Microkinetic Modeling of the Methanol Electro-oxidation Reaction on Platinum

The development of electrocatalysts with high activityat low overpotentialsfor the methanol electro-oxidation reaction is one of the challengesto overcome toward the wider applicability of this alcohol in energyconversion systems. Many works in the last decades have contributedwith mechanistic studies on this reaction. Nevertheless, the reactionscheme is intricate, which makes it difficult to correlate with thekinetic response in electrochemical experiments. In this paper, wepropose a microkinetic model for the methanol electro-oxidation reactionon polycrystalline platinum. The model was built on relevant mechanisticaspects available in the literature and formulated based on the mean-fieldapproach. The kinetic parameters were determined by optimization,and the validation was performed through comparison with distinctexperimental data obtained by cyclic voltammetry, chronoamperometry,and also oscillatory time-series recorded under galvanostatic conditions.The resulting model was able to successfully simulate the nonlineardynamics observed in galvanostatic experiments, including the chaoticbehavior, as well as a reasonable voltammetric profile with the sameset of electrokinetic parameters. The sensitivity analysis of thekinetic parameters showed that the electro-oxidation pathway throughthe formic acid intermediate is not significant under these experimentalconditions and that the OHad and COad speciesare mainly involved in the origin of the oscillations, while speciesthat affect the rate of formation/consumption of the latter causesthe mixed-mode oscillations. The microkinetic approach used in thisstudy can be extrapolated to other electrocatalytic reactions, allowingthe complementarity between laboratory experiments and computationalsimulations.