Electrochemical reduction and hydrogenation of co oxides

The electrochemical hydrogenation properties of CoO and Co3O4 powders were investigated and compared to those of hexagonal close-packed Co. The discharge capacity was measured in KOH aqueous solution under a controlled current density 500 mA/g. The maximum reversible discharge capacities of Co, CoO, and Co3O4 were 415 mAh/g (2 h charging), 389 mAh/g (2 h charging), and 426 mAh/g (5 h charging), equivalent to CoH0.91, CoH0.85, and CoH0.93, respectively. Because CoO and Co3O4 are mostly reduced to Co in the initial charge stage, the discharge capacities of both oxides are mainly from dehydrogenation of CoHx. (c) 2007 The Electrochemical Society.