Abstract
The development of energy storage devices with better performance relies on the use of innovative materials and electrolytes, aiming to reduce the carbon footprint through the screening of low toxicity electrolytes and solvent-free electrode design protocols. The application of nanostructured carbon materials with high specific surface area, to prepare composite electrodes, is being considered as a promising starting point towards improving the power and energy efficiency of energy storage devices. Non-aqueous electrolytes synthesized using greener approaches with lower environmental impact make deep eutectic solvents (DES) promising alternatives for electrochemical energy storage and conversion applications. Accordingly, this work proposes a systematic study on the effect of the composition of DES containing a diol and an amide as HBD (hydrogen bond donor: 1,2-propylene glycol and urea), on the electrochemical performance of graphene and graphite composite electrodes/DES electrolyte interface. Glassy carbon (GC) was selected as the bare electrode material substrate to prepare the composite formulations since it provides an electrochemically reproducible surface. Gravimetric capacitance was measured for commercial graphene and commercial graphite/GC composite electrodes in contact with choline chloride, complexed with 1,2-propylene glycol, and urea as the HBD in 1:2 molar ratio. The electrochemical stability was followed by assessing the charge/discharge curves at 1, 2, and 4 A g−1. For comparison purposes, a parallel study was performed using commercial graphite. A four-fold increase in gravimetric capacitance was obtained when replacing commercial graphite (1.70 F g−1) by commercial graphene (6.19 F g−1) in contact with 1,2-propylene glycol-based DES. When using urea based DES no significant change in gravimetric capacitance was observed when commercial graphite is replaced by commercial graphene.
Highlights
Carbon-based materials are excellent candidates as electrode materials for energy storage applications due to their physicochemical properties such as their low atomic number, making them lightweight, with long term stability, low residual current, and broad potential range
Brandão et al [24] studied the electrochemical behavior of commercial graphene and commercial graphite in ethaline, showing a specific capacitance of 5.45 ± 0.96 F g−1 and 4.27 ± 0.85 F g−1, respectively
It was demonstrated that the electrolyte can be a key factor for the optimization of the electrochemical performance of the carbon materials’ composite electrodes
Summary
Carbon-based materials are excellent candidates as electrode materials for energy storage applications due to their physicochemical properties such as their low atomic number, making them lightweight, with long term stability, low residual current, and broad potential range. Carbon nanomaterials, such as graphene and graphite, present remarkable physical, chemical, and mechanical properties [1] which have attracted considerable interest for a large diversity of applications, ranging from energy conversion (solar and fuel cells) [2,3,4], to energy storage (supercapacitors and batteries) [5,6,7], and to environmental remediation (removal of heavy metals from water and soils) [8,9]. The authors demonstrated the possibility to successfully use composite carbon allotropes electrodes immersed in DES electrolytes as promising electrochemical interfaces for advanced energy storage devices applications (e.g., supercapacitors)
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