Mitigating Pt Loss in Polymer Electrolyte Membrane Fuel Cell Cathode Catalysts Using Graphene Nanoplatelet Pickering Emulsion Processing

Abstract

Carbon-supported Pt nanoparticles are the leading catalysts for the cathode oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells. However, these ORR catalysts suffer from poor electrochemical durability, particularly the loss of electrochemical surface area (ECSA) due to Pt nanoparticle dissolution and agglomeration. Here, Pt loss is mitigated through a Pickering emulsion-processing strategy that employs graphene nanoplatelet dispersions stabilized by the polymer ethyl cellulose. The resulting graphene-Pt/Vulcan carbon (Pt/C) catalysts exhibit superior durability and ECSA retention throughout an accelerated stress test compared with a commercial Pt/C standard catalyst, both in a diagnostic-rotating disc electrode setup and in a membrane electrode assembly full cell. These graphene-Pt/C catalysts also improve durability at high-voltage conditions, providing further evidence of their exceptional electrochemical stability. Consistent with density functional theory calculations, postelectrochemical characterization reveals that Pt nanoparticles localize at graphene defects both on the basal plane and especially at the edges of the graphene nanoplatelets. Since this Pt nano particle localization suppresses Pt nanoparticle dissolution and agglomeration without hindering accessibility of the reactant species to the catalyst surface, the ORR performance under both idealized and practical experimental conditions shows significantly improved durability while maintaining high electrochemical activity.

Tailoring supports for enhancing the electrocatalytic hydrogen evolution performance of platinum species: a review

“…53 Therefore, the electronic state of the Pt 5d orbitals could be modulated via integrating the p-electron system, improving the catalytic activity. 54 To prove this, a novel approach for modifying the coordination environment of Pt SAs has been proposed, which leveraged the use of graphene edges as a support material for the alkaline HER. 55 Based on XAFS measurements and DFT calculations, Pt SAs anchored to graphene edges exhibited a robust interaction with the p-electrons of graphene.…”

Manipulating the interaction of Pt NPs with N-hollow carbon spheres by F-doping for boosting oxygen reduction/methanol oxidation reactions

“…[23][24][25] Therefore, for supported Pt catalysts, the electronic structure around Pt atoms can be manipulated by adjusting the interaction between Pt and the support, thereby optimizing the binding energy between the active center and the reaction intermediates, and thus improving the ORR/MOR catalytic activity and stability. [26][27][28] Carbon-based supports have been widely used in the ORR and MOR due to good electrical conductivity, stability, and corrosion resistance. The carbon substrate can not only increase the accessibility of the edge position but also improve the electron transfer at the interface, which will signicantly improve the catalytic performance.…”

Bimetallic PdY nanosponges for enhanced oxygen reduction electrocatalysis

“…Oxygen reduction reaction (ORR) has attracted extensive attention in fuel cells and metal-air cells, but its sluggish kinetics greatly limits their applications [1][2][3][4][5][6][7][8]. Platinum (Pt)based catalysts have high oxygen reduction activity, but the easy toxicity of Pt hinders its large-scale applications [9][10][11].…”