Nanoporous Pt@AuxCu100-x by Hydrogen Evolution Assisted Electrodeposition of AuxCu100-x and Galvanic Replacement of Cu with Pt: Electrocatalytic Properties

Electrodeposition of high-surface-area nanoporous Au-Cu foams under conditions of hydrogen codeposition is studied. The honeycomb-like AuxCu100-x foams with 0 <= x <= 100 are electrodeposited by controlling the amount of corresponding ions in the solution. The amount of metal ions in deposited films follows that in used electrolytes. Compared to monometallic foams, the AuxCu100-x structures are characterized by smaller ligament or particle sizes (less than 10 nm) and improved stability. The addition of even a small amount of Cu to the Au matrix is found to dramatically improve the stability of the structure in air environment or an acidic medium. Pt@AuxCu100-x structures are formed by the galvanic displacement of Cu from AuxCu100-x templates. During the displacement of Cu by Pt, Au serves as a buffer, decreasing mechanical stresses and preventing the detachment of the foam from the substrate. The surface ratio of Pt to Au atoms is controlled by adjusting the amount of Cu in the template. Pt@AuxCu100-x electrodes are investigated as novel electrocatalysts for methanol oxidation in alkaline media. The Au-enriched surfaces show higher catalytic activity toward methanol oxidation, while the electrodes with a higher amount of Pt are more stable.