Static Synthesis Of PANI/Pt As An Anode Of DFFC And Its Electrochemical Catalysis For HCOONa Oxidation

Polyaniline is a famous proton conductive polymer.It has attracted much attention because of its easy doping/de-doping H+,large surface area,simple production,low cost,high conductivity,excellent mechanical properties and chemical stability.In this paper,H+-doped conductive polyaniline（PANI）was prepared by a static chemical method,using aniline as raw material nitric acid as dopant,ammonium persulfate（APS）or silver nitrate（AgNO3）as oxidant.Further we prepared PANI-modified platinum（PANI/Pt）through a in situ chemical polymerizing method and studied its electrochemical catalysis as an anode of direct formate fuel cells（DFFCs）by cyclic voltammetry（CV）measure in sodium formate electrolytes blended with sodium hydroxide,respectively.The conductivity of PANI was measured by a standard four-probe method.The morphology and structure of PANI were characterized by scanning electron microscopy,infrared spectroscopy,X-ray diffraction and ultraviolet-visible spectrum experiments,respectively.The results show that aniline is successfully synthesized on the surface of platinum electrode.At the same time,the PANI produces show significantly different morphology and properties,depending on the oxidant used in the process.In the case of oxidant APS,PANI is clustered.And PANI synthesized with AgNO3 as oxidant shows fibrous.Moreover,PANI/Pt electrodes,synthesized respectively with APS and AgNO3 as the oxidant,show excellent electrocatalysis for formate oxidation in the mixtures of sodium formate and sodium hydroxide,but the catalysis is not significant in the mixtures of sodium formate and sulfuric acid.Further we studied the electrocatalysis of PANI/Pt electrode for formate oxidation by CV experiments in the mixtures of 0.1 mol/L sodium hydroxide and sodium formate with different concentration.The results indicate that,compared with oxidant AgNO3,the PANI/Pt electrode synthesized with oxidant APS shows better electrocatalysis for formate oxidation.Base on the above,we synthesized the PANI/Pt electrodes with APS as the oxidant,along with holding the static reaction system for one,two,three and four weeks,respectively.The CV curves in the mixture of sodium formate and sodium hydroxide demonstrate that the electrocatalytic performance of the PANI/Pt electrodes varies with the holding time.The best performace presents in the case of one week.Under the condition,an appropriate working concentration range of sodium formate is from 3.0 to 5.0 mol/L and the best working concentration is 3.5 mol/L.In the mixture of 3.5 mol/L sodium formate and 0.1 mol/L sodium hydroxide,the onset potential is as below as-0.20 V,which is even close to that of palladium for formic acid oxidation.And the oxidation peak current density is upto 90.3 mA/cm2,correspondingly,the peak potertial is 0.24 V.In addition,in the wide concentration range of sodium formate as above,the synthesized electrode reveals a special electrocatalysis for the direct formate oxidation,along with a strong inhibition on the indirect formate oxidation.