Morphology and electronic properties of Ni supported on Mn-doped CeO_2(l11) thin films

摘要

Well-ordered CeO2(1 1 1) thin films were prepared on a Ru(0001) single crystal substrate in an oxygen environment. Co-deposition of Ce and Mn during the CeO2(1 1 1) thin film growth can produce well-ordered Ce1-xMnxO2-d(1 1 1) mixed oxide films with a low Mn composition of similar to 6%. The incorporated Mn atoms in the ceria film exhibit the +2 oxidation state. Segregation of Mn to the ceria surface and formation of MnO islands occur upon heating with the increase of the Mn metal composition above 9%. Addition of Mn into the ceria lattice causes the reduction of ceria. Mn-doped ceria was also prepared by depositing submonolayer coverage of Mn over CeO2(1 1 1) thin films at room temperature followed by heating to 700 K, which forms two dimensional triangular structures of MnO at the CeO2-delta surface. Mn is oxidized to Mn2+ at the cost of Ce4+ reduction. Effects of Mn dopants in ceria were investigated for deposited Ni. Both metallic Ni and Ni2+ species are present in the particles upon Ni deposition over both types of Mn-doped ceria surfaces. Compared to pure ceria, addition of Mn dopants can provide different anchoring sites for Ni that can affect the size, thermal stability and interaction between deposited Ni and modified ceria.