Modeling Electrocatalytic Oxidation Of Formic Acid At Pt(111)

The formic acid oxidation reaction(FAOR),involving only two electrons and two protons,is an important model reaction in electrocatalysis for studying proton-coupled electron transfer reactions.Formic acid is one of the direct energy sources in fuel cells,investigation on it’s oxidation mechanism is helpful to design high efficiency anode catalyst.Therefore,the research on oxidation mechanism of FAOR has both scientific and engineering significance.In this paper,the mechanism of formic acid oxidation at a Pt(111)electrode was explored by a microkinetic mechanistic model.The specific work content is as follows:(1)Based on the summary of formic acid oxidation mechanisms in leteratures,the’dual-pathway’mechanism of formic acid oxidation at a Pt(111)electrode was postulated,including the monodentate formate HCOO_m pathway and bridged-bonded formate HCOO_b pathway.Morever,HCOO_m is the ture active intermediate and HCOO_b is mianly as the site-blocker at low potentials.(2)A microkinetic mechanistic model of formic acid oxidation was established,which gives a unified treatment of the pH-depent thermodynamics and kinetics,the multifaceted roles of adsorbates and the double layer effects.According to the comparison between the model results and the experimental data at different pHs,the feasibility of this model and the ratioanlity of this‘dual-pathway’mechanism is veryfied.(3)After parameterizing this microkenetic mechanistic model,the pH effect of FAOR is analyzed quantitativly,the precursor and rate-determining term of each pathway are determined,and the double-layer effects on FAOR activity are explored.Based on the systematic research on formic acid oxidation,three suggestions are proposed for some prevailing thoughts in the literatures:(1)For complex electrochemical reactions,which may involve multiple reaction pathways,these pathways should be considered in parallel;(2)Adsorbates have multifacted roles,not just as reactants and site-blockers;(3)When calculating the reaction rate constant,the double-layer effects and the interaction between adsorbates should be considered.