Peculiarities of electrocatalytic and corrosion behavior of palladium and palladium-molybdenum electrolytic deposits

• Published in: Journal of electroanalytical chemistry (Lausanne, Switzerland) Switzerland), 2023-02, Vol.931, p.117178, Article 117178
• Main Authors: Podlovchenko, B.I., Kuznetsov, V.V., Zhulikov, V.V.
• Format: Article
• Language: English
• Subjects: Corrosion resistance; FAOR and MOR; Influence of molybdenum; PdMo and Pd electrodeposits
• ISSN: 1572-6657; 1873-2569
• DOI: 10.1016/j.jelechem.2023.117178

•The electrodeposited PdMo (22 at.% Mo) is characterized by the SEM, EDX, XPS, ICP- AES, ICP-MS and CV methods.•The dissolution of both PdMo and Pd electrodeposits at the potentials of oxygen adsorption is compared quantitatively.•Larger overall solubility of PdMo deposits compared to Pd ones is due to an increase in EASA.•A decrease in specific Pd solubility caused by Mo additions is due to the inhibitory effect of oxides.•A drop in activity in FAOR and an increase in activity in MOR caused by molybdenum addition to Pd are found and discussed. PdMo deposits (∼22 at.% Mo) are obtained on the surface of glassy carbon electrodes by electrodeposition in galvanostatic mode from aqueous ammonium-acetate solutions containing palladium(II) chloride and ammonium heptamolybdate. The deposits are characterized by SEM, XRD, XPS, ICP–AES, and CV methods. It was found that the most of palladium is in a metallic state in the surface layers of the deposits, whereas molybdenum is in the forms of oxides in them. The effect of molybdenum inclusion in the palladium deposits on their anodic dissolution in 0.5 M H2SO4 is studied by cycling electrode potential in the range of 0.30 – 1.25 V (RHE) in various regimes with simultaneous determination of quantities of metals passed into the solution. The joint analysis of both coulometric and analytical data showed that Mo addition to palladium causes a decrease in the specific solubility of the deposits. This analysis also made it possible to conclude that Pd dissolution predominantly occurs on the part of the surface, which is not occupied by oxides. The addition of molybdenum to palladium deposits causes a sharp decrease in their activity in formic acid oxidation reaction (FAOR) and some increase in the activity in methanol oxidation reaction (MOR) in 0.5 M H2SO4. This can be explained by the different role of oxygen-containing species in the mechanisms of FAOR and MOR.