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Thin films, 0.5- and 1.0-nm thick, of CuMn 2 O 4 were synthesized on γ-Al 2 O 3 using Atomic Layer Deposition (ALD); and their catalytic activities for CO oxidation were measured and compared to that of bulk CuMn 2 O 4. For bulk CuMn 2 O 4 , the surface area decreased dramatically when the sample was calcined at 1073 K; but the area-specific rates for CO oxidation were the same for bulk samples calcined at 473 K and 1073 K. For thin films of CuMn 2 O 4 on γ-Al 2 O 3 , both the surface area and spinel structure were maintained following oxidation at 1073 K or reduction at 973 K. Area-specific, CO-oxidation rates on the ALD-prepared catalysts were somewhat lower than those found on bulk CuMn 2 O 4 ; however, adding an additional ALD cycle of Cu on the CuMn 2 O 4 /γ-Al 2 O 3 increased the rates to the same level as that of the bulk CuMn 2 O 4. [Display omitted] • 0.5-nm thick film of CuMn 2 O 4 was synthesized on γ-Al 2 O 3 by atomic layer deposition. • Thin-film CuMn 2 O 4 maintains a high surface area at elevated temperatures. • Cu-terminated CuMn 2 O 4 film has the same CO oxidation activity as bulk CuMn 2 O 4. [ABSTRACT FROM AUTHOR]

Conformal thin films of a cerium-manganese mixed oxide with a stoichiometry of CeMnO x were deposited on a high-surface-area γ-Al 2 O 3 support by Atomic Layer Deposition (ALD). Upon redox cycling, the CeMnO x film underwent a reversible phase transition between a reduced perovskite CeMnO 3 phase and an oxidized fluorite CeMnO 3.5 phase, as shown by X-ray diffraction (XRD) and High-Resolution Scanning/Transmission Electron Microscopy (HR-S/TEM). X-ray Photoelectron Spectroscopy (XPS) and Electron Energy Loss Spectroscopy (EELS) revealed that Ce and Mn were in +3-oxidation states in the reduced perovskite phase and +4 and + 3 respectively in the oxidized fluorite phase. The composition of the film as a function of P(O 2) at 1073 K was measured by coulometric titration and showed that a transition between Ce3+ and Ce4+ occurred at a P(O 2) of 10−9 atm, a value that is much higher than that required for oxidizing either reduced bulk ceria or thin-film ceria on γ-Al 2 O 3. These properties make CeMnO x films an interesting candidate for various catalytic applications. Conformal thin films of a cerium-manganese mixed oxide CeMnO x were deposited on a high-surface-area γ-Al 2 O 3 support by Atomic Layer Deposition. These films can reversibly transition between a reduced perovskite Ce+3Mn+3O 3 phase and an oxidized fluorite Ce+4Mn+3O 3.5 phase upon redox cycling at 1073 K. [Display omitted] • CeMnO x films undergo a reversible perovskite-fluorite phase transition at 1073 K. • Ce cations transition between +3- and +4-oxidation states upon redox cycling. • Mn cations remain in the +3-oxidation state throughout redox cycling. • Mn cations remain +3 in CeMnO 3 film even at P(O 2) as low as 10−19 atm at 1073 K. [ABSTRACT FROM AUTHOR]