Electrochemical behaviour of water in molten LiNO₃–KNO₃eutectic

Abstract

Contrary to previous reports, the electroreduction of water in nitrate melts appears to be coupled with nitrite reduction, probably involving an autocatalytic mechanism and an adsorbed intermediate.

Problems Associated with the Electrochemical Reduction of Metal Ions in LiNO3 ‐ KNO 3 and LiClO4 ‐ KClO4 Melts: The Reduction of Nitrato and Perchlorato Complexes

“…Instead, this reaction involves the reduction of the nitrate ion to form nitrite and hydroxide ions (39,40), i.e. The water wave in molten nitrates is unusual since water is not reduced to hydrogen gas.…”

Electrochemical Behavior of Nitrate and Nitrite Ions in the Molten NaOH ‐ KOH (49 m/o) Eutectic Mixture at 250°C

“…Our experimental results do not give any information on the nature of this new mechanism. The chemical reduction of nitrate ions by electrochemically generated hydrated electrons according to Espinola and Jordan (17) or the catalytic process proposed by Levering and co-workers (19) (Eq. [3] and [4]) could be suitable mechanisms.…”

“…In the latter media, water yields a reduction wave at a potential 0.4V less cathodic than the nitrate reduction peak (18). Jordan (16,17) attributed the so-called "water wave" to the diffusion controlled reaction NO~-+ H20 + 2e-~ NO2--I-2 OH- [1] Zambonin and co-workers (12) describe the reaction as H20 + e-~=~ 89 Hs + OH- [2] Lovering and co-workers (19) investigated a "nitrite free" nitrate melt and concluded that the presence of some nitrite ions in the melt (generated, for instance, by an initial cathodic scan) is necessary to observe the water reduction wave. They suggest the following mechanism H~O + NOs-+ 2e-:~-2 OH-+ NO- [3] NO-+ NOs-~=~ 2NOs- [4] Considering these reactions, it seemed interesting to investigate the electrochemical behavior of nitrate ions in dry and acidic hydroxide melts.…”

Electroactivity of hydrogen–nitrogen compounds in ionic liquids. Platinum rotating-disc electrode voltammetric behaviour of ammonia in the (Na, K)NO3 equimolar melt

“…2 5 9 26 or ammonia [see reactions (2) and (19), respectively]. The fact that the post-peak current contributions from water and ammonia are still controlled (almost to a first approximation) by the diffusion of the two species, seems to indicate that reactions (25) and ( 26) are fast and shifted to the right.…”

“…In dry melts only reactions (23) and (24) (prevalent) are r e ~p o n s i b l e ~~for the redissolving of the oxide layer and their rates determine the value of current h, in fig.1. In wet melts an additional important chemical contribution to the total dissolution rate from reaction(25). Similarly, reactions(26) or(25) and(26) increase the Na,O dissolution rate when anhydrous or wet ammonia is present in solution.From fig.1and 3 it can be inferred that the post-peak contributions from NH, and H,O are very close to the pre-peak diffusion currents of the two species.…”