Splitting steam via eutectic molten hydroxide assisted electrolysis for hydrogen gas production

Al-Shara, Nawar Kader Augla (2018) Splitting steam via eutectic molten hydroxide assisted electrolysis for hydrogen gas production. PhD thesis, University of Nottingham.

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Abstract

In recent years, the development of hydrogen gas production from renewable energy sources has become a major area of focus to cover the shortfalls in demands of global energy. The development of water electrolysis can be considered as a promising technique in this regard for increasing the production of hydrogen fuel to meet energy requirements.

In this research, the splitting steam via eutectic molten hydroxide (NaOH-KOH; 49-51 mol%) electrolysis for hydrogen gas production has been electrochemically investigated. A new reference electrode for eutectic molten hydroxide has been fabricated by covering Ni/Ni(OH)2 with an ionic membrane of alumina or mullite tube. It was found that the Ni/Ni(OH)2 covered with a mullite membrane was stable and reusable over a range of temperatures (225-300oC) without any deterioration. The Ni/Ni(OH)2 covered by a mullite tube reference electrode has been compared with silver and platinum quasi−reference electrodes. The results have shown the designed reference electrode had a more stable and effective performance towards controlling the platinum working electrode as compared to the other quasi-reference electrodes.

In addition, this work carried out a cyclic voltammetry investigation of different working electrodes such as Ni, Pt, Ag, Mo, and stainless steel (SS) using eutectic molten hydroxide at different operating temperatures to examine the occurring reaction on each electrode. The comparison of cyclic voltammetry for examined working electrodes found that the reduction potential for hydrogen evolution was in order of (more positive potential to negative): Ni>Pt>Ag>SS>Ag>Mo. This finding has been additionally confirmed by chronoamperometry.

Finally, the high-temperature eutectic molten hydroxide domain has been electrochemically investigated to split steam into hydrogen fuel. The electrolysis investigations were carried out using nickel, platinum, and stainless steel as the cathode while for the anode, stainless steel and graphite was used. Electrolysis was explored at a temperature range between 225 to 300oC and at different applied voltages of 1.5 to 2.5 V. The current efficiency achieved using stainless steel as an anode and using nickel, stainless steel and platinum as a cathode at 300oC were 90.5%, 80.0% and 68.6% respectively. The current efficiency using graphite anode for an individual cathode material was lower than that for stainless steel anode. Consequently, splitting steam via molten hydroxides for hydrogen was shown a promising alternative to current technology for hydrogen production, with beneficial implications to integrate with renewable energy sources to generate the process.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Chen, George Z.
Sun, Cheng-Gong
Keywords: Hydrogen gas; Electrolysis; Electrochemistry; Cyclic voltammetry; Electrodes; Molten salt reactors
Subjects: T Technology > TP Chemical technology
Faculties/Schools: UK Campuses > Faculty of Engineering
Item ID: 52109
Depositing User: Al-Shara, Nawar
Date Deposited: 13 Jul 2018 04:41
Last Modified: 13 Jul 2018 10:00
URI: http://eprints.nottingham.ac.uk/id/eprint/52109

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