Discharge mechanism of the manganese dioxide electrode

✍ Scribed by A. Era; Z. Takehara; S. Yoshizawa

• Publisher: Elsevier Science
• Year: 1967
• Tongue: English
• Weight: 918 KB
• Volume: 12
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(67)80035-5

✦ Synopsis

Ah&act-The discharge ove tential of manganese dioxide electrode was measured in various electrolyte solutions, wtth the

(1) The overpotential in much higher than in acidic or alkaline solution.

(2) In alkaline or neutral solution, the overpotential of a heat-treated manganese dioxide electrode was higher than that of an unheated one. In acidic solution, however, both electrodes showed the same nolarization behaviour.

The following explanation is proposed :

The primary product of the discharge reaction is M&OH, which is removed from the surface of electrode. The overpotential of manganese dioxide electrode is caused by the slowness of the removal procmses of MnOOH Such processes are:

(i) in acidic solution, MnOOH reaction with the solution, which produces Mn*+ and MnO,;

(ii) in alkaline solution, diffusion of H+ into MnO,; and (iii) in neutral solution; simultaneous occmrence of(i) and (ii). In the case of diffusion, the ditfusion resistance is closely related to the concentration of OH-ion in the solution and also dependent upon the amount of combined water in the manganese dioxide crystal lattice.