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

Area of Science:

• Electrochemistry
• Surface Science
• Catalysis

Background:

• Formic acid dehydration is a key reaction in electrocatalysis.
• Understanding reaction mechanisms on platinum surfaces is crucial for catalyst development.

Purpose of the Study:

• To investigate the potential dependence of formic acid dehydration to adsorbed CO on a polycrystalline Pt surface.
• To elucidate the reaction mechanism using in-situ spectroscopic and electrochemical techniques.

Main Methods:

• Time-resolved surface-enhanced infrared absorption spectroscopy in the attenuated total reflection mode (ATR-SEIRAS).
• Simultaneous recording of current transients after a potential step.
• Varying formic acid concentrations to study reaction kinetics.

Main Results:

• The rate of dehydration exhibits a bell-shaped potential dependence, peaking near the potential of zero total charge (pztc).
• Analysis of CO bands (CO_L and CO_B/M) indicates progressive population of active surface sites.
• Observed kinetics support a mechanism involving reversible HCOO_ad electroadsorption followed by rate-determining CO_ad formation.

Conclusions:

• The study confirms the bell-shaped potential dependence of formic acid dehydration rate on Pt.
• The findings provide insights into the reaction mechanism, highlighting the role of surface site population and potential.
• The proposed mechanism aids in optimizing electrocatalytic processes involving formic acid.