Codeposition of Pd and Pb and electrocatalytic properties of their composite

A mixed electrolytic deposit (e.d.) PdPb with 33 +/- 4 at.% Pb is obtained on the gold electrode from 5 mM PdCl2 + 0.7 mM Pb(ClO4)(2) + 0.1 M HClO4 under potentiostatic conditions in the region of lead underpotential deposition (+100 mV vs. RHE). The deposit is characterized by SEM, EDX, XPS, CVA and 1CP- AES methods before and after polarization measurements. The problem of thermodynamic instability of the deposit is discussed. It is shown that cycling of the potential of e.d. PdPb in the interval of 0.1-1.25 V results in preferential dissolution of Pb; however, no dense Pd shell is formed. The codeposition of Pb with Pd increases the degree of dispersion and the defectiveness of the deposit. The possible reasons for the lower specific activity of e.d. PdPb in formic acid oxidation reaction (FAOR) as compared with e.d. Pd are considered. The high solubility of Pd from e.d. PdPb as compared with e.d. Pd is observed. The latter effect cannot be explained by only the increased surface area of the Pd component; it is assumed that the defectiveness of the deposit structure is also responsible for this effect. (C) 2019 Elsevier B.V. All rights reserved.