Pulse‐Assisted Transformation of Electrodeposited ZIF‐67 Into Co(OH) 2 /CoOOH via Off‐Time Control for Supercapacitor Applications

ZIF‐67 has been widely studied for supercapacitor applications due to its structural stability. However, one way to enhance its electrochemical performance is to convert it into the redox‐active Co(OH) 2 /CoOOH phase. In this work, we achieved that by using anodic pulsed‐current electrodeposition in an alkaline medium. Introducing a rest period in the electrodeposition sequence enables a deeper transformation of the MOF phase, as ions have sufficient time to penetrate the pores, whereas constant current/voltage conditions confine transformation to the surface. Pulse‐5s, the electrode synthesized by introducing a 5s rest time, showed a morphology transformation from the rhombic dodecahedral of ZIF‐67 to a nanosheet structure of the Co(OH) 2 /CoOOH phase. The electrode also exhibited improved electrochemical performance, delivering a specific capacity of 124.7 mAh g −1 at 1 A g −1 in 2 M KOH. The cycling stability was high, with a coulombic efficiency and capacity retention of 99.8% and 81.2%, respectively, after 5000 GCD cycles.