Electro-oxidation catalyst

Mallouk, T. E., Reddington, E., Pu, C., Ley, K. L., Smotkin, E.S., Discovery of methanol electro-oxidation catalysts by combinatorial analysis. In Fuel Cell Semi-... 

Mcnicol BD, Short RT, Chapman AG (1976) Methanol electro-oxidation catalysts. Platinum promoted by tin. J Chem Soc Faraday Trans 1 72 2735-2743... 

Shah BC, Hillier AC (2000) Imaging the reactivity of electro-oxidation catalysts with the scanning electrochemical microscope. J Electrochem Soc 147 (8) 3043-3048. doi 10.1149/1.1393645... 

Andrew MR, McNicol BD, Short RT, Drury JS. Electrolytes for methanol-air lliel cells. I. The performance of methanol electro-oxidation catalysts in sulphuric acid and phosphoric acid electrol5des. J Appl Electrochem 1977 7(2) 153. 

McNicol BD, Short RT. The influence of activation conditions on the performance of platinum/mthenium methanol electro-oxidation catalysts surface enrichment phenomena. J Electroanal Chem 1977 81 249. 

Jayaraman S, Hillier AC. Construction and reactivity screening of a surface composition gradient for combinatorial discovery of electro-oxidation catalysts. J Comb Chem 2004 6 27-31. 

Preparation of Pt/mesoporous carbon catalysts and their application to the methanol electro-oxidation... 

Fig. 4 shows the current density over the supported catalysts measured in 1 M methanol containing 0.5 M sulfuric acid. During forward sweep, the methanol electro-oxidation started to occur at 0.35 V for all catalysts, which is typical feature for monometallic Pt catalyst in methanol electro-oxidation [8]. The maximum current density was decreased in the order of Pt/CMK-1 > Pt/CMK-3 > Pt/Vulcan. It should be noted that the trend of maximum current density was identical to that of metal dispersion (Fig. 2 and Fig. 3). Therefore, it is concluded that the metal dispersion is a critical factor determining the catalytic performance in the methanol electro-oxidation.

Mesoporous carbon materials were prepared using ordered silica templates. The Pt catalysts supported on mesoporous carbons were prepared by an impregnation method for use in the methanol electro-oxidation. The Pt/MC catalysts retained highly dispersed Pt particles on the supports. In the methanol electro-oxidation, the Pt/MC catalysts exhibited better catalytic performance than the Pt/Vulcan catalyst. The enhanced catalytic performance of Pt/MC catalysts resulted from large active metal surface areas. The catalytic performance was in the following order Pt/CMK-1 > Pt/CMK-3 > Pt/Vulcan. It was also revealed that CMK-1 with 3-dimensional pore structure was more favorable for metal dispersion than CMK-3 with 2-dimensional pore arrangement. It is eoncluded that the metal dispersion was a critical factor determining the catalytic performance in the methanol electro-oxidation. 

It is well established that the main products of ethanol electro-oxidation on Pt in acidic media are acetaldehyde and acetic acid, partial oxidation products that do not require C—C bond breaking, with their relative yields depending on the experimental conditions [Iwasita and Pastor, 1994]. Apart from the loss of efficiency associated with the partial oxidation, acetic acid is also unwanted, as it constitutes a catalyst poison. 

Another metal that has attracted interest for use as electrode material is rhodium, inspired by its high activity in the catalytic oxidation of CO in automotive catalysis. It is found that Rh is a far less active catalyst for the ethanol electro-oxidation reaction than Pt [de Souza et al., 2002 Leung et al., 1989]. Similar to ethanol oxidation on Pt, the main reactions products were CO2, acetaldehyde, and acetic acid. Rh, however, presents a significant better CO2 yield relative to the C2 compounds than Pt, indicating a... 

For the purpose of demonstrating the effects of surface coverage by Pd, 0pd, on the rate of electro-oxidation of formic acid and the ORR, Fig. 8.17 reveals that the i versus 0Pd relationship again has a volcano-like form, with the maximum catalytic activity being exhibited for 1 ML of Pd. The examples that we have given indicate that volcano relationships are the rule rather than the exception, emphasizing the importance of a systematic evaluation of the catalyst factors that control catalytic activity. A thorough... 

Igarashi H, Fujino T, Watanabe M. 1993. Hydrogen electro-oxidation on platinum catalysts in the presence of trace carbon monoxide. J Electroanal Chem 391 119-123. 

EFFECT OF CATALYST STRUCTURE AND COMPOSITION METHANOL ELECTRO-OXIDATION... 

A bifunctional catalyst should be able to activate two different reaction steps (methanol and water adsorption and surface reaction between adsorbed species), and so active sites with different properties are necessary. As an example, investigations of possibihty of enhancing activity with regard to methanol electro-oxidation with Pt-Ru-based electrodes are of great interest with regard to improving the electrical efficiency of DMFCs. Several approaches have been considered the effect of Pt-Ru... 

Finally, trimetallic compounds have been developed to enhance the electroactivity of Pt-based catalysts, for either methanol or ethanol electro-oxidation. A long time ago, it was reported that adsorption of molybdates (Na2Mo04) at a Pt black electrode... 

TABLE 11.2 Chemical Yields in Acetic Acid, Acetaldehyde, and CO2 for Pt/C and Pt-Sn (9 1)/C Catalysts during Ethanol Electro-oxidation under DEFC Operating Conditions at 80 "C for 4 Honrs ... 

At this stage, it should be pointed out that modihcation of a Pt-Sn catalyst by Ru atoms increases cell performance (and hence catalytic activity with regard to ethanol electro-oxidation), but has no effect on the OCV or on product distribution [Rousseau et al., 2006]. It seems, then, that the oxidation mechanism is the same on Pt-Sn and Pt-Sn-Ru, which supports the proposition that Ru allows OH species to be produced when the anode potential is increased and noncatalytically active tin oxides are formed. 

Vigier F, Coutanceau C, Hahn F, Belgsir EM, Lamy C. 2004a. On the mechanism of ethanol electro-oxidation on Pt and PtSn catalysts Electrochemical and in situ IR reflectance spectroscopy studies. J Electroanal Chem 563 81-89. 

In this section, we will present and discuss cyclic voltammetry and potential-step DBMS data on the electro-oxidation ( stripping ) of pre-adsorbed residues formed upon adsorption of formic acid, formaldehyde, and methanol, and compare these data with the oxidative stripping of a CO adlayer formed upon exposure of a Pt/ Vulcan catalyst to a CO-containing (either CO- or CO/Ar-saturated) electrolyte as reference. We will identify adsorbed species from the ratio of the mass spectrometric and faradaic stripping charge, determine the adsorbate coverage relative to a saturated CO adlayer, and discuss mass spectrometric and faradaic current transients after adsorption at 0.16 V and a subsequent potential step to 0.6 V. 

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