Methanol, electrooxidation

1 Pt andPt-MBinary Catalysts with Mother than Ru M = Mo, Os, Sn, Ni, 

The intermediates and reaction products depend synergistically on a number of factors such as electrode potential, eatalyst crystallographic features, elemental surface composition, methanol eoneentration, temperature, supporting electrolyte (e.g., HCIO4 vs. H2SO4), and reaetion time. 

The adsorbed formate intermediate (HCOOad) has been detected on polycrystalline Pt in 0.1 M HCIO4 only at potentials higher than 0.5 V vs. RHE [61]. Therefore, it is likely that oxide formation on the Pt surface plays a role in the 

However, one has to take into account the effect of temperature when discussing the dissociative dehydrogenation of methanol, which is missing from the theoretical analysis of Kua and Goodard. There is evidence that at high temperatures (333 K or above) methanol dehydrogenation can take place on Ru sites as well [66], 

Furthermore, the existence of other more reactive intermediates, namely adsorbed formate isomers (e.g., COOHad) was also put forward [65]. 

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The rate-determining step (rds) of the reaction on platinum is the oxidation of adsorbed CO with adsorbed hydroxyl species [step (26)]. The current density of the methanol electrooxidation can be obtained from the following equatiorf ... 

A third way to increase both the active surface area and the number of oxygenated species at the electrode surface is to prepare alloy particles or deposits and then to dissolve the non-noble metal component. This technique, which is similar to that used to prepare Raney-type catalysts, yields very high surface area electrodes and hence some improvements in the electrocatalytic activities compared with those of pure platinum. However, it is always difficult to be sure whether the mechanism of enhancment of the activities is due to this effect or the possible presence of remaining traces of the dissolved metal. Results with PtyCr and PtSFe were encouraging, although the effect of iron is still under discussion. From studies in a recent work on the behavior of R-Fe particles for methanol electrooxidation, it was concluded that the electrocatalytic effect is due to the Fe alloyed to platinum. ... 

Table 4 and Fig. 18 illustrate the performance levels achieved by the active players in DMFC R D. The main goal in DMFC research in the U.S. and European programs is to achieve a stable performance level of 200 mW/cm at a cell potential of 0.5 to 0.6 V. It is because of the relatively low activity of the electrocatalyst for methanol electrooxidation that this power level is less than half that of a PEMFC with Hj as a fuel. A higher power level of the DMFC is essential for a transportation application, but the present power level goal is quite adequate for small portable power sources. 

Housmans THM, Wonders AH, Koper MTM. 2006. Structure sensitivity of methanol electrooxidation pathways on platinum An on-hne electrochemical mass spectrometry study. J Phys ChemB 110 10021 10031. 

Cuesta A. 2006. At least three contiguous atoms are necessary for CO formation during methanol electrooxidation on platinum. J Am Chem Soc 128 13332-13333. 

Henero E, Chrzanowski W, Wieckowski A. 1995. Dual path mechanism in methanol electrooxidation on a platinum electrode. J Phys Chem 99 10423-10424. 

Sriramulu S, Jarvi TD, Stuve EM. 1999. Reaction mechaiusm and dynamics of methanol electrooxidation on platinum (111). J Electroanal Chem 467 132-142. 

Gasteiger HA, Markovic N, Ross PN, Caims EJ. 1993. Methanol electrooxidation on well-characterized platinum-mthenium bulk alloys. J Phys Chem 97 12020-12029. 

Lima A, Coutanceau C, Leger JM, Lamy C. 2001. Investigation of ternary catalysts for methanol electrooxidation. J Appl Electrochem 31 379-386. 

Schmidt TJ, Gasteiger HA, Behm RJ. 1999. Methanol electrooxidation on a colloidal PtRu-alloy fuel-cell catalyst. Electrochem Commun 1 1-4. 

Waszczuk P, Solla-Gull6n J, Kim HS, Tong YY, Montiel V, Aldaz A, Wieckowski A. 2001a. Methanol electrooxidation on platinum/ruthenium nanoparticle catalysts. J Catal 203 1-6. 

Gavrilov AN, Savinova ER, Simonov PA, Zaikovskii VI, Cherepanova SV, TsirUna GA, Parmon VN. 2007. On the irrfluence of the metal loading on the stmcture of carbon-supported PtRu catalysts and their electrocatal3ftic activities in CO and methanol electrooxidation. Phys Chem Chem Phys 9 5476-5489. 

Jarvi TD, Sriramulu S, Stuve EM. 1998. Reactivity and extent of poisoning during methanol electrooxidation on platinum (100) and (111) A comparative study. Colloids Surf A 134 145-153. 

Jusys Z, Kaiser J, Behm RJ. 2002a. Composition and activity of high surface area PtRu catalysts towards adsorbed CO and methanol electrooxidation. A DBMS study. Electrochim Acta 47 3693-3706. 

Petukhova RP, Stenin VF, Podlovchenko BI. 1977. About the composition of the products of methanol electrooxidation on smooth platinum. Elektrokhimiya 14 755-756. 

Pt-Ru anodes for methanol electrooxidation The catalytically most active samples are highly dispersed and contain, as indicated by the Mossbauer data, a mixture of two Ru(IV) species... 

Fig. 4.1. Current and mass signal during an on-line mass spectroscopic experiment showing the effect of adsorbed tin on platinum upon methanol electrooxidation. 1 M CH3OH/0.5 M H2S04 sweep rate 10 mV/s, 24 °C.

The catalytic properties of a Pt/Sn combination were observed on different kinds of electrode materials alloys [90], electro co-deposits of Pt and Sn [89, 90], underpotential deposited tin [42] or a mixture of tin oxide and platinum deposited on glass [95], All different materials present a marked influence on methanol electrooxidation. 

He, Z., et ah, Electrodeposition ofPt-Ru nanoparticles on carbon nanotubes and their electrocatalytic properties for methanol electrooxidation. Diamond and Related Materials, 2004.13(10) p.1764-1770. 

J. Luo, M. M. Maye, Y. Lou, L. Han, M. Hepel, and C. J. Zhong, Catalytic activation of core-shell assembled gold nanoparticles as catalyst for methanol electrooxidation, Catal. Today 77,127-138 (2002). 

Also, the catalytic ability of Zn electrode modified by Pt-doped nickel hexacyanoferrate for methanol electrooxidation was investigated [480]. 

The electrooxidation of methanol has attracted tremendous attention over the last decades due to its potential use as the anode reaction in direct methanol fuel cells (DMFCs). A large body of literature exists and has been periodically reviewed [130,131,156], [173-199]. Unlike for formic acid, a generally accepted consensus on the specific mechanistic pathways of methanol electrooxidation is still elusive. 

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