Methanol oxidation reaction thin films

Figure 12.13. (a) Peak current densities and (b) onset potentials of methanol oxidation reaction electrocatalyzed by the combinatorial (A) Pt-Ru-W and (B) Pt-Ru-Co systems. [22]. (Reprinted from Journal of Power Sources, 163(1), Cooper JS, McGinn PJ. Combinatorial screening of thin film electrocatalysts for a direct methanol fuel cell anode, 330-8, 2006, with permission from Elsevier.)... 

For example, PTV film was fabricated as follows. Polymerization of a sulphonium monomer, 2,5-thienylene bis (methylene-dimethyl-sulphonium chloride) was carried out in a methanol-water mixture at -20°C by adding a methanol solution of tetramethyl-ammonium hydroxide. The reaction was quenched by an addition of hydrochloric acid. A yellow precipitate (precursor polymer) appeared as the solution was warmed to room temperature. The precipitated precursor polymer was completely soluble in dich-loromethane. A precursor polymer thin film was obtained by spin-coating of the dichloromethane solution of the precursor polymer onto a fused silica glass substrate under inert atmosphere to prevent oxidation with air. The film was heated at 200-250°C in a vacuum of 10"2 Torr for 5 hours, to give a tough, flexible PTV film. The resulting PTV thin film was chemically stable in air. 

Pt-Mo-N thin films have been investigated for formic acid and methanol oxidation [92]. PtMoN showed enhanced activity over an equivalent PtMo alloy for both reactions indicating that the nitride phase improves the electrocatalysis. 

Effect of Water. Except in cases of high-tempa-a-ture oxidation, gas-metal reactions, fretting, and certain hot, anhydrous organic chemicals such as phenol and methanol, alurrrinum does not corrode unless water is present on the surface. The water can appear in the form of isolated droplets, as a thin film of moisture condensed on an aluminum surface below the dew point, or as an aqueous solution. Water in contact with air contains dissolved oxygen, which must be present for corrosion of aluminum to occur. Deaeration usually stops the corrosion reaction. The protective surface filrn on aluminum thickens on exposure to water. This reaction is more rapid in the absence of oxygen. 

Later the lattice parameter was emphasized as a casual factor [143]. A detailed rationalization of see was made for iron exposed to anhydrous ammonia-methanol, where anodic oxidation of ammonia leads to interstitial penetration of nitrogen [69,100]. According to the film-induced cleavage model, such very thin, brittle layers are sufficient to allow cleavage through several pm of a body-centered cubic (bcc) material, whereas in fee systems a nanoporous metallic layer lO-lOOnm thick is a specific requirement as it is the only way of epitaxially coupling a brittle reaction product of sufficient thickness to the fee substrate. A special case may be the SCC of pure copper or silver, where a micropitted or tunneled zone is a possible brittle layer that could nucleate cracking [144,145]. 

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