Performance of a conventional alkaline electrolyzer with Ni-Nb2O5 electrodes in alkalinized saline solutions

NADIA B. YSEA; MELISA J. GOMEZ; TERESITA HUMANA; FEDERICO FIORAVANTI; GABRIELA I. LACCONI,; LILIANA A. DÍAZ; ESTEBAN A. FRANCESCHINI

Mar del Plata

Congreso; 34th Topical Meeting of the International Society of Electrochemistry; 2023

International Society of Electrochemistry (ISE)

Currently, the electrolysis of water in alkaline medium represents a way of producing hydrogen on a large scale that is carried out at a high cost. To increase the profitability of electrolytic hydrogen production, it is necessary to decrease the associated costs. Conventional alkaline electrolysis requires the use of highly concentrated KOH solutions, commonly 30% W/V, which are prepared with purified water. The replacement of ultrapure water by other abundant and cheap electrolytes is a factor that directly affects the price of the resulting hydrogen. Seawater is an attractive natural electrolyte for use in electrolyzers. However, it contains chloride ions that are highly corrosive to the metals used in the electrodes, usually nickel. In previous works it was found that the Ni-Nb2O5 composite presents a high activity for the generation of hydrogen and high stability in 3.43% W/V NaCl solutions. Additionally, the alkalinization of seawater could prevent the oxidation of nickel, since the increase in pH brings the system to working conditions where the stable form of the metal is Ni0, instead of Ni2+.In the present work, Ni-Nb2O5 electrodes were synthesized and used as cathodes in a cell for hydrogen production in a conventional electrolyser (HYDROEL-1). The solutions used were: a) 30% W/V KOH, b) 30% W/V KOH with 3.43% W/V NaCl, c) 5.6% W/V KOH with 3.43% W/V NaCl, and d) 3.43% NaCl. W/V. Figure 1 shows the polarization curves, noting that as the KOH concentration increases, the cell potential decreases. This indicates that under normal operating conditions of a commercial electrolyser (0.3 to 0.5 A/cm2) the performance of the equipment with a 30% P/V KOH solution is similar when the solution is prepared with ultrapure water or with the presence of NaCl.