Zur sauerstoffreduktionsgeschwindigkeit an teflon-gebundenen Cd-elektroden gasdichter NiCd-akkumulatoren

Abstract

Oxygen reduction at the Cd electrode is investigated on smooth Cd model electrodes and on porous teflon-bounded Cd electrodes in sealed 2 Ah NiCd cells. The diffusion coefficient of oxygen in 30% KOH has been determined to be 4.1 × 10 −5 cm 2/s. The use of metal nets and active carbon pressed to the Cd electrode and the modification of the active Cd mass by Ni(II) activation led to a considerable acceleration of the oxygen reduction rate. Oxygen reduction is diffusion-determined and obeys Fick's law. This law includes one effective reaction area, which is characterized by the fact that the oxygen reduction rate becomes maximum. This is dependent on the metal-net area and mesh width, on the hydrophobicity of the active carbon mixture and the active mass structure. The effective area is also influenced by the gas pressure.