Hydrogen electrosorption properties of electrodeposited Pd-Ir alloys

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

Tuning hydrogen sorption properties of Pd by its alloying with Ru, Rh, and Pt: the study of binary alloys in concentrated alkaline media

The hydrogen electrosorption process was examined in 6 M KOH on Pd binary alloys, containing Rh, Ru, and Pt. Pd-alloys were electrochemically deposited on Au substrate. The electrodes were subjected to activation procedure—hydrogen pretreatment procedure (HPP) at first in 0.5 M H2SO4 and then in 6 M KOH. It was noticed that it was possible to achieve comparable reversibility of hydrogen electrosorption process in acid and in concentrated base. The obtained values of the α→β phase transition potential, hysteresis extent, and maximum hydrogen absorption capacity show good agreement with the data from acidic medium. The observed kinetics of hydrogen electrosorption were strongly hindered in concentrated alkaline media, whereas the influence of the electrolyte on the thermodynamic functions of hydrogen absorption is less pronounced.

Effect of Hydrogen Electrosorption on Mechanical and Electronic Properties of Pd80Rh20 Alloy

The interaction of hydrogen with Pt-group metals and alloys is at the center of research in the fields of electrochemistry, electrocatalysis, hydrogen technologies and fuel cells developed under the Hydrogen Economy. In this work, the material under study was Pd80Rh20 alloy (50 μm foil) subjected to hydrogen electrosorption at potentials corresponding to formation of α, α-β and β phase in 0.1 M H2SO4 at 25 °C. The total amount of hydrogen adsorbed at the surface and absorbed in octahedral interstitial positions of fcc Pd80Rh20 alloy, was determined from the oxidation charges. The H/(Pd+Rh) was 0.002, 0.4 and 0.8 for α, α-β, and β Pd80Rh20H, respectively. Microindentation hardness testing and nanoindentation showed weakening of mechanical properties of the Pd80Rh20 alloy after hydrogen electrosorption due to internal stresses. Decrease of work function with increasing amount of hydrogen absorbed occurred due to the surface roughness changes and the presence of electropositive hydrogen atoms absorbed in the crystal lattice responsible for the dipole interaction. The detailed mechanism of hydrogen absorption/diffusion in the Pd80Rh20 alloy structure is discussed. The obtained results give a new insight into the relationship between the amount of absorbed hydrogen and mechanical and electronic properties of the Pd80Rh20 alloy at the micro- and nanoscale.