Formation of the core-shell structure in the Pd-Ag system by electroleaching of the alloy. Electrocatalytic properties

An electrodeposit (e.d.) Pd0.5Ag0.5 is prepared in a mixed aqueous solution of PdSO4 + Ag2SO4 (0.5 M H2SO4 as the supporting electrolyte) under conditions of diffusion-controlled deposition of Pd2+ and Ag+. Using the SEM, MPA, XPS, CVA, and ICP-AES methods, it is shown that cycling of the PdAgin/GC electrode potential E in the range of 0.09-1.4 V (RHE) results in preferential dissolution of the Ag component. For a large number of cycles, the core(PdAg)-shell(Pd) structure is formed. The shell is sufficiently highly permeable for silver atoms escaping from the core to the surface. The possibility of assessing the electrochemically active surface area of the PdAg alloy by the adsorption of copper is analyzed. It is found that as regards the specific activity in the HCOOH electrooxidation, e.d. PdAg differs only slightly from e.d. Pd.