A perspective procedure for an environmentally-clean commercial production of hydrogen by seawater as an „in situ” utilisation of marine wave generated power is the seawater electrolysis. In this paper original studies in seawater, using the methods of steady-state polarisation curves and the impedance spectroscopy were made on Ni

Alina, CARABAN

Gabriela Elena, BADEA

Ion, CORBU

Petru, CRET

Munich RePEc Personal Archive

Munich Personal RePEc ArchiveSeawater electrolysis for hydrogenproductionGabriela Elena, BADEA and Ion, CORBU and Alina,CARABAN and Petru, CRETUniversitatea Oradea, Universitatea Spiru Haret Setko Impex srl2010Online at https://mpra.ub.uni-muenchen.de/117249/MPRA Paper No. 117249, posted 15 May 2023 14:21 UTCSEAWATER ELECTROLYSIS FOR HYDROGEN PRODUCTION   Gabriela Elena BADEA1, Ion CORBU2, Alina CARABAN1, Petru CRET1* 1University of Oradea, Str. Universităţii 1, 410087, Oradea, Roumania, gbadea@uoradea.ro acaraban@uoradea.ro, pcret@uoradea.ro, *Corresponding author 2University Spiru Haret  from Bucharest and Setko srl, Romania, vicobnoru@yahoo.fr   Abstract  A perspective procedure for an environmentally-clean commercial production of hydrogen by seawater as an „in situ” utilisation of marine wave generated power is the seawater electrolysis. In this paper original studies in seawater, using the methods of steady-state polarisation curves and the impedance spectroscopy were made on Ni.     Keywords:, seawater electrolysis, wave energy, hydrogen, electrochemical kinetics   1. Introduction  We can estimate that in 2050 the energy demand of energy could be over twice the demand of year 2010 If the actual developing rate is maintained,  about 3,4%[1,2].It is also estimated that if 0,1%  of the renewable energy stored in the world seas and oceans will be converted in electric power , the world demand of energy will be five times covered by this [3]. In the actual energetic context, the proposed model is based on formulae, considered prioritaire by the European Community, but also at world level-the renewable forms of energy. The proposed model deals with capturing of a larger part from the sea waves chaotic energy, that means 2/3 of the earth surface and its direct conversion in electrical energy, in mechanical and pneumatically energy. A part of this energy could be used directly in the national electric power systems or in a world power system, and another part could be used “in situ” for hydrogen production.  The technology for producing hydrogen is based on the renewable energy obtained by capturing the marine waves energy [4,5], under the form of electric continuous current and using this one for sea water electrolysis, less expensive than elsewhere, because the costs are reduced at the cost of initial investment and maintenance. In recent studies, regarding the necessity of alternative power sources development, researchers are concerned in obtaining electrical energy from marine waves and using it in situ for hydrogen generation by seawater electrolysis. The hydrogen kinetic was also study on stainless steel in artificial seawater [6,7]Nickel is a metal widely applied as the cathodic material in water electrolysis, due to its good catalytic activity and stability in alkaline media1and also in neutral solutions, even in seawater[2]. Recently, many studies were concerned in hydrogen evolution reaction (HER) on nickel, nickel alloys, Ni–P–titanium oxide electrodes in alkaline[8-19] and acid [20] solutions.  About the reaction mechanism, in alkaline solutions, the mainstream opinion is that atomic hydrogen is an intermediate product, the HER following the scheme[8,10,1,15-17]:       In the following is presented the investigation of kinetics of the hydrogen evolution reaction on Ni electrode in artificial seawater[8,16-19,21], using the classical steadystate polarisation curves and electrochemical impedance spectroscopy. The temperature effect on steady-state polarisation curves is also investigated.   2.Experimental  The used electrode was an working electrode, made of a sheet of nickel of 99.9% purity with active area of 2 cm2. Specimens were polished successively with 1000 and 1200-grade emery paper, washed with carbon tetrachloride, followed by pickling for 1 minute in a solution containing 3% HCl and washing with distilled water. A standard activation was adopted for all specimens consisting in a cathodic polarisation at –1.2 V/SCE for 1 minute in the studied solution.  The artificial seawater was prepared using chemically pure reagents and double distilled water.(table 1). A conventional three-compartment glass cell was used. Quasi-stationary potentiostatic curves were recorded with PS 2 potentiostat, by scanning the electrode potential with 30 mV steps after 1 min. As the current reached about 100 mA, the direction of potential was reversed (backward scan).  The effect of the temperature was studied by recording the steady-state polarisation curves of Ni (forward scan) in the Tafel potential range at: 20, 30, 40, 50 and 60oC, respectively.(Table 2). The ac impedance measurements were carried out with Bas-Zahner IM6e potentiostat, controlled by a computer. Bode diagrams were obtained in the frequency range from 30 mHz to 50 kHz, at the following constant potentials: open circuit potential after cathodic activation of Ni, –1.2 and –1.3 V/SCE.  