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• Graphene/PANI/MnO 2 composites are fabricated by facile two-step electrodeposition. • Graphene hydrogel films act as working electrodes for sequential electrodeposition. • The ternary composite electrode exhibits excellent capacitive performance. • The symmetric device performs well in rate capacity, stability and energy density. The incorporation of various capacitive materials to fabricate multi-component electrodes has emerged as a feasible methodology toward high-performance supercapacitors. In this paper, a facile two-step electrodeposition method is proposed to construct polyaniline (PANI)/MnO 2 hybrid nanostructure on reduced graphene oxide (RGO) matrix for the ternary supercapacitor electrodes. By the sequential potentiostatic methods, PANI is first electropolymerized on RGO hydrogel films before MnO 2 granules are electrodeposited on the RGO/PANI conductive substrates to obtain the free-standing composite films. The resulting RGO/PANI/MnO 2 ternary composite electrodes present significantly promoted capacitive properties compared with the binary RGO/PANI electrodes. Particularly, the optimized electrode and corresponding all-solid-state device could achieve the high specific capacitances of 942.6 and 205.0 F g–1 at 1 A g–1 with superb capacitance retention of 86.4% and 80.3% at 30 A g–1, respectively. The device delivers a maximum energy density of 41.0 Wh kg–1 and demonstrates outstanding capacitance holdings of 96.1% after 10,000 cycles at 30 A g−1, 87.8% after 5000 cycles at 10 A g−1, and 82.5% after 3000 cycles at 5 A g−1, respectively. The prominent electrochemical performances of the ternary composite can be ascribed to the fact that graphene supplies the conductive matrix to immobilize the active pseudocapacitive constituents, while PANI and MnO 2 can compensate each other to surmount the disadvantages of inferior conductivity or stability. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The hydrated GO/PANI film fixed on carbon cloth is achieved via water evaporation. • Integrated rGO/PANI/CC electrode is obtained by facile hydrazine reduction. • High rGO/PANI mass loading is realized via repeating dropping/evaporating process. • The integrated electrode displays excellent capacitance and rate performance. • The all-solid-state device exhibits high energy density toward promising potentials. The convenient fabrication of supercapacitor electrodes with high active material mass loading is of great significance to the practical application. In this paper, a novel and efficient strategy is proposed to prepare graphene/polyaniline (PANI) composite with controllable mass loading towards high-performance supercapacitor electrodes. The graphene oxide (GO)/PANI colloid layer is drop-coated onto carbon cloth (CC) before evaporating most of the water. The as-obtained hydrated GO/PANI/CC film undergoes a facile hydrazine reduction treatment and yields the porous reduced GO (rGO)/PANI active layer fixed on the CC current collector, which could directly act as the binder-free supercapacitor electrode. As a result, the excellent adhesion of active layer with CC and the uniform PANI distribution on porous rGO matrix contribute greatly to the fast electron and ion transport in the electrochemical activities. The integrated rGO/PANI/CC electrode achieves a high specific capacitance of 871.5 F g−1 at the current density of 1.5 A g−1 with superior rate performance. More importantly, repeating the drop-coating/water-evaporating process could conveniently realize the high rGO/PANI mass loading (up to 10 mg cm−2) on the current collector. The corresponding symmetric all-solid-state supercapacitors with different mass loadings can deliver the maximum energy densities of 39.1 Wh kg−1, 425.3 μWh cm−2, and 4.0 mWh cm−3, manifesting their promising practical prospect. This work would provide a new path for the fabrication of graphene-based supercapacitor electrodes and other functional film materials. [ABSTRACT FROM AUTHOR]

Developing high-capacity electrode materials is critical to enhance the energy-density of lithium-ion batteries. Here, a new graphene nanoplatelets-supported SiO x -disordered carbon composite (SiO x -C/GNPs) is fabricated by a Stöber-type process and high-temperature treatment. When used as an anode for lithium-ion batteries, SiO x -C/GNPs exhibits excellent cycle stability and rate capability even under deep charge–discharge cycling. A stable reversible capacity of about 630 mAh g −1 (calculated on the total mass of the composite) can be achieved at a current density of 100 mA g −1 and the capacity retention is nearly 100% after 250 cycles. Additionally, the plateau voltages of lithium extraction for the composite are only slightly higher than those for the commercial graphite, which ensures the high energy density of the assembled batteries. The superior electrochemical performance of this novel material is due to its unique features: excellent electronic conductivity, short transportation length for both lithium ions and electrons, elastomeric space to accommodate volume changes upon Li insertion/extraction and robust connection between SiO x and GNPs. [ABSTRACT FROM AUTHOR]

