Nafion®-stabilised Pt/C electrocatalysts with efficient catalyst layer ionomer distribution for proton exchange membrane fuel cells

Abstract

We report a facile method for the preparation of proton exchange membrane fuel cell (PEMFC) electrocatalysts from Nafion1-stabilised colloidal Pt nanoparticles (Nafion1-Pt/C), offering synthetically-directed formation of the Pt-ionomer interface and providing unprecedented control over the morphology of Pt particles on the carbon support. Electrochemical characterisation of the catalysts in aqueous acidic electrolytes using Rotating Disc Electrode (RDE) techniques revealed that Nafion1-Pt/C catalysts possessed similar specific activity and mass activity towards the oxygen reduction reaction (ORR) as commercial Pt/C catalysts, whilst requiring lower overall ionomer loadings. Combined with the near-100% utilisation measured for the Nafion1-Pt/C catalysts, this implies that Pt nanoparticles synthesised with Nafion1 as a stabiliser can be 'tuned' to have simultaneous access to the reactant gas, the electron conducting carbon support and the proton conducting polymer electrolyte in the catalyst layer, thereby optimising the triple-phase reaction zone. By taking advantage of this bottom-up approach, which allows nanoscale control of the Nafion1-Pt-carbon interface, new opportunities exist to lower the Pt loading and the cost of the fuel cell.

Oxygen Reduction Reaction Measurements on Platinum Electrocatalysts Utilizing Rotating Disk Electrode Technique

“…A review of the literature shows a wide range of cleaning procedures formulated by researchers including: soaks in Aqua Regia, 67 hot conc. nitric 26 or sulfuric acid, 19 acidified potassium permanganate, 5,68 mixtures of conc.…”

Oxygen Reduction Reaction Measurements on Platinum Electrocatalysts Utilizing Rotating Disk Electrode Technique

“…[78][79][80] A common factor in a majority of the TF-RDE studies for Pt/C catalysts encountered in the literature is the incorporation of Nafion ionomer either mixed in with the catalyst ink formulation or applied as a cap over the dried catalyst film on RDE disk. 6,[13][14][15]17,[48][49][50][51]61,62,69,[81][82][83][84] However, the ORR activity values that are measured with added Nafion represent a complex, poorly defined, and variable electrochemical interface that can be represented as "Pt/C | discontinuous Nafion film soaked in 0.1 M HClO 4 , free 0.1 M HClO 4 ". We use this notation to describe two parallel interfaces, Pt/C in contact with HClO 4 soaked Nafion and Pt/C directly in contact with free HClO 4 as shown in Fig.…”

Deactivation and Recovery of Pt/C with Commercial Glycol-Based Coolants in Rotating Disk Electrodes and Membrane Electrode Assemblies

“…After the first exposure, the loss of total Pt ECSA cannot be overcome by the more active form of the Pt nanoparticles. Note that the question of whether a particle size effect exists for ORR kinetics is still an active area of debate with recent experiments suggesting that there is no particle size effect at all (23)(24)(25). The salient point here is that while it is possible to clean coolant containing polyol from the Pt surface of the MEAs, deactivation still occurs through the loss of ECSA after multiple exposures.…”