Controllable Synthesis of Low-Platinum Oxygen Reduction Catalysts By Modified Atomic Layer Deposition Process
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abstract
The widespread deployment of polymer electrolyte membrane fuel cells (PEFCs) is still limited by cost and durability challenges that arise from the oxygen reducing cathode catalysts. Current state of the art catalysts are platinum (Pt) or Pt-alloy nanoparticles deposited on high surface area carbon supports. Lowering the Pt loading of PEFC cathodes requires the development of catalysts that combine good oxygen reduction activity and high Pt dispersion (i.e., electrochemically active surface area, ECSA) to achieve sufficient high-power performance [1]. It is therefore highly desirable to develop synthetic techniques that provide careful, atomic level control over the deposition of Pt onto catalyst supports. In this talk, we will report on a modified atomic layer deposition (ALD) process that provides excellent control over the nucleation and growth of Pt onto different substrate materials. This technique was leveraged to prepare catalysts for the ORR, which were found to show excellent activity that significantly surpasses that of state-of-the-art Pt/C catalysts through rotating disc electrode evaluation. Furthermore, this ALD process provides the ability to deposit Pt on substrates that generally have very poor interactions with Pt precursors, enabling the preparation of uniform, highly dispersed Pt nanoparticles on these materials. Strong catalyst-support interactions resulted from this synthetic technique, with prepared catalysts showing excellent activity and ECSA retention following stability testing, with very little changes observed to the Pt nanoparticle size and morphology. This provides opportunity to use non-traditional catalyst support materials that can potentially overcome corrosion challenges associated with high surface area carbon. Catalyst formulation optimization as well as membrane electrode (MEA) integration is currently underway. [1] Kongkanand, Mathias, Journal of Physical Chemistry Letters (2016) 7, 1127-1137.
