Ru nanoparticles supported on N-doped reduced graphene oxide as valuable catalyst for the selective aerobic oxidation of benzyl alcohol

[EN] The catalytic performance of a series of Ru-based catalysts was evaluated for the selective aerobic oxidation of benzyl alcohol to benzaldehyde under base-free mild conditions. The effect of metal precursor (RuCl, RuNO(NO) and Ru(CO)) and support on catalyst performance was investigated by comparing undoped (rGO) and N-doped (NrGO) reduced graphene oxide with commercial activated carbon and high surface area graphite supports. The surface chemistry and structure of materials were characterized by nitrogen physisorption (BET), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The average Ru nanoparticle sizes were in the range from 1.4 to 2.4 nm, with the smallest particle sizes obtained on rGO support owing to its highest surface area. Catalysts prepared from RuNO(NO) and Ru(CO) precursors exhibit the highest benzyl alcohol conversion to the corresponding aldehyde, with highest conversions observed when NrGO support is employed. Catalysts prepared from Ru(CO) on NrGO support exhibit the highest activity for benzaldehyde formation, which is over three times that of commercial activated carbon supported Ru catalysts. The differences in catalytic performance are attributed to interactions between the acidic product of the reaction and the basic surface sites of the NrGO support, and modification of the surface hydrophobicity. These factors confer a significant rate enhancement in the selective oxidation of benzyl alcohol over Ru/NrGO compared to Ru/rGO. Ru/NrGO is stable under reaction conditions, however progressive deactivation is observed owing to water accumulation at the active site. Catalysts are easily reactivated via heating, with >90% of the original activity recovered on reuse.CRB gratefully acknowledges financial support from Spanish Ministerio de Educacion, Cultura y Deporte, Grant Nº FPU15/01838. Also the financial support from the Spanish Ministerio de Economía y Competitividad under projects (CTQ2017-89443-C3-1-R and -3-R) is recognized.KW thanks the Royal Society for the award of an Industry Fellowship

Upgrading the Properties of Reduced Graphene Oxide and Nitrogen-Doped Reduced Graphene Oxide Produced by Thermal Reduction toward Efficient ORR Electrocatalysts

© 2019 by the authors.N-doped (NrGO) and non-doped (rGO) graphenic materials are prepared by oxidation and further thermal treatment under ammonia and inert atmospheres, respectively, of natural graphites of different particle sizes. An extensive characterization of graphene materials points out that the physical properties of synthesized materials, as well as the nitrogen species introduced, depend on the particle size of the starting graphite, the reduction atmospheres, and the temperature conditions used during the exfoliation treatment. These findings indicate that it is possible to tailor properties of non-doped and N-doped reduced graphene oxide, such as the number of layers, surface area, and nitrogen content, by using a simple strategy based on selecting adequate graphite sizes and convenient experimental conditions during thermal exfoliation. Additionally, the graphenic materials are successfully applied as electrocatalysts for the demanding oxygen reduction reaction (ORR). Nitrogen doping together with the starting graphite of smaller particle size (NrGO325-4) resulted in a more efficient ORR electrocatalyst with more positive onset potentials (Eonset = 0.82 V versus RHE), superior diffusion-limiting current density (jL, 0.26V, 1600rpm = −4.05 mA cm−2), and selectivity to the direct four-electron pathway. Moreover, all NrGOm-4 show high tolerance to methanol poisoning in comparison with the state-of-the-art ORR electrocatalyst Pt/C and good stability.This research was supported by the Spanish Agencia Estatal de Investigación (AEI) under projects CTQ-2017-89443-C3-1-R and CTQ-2017-89443-C3-3-R. C.S.R.B. gratefully acknowledges financial support from Spanish Ministerio de Educacion, Cultura y Deporte, Grant Nº FPU15/01838. D.M.F. also thanks Project UNIRCELL - POCI-01-0145-FEDER-016422 funded by European Structural and Investment Funds (FEEI) through - Programa operacional Competitividade e Internacionalização - COMPETE2020 and by national funds through FCT - Fundação para a Ciência e a Tecnologia, I.P.Peer reviewe