Electrocatalysis offers a sustainable pathway toward decarbonizing chemical industries by enabling chemical transformations to be driven by renewable electricity. Unfortunately, many electrocatalysts exhibit either poor activity or selectivity and consist of expensive elements. Thus, there is a need to develop electrocatalysts with superior intrinsic activity and reduced precious metal content. Intermetallics have recently been identified as a promising material for advanced electrocatalyst development. Intermetallics are a specific type of alloy that consists of electronically dissimilar metals. This electronic dissimilarity results in the formation of strong heteronuclear bonds, which induces significant electronic modifications that tune the surface reactivity of the constituent metals (electronic effect). The strong heteronuclear bonds also result in long range structural order, which results in the co-location of surface-active sites with different reactivity (geometric effect). Unfortunately, intermetallics are susceptible to segregation upon air exposure due to the significant differences in the oxophillicity of the constituent metals. Recently, electrochemical methods of preparing intermetallics have been devised based on co-electrodeposition. In the present work, a novel method of repeated underpotential deposition of Ge onto Pd is demonstrated to yield a near-surface PdxGe1-x intermetallic alloy. In-situ characterization of the catalyst was performed using operando electrochemical XAS as a function of potential, electrochemical CO stripping and electrochemical quartz crystal microbalance. Ex-situ characterization was performed using GIXRD, XPS, and Ne-LEIS. Comprehensive characterization showed that the incorporation of Ge into Pd imparts significant oxidative stability and corrosion resistance into the material. The incorporation of Ge into Pd significantly improved the electrocatalytic activity for CO oxidation and O2 reduction compared to pure Pd, despite significantly reducing the precious metal content. DFT calculations suggest that these activity enhancements are a result of electronic and geometric effects. This work demonstrates significant progress toward improving the intrinsic activity of intermetallic electrocatalysts while reducing the precious metal content.
