Thionine Functionalized 3D Graphene Aerogel: Combining Simplicity and Efficiency in Fabrication of a Metal‐Free Redox Supercapacitor

Abstract

transportation sector with electric vehicles. [1] The potential of renewable energy to power electric vehicles can contribute to a future world with cleaner skies, cheaper energy, and healthier air. Energy distribution can also be simplified by sending electrons over the grid, or even by locally generating energy using solar panels, instead of shipping chemical fuels through pipelines or via road transport. One of the core technologies required to realize the viability of renewable energy sources is to develop improved electrochemical energy storage systems. [2] Electric doublelayer capacitors (EDLCs) are more appropriate for high-power applications, while secondary batteries are well suited for high-energy applications. EDLCs are thus sometimes used in tandem with batteries so that the former provide power and the latter provide energy for the integrated system. Current research in the field of energy storage is converging to target single devices that have EDLClevel power density as well as cycling stability and battery-level energy density. [3] Supercapacitors are an important technology for the future of energy storage. Supercapacitors are especially designed for applications that require a high rate capability, where a sudden burst of energy in a very short time interval is needed. However, supercapacitors have a rather limited energy density. Thus, different charge storage mechanisms, in addition to and/or in place of EDLCs, have been developed to boost the energy content of supercapacitors. [4] The most intriguing approach is the incorporation of nanostructured solid-state electrode materials, mainly transition metal oxides/sulfides, [5] layered double hydroxides, [2b] or conductive polymers, [6] that utilize fast Faradaic redox reactions for energy storage. Another intriguing approach is the development of hybrid ion capacitors, which are intermediate in energy between batteries and supercapacitors, while demonstrating supercapacitor-like power performance and cycling stability. [7] Inspired by the solid-state pseudocapacitive charge storage mechanism, the concept of liquid-state redox electrolytes has also been developed to supply extra energy. [8] Via this fascinating approach, the dead weight of the formerly inert electrolytes is utilized as an active component to augment the energy storage performance, and the wasted Discovering efficient pseudocapacitive charge storage materials has become one of the grand challenges to reduce the gap between high energy density batteries and high power density and durable electrical double-layer capacitors.This research direction is facilitated by the introduction of redox-active species that add Faradaic charge storage to the system. However, the astonishing abilities of organic redox species to increase energy density are insufficient to compensate for their poor electrical conductivity and inferior cyclability. Herein, it is proposed that these challenges can be simultaneously met by thoughtful selection of a redox species, thionine, that can be conjugate...

Supercapatteries as High-Performance Electrochemical Energy Storage Devices

“…To address this, various hybrid EES devices have been proposed and preliminarily demonstrated in which such hybrid devices can combine the merits of supercapacitors with those of rechargeable batteries into one device. However, a unified generic term was lacking for these devices and researchers have generally referred to them using different nomenclatures such as 'redox capacitors' [2,3], 'Li-ion capacitors' [4][5][6][7][8], 'Naion capacitors' [8][9][10], 'hybrid electrochemical capacitors' [11][12][13][14], battery-supercapacitor hybrids [15] or 'pseudocapacitors' [16][17][18] corresponding to electrode material and device design and engineering. As a result, a generic term 'supercapattery' (= supercapacitor + battery) was proposed to represent these EES hybrid devices that are different from either supercapacitors or rechargeable batteries in terms of fundamental principles and technological prospects.…”

High‐efficiency utilization of carbon materials for supercapacitors

“…To date, a variety of quinones mainly including anthraquinone, 1,4,5,8-tetrahydroxy anthraquinone, 2,5-dimethoxy-1,4-benzoquinone, 9,10phenanthrenequinone, and so on have been investigated as the electrode materials for supercapacitors. [91] Yury Gogosi et al used the 2,5-dihydroxy-1,4-benzoquinone (DBQ) modified RGO as positive electrode materials for aqueous supercapacitors, showing outstanding capacitive and rate capabilities of 500 F g −1 / 800 F cm −3 at 2 mV s −1 , 83 F g −1 /133 F cm −3 at 10 V s −1 , and remarkable cycle life of 83% capacitance retention after 100,000 cycles. [88] When paired with pseudocapacitive Ti 3 C 2 T x MXene, the assembled device delivered ultra-high energy density of F I G U R E 7 A, Nile blue conjugated graphene aerogel and their gravimetric/volumetric capacitances at various current densities in 1 mol L −1 H 2 SO 4 electrolyte.…”

<p>Engineering of Aerogel-Based Biomaterials for Biomedical Applications</p>

“…8 Therefore, aerogel can be regarded as a state of matter with similar porous structure to solid networks of a gel with gas or vacuum in-between the skeletons. 9 Due to the outstanding physicochemical properties, diverse aerogels have been developed and recognized as promising candidates for various applications, such as thermal insulation, 10 photocatalysts, 11 sensor, 12,13 supercapacitor, 14,15 and water treatment. 16 Presently, clinical treatments have impressively requirements on the generation of functional biomaterials with designable structures.…”