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5, 7, 12, 14-pentacenetetrone (PT), polycyclic quinone derivatives, are rich in carbonyl, which were investigated as a novel organic electrode material for supercapacitors. PT with a π conjugated system, is a flat molecule, generating strong π–π interactions between molecules. PT molecules were uniformly fixed on conductive reduced graphene oxide (rGO) through π–π interaction by one-step solvothermal method, forming a three-dimensional cross-linked PT@rGO hydrogel. This composite structure was conducive to reducing the charge transfer resistance and promoting the Faraday reaction of electrode, which achieved the superposition of electric double-layer capacitance and pseudocapacitance. Appropriate organic molecular loading can effectively improve electrochemical performance. The optimal PT@rGO electrode material displayed the specific capacitance of 433.2 F g−1 at 5 mV s−1 with an excellent rate capability in 1 mol l−1 H2SO4 electrolyte. Finally, the fully pseudocapacitive asymmetric supercapacitor has been assembled by using PT@rGO as positive electrode and benz[a]anthracene-7,12-quinone (BAQ) modified rGO(BAQ/rGO)as negative electrode, which exhibited the good energy storage performance in a cell voltage of 1.8 V. [ABSTRACT FROM AUTHOR]

Cu–Sn binary sulfide is a promising candidate for an electrode material due to its superior properties, and it has been extensively reported in solar cells and Li-ion batteries. However, there are only a few pieces of work about its use in either supercapacitors or electrocatalysts. In this work, self-assembled binary sulfides with different morphologies in terms of 1D Cu–Sn–S micron-tubes (MTs-CTS), 1D Cu–Sn–S submicron-tubes (SMTs-CTS) and 3D Cu–Sn–S hoya-like micron-spheres (MPs-CTS) with honeycomb pores were successfully fabricated via a facile gelation–solvothermal–annealing three-step method. The results show that MPs-CTS achieve better electrochemical performance compared with MTs or SMTs. The optimized MPs-CTS exhibit a higher capacitance value (1134.2 F g−1 at 1 A g−1), better rate capability, and longer-term cycle stability (94.2% retention after 2000 cycles at 5 A g−1). Moreover, the MPs-CTS also display excellent hydrogen evolution reaction (HER) performance at a current density of 10 mA cm−2 with the lowest overpotential of 302 mV and a small Tafel slope of 78 mV dec−1. This work provides an effective route for the design and preparation of a 3D hoya-like structure with multiple functions, such as energy storage and electrocatalysis. [ABSTRACT FROM AUTHOR]

Green and renewable organic redox molecules are greatly advantageous over conventional inorganic intercalation electrode materials in terms of electrochemical reversibility and cycling stability. However, their electrical insulation prevents them from being used alone as electrode materials for supercapacitors. Herein, 2-amino-3-chloro-1,4-naphthoquinone (ACNQ) molecules were covalently grafted onto graphene nanosheets (GNS) via diazotization. The ACNQ-functionalized GNS (CNQ-GNS) electrode material exhibited a high specific capacitance of 364.2 ± 10 F g−1 at a current density of 1 A g−1, which is much larger than that of bare GNS (190 ± 6 F g−1). Moreover, the electrode exhibited an outstanding rate capability (capacitance retention of 76.8% at 100 A g−1). Finally, an asymmetric supercapacitor device was fabricated using graphene nanosheets as the positive electrode and the optimized CNQ-GNS as the negative electrode, which displayed a high energy density of 19.1 W h kg−1 at a power density of 0.8 kW kg−1 with a long cycling life span (nearly no loss after 10 000 cycles at 5 A g−1) in 1 M H2SO4 electrolyte. Briefly, the highly conductive GNS scaffold delivers a high electrical double-layer capacitance, while the organic functional groups covalently bonded on the GNS contribute additional faradaic pseudocapacitance, resulting in outstanding electrochemical energy storage. [ABSTRACT FROM AUTHOR]

• BAQ and DHBQ are anchored on graphene to form organic molecules electrodes. • The BAQ (DHBQ)/rGO electrodes achieve capacitance all in excess of 400 F g−1 at 1 A g−1. • DFT calculations are employed to understand the experimental mechanism. • The two ASCs device in series easily lights 47 red light-emitting diodes compounding in parallel. Organic molecules electrodes with high electrochemical reversibility has enormous potential in energy storage. Here, benz[a]anthracene-7, 12-quinone (BAQ) and 2, 5-dihydroxy-p-benzoquinone (DHBQ) are anchored on reduced graphene oxide (rGO) [BAQ (DHBQ)/rGO] by non-convent method to form the porous 3D dry aerogels. The optimal BAQ (DHBQ)/rGO electrode materials display capacitance all in excess of 400 F g−1 at current density of 1 A g−1 and an excellent rate capability in 1 M H 2 SO 4 electrolyte. And BAQ/rGO and DHBQ/rGO are used respectively as the negative and positive electrode to fabricate the asymmetric supercapacitor (ASC), which achieves high energy density of 30.33 Wh kg−1 with power density of 802.9 W kg−1. Finally, 47 light-emitting diode (LED) bulbs aligned in a 'NWNU' shape are lit by two ASCs device in series, demonstrating its outstanding energy storage performance. Moreover, density functional theory (DFT) calculations are employed to understand the adsorption orientations, binding interactions and charge storage mechanism of BAQ on rGO surface, elucidating the superior electrochemical performance of the tested organic molecule electrode. In short, quinones non-covalently modified graphene is a promising and effective strategy for energy storage devices in future. [ABSTRACT FROM AUTHOR]

