Study On The Electrocatalysis Of PANI/PPy/Pt For Formate Oxidation

Direct Formate Fuel Cell(DFFC)has attracted much attention due to its non-toxicity,easy storage and good oxidation.Pt-based catalyst is still widely used in DFFCs.However,the anode catalysts are easily poisoned by some intermediates.Conductive polyaniline(PANI)and polypyrrole(PPy)could be used as carriers for Pt catalyst due to their large surface area,good stability,unique π-conjugated structure and electron conductivity.Herein,the PANI/Pt,PPy/Pt and PANI/PPy/Pt electrodes were prepared by in-situ oxidant-induced method.SEM,EDS,FT-IR,Raman,XRD,TG and XPS methods were used to characterized PANI,PPy and PANI/PPy.Cyclic voltammetry(CV),current-time curve(j-t)and electrochemical impedance spectroscopy(EIS)technologies were used to research the electrochemical properties of PPy/Pt,PPy/Pt and PANI/PPy/Pt.The results show that PANI deposited on Pt surface presents dense nanoparticles.PPy is spherical particles with a diameter of about 100 nm,and partly aggregates into coralline.PANI/PPy shows porous network cross-linking structure,which should be conducive to the construction of conductive network and charge transfer.The electrochemical experimental results indicate that the catalytic activity,poisoning-tolerance and stability of PANI/PPy/Pt catalyst are superior to that of PANI/Pt and PPy/Pt.The PANI/PPy/Pt catalyst exhibites relatively high catalytic efficiency in a wide pH range.In the mixture of 0.2 mol/L NaOH and 2.0 mol/L HCOONa,the current density reaches 91.3 mA/cm2,which is 2.7 and 2.9 times higher than that of PANI/Pt and PPy/Pt,respectively.The results of stability test show that the current retention rate of PANI/Pt is about 80%,and in the case of PPy/Pt and PANI/PPy/Pt,the value is only 50-60%and 70-80%,respectively.At the same time,the steady-state current density of PANI/PPy/Pt is also higher than that of PANI/Pt and PPy/Pt.After 500 CV cycles,the current losses of PANI/PPy/Pt,PPy/Pt and PANI/Pt are 22.1%,24.2%and 46.6%,respectively.In addition,PANI/PPy/Pt catalyst also exhibits an excellent anti-poisoned quility and a fast electrocatalytic rate for sodium formate oxidation.The mechanism study related the system shows that the electrocatalysis of PANI/PPy/Pt for formate oxidation shows enhancing with the pH of an electrolyte.We believe that an alkaline electrolyte is more conducive to reducing the oxidation potential of formate,as well as the intermediate toxicant CO.That is,the toxicant produced in the process of formate electrooxidation could be oxidized to CO2 rapidly at a low potential and therefore improving the performance of PANI/PPy/Pt.