Kinetic study of formic acid oxidation on carbon-supported platinum electrocatalyst

Oxidation of formic acid on the platinum catalyst supported on high area carbon was investigated by potentiodynamic and quasi-steady-state polarization measurements. It was found that the poisoning of the reaction occurred both in the hydrogen region and in the double-layer region, but poisons were formed faster at lower potentials. Kinetics of the reaction was consistent with the dual path mechanism. At lower potentials HCOOH was oxidized to CO2 at the Pt sites uncovered by COads. If high coverage by the poisoning species was attained, the reaction reached the limiting current plateau and further increase of the current densities started at the potential of COads oxidation. Kinetic parameters of the HCOOH oxidation suggested that the rate determining step was the transfer of the first electron from HCOOHads, which was adsorbed under the Temkin conditions. Oxidation of formic acid became pH-dependent reaction in the electrolytes of pH < 1 with the reaction order with respect to H+ ions of about −0.8.