Abstract
The urgent need to reduce the consumption of fossil fuels drives the demand for renewable energy and has been attracting the interest of the scientific community to develop materials with improved energy storage properties. We propose a sustainable route to produce nanoporous carbon materials with a high−surface area from commercial graphite using a dry ball−milling procedure through a systematic study of the effects of dry ball−milling conditions on the properties of the modified carbons. The microstructure and morphology of the dry ball−milled graphite/carbon composites are characterized by BET (Brunauer–Emmett–Teller) analysis, SEM (scanning electron microscopy), ATR−FTIR (attenuated total reflectance–Fourier transform infrared spectroscopy) and Raman spectroscopy. As both the electrode and electrolyte play a significant role in any electrochemical energy storage device, the gravimetric capacitance was measured for ball−milled material/glassy carbon (GC) composite electrodes in contact with a deep eutectic solvent (DES) containing choline chloride and ethylene glycol as hydrogen bond donor (HBD) in a 1:2 molar ratio. Electrochemical stability was tracked by measuring charge/discharge curves. Carbons with different specific surface areas were tested and the relationship between the calculated capacitance and the surface treatment method was established. A five−fold increase in gravimetric capacitance, 25.27 F·g−1 (G40) against 5.45 F·g−1, was found for commercial graphene in contact with DES. Optimal milling time to achieve a higher surface area was also established.
Highlights
Carbon nanomaterials such as graphene and graphite present unique physical, chemical and mechanical properties [1]
Water content is a parameter that can affect the physical properties of deep eutectic solvent (DES) [47,48,49], namely the viscosity
The commercial graphene used in this study presents significantly lower values of specific surface area and pore volume, showing that the present commercial graphene sheets are less exposed
Summary
Carbon nanomaterials such as graphene and graphite present unique physical, chemical and mechanical properties [1]. The synthesis of these carbon materials can be made using environmentally−friendly methods, with the use of nontoxic chemicals [25] Another possible route to synthesize graphitic materials is ball milling, known to be an effective and ecological way to prepare high surface area materials compared to other methods such as chemical exfoliation [26] and allowing the reduction of particle size and the refinement of grains to a size below 1 μm. TheThe dry ball−milling methods described in this work, may present aand valuable route to modify commercial graphite powder. The obtained carbon nanomaterials will contribute to open the way to the development
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