Electrochemical data are reported for oxygen reduction on platinized coconut-shell charcoal electrodes in 2.5M H*SO,, and 7M HsF'04. In both these media the electrodes exhibit good activity and can sustain currents up to 600 mA cm-* at a polarization of about 400 mV from their rest potentials. The overall performance is comparable with the best type of carbonsupported platinum electrodes reported in the literature.
Various types of active carbon have been examined [ 1 -41 as supports for platinum metal catalysts used for the reduction of oxygen in acid solutions. Both the activity as well as the corrosion resistance of such electrodes have been found to depend markedly on the nature of the carbon substrate. When suitably pretreated, carbon derived from coconut-shell charcoal has been shown [5 -91 to be nearly ashless and to be an excellent substrate for oxygen-reducing electrodes in alkaline fuel cells. In particular, it appears that oxygen is reduced to water without detectable formation of hydrogen peroxide [8, 91 as an intermediate species. A study of the feasibility of coconut-shell charcoal as a support for platinum metal catalysts in acidbased fuel cells is reported here.
A high surface-area carbon substrate was prepared from coconut shells using the method described previously . The desired quantity of platinum was dispersed on to the carbon substrate by reducing chloroplatinic acid with sodium for-mate solution using the following procedure. A solution of chloroplatinic acid containing 8 mg of platinum/ml was mixed with half its volume of isopropanol and then neutralized with a dilute solution of sodium carbonate. An appropriate quantity of treated carbon was added to this solution and the resulting mixture was then dried in an air oven. The residue was added, with vigorous stirring, to an excess of boiling 5 wt.% sodium formate in order to reduce the chloroplatinic acid to platinum. After filtration, the prepared material was washed repeatedly with hot, distilled water and finally dried in an air oven. The optimum deposit of platinum on to the carbon substrate was determined by conducting electroactivity tests on