Hexamethylenetetramine-assisted morphological evolution of nanowire-net and nanosheet-structured cobalt hydroxide

Nanowire-net and nanosheet-structured cobalt hydroxide (Co(OH)(2)) was prepared directly on a fluorinedoped tin oxide (FTO)-coated glass substrate using aqueous solutions of cobalt nitrate hexahydrate (10 mM) and hexamethylenetetramine (HMT, 2-30 mM), synthesized at 60 degrees C. With increasing HMT amount, the morphology changed from nanowire-net to nanosheet, resulting from the promotion of growth under sufficient OH- ions provided by the HMT. The binder-free Co(OH)(2) sample prepared with 30 mM HMT showed a good areal specific capacitance of similar to 60 mF/cm(2) at a scan rate of 2 mV/s, as well as excellent capacity retention (similar to 84% over 5000 cycles). The proposed facile method allows the morphological engineering of Co(OH)(2) nanostructures with superior electrochemical performance. (C) 2019 Elsevier B.V. All rights reserved.