Application Of Proton Conductor Based On Poly(Ionic Liquid) In Oxidation Reduction Catalyst Layers

Ionic liquids?ILs?have been realized as ideal ionic conductor because of their unique characteristics including low volatility,great ionic conductivity and excellent electrochemical stability.The composite catalytic system?ILs-Pt/C-Nafion?composed of suitable ILs,Pt/C and Nafion can significantly improve the oxygen reduction performance and tolerance to cell reversal of Proton Exchange Membrane Fuel Cells?PEMFCs?.However,during the long-term operation of the battery,the leaching of ILs will not be avoided.Poly?ionic liquid??PILs?can combine the characteristics of ILs and polymers.This work innovatively proposes to construct a new catalyst layer,PILs-Pt/C,by replacing Nafion in the traditional catalyst layer?Nafion-Pt/C?of PEMFCs with PILs as a proton conductor and a binder,to overcome the leaching of ILs in the ILs-Pt/C-Nafion catalytic system and improve the oxygen reduction performance.And,it will also provide a beneficial idea for the design of cathode catalyst layer for PEMFCs with high performance and low platinum loading.Firstly,this work summarized the key issues faced by the cathode catalyst layer of PEMFCs with high performance and low platinum loading,and the research status of proton conductors in catalyst layer;then,PILs with different monomer segment ratios were prepared by free-radical copolymerization and protonation reaction,the properties of them were characterized,and the proton conductivity of PILs-based membrane material was also explored;finally,the proton transfer impedance and oxygen reduction performance of PILs-Pt/C were evaluated.The main conclusions are as follows:?1?The free-radical copolymerization of styrene and N,N-dimethylvinylbenzylamine is closed to the ideal constant ratio copolymerization;the prepared PILs have good thermal stability,and the solubility and glass transition temperature of them are similar to Nafion;?2?The PILs-based membrane material has a proton conductivity of 10^-5 Scm^-1and 10^-1 Scm^-1,respectively,in the dry state and the fully hydrated state;and the Proton conductivity of PILs-Pt/C is superior to Nafion-Pt/C;?3?The combination of PILs and Pt/C can significantly reduce the coverage of unreactive oxides on the platinum surface.The area specific activity and mass specific activity of PILs-Pt/C can reach 3.16 and 3.06 times of Nafion-Pt/C,respectively.However,the hydrocarbon nature of PILs renders PILs-Pt/C less resistant to oxygen reduction than Nafion-Pt/C,but the protective effect of protic ionic liquid groups on platinum makes PILs-Pt/C smaller Pt nanoparticle size after endurance testing.