β‐Ni(OH)₂Nanosheet Arrays Grown on Biomass‐Derived Hollow Carbon Microtubes for High‐Performance Asymmetric Supercapacitors

Abstract

The design and fabrication of biomass-based energy storage devices is becoming a new trend to reduce the depletion of non-renewable resources. Herein, b-Ni(OH) 2 nanosheet arrays grown on willow catkins-derived hollow carbon microtubes is prepared for the first time through a facile acid treatment and subsequent hydrothermal process. In the b-Ni(OH) 2 @acidtreated carbon microtube [b-Ni(OH) 2 @ACMT] composite, b-Ni(OH) 2 nanosheet arrays can be controllably grown on both internal and external surfaces of carbon microtubes, realizing effective utilization of the hollow tubular structure. In addition, carbon microtubes are not only employed as an effective support for the dispersion of b-Ni(OH) 2 nanosheets, but also served as a long-range conductive micro-current collector for electron transfer. Furthermore, the hollow tubular structure accompanied by the capillary effect provides fast channels for ion diffusion. As a consequence of this unique hierarchical structure, the electrode based on the b-Ni(OH) 2 @ACMT composite exhibits a high specific capacitance of 1568 F g À1 at 1 A g À1 , remarkable capacitance retention of 51.0 % even at 20 A g À1 , and excellent cycling stability of 84.3 % retention after 3000 cycles. An asymmetric supercapacitor, with b-Ni(O-H) 2 @ACMT composites as the positive electrode and porous carbon microtubes as the negative electrode, achieves a high energy density of 37.8 W h kg À1 at 750 W kg À1 , indicating its potential application in energy storage devices.

Biomass‐Derived Carbon: A Value‐Added Journey Towards Constructing High‐Energy Supercapacitors in an Asymmetric Fashion

“…This may be attributed to the larges ize of the CO 2 molecules, which prevents their accessibility into the micropores present in carbon materials. [52,89] Another commonly used chemical activating agent for BDC is ZnCl 2 ,w hich has deoxygenation properties at high temperature and can remove oxygen in the form of water or through carbothermal reduction. [52,86] Steam is al ow-cost,r eadily availablea ctivating agent that does not require ap ostactivation process for byproduct removal.…”

“…[89] Furthermore, the authors fabricated an ASC by using porous carbon microtubes (PCMTs) derived from willow catkin biomass as the negative electrode. [89] Furthermore, the authors fabricated an ASC by using porous carbon microtubes (PCMTs) derived from willow catkin biomass as the negative electrode.…”

“…Based on the value of these parameters and type of carbon source, KOH activation can result in AC with in-creasedS SA, uniform PSD, and controllable surface functional groups.Incomparison with asingle step, the two-stepK OH activation methodi so ften used to prepare BDC for SCs. [52,89] Another commonly used chemical activating agent for BDC is ZnCl 2 ,w hich has deoxygenation properties at high temperature and can remove oxygen in the form of water or through carbothermal reduction. Therefore, it can act as ad ehydrating agent during the activation process.…”

“…BDC materials with hierarchical porous structures, periodic patterns, specific nanoarchitectures, controlledm orphologies, and modified surfacec hemistry can be derived from naturally abundant biomass materials.A monga ll electrode materials available, BDC materials are preferred due to their low ash content, low cost, facile processing techniques, stability, versatile morphology,a nd mechanical properties. [16,52,54,71,88,89,99,[107][108][109][110][111][112] Similar to other carbon materials, BDC stores chargethrough an electrical double-layerm echanism and generally forms EDLC-type SCs.T omake ap erfect EDLC electrode, the BDC material should have the following properties:1 )large surface area ands uitable PSD that correspondst oal arge specific capacitance, whiche nsures high energya nd power density of the device;2 )low ESR to ensure am inimal voltage drop in the device;a nd 3) high stabilityt oe nsure good cyclability and long working life. [78] BDC materials have aw ide range of appli-ChemSusChem 2019, 12,4353 -4382 www.chemsuschem.org cations,i ncluding in energy-storage devices,b ut the challenge of optimizing their structure or surface properties still needs furtherr esearch.…”

“…Li et al established the idea for the development of a BDC/metal hydroxide hybrid composite. [89] Furthermore, the authors fabricated an ASC by using porous carbon microtubes (PCMTs) derived from willow catkin biomass as the negative electrode. Willow catkin is a good biomassp recursor with ah ollow tubular microstructure, which can serve as ab iotemplate to prepare ac arbon matrix used to support active nanomaterials.…”