Graphene Based Aerogels: Fundamentals and Applications as Supercapacitors

Super Capacitors have attained a huge amount of attention due to their outstanding features and characteristics such as high-power density, excellent charge/discharge routine, and tendency of a longer lifetime. Graphene, a single layer of hexagonally crammed carbon atoms, has always been considered as an outstanding material for super capacitor fabrication due to its higher theoretical surface area, high electrical conductivity, stable thermal properties, and its mechanical and chemical properties. Super capacitor electrode resources which are based on 3D network/aerogel structures are resultant of graphene is a prime area of research due to their porous structure and lattice which meets the expense of rapid electron transport, higher stability, and a good cycle performance. This review intents to summarize the fundamentals and the fabrication strategies of 3D graphene aerogels.This work was supported by the NPRP grant # NPRP11S-1221-170116 from the Qatar National Research Fund (a member of Qatar Foundation). Y.B Pottathara and Z. Ahmad would like to thank the financially support by the TNB Research Sdn Bhd. Malaysia (grant no: 100-IRMI P. 37/7/ 20160419007) and Universiti Teknologi Mara, Selangor Malaysia. The statements made herein are solely the responsibility of the authors.Scopu

High-performance supercapacitors of carboxylate-modified hollow carbon nanospheres coated on flexible carbon fibre paper: Effects of oxygen-containing group contents, electrolytes and operating temperature

Although carbon black nanoparticles (CBs) at ca. 10 wt.% are widely used as a conductive additives for energy storage electrodes for lithium ion batteries and supercapacitors, they are not extensively used as the active materials for such devices due to their poor ionic conductivity and wettability. In this work, CBs were oxidized by a process of refluxing with conc. HNO3 for 6-72 h, providing oxidized CBs (OCBs) with different oxygen-containing groups (i.e., carboxyl, hydroxyl, and carbonyl) and contents. The OCBs refluxed for 12 h have ca. 2.0-fold higher accessible active surface area than that of the pristine CBs. The as-fabricated symmetric supercapacitor using OCBs refluxed for 12 h with a [BMP][DCA] ionic liquid electrolyte exhibits specific energy and maximum specific power of 88 Wh kg-1 and 8429 W kg-1, respectively with the capacitance retention over 97% after 6000 cycles. A single coin-cell supercapacitor prototype fully charged can supply electrical power to a red LED over 24 min. This device may be practically used as a battery replacement in high power applications

High-performance supercapacitors of carboxylate-modified hollow carbon nanospheres coated on flexible carbon fibre paper: Effects of oxygen-containing group contents, electrolytes and operating temperature

Although carbon black nanoparticles (CBs) at ca. 10 wt.% are widely used as a conductive additives for energy storage electrodes for lithium ion batteries and supercapacitors, they are not extensively used as the active materials for such devices due to their poor ionic conductivity and wettability. In this work, CBs were oxidized by a process of refluxing with conc. HNO3 for 6-72 h, providing oxidized CBs (OCBs) with different oxygen-containing groups (i.e., carboxyl, hydroxyl, and carbonyl) and contents. The OCBs refluxed for 12 h have ca. 2.0-fold higher accessible active surface area than that of the pristine CBs. The as-fabricated symmetric supercapacitor using OCBs refluxed for 12 h with a [BMP][DCA] ionic liquid electrolyte exhibits specific energy and maximum specific power of 88 Wh kg-1 and 8429 W kg-1, respectively with the capacitance retention over 97% after 6000 cycles. A single coin-cell supercapacitor prototype fully charged can supply electrical power to a red LED over 24 min. This device may be practically used as a battery replacement in high power applications

Transparent and Flexible Mn 1−

Control over the fabrication of state-of-the-art portable pseudocapacitors with the desired transparency, mechanical flexibility, capacitance, and durability is challenging, but if resolved will have fundamental implications. Here, defect-rich Mn1−x−y(CexLay)O2−δ ultrathin films with controllable thicknesses (5–627 nm) and transmittance (≈29–100%) are fabricated via an electrochemical chronoamperometric deposition using a aqueous precursor derived from end-of-life nickel-metal hydride batteries. Due to percolation impacts on the optoelectronic properties of ultrathin films, a representative Mn1−x−y(CexLay)O2−δ film with 86% transmittance exhibits an outstanding areal capacitance of 3.4 mF cm−2, mainly attributed to the intercalation/de-intercalation of anionic O2− through the atomic tunnels of the stratified Mn1−x−y(CexLay)O2−δ crystallites. Furthermore, the Mn1−x−y(CexLay)O2−δ thin-film device exhibits excellent capacitance retention of ≈90% after 16 000 cycles. Such stability is associated with intervalence charge transfer occurring among interstitial Ce/La cations and Mn oxidation states within the Mn1−x−y(CexLay)O2−δ structure. The energy and power densities of the transparent flexible Mn1−x−y(CexLay)O2−δ full-cell pseudocapacitor device, is measured to be 0.088 μWh cm−2 and 843 µW cm−2, respectively. These values show insignificant changes under vigorous twisting and bending to 45–180° confirming these value-added materials are intriguing alternatives for size-sensitive energy storage devices.</p