The discharge of nitrite ions in the electrolysis of molten nitrites on graphite electrodes of known porosity has been studied in the temperature range 245–340° C. Conventional current/voltage curves, and build-up and decay of the working electrode potential, were determined. In the whole range of current density and temperature investigated the anodic process is characterized by a Tafel slope of 2RT/3F. Decay and Tafel slopes tend to coincide at the highest current densities. Electrode capacitance measurements at the initial potential suggest a roughness factor of about 50 for graphite electrodes. The results are interpreted in terms of the following reaction schemes:
(Ia) NO2− + C ⇌ (NO2)C + e,
(IIa) (NO2)C + NO2− → (N2O4) + C + e,
(IIIa) (N2O4) ⇌ 2NO2,
and
(Ia) NO2− + C ⇌ (NO2)C + e,
(IIb) (NO2)C → NO2+ + C + e,
(IIIb) NO2+ + NO2− ⇌ (N2O2) ⇌ 2NO2,
where either reaction (IIa) or (IIb) is the rate-determining step, assuming a low electrode surface coverage by reaction intermediates. Data from non-steady measurements are rather scattered and this is ascribed to probable diffusion of nitrogen dioxide through the porous electrode material.