Nanoparticles formic acid oxidation

Yang, J., et ah, An effective strategy for small-sized and highly-dispersed palladium nanoparticles supported on graphene with excellent performance for formic acid oxidation. Journal of Materials Chemistry, 2011. 21(10) p. 3384-3390. 

PANI-NTs synthesized by a template method on commercial carbon cloth have been used as the catalyst support for Pt particles for the electro-oxidation of methanol [501]. The Pt-incorporated PANl-NT electrode exhibited excellent catalytic activity and stabUity compared to 20 wt% Pt supported on VulcanXC 72R carbon and Pt supported on a conventional PANI electrode. The electrode fabrication used in this investigation is particularly attractive to adopt in solid polymer electrolyte-based fuel cells, which arc usually operated under methanol or hydrogen. The higher thermal stabUity of y-Mn02 nanoparticles-coated PANI-NFs on carbon electrodes and their activity in formic acid oxidation pomits the realization of Pt-free anodes for formic acid fuel cells [260]. The exceUent electrocatalytic activity of Pd/ PANI-NFs film has recently been confirmed in the electro-oxidation reactions of formic acid in acidic media, and ethanol/methanol in alkaline medium, making it a potential candidate for direct fuel cells in both acidic and alkaline media [502]. 

The interest in formic acid oxidation (FAO) rose up in the 1970s with the aim of shedding light on the mechanism of methanol oxidation beyond the commercial interest in direct formic acid oxidation in fuel cells [90]. The FAO in acid solution was extensively investigated on surfaces of platinum [91-100] The FAO on other pure metallic surfaces seems to have been restricted to the palladium surface [98, 101-104]. In the 1980s, the remarkable contribution was done by the studies on the influence of the ad-atom in the activity of the platinum electrode [91—94]. In the 1990s, superficial spectroscopic techniques were employed to describe the electrochemical mechanism on palladium surface [98, 101—103] as well as platinum surface [97, 98, 105]. In the last 10 years, there was a triplication of publications about the FAO, specially driven by the use of nanoparticles. 

Zhang S, Shao Y, Yin G, Lin Y (2010) Facile synthesis of PtAu alloy nanoparticles with high activity for formic acid oxidation. J Power Sources 195 1103-1106... 

Suo Y, Hsing IM (2009) Size-controlled synthesis and impedance-based mechanistic understanding of Pd/C nanoparticles for formic acid oxidation. Electrochim Acta 55 210-217... 

Wieckowski s group has studied formic acid electrooxidation on Pt nanoparticles decorated with controlled amounts of Pd and Pd-l-Ru adatoms [41]. They reported two orders of magnitude increase in the reactivity of the Pd-decorated catalyst compared to pure Pt towards formic acid oxidation. Also, it was concluded that the impact of COads on the Pt/Pd catalyst through the dual pathway mechanism is much lower even though the potential required to remove COads from the surface was the highest. 

An attempt to produce PtBi alloy nanoparticles on carbon produced highly active catalysts for formic acid oxidation, although XRD showed no evidence of alloy formation [27]. Highest performances were obtained with a Bi Pt mole ratio of just 0.07. 

The most widely studied conducting polymer support is polyaniline (PANl), which has been shown to decrease the poisoning of Pt by COads [88]. Gharibi et al. have recently explored the factors responsible for the enhanced formic acid oxidation activity of Pt supported on a carbon/PANI composite [89]. They concluded that improvements in both electron and proton conductivities, as well as the increased methanol diffusion coefficient and decreased catalyst poisoning, could be involved. A carbon nanotubes/PANI composite [90], poly(o-methoxyaniline) [91], and polyindole [92] have recently been reported as effective supports for formic acid oxidation at Pt nanoparticles, while polycarbazole [93] has also been used to support PtRu nanoparticles. 

Future advances in the catalysis of formic acid oxidation will benefit from further development of our understanding of the fundamental processes involved via single crystal and computational studies. Refinement of synthesis methods to produce nanoparticles with the most active and durable geometries and structures will allow fine-timing of catalysts. Continued discovery of support effects and advances in the understanding of such effects will create additional opportuitities to improve performances, lower costs, and enhance durability. 

Liu Z, Zhang X (2009) Carbon-supported PdSn nanoparticles as catalysts for formic acid oxidation. Electrochem Commun 11 1667-1670... 

Matsumoto F, Roychowdhury C, DiSalvo FJ, Abruna HD (2008) Electrocatalytic activity of ordered intermetallic PtPb nanoparticles prepared by borohydride reduction toward formic acid oxidation. J Electrochem Soc 155 B148-B154... 

Mazumder V, Sun SH (2009) Oleylamine-mediated synthesis of Pd nanoparticles for catalytic formic acid oxidation. J Am Chem Soc 131 4588- 589... 

