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The ability to mimic protein-based oxidase with multi-functional inorganic nanozymes would greatly advance biomedical and clinical practices. Praseodymia (PrOx) nanorods (NRs) and nanoparticles (NPs) have been synthesized using hydrothermal and precipitation methods. Both PrOx catalysts with different morphologies exhibit significantly higher oxidase-like activities (Michaelis-Menten constant Km < 0.026 mM) than commercial PrOx and most so-far-reported artificial enzymes. One of the substrates, dopamine, can be oxidized and further polymerized to generate polydopamine in acidic conditions. Akin to CeO2, which is a well-studied nanozyme, a different mechanism involving holes+, oxygen vacancies and oxygen mobility over PrOx catalysts has been proposed in this work. However, fluoride ions were found to impose opposite effects on the oxidase-mimicking activity of PrOx and CeO2, implying a promising path for the exploration of new nanozymes. In support of this, PrOx was further applied in colorimetric sensing of L-cysteine and fluoride with high sensitivity., Comment: 13 pages, 12 figures

A bimetallic Au-Pd catalyst supported on ceriazirconia with Au:Pd molar ratio 0.8 has been synthesized using a simultaneous deposition-precipitation method and oxidized at 250, 450, and 700 $^\circ$C in order to modify its particle size, nanostructure, and composition. Combined Xray energy dispersive spectroscopy and Xray photoelectron spectroscopy analysis clearly evidence that the bimetallic Au-Pd catalyst oxidized at 250 $^\circ$C is made up of a mixture of monometallic Au and Pd and bimetallic Au-Pd nanoparticles with Au:Pd ratios varying over a wide range. Increasing oxidation temperature leads to a stronger interaction between Au and Pd. Meanwhile, a slight increase of particle size and a narrowing of the Au:Pd ratio in the bimetallic nanoparticles take place. Compared with titania and activated carbon supports, the resistance against sintering at high temperatures of Au-Pd metal particles supported on ceriazirconia is proven to be higher. A synergistic effect has been observed for selective oxidation of benzyl alcohol on these catalysts. The catalytic activity decreases only slightly after oxidation at 450 $^\circ$C. However, oxidation at 700 $^\circ$C results in much lower catalytic activity. Migration of Pd onto Au particles during oxidation of benzyl alcohol enhances the catalytic activity of a physical mixture of monometallic Au and Pd supported on ceriazirconia catalysts. This fact, jointly with an analysis of the intrinsic activity, reveals the influence of the actual nature of Au-Pd interactions in the bimetallic particles, which points to higher activity of Au@Pd or Au@Pd@Pd nanostructures on ceria-zirconia support., Comment: 12 pages, 8 figures

Two series of ceria-praseodymia promoted Ni-alumina catalysts were prepared from two different commercial modified alumina supports by the incipient wetness impregnation method in two successive steps.The resulting materials were characterized in terms of their physico-chemical properties. Furthermore, the as-prepared catalysts were tested for the CO2 methanation reaction. The influence of the nominal Ni loading, molar composition of the Ce-Pr mixed oxide promoter and alumina modifier on the catalytic performance was carefully analyzed. Among these three composition parameters, the alumina dopant and especially the Ni content appear to have by far a much more pronounced effect on both the CO2 conversion and CH4 selectivity as compared to the Ce-Pr mixed oxide composition., Comment: 12 pages, 7 figures

Redox and catalytic performance in total methane oxidation of a nonostructured ceria-terbia catalyst supported on magnesia is presented and compared to that of a pure ceria catalyst supported on MgO. The investigated material, Ce0.5Tb0.5Ox (3% mol.)/MgO, features several remarkable properties: a quite low total molar loading of the two lanthanide elements, high reducibility, as well as very high oxygen storage capacity al low temperatures and higher activity than MgO-supported ceria. In terms of lanthanide atomic content the catalytic performance of Ce0.5Tb0.5Ox (3% mol.)/MgO largely improves compared to that of bulk type ceria and ceria-magnesia solid solutions. Such a behavior implies proper optimization of the usage of lanthanide elements. A second contribution to atomic economy in the catalyst design relates to the fact that the new formulation demonstrate a stabilyty in the redox and catalytic performance against very high temperature treatments. An investigation on the structure of both the fresh and high-temperature-aged catalyst at the atomic scale by means of complementary aberration corrected microscopy techniques, reveals the ocuurrence of a variety of exotic, lanthanide-containing nanostructures, which span fron isolated, atomically dispersed Ln species to nonometer-sized CeTbO2-x patches, extended CeTbO2-x bilayers and 2D CeTbO2-x nanoparticles. Nanoanalytical results evidence the mixing of the two lanthanides at atomic levels in these nanostructures. The combined effects of nanostructuring, mixing of the lanthanides at the atomic level, and interaction with the MgO oxide are the roots of the improvement in funtional, redox and catalytic properties of the novel Ce0.5Tb0.5Ox (3% mol.)/MgO catalyst., Comment: 11 pages, eight figures, 3 tables, 60 references