Microfluidic-Oriented Synthesis of Graphene Oxide Nanosheets toward High Energy Density Supercapacitors

Abstract

Graphene oxide (GO) has aroused worldwide interests in recent years because of perfect solubility, easy processing nature, and intriguing mechanical properties. However, safety risk, high pollution, and low synthesis rate involved in the synthesis process of GO limit its practical applications. In this work, we propose a new strategy to efficiently produce the high-quality GO based on microfluidic synthesis technology. By use of the H2SO4/H3PO4/graphite hybrid microdroplet as the microreactor, the exfoliation and oxidation of graphite can be confined in a microscale reaction environment, indicating the enhanced reaction kinetics, high reaction rate (reaction time of 2 h), and minimum safety risk. Notably, the microfluidic synthesis of GO has nearly the same chemical structure when compared with the Hummers method. More importantly, the rGO fibers processed from GO solutions possess a high specific capacitance of 716.2 mF cm–2 (23.86 F g–1) and an energy density of 14.5 μWh cm–2 (0.53 Wh kg–1), which can enduringly power a smart watch. These versatile strategies open a promising access to the fast synthesis and commercial applications of graphene.

Comparing Graphite and Graphene Oxide Supercapacitors with a Constant Potential Model

“…Since the beginning of its use in the electrolytic cell assembly, GOs have shown higher capacitance compared to graphene-based systems. This superior performance is attributed to functional groups containing surface oxygen, mainly carbonyls and hydroxyls, which provide great pseudocapacitance, less aggregation, and good wettability properties. , In addition, GO also exhibits higher performance rate, cyclability, and durability comparable to graphene. , In the literature, it is possible to find applications of GOs as electrodes alone in supercapacitors based on liquid electrolytes − and solid-state supercapacitors. − In addition, they have also served as a basis for as well as a component of hybrid electrodes. − …”

Ionic Liquids for Supercapacitive Energy Storage: A Mini-Review

“…(Quasi-)­solid-state electrolytes are highly desirable in supercapacitor applications to satisfy the growing power need for wearable and flexible electronics . The exploitation of diverse IL (quasi-)­solid-state electrolytes is expected to relieve the intrinsic environmental risks associated with liquid leakage, component corrosion, and assembly issues for compact energy storage. ,, Ionogels comprising ILs with polymer matrices ( e.g. , poly­(ethylene oxide) (PEO), poly­(vinyl alcohol) (PVA), poly­(methyl methacrylate) (PMMA)) provide great promise by virtues of mechanical flexibility, a leak-proof character, high room-temperature ion mobility, and a wide electrochemical stability window. − Park’s group developed a green cellulose-derived ionogel electrolyte through phosphorylating and mixing a microcrystalline cellulose scaffold in the 1,3-dimethylimidazolium methyl phosphite medium coupled with subsequent polymerization; the as-obtained ionogel electrolyte possessed a maximum toughness of 1.46 MJ m –3 and high ion mobility (2.6–22.4 mS cm –1 ) in the broad operational temperature range of 30–120 °C, endowing the resultant activated carbon-loaded flexible supercapacitor with an outstanding specific capacitance of 174 F g –1 under 2.5 V at 120 °C .…”

Virtual Special Issue of Research Highlights on Sustainable Energy and Clean Fuels at State Key Laboratory of Materials-Oriented Chemical Engineering (SKL-MCE), China

“…There is one paper on this topic. Qiu et al 32 propose a new strategy to efficiently produce high-quality GO based on microfluidic synthesis technology using a H 2 SO 4 /H 3 PO 4 / graphite hybrid microdroplet as the microreactor. The supercapacitor assembled by reduced GO (rGO) fiber processed from GO solutions displays outstanding specific capacitance and energy density in the H 3 PO 4 /PVA gel electrolyte.…”