(701b) Electrodeposition of Pt Alloy Electrocatalysts From Chloride Based Electrolytes

Binary and multicomponent Pt alloys, particularly those containing early transition metals, are recognized as an important class of catalytic materials for low temperature fuel cell technology.  Select base metals shift the electronic structure and/or introduce bifunctionality at the Pt surface, tuning the electrocatalytic performance for a number of different reactions. 

While the formation of these alloys and integrated design strategies are of critical interest, electrochemical deposition has not garnered significant interest.  This reflects the limited mechanistic understanding of Pt electrodeposition, despite frequent use as an enabling tool, including decades of work on “platinized platinum”.

In this talk I will give an overview of recent work on binary and ternary Pt alloy electrodeposition examining underpotential codeposition from its elemental constituents over a large potential range.  Electrodeposition coupled with quartz crystal microbalance and energy dispersive X-ray spectroscopy was utilized to extract potential dependent trends and ion effects.  For instance, inhibition of Pt deposition in the hydrogen evolution reaction regime is lifted by the presence of iron group salts.  This behavior is understood as a shift in the potential of zero charge from neighboring iron group atoms in the deposit, weakening the binding strength and coverage of the passivating underpotential deposited hydrogen layer.  Adsorption will also be shown to play an important role in the onset of Pt electrodeposition and efficiency, with considerable effects from chloride and H_UPD, respectively.  Finally, I will touch upon potential control of these adlayer processes to create divergent catalyst structures for electrolyzers and proton exchange membrane fuel cells.