Tuning hydrogen sorption properties of Pd by its alloying with Ru, Rh, and Pt: the study of binary alloys in concentrate
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ORIGINAL PAPER
Tuning hydrogen sorption properties of Pd by its alloying with Ru, Rh, and Pt: the study of binary alloys in concentrated alkaline media K. Hubkowska 1
&
A. Czerwiński 1,2
Received: 19 May 2020 / Revised: 19 July 2020 / Accepted: 19 July 2020 # The Author(s) 2020
Abstract 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. Keywords Hydrogen sorption . Palladium-rhodium alloys . Palladium-ruthenium alloys . Palladium-platinum alloys . 6 M KOH
Introduction In spite of the fact that hydrogen sorption properties of Pd and its alloys are examined for many years, still many aspects of this process are not explained or confusing. Researchers are mostly focused on the synthesis of new electrode material and hydrogen sorption from gas phase [1–4], wherein the impact of the electrolyte is often overlooked. Therefore, in the literature, there are many publications dedicated to hydrogen electrosorption in Pd-based electrodes from acidic water solutions [5–21]. Unfortunately, not many researchers address the problem of hydrogen sorption in alkaline media [22–35] being confined predominantly to Pd examination in diluted solutions. Moreover, there are limited works concerning the hydrogen sorption in Pd from non-aqueous media [36–39]. The The authors dedicate this article to Professor Fritz Scholz on the occasion of his 65th birthday in recognition of his achievements and wishing him further scientific and publishing success. * K. Hubkowska [email protected] 1
University of Warsaw, Faculty of Chemistry, Pasteura 1, 02-093 Warsaw, Poland
2
University of Warsaw, Biological and Chemical Research Centre, Żwirki i Wigury 101, 02-089 Warsaw, Poland
behavior of Pd-based materials in concentrated alkaline media seems to be very important having regard for the fact that Pd and its alloys are considered as efficient modifiers of hydrogen sorption properties of AB-type alloys [40–42]. It was recently found that hydrogen sorption kinetics are strongly enhanced when the surface of an AB5 alloy is modified with Pd nanoparticles [43]. Since hydride batteries still work in concentrated alkaline media, it is crucial to use these electrolytes to examine the process of hydrogen sorption in Pd alloys. Pd-Rh and Pd-Ru alloys belong to the class
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