Weaver and co-workers explained the particle size effect in terms of an ensemble effect related to surface morphology [230]. For Pt nanoparticles of diameter < 4 mn it was experimentally determined [231] that the fraction of flat terrace sites diminished considerably as compared to edge sites. Therefore, the probability of ensemble of active site formation situated on the terraces and needed for methanol dehydrogenation (especially for the removal of the first three hydrogen atoms) is lower for particles with diameters below 4 nm. It was estimated that the 2.5 nm diameter particle has an approximately five times lower availability of adjacent Pt atoms compared to the 8.8 mn diameter particle [230]. In the case of formic acid oxidation, on the other hand, it was proposed that Pt ensembles are not required for catalysis. Interestingly, the COad surface coverage decreased with particle size for both CFI3OFI and FICOOFI. 

Tripkovic AV, Popovic KDJ, Lovic JD, Markovic NM, RamUovic V. Formic acid oxidation on Pt/Ru nanoparticles temperature effects. Materials Science Forum 2005 494 223-8. 

Fig. 2.13 TEM image of a Pt-Pd composite nanoparticle and cyclovoltammograms showing electrocatalytic formic acid oxidation for Pt cube and Pt-Pd composite nanoparticles (adapted from ref [48])...

Palladium(II) bromide is also the palladium(II) salt of choice for the synthesis of monodisperse cobalt-palladium nanoparticles (CoPd NPs) that are active catalysts for formic acid oxidation and the methanolysis of ammonia borane7 The bromide anion is thought to play a role in the growth process of the CoPd NPs7 PdBr2(SMe2)2 is used in the synthesis of palladium-polyimide films. ... 

Wang, S., Wang, X., and Jiang, S.P. (2011) Self-assembly of mixed Pt and Au nanoparticles on PDDA-functionalized graphene as effective electrocatalysts for formic acid oxidation of fuel cells. Physical Chemistry Chemical Physics, 13 (15), 6883-6891. 

A number of authors have investigated the use of Pt/Au alloy and Pt-decorated Au (shell-core) nanoparticles as catalysts for formic acid oxidation in acid solution. Park et al. [94] described chemical reduction techniques for preparing Pt/Au alloy, pure Au, and Pt-modified Au nanoparticles on carbon supports. The Pt/Au alloy and Pt-modified Au nanoparticles showed higher activities for formic acid oxidation than pure Pt, especially at low potentials in the region of 0.2 V. These results of Park et al. [94] are supported by the data of Kristian et al. [95]. Although the detailed mechanism of operation of these new electrocatalysts remains to be fully clarified, the combination of improved performance, combined with a substantial reduction in the use of Pt, are attractive features of Pt-decorated Au nanoparticle electrocatalysts from a fuel cell viewpoint. 

Methanol, Formaldehyde, and Formic Acid Adsorption/Oxidation on a Carbon-Supported Pt Nanoparticle Fuel Cell Catalyst A Comparative Quantitative OEMS Study... 

Zhao, H., et al., Fabrication of a palladium nanoparticle/graphene nanosheet hybrid via sacrifice of a copper template and its application in catalytic oxidation of formic acid. 

Chen, W. Kim, J. Xu. L-P. Sun, S. Chen, S. Langmuir-Blodgett Thin Films of Fe Ptso Nanoparticles for the Electrocatalytic Oxidation of Formic Acid. J. Phys. Chem. C2007, 111,13452-13459. 

Different electron-conducting polymers (polyaniline, polypyrrole, polythiophene) are considered as convenient substrates for the electrodeposition of highly dispersed metal electrocatalysts. The preparation and the characterization of electronconducting polymers modified by noble metal nanoparticles are first discussed. Then, their catalytic activities are presented for many important electrochemical reactions related to fuel cells oxygen reduction, hydrogen oxidation, oxidation of Cl molecules (formic acid, formaldehyde, methanol, carbon monoxide), and electrooxidation of alcohols and polyols. 

SERS data were used to study the adsorption and electro-oxidation of CO at a platinum-formic acid interface.155 In situ microscopic FTIRS studies were reported for the carbonyl species formed by CO adsorption on nanostructured platinum micro-electrodes.156 The nature of the surfaces of Ptn nanoparticles and their aggregates were probed by examining vCO bands of the carbonyl species formed on CO adsorption.157... 

Park, S., Y. Xie, and M.J. Weaver, Electrocatalytic pathways on carbon-supported platinum nanoparticles Comparison of particle-size-dependent rates of methanol, formic acid und formaldehyde electrooxidation. Langmuir, 2002. 18(15) pp. 5792-5798 Vinodgopal, K., M. Haria, D. Meisel, and P. Kamat, Fullerene-based carbon nanostructures for methanol oxidation. Nano Letters, 2004. 4(3) pp. 415 18 Sun, N.X. and K. Lu, Physical Review B, 1997. 54 pp. 6058... 

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