Charge/discharge characteristics of electroless CoB films

CoB thin films were obtained by the electroless coating technique and their charge/discharge cyclic characteristics were investigated. The effect of heat-treatment on the structure and the discharging behavior of CoB films was also investigated. It was observed that both the amorphous/nano-crystalline and crystallized CoB films had very limited hydrogen storage capacity. Upon heat treatment at 550 degrees C the electrode performance of the CoB film deteriorated significantly due to Co3B phase formation in the film structure. The discharging process yielded Co(OH)(2) and CoOOH formations on the electrode surface. After activation, the charge/discharge process was mainly controlled by the reversible oxidation/reduction reactions of Co. The surface of the crystallized CoB films was observed to be more catalytic than that of the as-deposited amorphous/nano-crystalline CoB films. (C) 2012 Elsevier B. V. All rights reserved.