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Towards the Sub-15nm CeO2 Nanowires with Increased Oxygen Defects and Ce3+ Sites for Selective Oxidation of Aniline at Room-temperature with a Non-Noble Metal Catalyst

Abstract

We described herein the facile synthesis of sub-15 nm CeO2 nanowires based on a hydrothermal method without the use of any capping/stabilizing agent, in which an oriented attachment mechanism took place during the CeO2 nanowires formation. The synthesis of sub-15 nm CeO2 nanowires could be achieved on relatively large scales ( 2.6 grams of nanowires per batch), high yields (> 94 %), and low cost. To date, there are only a limited number of successful attempts towards the synthesis of CeO2 nanowires with such small diameters, and the reported protocols are typically limited to low amounts. The nanowires displayed uniform shapes and sizes, high surface areas, increased number of oxygen defects sites, and a high proportion of Ce3+/Ce4+ surface species. These features make them promising candidates for oxidation reactions. To this end, we employed the selective oxidation of aniline as a model transformation. The sub-15 nm CeO2 nanowires catalyzed the selective synthesis of nitrosobenzene (up to 98 % of selectivity) from aniline at room temperature using H2O2 as oxidant. The effect of solvent and temperature during the catalytic reaction was investigated. We found that such parameters played an important role in the control of the selectivity. The improved catalytic activities observed for the sub-15 nm nanowires could be explained by: i) the uniform morphology with typical dimensions of 11 ± 2 nm in width, which provide higher specific surface areas relative to conventional catalysts; ii) the significant concentration of oxygen vacancies and high proportion of Ce3+/Ce4+ species at the surface that represent highly active sites towards oxidation reactions, iii) the crystal growth through (110) highly catalytically active crystallographic directions, and iv) the mesoporous surface which is easily accessible by liquid substrates. The results reported herein demonstrated high activities under ambient conditions, provided novel insights over selectivities, and may inspire novel metal oxides-based catalysts with desired performances.

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Publication details

The article was received on 24 Nov 2017, accepted on 14 Feb 2018 and first published on 14 Feb 2018


Article type: Paper
DOI: 10.1039/C7CY02402A
Citation: Catal. Sci. Technol., 2018, Accepted Manuscript
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    Towards the Sub-15nm CeO2 Nanowires with Increased Oxygen Defects and Ce3+ Sites for Selective Oxidation of Aniline at Room-temperature with a Non-Noble Metal Catalyst

    A. da Silva, D. Batalha, T. Rodrigues, E. Candido, S. Luz, I. De Freitas, F. C. Fonseca, D. de Oliveira, J. G. Taylor, S. Cordoba de Torresi, P. Camargo and H. V. Fajardo, Catal. Sci. Technol., 2018, Accepted Manuscript , DOI: 10.1039/C7CY02402A

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