Session: Research Posters

Paper Number: 120130

120130 - Self-Promoting Energy Storage in Balsa Wood-Converted Porous Carbon Coupled With Carbon Nanotubes 

Supercapacitors, owing to high power density and fast charging and discharging, are popular electrochemical energy storage devices. Various materials such as carbon, transition metal oxides/hydroxides/sulfides/selenides/phosphates, MXenes conductive polymers have been employed to fabricate supercapacitor electrodes. For most electrodes, the capacitance may deteriorate with cyclic charging and discharging. Thus, an electrochemically stable supercapacitor has long been pursued by researchers.

Herein, we engineered biomass derived carbon electrode with enhanced cyclic stability. Abundant fast-growing balsa wood was preferred as precursor due to their hierarchical structure. Even after carbonization this hierarchical structure was preserved providing an excellent supporting framework to fabricate electrodes for supercapacitors. In a typical process, the balsa wood sheet was carbonized in two steps: first the stabilization takes place at 250 °C for 6 hours followed by carbonization at 1,000 °C for 6 h in inert atmosphere. Carbonized balsa was utilized as framework for in-situ growth of CNTs using xylene as carbon precursor and ferrocene and nickel nitride as Fe and Ni catalyst precursors. Well-grown carbon nanotubes (CNTs) on the interior and exterior surfaces of balsa carbon channels provided two advantages including (1) offering more specific surface area to boost capacitance via electronic double layer capacitance (EDLC) and (2) offering more active Fe and Ni sites to participate in oxidation-reduction reactions to enhance capacitance of the balsa carbon/CNTs electrode.

The balsa carbon/CNTs electrode demonstrated excellent electrochemical performance with specific capacitance reaching 1940 mF cm^-2 at a current density of 1 mA cm^-2. The capacitance retention rate at 20 mA cm^-2 is 66.0% corresponding to the capacitance at 1 mA cm^-2. This performance originates from not only EDLC depending on the surface adsorption of electrolyte ions, but also the pseudo-capacitance from Fe²⁺/Fe³⁺, Ni²⁺/Ni³⁺ redox couples. Although most biomass-enabled carbon electrode capacitances decay with increase in charge/discharge cycles, the capacitance of balsa carbon/CNTs electrodes increases. After 4000 cycles, the capacitance increased 66% compared to the first few cycles. The self-promoting behavior of the balsa carbon/CNTs originates initially from the slow release of active sites of Fe and Ni nanoparticles and later by the penetration of electrolyte into CNTs, resulting in increased active sites from the inner walls of the CNTs. Thus, hierarchical structures inherited from biomass materials coupled with advanced nanostructures (such as CNTs, transition metal compounds, and/or two-dimensional materials) can be explored to design electrodes with high electrochemical performance, excellent cyclic stability, and low cost.

Presenting Author: MANISH NEUPANE The University of Maine

Presenting Author Biography: Manish Neupane is a Ph.D. candidate at The University of Maine conducting research in the field of advanced manufacturing, energy, nanotechnology and nano mechanics in Prof. Yingchao Yang Research Lab. He has completed his MS in Mechanical Engineering from The University of Toledo.

Authors:

MANISH NEUPANE The University of Maine
Yingchao Yang University of Maine