Effects of heat treatment on the structure, morphology and electrocatalytic activity of cobalt hydroxide electrocatalyst

In this study, effects of heat treatment on structure, morphology and electrocatalytic activity of polypyrrole-modified carbon-supported Co(OH)2 (Co(OH)2-PPY-C) are investigated. The Co(OH)2-PPY-C is heated under N2 atmosphere at temperature ranging from 400 to 800 °C. CoO will be formed when heating the precursor to 400 °C. With elevating heat treatment temperature to 600 °C, metallic Co and Co3O4 are formed. Spheroidal particles composed of CoO, Co3O4 and metallic Co will be formed when heating the Co(OH)2-PPY-C to 800 °C. It is found that the composite of CoO, Co3O4 and metallic Co with platelet shape is beneficial to oxygen reduction reaction (ORR). The electron transfer number of this catalyst towards ORR in alkaline medium is determined to be 4.