FORMALDEHYDE YIELDS FROM METHANOL ELECTROCHEMICAL OXIDATION ON PLATINUM

Formaldehyde formed in the electrochemical oxidation of methanol was m easured in order to assess its importance as a reaction intermediate a nd potential source of efficiency loss in direct methanol fuel cells. Formaldehyde generated from 15 mM methanol in 0.1 M HClO4 at fixed pot entials with a small volume electrolysis arrangement was determined wi th a sensitive fluorescence assay. The formaldehyde yields approached 30% of the total electrolysis charge at 0.2-0.3 V (vs Ag/AgCl). The pe rcentages dropped at more positive potentials, as other oxidation path ways became dominant. However, formaldehyde production continued to in crease with potential, maximizing near 0.5 V. This study demonstrates that formaldehyde, which is often not detectable with modern in situ a nalysis techniques, can be produced during methanol electrochemical ox idation in significant amounts. A fluorescence assay specific for form aldehyde is suggested for use in parallel with in situ measurements.