Abstract
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.
Highlights
The current need for economic and scientific progress in the field of hydrogen technologies is enormous
In our previous study of the Pd80 Rh20 alloy, we revealed that hydrogen adsorption inhibited the kinetics of hydrogen absorption and proceeded much faster in the presence of crystal violet added into 0.1 M H2 SO4 [29]
It is known a decisive influence and on the course of the absorption of of hydrogen metals their alloys has thethat purity of both hydrogen metal, and especially the purity the metalby surface, and their alloys has the purity of both hydrogen and metal, and especially the purity of the metal which can be provided by preliminary mechanical or thermal treatment, etc
Summary
The current need for economic and scientific progress in the field of hydrogen technologies is enormous. Reversible hydrogen storage for stationary applications based on established technologies of compressed, liquid or slush hydrogen is no longer a special problem, but the satisfactory results for hydrogen storage in containers intended for vehicles using hydrogen as fuel have still not been achieved [1,2]. Hydrogen is very reactive and forms a hydride phase or can be dissolved in a solid solution with many metals and alloys. Intensive research has been carried out on the safe storage of hydrogen in the crystal structures of metals and their alloys [1,3]. Conventional metallic hydrides (MHs) have been well characterized and there is reliable information about interstitial hydrogen storage
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