Kinetics of formic acid dehydration on Pt electrodes by time-resolved ATR-SEIRAS.

The potential dependence of the rate of dehydration of formic acid to adsorbed CO (CO ad ) on Pt at pH 1 has been studied on a polycrystalline Pt surface by time-resolved surface-enhanced infrared absorption spectroscopy in the attenuated total reflection mode (ATR-SEIRAS) with simultaneous recording of current transients after a potential step. A range of formic acid concentrations has been used to obtain a deeper insight into the mechanism of the reaction. The experiments have allowed us to confirm that the potential dependence of the rate of dehydration has a bell shape, going through a maximum around the potential of zero total charge (pztc) of the most active site. The analysis of the integrated intensity and frequency of the bands corresponding to CO L and CO B/M shows a progressive population of the active sites on the surface. The observed potential dependence of the rate of formation of CO ad is consistent with a mechanism in which the reversible electroadsorption of HCOO ad is followed by its rate-determining reduction to CO ad .