The electrocatalytic properties of the oxides of noble metals in the electrooxidation of methanol and formic acid

Abstract

The electrooxidation of 0.25 M methanol as well as of 0.25 M formic acid was examined on oxides formed on the Au(111) electrode surface in 0.5 M H2SO4 and 0.5 M NaHCO3 at a sweep rate of 0.5 mV/s. In the case of methanol, the Au(111) surface in 0.5 M H2SO4 must be covered by oxides in order to catalyse its oxidation significantly. The current of formic acid oxidation also appears in the potential region before the oxide formation, but the catalytic activity is apparently deeper in the potential region of oxide formation. In 0.5 M NaHCO3 the inhibition of methanol oxidation and the apparent catalytic activity of Au oxides in the case of formic acid oxidation are observed. The methanol electrooxidation on polycrystalline silver electrode was observed only in the potential region where the surface was covered by oxides in 0.1 M NaOH and at a sweep rate of 0.1 mV/s. This reaction was used to measure the concentration of methanol in the methanol–formaldehyde mixture in the same electrolyte.