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Institute of Physics

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08/02/2017

Nanoporous Activated Carbon Cloth: a versatile material for energy storage

Scientists from 6 different countries (including scientists form the Chair of Functional Materials and Materials Systems and the Institute of Physics; MU Leoben) investigated the use of nanoporous activated carbon cloth as a material for hydrogen adsorption, selective gas separation and electrochemical energy storage was investigated.

This research was published in Nano Energy under the title “Nanoporous activated carbon cloth as a versatile material for hydrogen adsorption, selective gas separation and electrochemical energy storage”.

 

Link to publication: http://www.sciencedirect.com/science/article/pii/S221128551730469X

 

Abstract:

The efficient storage of energy combined with a minimum carbon footprint is still considered one of the major challenges towards the transition to a progressive, sustainable and environmental friendly society on a global scale. The energy storage in pure chemical form using gas carriers with high heating values, including H 2 and CH 4, as well as via electrochemical means using state-of-the-art devices, such as batteries or supercapacitors, are two of the most attractive alternatives for the combustion of finite, carbon-rich and environmentally harmful fossil fuels, such as diesel and gasoline. A few-step, reproducible and scalable method is presented in this study for the preparation of an ultra-microporous (average pore size around 0.6 nm) activated carbon cloth (ACC) with large specific area (> 1200 m 2/g) and pore volume (~ 0.5 cm 3/g) upon combining chemical impregnation, carbonization and CO 2 activation of a low-cost cellulose-based polymeric fabric. The ACC material shows a versatile character towards three different applications, including H 2 storage via cryo-adsorption, separation of energy-dense CO 2/CH 4 mixtures via selective adsorption and electrochemical energy storage using supercapacitor technology. Fully reversible H 2 uptake capacities in excess of 3.1 wt% at 77 K and ~ 72 bar along with a significant heat of adsorption value of up to 8.4 kJ/mol for low surface coverage have been found. Upon incorporation of low-pressure sorption data in the ideal adsorbed solution theory model, the ACC is predicted to selectively adsorb about 4.5 times more CO 2 than CH 4 in ambient conditions and thus represents an appealing adsorbent for the purification of such gaseous mixtures. Finally, an electric double-layer capacitor device was assembled and tested for its electrochemical performance, constructed of binder-free and flexible ACC electrodes and aqueous CsCl electrolyte. The full-cell exhibits a gravimetric capacitance of ~ 121 F/g for a specific current of 0.02 A/g, which relative to the ACC's specific area, is superior to commercially available activated carbons. A capacitance retention of more than 97% was observed after 10,000 charging/discharging cycles, thus indicating the ACC's suitability for demanding and high-performance energy storage on a commercial scale. The enhanced performance in all tested applications seems to be attributed to the mean ultra-micropore size of the ACC material instead of the available specific area and/or pore volume.

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