27 research outputs found
Cleavage of the C-C bond in the ethanol oxidation reaction on platinum. Insight from experiments and calculations
"This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry C, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/acs.jpcc.6b03117, see http://pubs.acs.org/page/policy/articlesonrequest/index.html".[EN] Using a combination of experimental and computational methods, mainly FTIR and DFT calculations, new insights are provided here in order to better understand the cleavage of the C–C bond taking place during the complete oxidation of ethanol on platinum stepped surfaces. First, new experimental results pointing out that platinum stepped surfaces having (111) terraces promote the C–C bond breaking are presented. Second, it is computationally shown that the special adsorption properties of the atoms in the step are able to promote the C–C scission, provided that no other adsorbed species are present on the step, which is in agreement with the experimental results. In comparison with the (111) terrace, the cleavage of the C–C bond on the step has a significantly lower activation energy, which would provide an explanation for the observed experimental results. Finally, reactivity differences under acidic and alkaline conditions are discussed using the new experimental and theoretical evidence.This work has been financially supported by the MINECO (Spain) (project CTQ2013-44083-P) and Generalitat Valenciana (project PROMETEOII/2014/013).Ferre Vilaplana, A.; Buso-Rogero, C.; Feliu, JM.; Herrero, E. (2016). Cleavage of the C-C bond in the ethanol oxidation reaction on platinum. Insight from experiments and calculations. Journal of Physical Chemistry C. 120(21):11590-11597. https://doi.org/10.1021/acs.jpcc.6b03117S11590115971202
Oxidation mechanism of formic acid on the bismuth adatom-modified Pt(111) surface
In order to improve catalytic processes, elucidation of reaction mechanisms is essential. Here, supported by a combination of experimental and computational results, the oxidation mechanism of formic acid on Pt(111) electrodes modified by the incorporation of bismuth adatoms is revealed. In the proposed model, formic acid is first physisorbed on bismuth and then deprotonated and chemisorbed in formate form, also on bismuth, from which configuration the C-H bond is cleaved, on a neighbor Pt site, yielding CO2. It was found computationally that the activation energy for the C-H bond cleavage step is negligible, which was also verified experimentally.This work has been financially supported by the MINECO (Spain) (project CTQ2013-44083-P) and Generalitat Valenciana (project PROMETEOII/2014/013).Perales Rondón, JV.; Ferre Vilaplana, A.; Feliu, J.; Herrero, E. (2014). Oxidation mechanism of formic acid on the bismuth adatom-modified Pt(111) surface. Journal of the American Chemical Society. 136(38):13110-13113. https://doi.org/10.1021/ja505943hS13110131131363
An Aza-Fused π‑Conjugated Microporous Framework Catalyzes the Production of Hydrogen Peroxide
In order to produce hydrogen peroxide
in small-scale electrochemical
plants, selective catalysts for the oxygen reduction reaction (ORR)
toward the desired species are required. Here, we report about the
synthesis, characterization, ORR electrochemical behavior, and reaction
mechanism of an aza-fused π-conjugated microporous polymer,
which presents high selectivity toward hydrogen peroxide. It was synthesized
by polycondensation of 1,2,4,5-benzenetetramine tetrahydrochloride
and triquinoyl octahydrate. A cobalt-modified version of the material
was also prepared by a simple postsynthesis treatment with a CoÂ(II)
salt. The characterization of the material is consistent with the
formation of a conductive robust porous covalent laminar polyaza structure.
The ORR properties of these catalysts were investigated using rotating
disk and rotating disk–ring arrangements. The results indicate
that hydrogen peroxide is almost exclusively produced at very low
overpotentials on these materials. Density functional theory calculations
provide key elements to understand the reaction mechanism. It is found
that, at the relevant potential for the reaction, half of the nitrogen
atoms of the material would be hydrogenated. This hydrogenation process
would destabilize some carbon atoms in the lattice and would provide
segregated charge. On the destabilized carbon atoms, molecular oxygen
would be chemisorbed with the aid of charge transferred from the hydrogenated
nitrogen atoms and solvation effects. Due to the low destabilization
of the carbon sites, the resulting molecular oxygen chemisorbed state,
which would have the characteristics of a superoxide species, would
be only slightly stable, promoting the formation of hydrogen peroxide