Table 1   Table 2.     3.Results and discusions  The cathodic polarisation curves, obtained on Ni electrode at the temperature of 25oC in artificial     seawater at forward and backward scan of the potential, are shown in Fig. 1. The values of the exchange current density are: i 0,1 = 2.05x10−5 and  i 0,2 = 7.62x10−6 A/cm2 [10, 13-15].      Figure 1. Polarisation curves for HER from artificial seawater on Ni electrode at 25oC: 1-forward scan, 2- backward scan of potential  Figure 3 shows the polarisation curves for the HER within Tafel potential region on Ni in artificial seawater. The Tafel slope values increase with temperature as was expected, whereas the charge transfer coefficient decreases (Figure 3).We have noticed that the exchange current density (i0) of the HER significantly increases with temperature (Tab. 3). Thus, at the temperature of 333 K, i0 value is about 20 times higher than that obtained at 293 K.    Figure 2- Tafel lines for HER on Ni electrode in artificial seawater at 25 oC: 1-forward scan, 2- backward scan of potential  Table 3.   The electrochemical impedance spectra in the complex plane, as Nyquist diagram and Bode plot, recorded at various potentials for Ni electrode, are shown in Fig. 4 and Fig. 5, respectively. At open circuit potential (OCP) of –0.373 V/SCE, the impedance data do not have a shape of a semicircle in the Nyquist plot (Fig. 4), suggesting a high value of corrosion resistance of Ni in artificial seawater, as shown previously.2 The Bode plot (Fig. 5) also suggests a capacitive behaviour of the Ni electrode at OCP. The EIS data suggest that, in this potential region, the Tafel step may be the rate-determining step of the reaction, due to the slow diffusion of Hads atoms to form H2 molecule (reaction 3).    Figure 3. Potentiostatic polarisation curves of the HER on Ni in artificial seawater in the Tafel potential  region at the following temperatures: 1-293; 2-303; 3-313;4-323, 5-333 K.    Figure 4. Nyquist diagrams for the HER on Ni electrode in artificial seawater,recorded at temperature of 25oC and various potentials     Figure 5. Bode diagrams at Ni electrode in artificial seawater at 25oC  4.Conclusions  The nickel is corrosion resistant both in the open circuit and by polarizing in the cathodic potential region. By polarizing at potentials more cathodic than −1.2 V/SCE, the Nyquist and Bode diagrams indicate a process controlled by charge transfer step (Volmer step) and by mass transfer of the intermediate reaction product Hads on electrode surface to combine in H2 molecules (Tafel step). A possible new energetic paradigm is based on the invention “Ecological sea electro power station” which is protected by an international copyright © AMPI 205072 and for which was submitted an invention patent request A/00840/05.10.2004. This invention was presented as a functional model al the Invention Saloon from Geneva 2005, Eureka 2005 and Pittsburgh 2006 and it has received gold medals, cups and diplomas.  In the energetic actual context the proposed model is oriented towards formulae considered prioritary both at EU and world level, respectively of renewable energies[5] The proposed model deals with capturing of a larger part from the sea waves chaotic energy, and its direct conversion in electrical energy, in mechanical and pneumatically energy and later into electrical energy and hydrogen. Such an electro power station may be executed in any ocean or sea, it is able to run continuously and can provide electrical energy and hydrogen with no additional fuel consumption.   References  [1] Nations Unites, Raport, «Situation et perspectives de l’economie mondiale», http://www.un.org/esa/policy/wess/cesp.html [2] I. Corbu,  A possible solution for the achievement of an energetic mondosystem, Setko Impex & University Spiru Haret Bucharest [3] N. Hölzinger,  T. Kampet, A. Jahn, J. Mühling, INCO : International Scientific Cooperation Projects (1998-2002), Contract number : ICA2-CT-2000-10049, Project Acronym: MARINECO,  Development of components for an environmentally compatible system for economic progress in arctic coastal areas based on the use of regional renewable resources, Formation, trends and perspectives of hydrogen power engineering, October 25, 2004 [4].Raport CEEX 103/2005-2008, „Cercetari multidisciplinare privind  modelul teoretic si experimental al unei electrocentrale ecologice bazate pe energia valurilor marine” Acronim, CMTEEEM Contract AMCSIT. [5] I. Corbu, Invenţie « Electrocentrală ecologică marină”, protejată printr-un copyright internaţional  ©AMPI  205072 şi o cerere de brevet de invenţie A/00840/05.10.2004.  [6]G.E.Badea, I.Maior, A.Cojocaru, I.Pantea, T.Badea, Revue Roumaine de Chimie, 2009, 54(1), 55–61,  [7]A.Cojocaru, G.E.Badea, I. Maior, P.Cret, T. Badea, Revue Roumaine de Chimie, 2009, 54(1), 49–54. [8]. N. Krstajić, M. 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Seawater electrolysis for hydrogen production

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Seawater electrolysis for hydrogen production

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