Hydrogen electrosorption properties of electrodeposited Pd-Ir alloys

Abstract

The study of the hydrogen sorption process in metals/alloys of different forms is crucial for developing the fields of catalysis and energy storage. The objective of this research was to examine basic hydrogen electrosorption properties of Pd-Ir alloy thin films obtained through electrodeposition. Pd-Ir alloys, containing more than 87% at. Pd, were successfully potentiostatically electrodeposited from aqueous baths containing PdCl2 and IrCl3. X-ray diffractometry confirmed the Pd-Ir alloy formation and homogeneity of the deposits. The hydrogen electrochemical absorption was carried out with the use of cyclic voltammetry and chronoamperometry. The values of H/(Pd+Ir) for Pd-Ir alloys containing less than 3% at. Ir are similar, comparable to Pd. The further increase of Ir content results in the abrupt drop of hydrogen absorbing capacity. The linear decrease of the potential of α→β phase transition versus Pd content is observed, confirming classification of the Pd-Ir alloys to the group of the contracted alloys. Graphical abstract

The Effect of the Iridium Alloying and Hydrogen Sorption on the Physicochemical and Electrochemical Properties of Palladium

“…As previously stated [ 16 ], Pd-Ir alloys exhibit interesting properties in relation to their interaction with hydrogen. For the alloys containing relatively high amounts of Pd, β-phase of hydrogen was created.…”

“…3 at.% of Ir, the capacity was comparable to pure Pd (H/Pd ca. 0.72) [ 16 ]. In Figure 9 a, the dependence of the transition potential of hydrogen absorption and desorption on the Pd bulk content in acidic medium is visible.…”

“…Therefore, Pd and its alloys, due to the ability of hydrogen absorption and good electrochemical properties, are important in view of energy storage and conversion, especially as a model system to be utilized for the interpretation of the hydrogen sorption process in other hydrogen-absorbing materials. Whilst Pd and its binary or ternary alloys with other noble metals such as Pt, Rh, Ru, Ag, or Au were extensively studied and electrochemically characterized [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ], in the literature there is a lack of information regarding electrodeposited Pd-Ir alloys, and their properties in terms of hydrogen electrosorption are still not thoroughly examined [ 16 , 17 ]. Alloying with transition metals is an efficient way to improve the utility of the Pd constituent [ 18 ].…”

“…Pd-Ir constitutes face-centered cubic alloys with a reduced lattice constant compared to pure metals. The alloy lattice constant decreases with the increasing content of Ir, with a small negative deviation from Vegard’s law [ 16 , 17 ].…”

“…A detailed understanding of these systems is of interest due to their catalytic properties and because they form a model system for other hydrogen-absorbing materials. In our previous study [ 16 ], we showed the basic hydrogen sorption properties of Pd-Ir alloys, such as: the influence of the Pd bulk content on the α → β phase transition potential and the maximum absorption capacity in acidic medium. Moreover, X-ray diffraction studies were performed to confirm the creation of the contracted alloy.…”