Hierarchical Cobalt Hydroxide and B/N Co-Doped Graphene Nanohybrids Derived from Metal-Organic Frameworks for High Energy Density Asymmetric Supercapacitors

Abstract

To cater for the demands of electrochemical energy storage system, the development of cost effective, durable and highly efficient electrode materials is desired. Here, a novel electrode material based on redox active β-Co(OH)2 and B, N co-doped graphene nanohybrid is presented for electrochemical supercapacitor by employing a facile metal-organic frameworks (MOFs) route through pyrolysis and hydrothermal treatment. The Co(OH)2 could be firmly stabilized by dual protection of N-doped carbon polyhedron (CP) and B/N co-doped graphene (BCN) nanosheets. Interestingly, the porous carbon and BCN nanosheets greatly improve the charge storage, wettability, and redox activity of electrodes. Thus the hybrid delivers specific capacitance of 1263 F g−1 at a current density of 1A g−1 with 90% capacitance retention over 5000 cycles. Furthermore, the new aqueous asymmetric supercapacitor (ASC) was also designed by using Co(OH)2@CP@BCN nanohybrid and BCN nanosheets as positive and negative electrodes respectively, which leads to high energy density of 20.25 Whkg−1. This device also exhibits excellent rate capability with energy density of 15.55 Whkg−1 at power density of 9331 Wkg−1 coupled long termed stability up to 6000 cycles.

Electrocatalytic oxygen reduction by a Co/Co3O4@N-doped carbon composite material derived from the pyrolysis of ZIF-67/poplar flowers

“…N, as a heteroatom, is able to produce good synergistic effects by coordinating itself with free metal and functional elements. 23,24 In this work, we developed a simple route to synthesize Co/ Co 3 O 4 @N-doped active carbon nanostructures (denoted as Co/ Co 3 O 4 @NC) derived from the pyrolysis of a zeolite imidazolate framework (ZIF-67) and the economical, abundant and renewable biomass of poplar owers. The resulting Co/Co 3 O 4 @NC catalyst, containing active sites from Co/Co 3 O 4 and N-doped carbon, displays excellent ORR activity in 0.1 M KOH (E onset ¼ 0.94 V, E 1/2 ¼ 0.85 V, as well as a small Tafel slope of 90 mV dec À1 ), which, via a 4-electron pathway, has long-term durability and resistance to methanol poisoning.…”

Laser-Assisted Fabrication of Nanostructured Substrate Supported Electrodes for Highly Active Supercapacitors

“…This peak is reflection from (100) planes which is associated with the in-plane structure of LIG. The phenomenon of laser induced graphitization is attributed to the presence of repetitive aromatic and amide units in PI (Fagihi and Ashouri, 2013;Lin et al, 2014;Tabassum et al, 2017).…”

Zeolitic imidazolate framework (ZIF)-derived porous carbon materials for supercapacitors: an overview

“…The MOF-derived Co(OH) 2 maintains its unique porous structure, which is valuable for rapid ion transportation, rich redox reactions and robust structure stability of supercapacitor electrodes. 124 Nanoporous MOF-derived Co 3 O 4 electrodes have been developed for application in asymmetric supercapacitors. 83 Of signicance, the polyhedral shape of the MOF precursor (e.g., ZIF-67) could be well preserved by Co 3 O 4 by ne-tuning the synthesis procedures.…”