The influence of dissolved O2 on the electrochemical behaviors of Co-B alloy electrode

The influence of dissolved oxygen on the electrochemical behaviors of the CoB alloy electrode has been investigated by open circuit potential (OCP) measurement and galvanostatic charge-discharge method. It was found that the alloy electrode in oxygen-containing electrolyte has more positive OCP due to the existence of the redox couple O2/OH−. Dissolved oxygen can greatly enhance the high-rate dischargeability of the alloy electrode. Specifically, in oxygen-containing electrolyte, the electrode delivers a reversible discharge capacity of 530 mAh/g at 300 mA/g and its discharge capacity is still up to 480 mAh/g even at a high current density of 1200 mA/g. However, in the case of the electrode in oxygen-free electrolyte, its discharge capacity is 438 mAh/g at 300 mA/g and is reduced to only 234 mAh/g at 1200 mA/g. Exchange current densities (i0) of the alloy electrode in oxygen-containing and oxygen-free electrolyte are 78 mA/g and 54 mA/g, respectively. The significant improvement in the high-rate dischargeability of the alloy electrode should be attributed to that oxygen reduction accelerates the kinetics of Co oxidation reaction.