Modified 3D-electrodes for the efficient hydrogen production
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COVALIOV, Victor, COVALIOVA, Olga, DROVOSEKOV, Andrei, DUKA, Gh., ROMANCIUC, Lidia. Modified 3D-electrodes for the efficient hydrogen production. In: Ecological and environmental chemistry : - 2022, Ed. 7, 3-4 martie 2022, Chișinău. Chisinau: Centrul Editorial-Poligrafic al USM, 2022, Ediția 7, Vol.1, p. 33. ISBN 978-9975-159-07-4.. 10.19261/eec.2022.v1
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Ecological and environmental chemistry
Ediția 7, Vol.1, 2022
Conferința "Ecological and environmental chemistry 2022"
7, Chișinău, Moldova, 3-4 martie 2022

Modified 3D-electrodes for the efficient hydrogen production

CZU: 544+621.357.6+66.011

Pag. 33-33

Covaliov Victor1, Covaliova Olga2, Drovosekov Andrei3, Duka Gh.2, Romanciuc Lidia2
 
1 Moldova State University,
2 Institute of Chemistry,
3 A.N.Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Science
 
Proiecte:
 
Disponibil în IBN: 2 martie 2022


Rezumat

Although hydrogen is considered to be a secondary energy carrier, i.e. it‘s cost is generally higher than that of the natural fuels, its application is expedient in many cases, being economically feasable and environmentally friendly. Electrochemical technology is one of the most important among hydrogen production technologies, as it allows to obtain 99-99.5% gaseous H2. Advantages of this method involve process simplicity, continuity, possibility of automation, absence of moving components in elecrolytic cell, obtaing of precious by-products, such as heavy water and oxygen. However, conventional hydrogen electrolysis is connected with the high overvoltage of hydrogen evolving from water solutions, provoking the elevated energy consumption. In terms of electrochemical hydrogen production costs, according to various sources, they make in average $4-5/kg H2. Therefore, the main task of this research was to elaborate the type new electrode materials to be used as cathodes for the essential reducing of hydrogen evolving overvoltage on their surface, and thus, to make the hydrogen electrolysis more efficient and cheap. To obtain the type new electrode material with the developed surface, making it possible to apply the lower current intensity during the electrolysis and at the same time to reach the optimal current density for hydrogen evolution, the coatings were deposited on the new 3D materials – metal foams (Cu and Ni). Chemical-catalytical deposition process was performed without the application of external current and had the autocatalytic nature. The advantage of this plating process is a possibility to metalize the dielectrics, to obtain the uniform layers on details with complex configuration. NaBH4 and DMAB – dimethylamine borane – (CH3)2 HN.BH3 were used as reducing agents. To ensure the comparability of results while studying the effect of doping Ni-B alloys with Mo, W or Re, pyrophosphate solutions with rather similar compositions have been selected. The studies of structural-phase transformations of Ni-B coatings were performed using the electronographic, X-ray and thermoderivatographic methods. The effect of potassium molybdate, sodium tungstate and potassium perrhenate concentration on main parameters of metal ion chemical-catalytic reduction and hydrogen emission was studied. The mechanisms of coating processes were considered, including the possibility of auto-catalytic electrochemical reactions. Chemical state of elements and coatings‘ composition was studied using the X-ray photoelectron spectroscopy. Amount of molecular hydrogen evolved was determined volumetrically and that of hydrogen adsorbed by the deposit was measured using the vacuum extraction method at 4000 C. Catalytic activity, chemical composition and structure of Ni-Mo-B, Ni-W-B and Ni-Re-B coatings were studied. The aim of this study was to elucidate the causes for nonlinear, volcano-like dependence of partial rates of DMAB hydrolysis and hydrogen evolution on the doping element concentration in the alloy. It was found that the doping element (Mo, W and Re) introduction into the Ni-B alloy has substantially modified the catalytic activity of the alloy‘s surface with regard to the concurrent partial reaction, including heterogeneous hydrolysis of DMAB, reduction of Ni ions, and evolving of the molecular H2. With the increase in the alloying element amount, B contents in coatings was sharply decreased. Effect of alloys composition on H2 evolving overvoltage was studied in acidic and alkaline mediums by the potentiodynamic polarization curves. It was shown that alloying of Ni-B with Re (11 wt.%) reduces the overvoltage of hydrogen evolution by 200 mV. Due to the low overvoltage of H2 emission on the alloy Ni-Re-B surface, it was used as a cathode for H2 from water in the electrolytic cell with novel design and improved technical-economic indicators. Based on these studies, the new 3D electrode materials, with high active specific surface, were proposed ensuring the low hydrogen evolving overvoltage, for using in the reactors for hydrogen electrochemical generation with the improved power efficiency.