Formic Acid oxidation on platinum- a simple mechanistic study
Kathleen A. Schwarz, Ravishankar Sundararaman, Thomas P. Moffat, Thomas C. Allison
The oxidation of organic acids on noble metal sur-faces is of importance for industrial processes and of academic interest, but the basic reaction mechanisms continue to be a matter of debate. Historically, mechanisms involving the formic acid molecule have been proposed, but recently a theory has been advanced that formate is the key reactant on the metal surface. 1 Ab initio calculations of this reaction on a Pt(111)surface have been performed to explore this reaction and help resolve the debate. When a formate molecule approaches the platinum surface from above, with the H pointing down, it re-acts to form CO 2 and adsorbed H. Furthermore, this reaction is nearly barrierless at relevant voltages on a clean Pt surface, but high coverages of adsorbates lead to large reaction bar- riers. This mechanism explains the elusiveness of an active surface intermediate, and leads to a proposed rate equation on the pristine metal proportional to the formate concentration times the number of available platinum sites; in practice the availability of these sites appears to limit the reaction.