Effect of Bi Addition on the Electrochemical Behavior of Zinc Electrodes in Concentrated Alkaline Solutions

Abstract

The electrochemical behavior of zinc electrode with bismuth addition in 35%KOH solutions has been investigated systematically by electrochemical methods including linear polarization, potentiostatic polarization, potential-time measurements at a constant current density, combining the observations of scanning electron microscopy (SEM). Linear polarization results showed that the open circuit potential shifted positively with increasing bismuth content, which is explained based on the gassing data and change in the exchange current of the zinc electrode. Addition of bismuth increased the exchange current of zinc reaction and caused an increase in the measured open circuit potential. Galvanostatic results showed that the addition of bismuth shortened the passivation time. Scanning electron microscopy images showed that the addition of bismuth aggravated the corrosion of zinc electrode which may be responsible for the increased tendency to passivation at high current densities. It has been found that at low current densities the reaction kinetics may be increased by addition of Bi, which is general agreement with the discharging test of actual alkaline batteries.