Scalable Sacrificial Templating to Increase Porosity and Platinum Utilisation in Graphene-Based Polymer Electrolyte Fuel Cell Electrodes

Abstract

Polymer electrolyte fuel cells hold great promise for a range of applications but require advances in durability for widespread commercial uptake. Corrosion of the carbon support is one of the main degradation pathways; hence, corrosion-resilient graphene has been widely suggested as an alternative to traditional carbon black. However, the performance of bulk graphene-based electrodes is typically lower than that of commercial carbon black due to their stacking effects. This article reports a simple, scalable and non-destructive method through which the pore structure and platinum utilisation of graphene-based membrane electrode assemblies can be significantly improved. Urea is incorporated into the catalyst ink before deposition, and is then simply removed from the catalyst layer after spraying by submerging the electrode in water. This additive hinders graphene restacking and increases porosity, resulting in a significant increase in Pt utilisation and current density. This technique does not require harsh template etching and it represents a pathway to significantly improve graphene-based electrodes by introducing hierarchical porosity using scalable liquid processes.

Platinum deposition on functionalised graphene for corrosion resistant oxygen reduction electrodes

“…29,30 The extent of Pt utilisation follows the trend Pt/C > Pt/FLG-functionalised > Pt/FLG, suggesting that the functionalised groups play a useful role in preventing restacking of the graphene and the associated loss in initial ECSA. 31 ORR RDE experiments are typically compared via several different parameters across different parts of the LSV, these include j k (current in kinetic controlled regime), j d (current in diffusion-controlled regime) and half wave potential (potential at half j d ); these parameters are reported in the ESI, † along with current density and Tafel plots for each material (Tables S1-S3 and Fig. S4, S5 †).…”

“…29,30 The extent of Pt utilisation follows the trend Pt/C > Pt/FLG-functionalised > Pt/FLG, suggesting that the functionalised groups play a useful role in preventing restacking of the graphene and the associated loss in initial ECSA. 31…”

Multiscale Architectured Membranes, Electrodes, and Transport Layers for Next‐Generation Polymer Electrolyte Membrane Fuel Cells

“…Fuel cell performance considerably depends on proton and electron conduction, reactant gas (H 2 and O 2 ) transport, and water management. [101] To enhance the oxygen transport in thick electrodes, the structure of electrodes is typically tailored to secure macropores (pores exceeding 50 nm in size) using pore-forming agents by lowering the tortuosity of gas diffusion and alleviating water clogging, which hampers the oxygen access to active sites. [102][103][104] From Watanabe's work, [105] the electrode consisting of Pt/C and ionomers has two types of pores with different size distributions.…”

Graphene-Derived Carbon Support Boosts Proton Exchange Membrane Fuel Cell Catalyst Stability

“… 7 Consequently, new synthesis pathways are required to enable the synthesis of GD-supported analogues comparable with today’s state-of-the-art CB-supported Pt-based catalysts. This has led to many the strategies attempting to improve poor performance of the GDs using (i) various additives such as urea in the catalyst ink for the electrode preparation 22 or (ii) using additives such as CBs to act as spacers that prevent restacking of GD-supported catalysts 23 or (iii) synthesis of hybrid CB/GD 15 , 24 − 26 or even MO x /GD-supported catalysts. 27 Such strategies hypothesize the issues in the porosity of the catalyst layer and/or insufficient conductivity of the (usually) partly oxidized GD supports.…”