Intermetallic Passivation Imparts Corrosion Resistance and Enables Intrinsic Electrocatalytic Activity Promotion

Electrocatalytic technologies are limited by reliance on precious metal catalysts with low activity. Intermetallics can alleviate these challenges but have limited efficacy due to corrosion susceptibility. Herein, we demonstrate that electrochemical cycling produces a near-surface Pd + Ge intermetallic with corrosion resistance far exceeding that of bulk PdGe. Corrosion resistance is enhanced by the presence of more cationic Ge at the surface, which acts as an intermetallic passivation layer. This enhanced corrosion resistance enables the material to be utilized as an electrocatalyst under conditions where bulk PdGe rapidly corrodes. The material exhibits exceptional activity for O2 reduction, which is enhanced by roughly an order of magnitude compared to Pd on a per Pd surface atom basis. Density functional theory suggests that activity promotion occurs via electronic and bifunctional effects. This work demonstrates that electrochemical near-surface alloying can produce remarkably corrosion resistant materials with superior electrocatalytic activity despite a reduced precious metals content.