Study On The Electrochemical Oxidation Of Methanol And Formic Acid On Pt Electrode

The small organic molecule fuel cell has attracted wild attention of researchers in recent years since its high efficiency,friendly environment,low temperature and so on,which can be used to solve the environment pollution and energy crisis.While the electrochemical oxidation process of small organic molecules and mass transfer mechanism hasn't been clear,which limits its development,for example the problem of anode catalyst was poisoned by CO and surface adsorption.So it's necessary to develop the researches on the mechanism of anodic reaction,which will help people further understand the organic small molecule oxidation process and guide people to improve the catalyst performance.The rotating disk electrode(RDE)can be used to accurately deal with the electrode surface reaction by precisely controlling the rotation of electrode,so it's widely applied to study the electrode kinetics.In this paper,mass transfer process on the electrochemical oxidation behavior of methanol on polycrystalline platinum electrode was investigated by cyclic voltammetry(CV)combined with rotating disk electrode(RDE)technique.In addition,Multi-poteatial steps(STEP)technique will be used to study the nucleation mechanism of HCOOH oxidation on single crystal Pt(100)electrode.Main conclusions are as follows:1)It's necessary to maintain the cleanness of whole experiment system when using the RDE technology to study the effect of mass transport process on methanol oxidation,what's more,the preparation work of cleaning electrode and bubbling N2 into solution should be done before each experiment.2)When the potential sweep was slower(5,10,100 mV/s),the methanol oxidation current has no dependence with rotation rates and was close to 0 mA/cm2 during the potential range of-0.2 V to 0.2 V,this was due to Pt electrode surface active sites were occupied by CO,thus leading to lose activity in methanol oxidation,while with potential increased,the methanol oxidation current decreased with rotation rates increased,this was due to enhance the production of soluble intermediates(formaldehyde and formic)through a parallel path of methanol oxidation,which diffused to the electrolyte from the electrode surface,thus leading to a decreased current.3)When the potential sweep was faster(200,400 mV/s),the methanol oxidation current has no dependence with rotation rates while there are two obvious red-ox peaks,and the peak current was 1 mA/cm2 during the potential range of-0.2 V to 0.2 V,which may be due to methanol oxidation intermediates didn't firmly absorbed on Pt electrode surface when increased sweep speed.With potential increased,the methanol oxidation current increased with rotation rates increased,the result is different with low scan rates,this may be the poisoning effect was decreased when increased reaction rates.What's more,more methanol will be spread from solution to electrode surface with rotation rates enhanced,which promotes methanol to be oxidized,thus the current increased with rotation rates increased.4)Adopting the multiple-potential steps(STEP)technique,the i-t curves fitting results showed that nucleation process of HCOOH oxidation on single crystal Pt(100)electrode conformed to two-dimensional instantaneous nucleation process,and the adsorption time is longer,the more obvious.