The present work reports an organic molecule electrode (OME) based on the graphene and graphene nanomesh (GNM) hydrogel non-covalently functionalized by caffeic acid (CFA) molecules (denoted as G&GMH-CFA). In such electrode system, the three-dimensional conductive network has a cross-linking channel constructed by means of the in-plane pores on the graphene nanomesh, which is benefit for exposing more active sites accessible to electrolyte and accordingly enhancing supercapacitive behaviors of the OME. The G&GMH-CFA delivers a specific capacitance of 482.6 F g−1 at current density of 1 A g−1. And it is noted that the Faraday current response peaks are located in the positive potential range of 0.6 V, which is superior to the organic molecules electrode reported in the correlative works. In addition, the density functional theory (DFT) calculations are used to illuminate the core issue of charge storage mechanism and binding interactions between CFA and graphene. To match with the resultant positive electrode, AQ functionalize graphene-like nanoflower (CNF-AQ) was prepared as counterpart (negative) electrode. The assembled asymmetric supercapacitors (ASC) CNF-AQ//G&GMH-CFA2 could exhaustively release the supercapacitive performance due to match and self-coordination based on the reasonable matching of two electrodes in structure, charge quantity and kinetics during the electrochemical energy storage process. The CNF-AQ//G&GMH-CFA2 delivered energy density of 26.4 Wh kg−1 at the power density of 0.7 kW kg−1. Two tandem CNF-AQ//G&GMH-CFA2 devices could easily light 88 LEDs. The organic molecule electrode is fabricated by the CFA functionalized graphene hydrogel with plentiful transport channels inside of the conductive skeleton, matching with CNF-AQ to assemble full-carbon ASC could easily light 88 LEDs. Image 1 [ABSTRACT FROM AUTHOR]

A redox-active organic molecular electrode is prepared for supercapacitors. Benzo[1,2-b:4,5-b']dithiophene-4,8-dione (BDTD), planar molecule with fused heteroaromatic structure, has been adsorbed on conductive reduced graphene oxide (rGO) by π–π interactions to form a 3D interconnected and functionalized xerogel (BDTD-rGO). Because the five-membered aromatic heterocycle is more electron-rich than the six-membered aromatic ring, which enlarges the electronic interaction between the BDTD molecule and the conjugated graphene network and accordingly reduce the solubility of BDTD molecule in electrolyte. As a result, the optimized BDTD-rGO electrodes achieve specific capacitance of 360 F g−1 at 1 A g−1, with ultra-long cycle life of 96.4% after 10,000 cycles, and even 80% after 50,000 cycles at 5 A g−1 in 1 M H 2 SO 4. Furthermore, the asymmetric supercapacitor (ASC), which is assembled by using the BDTD-rGO as the negative electrode and lamellar holey graphene hydrogel (LGH) as the positive electrode respectively, exhibits better energy storage performance. Image 1 • Reduced graphene oxide was non-covalently functionalized by organic molecules. • The BDTD-rGO exhibits an ultra-long cycle life (96.4% for 10,000 cycle). • The BDTD-rGO possesses an excellent specific capacitance of 360 F g−1 at 1 A g−1. • Negative and positive electrodes can generate potential self-matching behavior. • As-fabricated the asymmetric supercapacitor delivers a superior cyclic stability. [ABSTRACT FROM AUTHOR]

The Fe 3 C is nanocrystallized and stabilized by core–shell structure. The scattered core–shell cells are integrated together by rGO to build a complete electrode with high conductivity. The assembled hybrid supercapacitor delivers a high energy density as 84.8 Wh kg−1 with the power density of 840 W kg−1. [Display omitted] • In-situ grow a Fe 3 C-based core–shell architecture on the surface of reduced graphene oxide, under melamine atmosphere. • Fe 3 C in the formation of nanocrystallization is encapsulated in the separate N-doping carbon "room". • The elaborate construction improves the rate ability and stability of supercapacitor. • The resultant electrode can be suitably used as a negative electrode, and the assembled device delivers high energy density. Herein, we synthesize a hybrid negative electrode (Fe 3 C@NC/rGO) by using the ammonium ferric citrate (AFC) as Fe-source, under melamine atmosphere, in-situ growing the core–shell architecture, in which the Fe 3 C particles are encapsulated into the N-doping carbon (NC) shell on the surface of reduced graphene oxide (rGO). Resulting from the dual effect of NC and rGO, the Fe 3 C@NC/rGO exhibits high specific capacitance of 1091.9F g−1 at 10 mV s−1 (70% capacitance retention when the scan rate increased to 100 mV s−1) and long-term stability (96% capacitance retention after 8000 cycles), which outperforms all Fe-based electrodes reported so far in aqueous electrolytes. The Fe 3 C@NC/rGO-5 as negative electrode is matched with CNT-Ni(OH) 2 positive electrode to fabricate an aqueous asymmetric supercapacitor (ASC). Based on the larger potential difference between peak potentials of the negative and positive electrodes, the assembled ASC can deliver the energy density of 84.8 Wh kg−1 along with the power density of 840 W kg−1 (the maximum power density could reach up to 42 kW kg−1), and shows only 2.3% capacitance decay after 10,000 cycles. Two assembled ASCs in series can easily light 55 LEDs. [ABSTRACT FROM AUTHOR]