Activation Energies of the Electrooxidation of Formic Acid on Pt(100)

The electrooxidation of small organic molecules on platinum surfaces usually involves different structure-dependent steps that include adsorption and desorption of various species and multiple reaction pathways. Because temperature plays a decisive role on each individual step, understanding its global influence on the reaction mechanism is often a difficult task, especially when the system is studied under far from equilibrium conditions in the presence of kinetic instabilities. Aiming at contributing to unravel this problem, herein, we report an experimental study of the role played by temperature on the electrooxidation of formic acid on a Pt(100) electrode. The system was investigated under both close and far from equilibrium conditions, and apparent activation energies were estimated using different strategies. Overall, comparable activation energies were estimated under oscillatory and quasi-stationary conditions, at high potentials. At low potentials, the poisoning process associated with the formic acid dehydration step presented a negligible dependence with temperature and, therefore, zero activation energy. On the basis of our experimental findings, we suggest that formic acid dehydration is the main, but maybe not the unique, step that differentiates the temperature dependence of the oscillatory electrooxidation of formic acid on Pt(100) with that on polycrystalline platinum.

MEC (Spain)

MEC (Spain)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

CAPES (Brazil)

MEC-FEDER, Spain[CTQ2006-04071]

MEC-FEDER, Spain

Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)[04/04528-0]

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)[302698/2007-8]