Platinum–rare earth nanoalloys as electrocatalysts for oxygen reduction in PEMFCs

Hawkings, Sophie, Fisher, Janet, Burdett, Harriet, Dunseath, Olivia, Brooke, Emily, Marchbank, Huw, Seljamäe-Green, Riho T. and Spikes, Geoffrey H. 2026. Platinum–rare earth nanoalloys as electrocatalysts for oxygen reduction in PEMFCs. Journal of Materials Chemistry A: materials for energy and sustainability 10.1039/d6ta01839d

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Abstract

Carbon-supported platinum–rare earth (Pt–RE) nanoalloys were synthesised using a facile incipient wetness impregnation route and subsequently via an aqueous base-precipitation route for evaluation as electrocatalysts for the oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells (PEMFCs). Heat-treatment of Pt–RE catalysts containing La, Ce, Pr, Nd or Gd yielded intermetallic Pt5RE phases with sub-10 nm particle sizes, as confirmed by pXRD and AC-TEM. Ce- and Nd-based catalysts formed well-defined hexagonal P6/mmm Kagome-structured cores, and acid leaching removed surface RE oxides to generate Pt-rich shells, increasing electrochemically active surface area. Pt–RE catalysts exhibited high specific activities compared to a heat-treated Pt-only analogue; however, mass activity and performance at high current densities in catalyst-coated membranes (CCMs) were limited by particle size, with lower performances seen than for non-heat-treated Pt-only catalysts. RE dissolution was demonstrated during ink formulation and during operation, leading to Pt-shell thickening and ionomer contamination. This meant that none of the materials prepared were considered candidates to proceed to operando stability testing without further optimisation. Among the catalysts studied, Pt5Nd showed the best balance of extent of alloying at lower temperatures, subsequent RE metal retention and structural stability upon ex situ acid-treatment and mass and specific activity in the CCM but was shown to be unstable to subsequent Nd dissolution in initial CCM testing. Pt5Y, which required the highest formation temperatures of the materials studied to provide alloying and consequently gave the largest particle sizes, formed an orthorhombic rather than hexagonal phase by pXRD, demonstrated the highest specific activity in a rotating disc electrode (RDE), but this was not replicated in CCM testing. This study demonstrates the increased intrinsic ORR catalytic activity of Pt–RE intermetallics compared to Pt-only particles in the same size range, whilst identifying RE stabilisation at small particle sizes as the critical barrier to durable, high-mass-activity cathodes.

Item Type:	Article
Date Type:	Published Online
Status:	In Press
Schools:	Schools > Chemistry Research Institutes & Centres > Cardiff Catalysis Institute (CCI)
Publisher:	Royal Society of Chemistry
ISSN:	2050-7488
Date of Acceptance:	3 September 2026
Last Modified:	05 Oct 2026 10:15
URI:	https://orca.cardiff.ac.uk/id/eprint/189982

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