Using the binding energy of OH* and CO* on close-packed surfaces as reactivity descriptors, we screen bulk and surface alloy catalysts for methanol electro-oxidation activity. Using these two descriptors, we illustrate that a good methanol electro-oxidation catalyst must have three key properties: (1) the ability to activate methanol, (2) the ability to activate water, and (3) the ability to react off surface intermediates (such as CO* and OH*). Based on this analysis, an alloy catalyst made up of Cu and Pt should have a synergistic effect facilitating the activity towards methanol electro-oxidation. Using these two reactivity descriptors, a surface PtCu₃ alloy is proposed to have the best catalytic properties of the Pt–Cu model catalysts tested, similar to those of a Pt–Ru bulk alloy. To validate the model, experiments on a Pt(111) surface modified with different amounts of Cu adatoms are performed. Adding Cu to a Pt(111) surface increases the methanol oxidation current by more than a factor of three, supporting our theoretical predictions for improved electrocatalysts.

The work exploring the stoichiometry of Pt deposition via surface-limited redox replacement of the underpotentially deposited (UPD) Cu monolayer on Au(111) is presented. The Cu UPD monolayer is formed from solution, whereas the Pt deposition via surface-limited redox replacement reaction is carried out in solution at open-circuit potential. Our results indicate that the Pt submonolayers have two-dimensional morphology and linear dependence of their coverage on the amount (coverage) of the replaced Cu UPD monolayers. Our analysis shows that the oxidation state of Cu during redox replacement reaction is , suggesting that four Cu UPD adatoms are replaced by each deposited Pt adatom. This work stresses the general importance of the anions, determining the stoichiometry of metal deposition reaction via surface-limited redox replacement of the UPD monolayers.

The interactions of nitrate with Cu(100) and Cu(111) in acidic solution are studied by cyclic voltammetry (CV) and in situ electrochemical scanning tunneling microscopy (EC-STM). CV results show that reduction of nitrate on Cu(111) commences at 0.0 V vs. Ag/AgCl while the corresponding potential is −0.3 V on Cu(100). EC-STM images show that the terrace of both Cu(111) and Cu(100) are atomically flat at potentials more negative than −0.7 V. The Cu(100) surface exhibits flat terraces throughout the entire cathodic potential range. Close to OCP, step edges start to corrode. In contrast to Cu(100), the first layer of Cu(111) is converted to an atomically rough and defected surface—associated with nascent surface oxidation at potentials positive of −0.7 V. This surface oxidation is correlated with nitrate reduction.