New PtMg Alloy with Durable Electrocatalytic Performance for Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cell

Polycrystalline alloy electrodes of Pt with alkaline earth metals (Ca, Sr, and Ba) have been shown to exhibit enhanced electrocatalytic performance for oxygen reduction reaction (ORR) relative to Pt electrodes. The large oxophilicity of the alkaline earth metals makes it challenging to synthesize such alloys. Here, we synthesize a carbon-supported platinum-magnesium (PtMg) alloy with enhanced catalytic activity and durability for the ORR in both a half-cell and single cell when compared to the state-of-the-art Pt/C catalyst. Employing metallic Mg powder as a precursor can overcome the large oxophilicity of Mg and induce alloying of Mg with Pt, whereas conventional Mg salts do not form an alloy. Density functional theory calculations elucidate the origin of the enhanced catalytic activity and durability. Complementary physical and electrochemical analyses also evidence them in this work. This material holds great application potential and will contribute to elucidation of the effects of alloying Pt with electropositive metals.