Sub-monolayer Deposition of Ad-metals

An interesting formation of bi-metallic catalysts involves flic use of underpotential deposition (UPD) of Cu onto, e.g., Au [98]. Subsequently, die copper can be displaced by metals such as Pt, Pd, or Ag that are driven through favorable AG values. The replacement of Cu with metal, M, is an irreversible, spontaneous redox process, expressed through the respective equilibrium potentials (E), as follows  

Sub-monolayers of Pt, Pd, and a bilayer of Ag have been formed in this manner onto Au(l 11) surfaces. 

The adsorbed RUO2 can then be electro-reduced according to Equations 9.17 and 9.18  

As discussed in Section 9.4.1.1, preferential layers of Pt can be formed by annealing alloy catalysts. Promising examples of carefully annealed Pt catalysts have been reported recently [99, 100]. The annealed samples show a high activity towards the ORR, which is attributed to a lower tendency to form surface oxides. 

Bulk Pt3Ni alloys were annealed in ultra-high vaeuum to form a single atom Pt skin layer. The challenge remains to synthesize nanosized structures of these catalysts. 

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