Electrocatalytic properties of Au electrodes decorated with Pt submonolayers by galvanic displacement of copper adatoms

•Pt0 coatings are deposited on pc Au by galvanic displacement of xMLCuad (x = 0.25÷1.0) in PtCl42− solution.•Ptx0Au electrodes are characterized by CVA, SEM, XPS and Auger spectroscopy.•For Ptx0Au electrodes, the inhibition of MOR and strong acceleration of FAOR (calculated per cm2 of Pt) as compared with pc Pt are observed.•An explanation of these peculiarities of the electrocatalytic behavior of Ptx0Au is put forward.

Submonolayer Pt0 coatings are synthesized by the displacement of copper adatoms (Cuad) on polycrystalline (pc) Au in PtCl42− solutions (supporting electrolyte 0.5 М Н2SO4). Cyclic voltammograms (CVA) measured on Pt0Au demonstrate that for initial surface coverages θCu < 0.5, the Pt0 adatoms that have displaced Cuad are mainly deposited in the first layer. At large surface coverages, the agglomeration of Pt0 and its partial deposition into the second layer take place; ∼30% of Au surface remains free. SEM, XPS and Auger-spectroscopic data confirm the absence of multilayer Pt0 agglomerates. The specific rates of СН3ОН electrooxidation (per cm2 of Pt) on Pt0Au turn out to be much lower than on pc Pt0. This is explained by the fact that dehydrogenation of СН3ОН requires the presence of «areas» formed by a large number of platinum atoms (> 3). For НСООН, the strong increase (more than by one order of magnitude) in both non-steady-state and steady-state specific electrooxidation currents is observed. It is assumed that new active sites are formed for the current-determining reaction that proceeds through the one-site adsorption of НСООН molecules.