M-O-M. The 0.5Cu–Mn2O4 catalyst had excellent water resistance at 150 °C, at which the influence of water (up to 5%) on CO oxidation could be completely eliminated.

Unveiling the Surface Chemical Reactions during Multi-Phase Catalytic Oxidation of Soot on Nanoengineering/Interfacing/Doping-Prepared Mn-CeO2 Catalysts Using TG-MS and Operando DRIFTS-MS

“…Mn-doped CeO 2 (Mn-CeO 2 ), CeO 2 , and Mn 2 O 3 catalysts were prepared using nitrate aerosol pyrolysis . The atomic ratios (Mn/(Mn + Ce)) were 0, 0.33, 0.43, 0.5, 0.57, 0.67, and 1.0 by controlling the amounts of Ce­(NO 3 ) 4 ·6H 2 O) and manganese nitrate (Mn­(NO 3 ) 2 ) purchased from Shanghai Maclin Bio-Chemical (China) (Table S1).…”

“…In this study, Mn-CeO 2 catalysts were prepared using the nitrate aerosol pyrolysis method . The soot was simulated with a Printex-U (PU).…”

“…To encourage soot combustion by better catalyst preparation, it is important to undertake efforts to increase the soot-catalyst interaction efficiency. The aerosol pyrolysis method is based on heating, nanoengineering, interfacing, and doping and can prepare the catalysts with rational performances. − However, no report could be found on soot oxidation using a catalyst prepared using aerosol pyrolysis.…”

Revealing the intrinsic nature of Ni-, Mn-, and Y-doped CeO2 catalysts with positive, additive, and negative effects on CO oxidation using operando DRIFTS-MS

“…Ni-doped CeO 2 (Ni-CeO 2 ), Mn-doped CeO 2 (Mn-CeO 2 ), Y-doped CeO 2 (Y-CeO 2 ), NiO, Mn 2 O 3 , CeO 2 , and Y 2 O 3 were prepared using an aerosol pyrolysis method. 31 The atomic ratio of the dopants (Ni, Mn, or Y) to Ce (host) was 1 : 1 by controlling the amounts of cerium nitrate and the dopant metal nitrate precursors. The pyrolysis temperature was 600 °C to ensure the complete decomposition of the nitrate precursors.…”

“…CO oxidation on each catalyst was evaluated using a continuous flow-bed reaction system as per the literature. 31 The reaction gas containing 1 vol% CO, 10 vol% O 2 balanced with N 2 was fed to a tubular quartz reactor at 100 mL min −1 with an weight hourly space velocity (WHSV) of 30 000 mL g −1 h −1 . The temperature values of T 50 for 50% CO conversion were used to indicate the CO oxidation activities of each catalyst.…”