Polydopamine As a Promising Candidate for the Design of High Performance Polymer Electrolyte Fuel Cell Electrodes(PEMFC)
Authors: Long Hongtao , Ball Vincent , Michel Marc 
Published: February 2020

Polymer electrolyte membrane fuel cells (PEMFC), which chemical energy directly converted to electricity, show promising features for mobile and portable applications because of their high energy-conversion efficiency and low pollution. The major barrier for large-scale commercialization of PEMFC is the high cost of the noble metal Pt, which is the best known catalyst for the oxygen reduction reaction (ORR). Furthermore, the performance of the membrane electrode assemblies (MEA) depends mostly on a balance between electronic and proton conductivity， therefor, PEMFC require optimization of their intermixing of the supplied Pt supported on carbon support to reach performance parameters, which include enhanced power density, increased catalyst utilization and reduced cost. One of the solutions is looking for alternative support materials like conductive polymers. In our present paper, fuel cell membrane will be prepared according to sprayed assisted layer-by-layer assembly，deposition method from polydopamine (PDA) and carbon nanotubes (MWNTs). Pt nanoparticles were attached to the MWNTs in a reaction of selective heterogeneous nucleation. MWNTs as an electron acceptor were coated with mussel-inspired PDA in artificial photosynthesis. After functionalization, Nafion perfluorinated resin solution was add to the suspension to obtain a stable dispersed solution for LBL assembly. The MEAs were sandwiching by two pieces gas diffusion layer and fed with H2/O2. Polarization curves were collected by using a fuelcon AG. The cells were analysed by scanning electron microscopy (SEM), thermo gravimetric analysis (TGA), and cyclic voltammetry (CV).

The images show that the composite is well-packed and very homogenous; this morphology improves the quality of the molecular contacts among the reactants. The three polarizations curves show some difference especially for the activation losses and the concentration losses. The power density of the electrode (Pt/ MWNTs-PDA)50 at 80°C is 780mW/cm2 ,525mW/cm2 for the electrode (Pt/ MWNTs)50, which are much higher than commercial 20% Pt/C.

The presented work describes a new technique produces ‘‘fast-prepared’’ electrode, which is allowed to reduce the electrode manufacturing time from 3 days to 10 min. The Pt/MWNTs-PDA ultrathin MEA demonstrated promising large accessible active surface for the reaction electrochemical. The porous architecture seems to ease the gas permeability leading to a better accessibility of the active sites of Pt. This has been proved by SEM and electrochemical measurements.  Consequently, the power density of the electrode (Pt/ MWNTs-PDA)50 at 80°C is 780mW/cm2, which is significantly better than the electrode without PDA (525mW/cm2) and our previous electrodes made with carbon black as carbon support. There is not very stable around 1600mA/cm2This might be due to the fact that the cathode side undergoes some change in morphology especially at the cathode side (see topview image). At high values of current density the system might be disturb and problem of diffusion might occur. This sentence has been added in the text.

Figure 1