Synthesis, Electrocatalytic and Gas Transport Characteristics of Pentagonally Structured Star-Shaped Nanocrystallites of Pd-Ag

Abstract

The method of synthesis of bimetallic Pd–Ag pentagonally structured catalyst “nanostar” on the surface of Pd-23%Ag alloy films has been developed. The resulting catalyst was studied as a highly active functional layer for methanol oxidation reaction (MOR) in alkaline media and the intensification of hydrogen transport through the Pd-23%Ag membrane in the processes of hydrogen diffusion purification. A modifying layer with a controlled size, composition and excellent electrocatalytic activity was synthesized by electrochemical deposition at a reduced current density compared to classical methods. The low deposition rate affects the formation of pentagonally structured nanocrystallites, allowing Pd and Ag particles to form well-defined structures due to the properties of the surfactant used. Electrochemical studies have demonstrated that the catalyst synthesized by the “nanostar” method shows better electrocatalytic activity in relation to MOR and demonstrates a higher peak current (up to 17.82 µA cm−2) in comparison with one for the catalyst synthesized by the “nanoparticle” method (up to 10.66 µA cm−2) in a cyclic voltammetric study. The nanostar catalyst electrode releases the highest current density (0.25 µA cm−2) for MOR and demonstrates higher catalytic activity for the oxidation of possible intermediates such as sodium formate in MOR. In the processes of diffusion membrane purification of hydrogen, a multiple increase in the density of the penetrating flux of hydrogen through the membranes modified by the “nanostar” catalyst (up to 10.6 mmol s−1 m−2) was demonstrated in comparison with the membranes modified by the “nanoparticles” method (up to 4.49 mmol s−1 m−2). Research data may indicate that the properties of the developed pentagonally structured catalyst “nanostar” and its enhanced activity with respect to reactions involving hydrogen increase the desorption activity of the membrane, which ultimately accelerates the overall stepwise transfer of hydrogen across the membrane.

Reduction of Deuterium Level Supports Resistance of Neurons to Glucose Deprivation and Hypoxia: Study in Cultures of Neurons and on Animals

“…We used DDW containing δ 2 H = −679‰, produced on a set-up developed at Kuban State University [ 19 , 20 ]. Water that was physiologically complete in terms of mineral components and with a deuterium content of −679‰ was obtained by adding mineral salts to it (mineralization 314–382 mg/L: hydrocarbonates—144–180, sulfates <1, chlorides—60–76, calcium—6, magnesium—3, sodium—50–58, potassium—50–58).…”

Gas-Transport Characteristics of PdCu–Nb–PdCu Membranes Modified with Nanostructured Palladium Coating

“…Hence, it can be concluded that the formation of a classical smooth palladium layer on the niobium membranes surface does not provide the maximum possible permeability of niobium under operating conditions, since it does not remove all surface limitations. In this case, one way to increase hydrogen recovery may be to increase the active surface area of the membrane by applying a modifying nanostructured coating [ 22 , 23 , 24 ]. Such solution can play a positive role in the acceleration of dissociative–associative processes on the surface, significantly increasing the hydrogen permeability [ 25 , 26 , 27 ].…”

Promising Isotope Effect in Pd77Ag23 for Hydrogen Separation

“…For example, a different range of pressure of the H 2 -N 2 atmosphere has been considered for their application [27] and low temperature bonding has been proved to give good sealing properties [28]. Moreover, on-site repair was exploited [29], various types of nanostructuring of the surfaces were considered [30,31], and the extraction of H 2 from biomaterials was achieved [32].…”