Towards High-Performance Proton Exchange Membrane Fuel Cells Using Polymer Coated Heteroatom Doped Partially Unzipped Carbon Nanotubes As Catalyst Support

Abstract

Enhancing the durability and reducing the cost of Proton Exchange Membrane Fuel Cells (PEMFC) are the bottlenecks for the commercialization. Platinum is reported as the best electrocatalyst for both anode and cathode due to its optimum binding energy towards hydrogen, oxygen atoms and products during the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR). The electrocatalyst loading at the anode and the cathode can be minimized by dispersing Pt nanoparticles (NPs) on high surface area and conductive carbon support material. The durability and performance of PEMFC depend on the interaction between the support and Pt NPs as well as the number of active sites available for the reactions, which can be enhanced by selective coating of proton conducting polymer on the hetroatom doped supporting material. In the present work, we have synthesized highly proton conducting polymer polyvinyl phosphonic acid (PVPA) coated heteroatom doped partially unzipped carbon nanotubes (H-PECNT) and used as the catalyst support material for Pt NPs. The heteroatom doping increases the ORR activity of the support material and the PVPA coating adhere Pt NPs to the support during cycling and also increases the active sites. Moreover, we have coated PVPA on H-PECNT by varying different ratios of PVPA to H-PECNT and to find the optimum PVPA percentage on H-PECNT, which enhances the performance of PEMFC. The single cell measurements deliver a high power density with 6% of PVPA than the commercial Pt/C as well as other PVPA ratios wherein both electronic conductivity of the support material and proton conductivity of PVPA contribute significantly to the performance.