R. Manoharan

Methanol oxidation on unsupported and carbon supported Pt + Ru anodes

A novel Pt + Ru electrode material is shown to be highly active for the direct electro-oxidation of methanol in H2SO4 solutions and to show very little tendency to poison. X-ray photoelectron spectroscopy of this material before use as an anode showed that the ruthenium is oxidised and that there is an important surface concentration of oxidised platinum. After prolonged use as a methanol-oxidation anode, the concentration of oxidised platinum is somewhat increased and there is no evidence for any Pt-CO or Pt2 = CO species; rather adsorbed formate is present. These data are consistent with Ru acting as a promoter of active surface oxygen. Dispersion of the Pt and Ru on a pure carbon support gives a much greater performance per gram of precious metal; however, the initial increase in overpotential is greater by over 100 mV. The differences in the catalytic behaviour of these two materials is discussed, and the importance of competing reactions is considered.

Porous carbon anodes for the direct methanol fuel cell—I. The role of the reduction method for carbon supported platinum electrodes

The efficiency of platinised porous-carbon electrodes for the electrooxidation of methanol in H2SO4 is found to vary quite markedly with the method used to deposit the platinum. This is shown to be a consequence of both the size and the electronic nature of the platinum crystallites. The most efficient electrodes are those that possess both small crystallite sizes, ∼ 20 A diameter, and a minimum amount of ionic platinum species as identified by XPS studies. A comparison is drawn with optimised platinised carbon electrodes for oxygen reduction, and an explanation for the different requirements of these two types of electrode suggested.

Efficient oxygen reduction in alkaline solution with platinum phthalocyanine on porous carbon

Porous carbon electrodes coated with platinum phthalocyanine are found to be stable at 35°C towards electroreduction of oxygen in concentrated alkali. Moreover, the concentration of Pt is substantially reduced relative to an electrode carrying dispersed Pt.

High efficiency cathodes for alkaline air electrodes

Carbon electrodes have been used as cathodes in alkaline air fuel cells with some success [1-3]. The material is reasonably durable though forms that yield significant concentrations of hydrogen peroxide are slowly degraded. However, the activity of carbon can be enhanced onsiderably by impregnation with a suitable catalyst. The most ffective of these catalysts to date have proved to be noble metals uch as platinum, and 7-15 wt % platinum is commonly sed.This is a very costly route, and macrocyclic ransition-metal derivatives have also been explored as less expensive alternatives [4, 5], either as films on metallic substrates or impregnated on various forms of carbon.

High-performance carbon electrodes for acid methanol-air fuel cells

High-performance, Teflon-bonded carbon electrodes, catalysed with highly dispersed platinum metal, have been developed for oxygen reduction in H2SO4. Surface-treated Vulcan XC-72 carbon has been used as the substrate material. The electrodes can be loaded with current densities of 1.1 A cm−2 intermittently and 900 mA cm−2 for extended periods without serious degradation. The performance of these electrodes in the presence of methanol has also been examined.