One of the most important scientific and technological challenges facing humanity is the switch from fossil fuels to clean energy. Polymer electrolyte membrane (PEM) fuel cells and electrolyzers are expected to play a key role in this switch. However, the high loadings of precious metals required to compensate for the slow kinetics of the oxygen reduction and evolution reactions (ORR and OER) impede the widespread uptake of these technologies. In order to reduce the Pt loading at the fuel cell cathode, researchers have intensively studied alloys of Pt with late transition metals such as Ni and Co. However, these compounds typically degrade under fuel cell conditions, due to dealloying. In contrast, alloys of Pt and lanthanides present exceptionally negative alloying energy, which should increase their resistance to degradation.<br/>Herein we present new catalyst materials for reactions taking place at PEM fuel cells and electrolyzers. Pt-lanthanide alloys present up to a 6-fold increase in ORR activity, relative to Pt. The active phase consists of a compressed Pt overlayer formed by acid leaching. In order to study the trends in ORR activity for different levels of compression, we studied eight novel polycrystalline Pt-lanthanide and Pt-alkaline earth electrocatalysts. Notably, the experimental ORR activity versus the bulk lattice parameter from X-ray diffraction follows a “volcano” relation. We use the lanthanide contraction to control strain effects and tailor the active site of Pt alloys. We have used similar methods to design more efficient catalysts for water electrolysis, and we present new strategies for both the hydrogen and oxygen evolution reactions for PEM electrolyzers.

Enhanced electrocatalysis for polymer electrolyte membrane fuel cells and electrolyzers

253rd National Meeting (2017)

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