Christopher Tremblay

Topic

Strategies for increasing the durability of platinum electrocatalysts for proton exchange membrane fuel cell applications

Department of Chemistry

Date & location

• Tuesday, January 13, 2026
• 1:30 P.M.
• Elliott Building, Room 230

Examining Committee

Supervisory Committee

• Dr. Heather Buckley, Department of Chemistry, University of Victoria (Supervisor)
• Dr. Alexandre Brolo, Department of Chemistry, UVic (Member)
• Dr. Peter Loock, Department of Chemistry, UVic (Member)
• Dr. Arthur Blackburn, Department of Physics and Astronomy, UVic (Outside Member)

External Examiner

• Dr. Byron Gates, Department of Chemistry, Simon Fraser University

Chair of Oral Examination

• Dr. Sarah Nutter, Counselling Psychology, UVic

Abstract

This thesis explores two different methods for improving the durability of platinum catalysts in proton exchange membrane fuel cells (PEMFCs), through both carbon support modification and alloying the platinum catalyst with rare earth elements (REs). Nanoparticles are synthesized through burst nucleation and high temperature H₂/Ar treatment, and characterized using X-ray diffraction, electron microscopy, X-ray photoelectron spectroscopy, X-ray absorption spectroscopy and energy dispersive spectroscopy. The electrocatalysts are then screened for their electrochemical activity for the oxygen reduction reaction at a rotating disk electrode, and electrochemical impedance spectroscopy is used to elucidate information about the electrokinetics of each electrocatalyst.

Chapter 1 introduces the relevant background for the thesis, starting with the proton exchange membrane fuel cell and the oxygen reduction reaction. The thermodynamics and mechanisms of nanoparticle synthesis are then covered, along with platinum alloy formation. Lastly, the key characterization methods are covered in detail, including voltammetry, electrochemical impedance spectroscopy, electron microscopy, powder X-ray diffraction and X-ray photoelectron spectroscopy.

Chapter 2 details our work done in collaboration with XLynX Materials, where we have investigated the effects of hydrogenation of a carbon support in relation to platinum nanoparticle growth and electrochemical stability. It was hypothesized that due to hydrogenated graphene’s intrinsic hydrophobicity, carbon corrosion could be reduced by using a hydrogenated support. We found that when growing hollow porous PtNi on hydrogenated graphene, controlling the mole ratios of the metallic precursors was key in affording the desired nanostructure due to the interactions of hydrogenated graphene with the initial crystallite formation. Moreover, we found that the hydrogenated composite was less susceptible to carbon corrosion, as indicated by electrochemical methods, Raman spectroscopy and identical location TEM (IL-TEM).

Chapter 3 details the work on optimizing carbodiimide synthesized PtGd catalysts for use in PEMFCs. It has been identified that the conventional carbodiimide route results in Pt-RE catalysts that are unsuitable for use in a PEFMC, as the nanoparticle formation occurs on the outside of the carbon black, and not inside the pores. We have proposed a key synthesis intervention: through introducing a wet mixing step, we allow precursors to diffuse into the pores of the carbon black. This allows for nanoparticle nucleation and growth to occur in the pores of the carbon support, leading to a catalyst material that is less susceptible to ionomer poisoning. We demonstrate the increased ionomer poisoning resistance using electrochemical methods and in-situ PEMFC studies, as well as extensively characterize the nanoparticle formation using X-ray and spectroscopic methods.

Chapter 4 builds upon Chapter 3 and targets the toxic C-N precursor used in the carbodiimide route. Since cyanamide is identified as a human health and environmental hazard, it must be replaced with a greener precursor for scale up to viable. We explore two new C-N precursors for the carbodiimide route, dicyandiamide and melamine, and investigate how they affect the nanoparticle formation and electrochemical ORR behavior. A comprehensive hazard analysis is also conducted, in which we compare the relative hazard level between cyanamide, dicyandiamide and melamine.

Chapter 5 builds on both Chapters 3 and 4, and uses the modified carbodiimide route along with melamine to explore platinum-alloy systems with “variable valence” rare earth elements. Variable valence transition metals like Cr, Nb and V have recently been identified to act as electron buffers in platinum electrocatalysts, reducing surface polarization and extending their durability. We hypothesized this could be extended to the rare earth elements, and investigate the crystal structure, surface composition and electrochemical behavior of Pt-Eu and Pt-Yb systems.

Lastly, Chapter 6 details the conclusions from each chapter, outlooks and the planned future work. This includes the use of earth abundant cerium and calcium as alloying agents.