Comparative Physicochemical and Electrochemical Characterization of the Structure and Composition of Thin Pd Binary and Ternary Codeposits with Pt, Ru, and Rh.

Pd-Ru, Pd-Rh, Pd-Pt-Ru, and Pd-Rh-Ru electrodes were prepared as thin layers by potentiostatic codeposition or chemical co-precipitation of metals from baths containing mixtures of chloride salts. The formation of substitutional solid solutions, with lattice parameters smaller than that of pure Pd, was confirmed by X-ray diffraction (XRD). The compositions at various levels of sample volume and thickness were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-AES), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and also electrochemically by cyclic voltammetry (CV) in 0.5 M H₂SO₄. The differences between surface, subsurface, and bulk compositions were compared for various systems in a wide composition spectrum.