Solvent‐free synthesis of ZIF‐67 thin films as the catalyst for the direct growth of carbon nanotubes for the fabrication of electrical double‐layer capacitors

Abstract

AbstractObjectiveThis work is focused on the direct growth of vertically aligned carbon nanotubes (CNTs) onto the flexible stainless‐steel mesh (SM) substrate using ZIF‐67 as the catalytic layer.Materials & MethodsThe CNTs/SM electrode is prepared by two‐step chemical vapor deposition (CVD) method using ZIF‐67 thin films as the catalytic layers. The time duration for the deposition of ZIF‐67 thin films by an atmospheric CVD process is controlled for direct, vertically aligned, dense and uniform growth of CNTs by a low‐pressure CVD process at a low temperature of 450 °C.Results & DiscussionThe electrochemical performance of CNTs/SM electrode is studied by cyclic voltammetry and galvanostatic charge/discharge measurements using KOH aqueous electrolyte which showed their better EDLC features and outstanding rate capability. The binder‐free directly grown CNTs/SM electrode displayed a low interfacial resistance between CNTs and SM substrate which comes from their synergistic effect of lower charge loss and better charge collection. Moreover, vertically aligned one‐dimensional CNTs could be rendered as the charge highway in the axial direction, which can promote the rapid charge transportation.ConclusionsThe directly grown CNTs on the commercial SM substrate using the ZIF‐67 catalytic layer fabricated via the solvent free technology can be regarded as a promising EDLC electrode for flexible super capacitors.