ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Electrochemical investigation of NaOH–Na2O–Na2O2–H2O–NaH melt by EMF measurements and cyclic voltammetry

Antonín Klečka, Šárka Langová, Pavel Raška, Juraj Leško, and Roman Pěnčík

Bochemie a.s. Lidická 326, Bohumín 735 95, Czech Republic

E-mail: Sarka.Langova@vsb.cz

Abstract: Thermodynamic activity of sodium oxide and oxidation potential in NaOH-Na₂O-Na₂O₂-H₂O- NaH melt at the temperature of 400°C was investigated. Galvanic cell for the potentiometric measurements consisted either of a sodium electrode formed by β and βʺ-alumina semi-closed tube filled with liquid sodium or a platinum wire and of an oxygen electrode made from ZrO₂ (Y₂O₃) solid electrolyte with the Bi-Bi₂O₃ reference mixture. The number of exchanged electrons determined from the electromotive force measurements was in good agreement with the assumed reactions. The activity coefficient of sodium oxide was lower than one. Voltammetric measurements were carried out with a sodium reference electrode and a nickel auxiliary electrode. Behaviour of platinum, gold, silver and nickel as working electrodes was studied. The experiments were carried out in nitrogen atmosphere. Several types of zirconia semi-closed tubes were tested for long-term measurements under the process conditions.

Keywords: sodium oxide activity – molten sodium hydroxide – sodium hydride – basicity – solid electrolyte – platinum – cyclic voltammetry

Full paper is available at www.springerlink.com.

DOI: 10.1515/chempap-2015-0136

Chemical Papers 69 (10) 1312–1318 (2015)