Fabrication of platinum submonolayer electrodes and their high electrocatalytic activities for ammonia oxidation

• Pt submonolayer on the Au electrode for ammonia oxidation.
• The surface coverage of the Pt submonolayer can be effectively controlled by the Cu UPD potential.
• Pt submonolayer on the Au electrode has both high mass activity and specific activity.

Pt submonolayer with different coverage on the Au electrode for ammonia oxidation was prepared by Cu underpotential deposition (UPD) followed by redox replacement of UPD Cu by Pt. The effects of the Cu UPD potential and time on the deposited Cu and the redox replaced Pt layer on the electrode were investigated. The amount of the deposited Cu and Pt was determined by the anodic stripping method. The electrocatalytic activity of the Pt decorated electrodes for ammonia oxidation was characterized by cyclic voltammetry. The results showed that the Cu UPD potential has a significant influence on the formed Cu layer and the subsequent Pt submonolayer. The Cu deposition behaviour changes from UPD process to overpotential deposition (OPD) process with the decrease of deposition potential. Besides, the amount of the deposited Cu increases as the Cu deposition potential decreases. Consequently, Pt layer with different coverage on the electrode can be effectively controlled by adjusting the Cu UPD potential. The Pt submonolayer electrodes prepared by the redox replacement of Cu UPD layer have a high mass activity for ammonia oxidation, and their mass activities are more than two times higher than that of the Pt decorated electrodes obtained by redox replacement of Cu OPD layer. Besides, the Pt submonolayer electrodes also have a higher specific activity possibly due to the modification in structural and electronic properties of the Pt submonolayer induced by the Au substrate.