• A novel active layer configuration with enhanced interfacial effect is proposed. • Reduced graphene oxide film is cut into two for each polyaniline electrodeposition. • The twin composite films are parallelly assembled for supercapacitor electrode. • The electrode displays excellent specific capacitance and cycling stability. • The all-solid-state device exhibits high energy density toward application potential. For the traditional supercapacitors based on the graphene@polyaniline (PANI) film prepared by electropolymerization, the interfacial contact between the graphene substrate and PANI shell plays a vital role in improving the PANI stability and the electrochemical capacitance of the active layer. In this work, we propose a novel strategy that the reduced graphene oxide (RGO) hydrogel film with given size could be divided into two for respective PANI electrodeposition and the two graphene@PANI films are assembled parallelly on carbon cloth to obtain the supercapacitor electrode. Owing to the additional lateral RGO/PANI interface, the resulting electrode delivers a high specific capacitance of 949 F g−1 at 1 A g−1 and 760 F g−1 even at the high current density of 20 A g−1. The corresponding binder-free symmetric supercapacitor device could attain a maximum energy density of 18.2 Wh kg−1 and a maximum power density of 4.75 kW kg−1, with a high capacitance retention of 93.1% after 10000 charge/discharge cycles. These superior properties of the electrodes based on the parallel RGO/PANI films testify the rational design of the active layer configuration for enhanced interfacial effect. This work would provide a novel pathway towards the preparation of high-performance supercapacitor electrodes. [Display omitted] [ABSTRACT FROM AUTHOR]

A series of K 2 SiF 6 :0.066Mn4+@Cl-GQDs (KSF:K 2 SiF 6 , Cl-GQDs: Cl containing graphene quantum dots) phosphors were prepared with a H 2 O 2 -free hydrothermal method, and the optimal sample was KSF:0.066Mn4+@Cl-GQDs 8 mg/mol. Enhanced effects on luminescent intensity and thermal stability inducing by coating of Cl-GQDs are observed: (a) Integrated emission intensity is 4.60 times of that of KSF:0.066Mn4+, (b) The luminescent thermal stability is greatly enhanced, which integrated emission intensities at 180 and 240 °C are 282.9 and 135.3% of that at 30 °C, respectively. The mechanisms of the above behaviors are discussed and proposed: Coordination between conjugated large π bond of GQDs and Mn4+ leads to the enhancement of emission intensity and luminescent thermal stability. Thermal stability analysis results show that the optimal samples suitable for high power WLEDs. Warm white light with low correlated color temperature and high color rendering index was produced from prototype WLEDs using the optimal sample as red emitting component. Image 1 • K 2 SiF 6 :Mn4+@Cl-GQDs were synthesized with a H 2 O 2 -free hydrothermal method. • Emission intensity and thermal stability are dramatically improved by coating of Cl-GQDs. • Integrated intensity of PL can be enhanced 4.60 times by coating of Cl-GQDs. • Integrated PL intensities at 180 and 240 °C are 282.9 and 135.4% of that at 30 °C. [ABSTRACT FROM AUTHOR]

A sheet-on-sheet and metal-free graphene/C 3 N 4 /carbon dots (GR/C 3 N 4 /CDots) ternary heterostructure with efficient visible-light photocatalysis for pollutants degradation has been reported. Via a convenient and hydrothermal method, large-sized GR nanosheets can serve as substrate for monodispersed dispersion of C 3 N 4 nanosheets. A subsequent loading of very small amount of CDots (1 wt%, 2–5 nm) onto sheet-on-sheet heterostructure significantly enhance visible-light-driven photoredox performances of catalysts, including oxidation of organics pollutant (RhB, 96.0%) and reduction of heavy metals [Cr(VI), 83.6%]. Excellent catalytic properties of GR/C 3 N 4 /CDots heterostructure can be predominantly ascribed to the intimate interfacial contact among constructing ingredients, increased specific surface area and enhanced light adsorption derived from GR and CDots carbon materials. Particularly, the synergistic sheet-on-sheet interaction between C 3 N 4 and carbon materials (GR and CDots) remarkably accelerate the electrons/holes separation, giving rise to significantly enhanced photoredox performances of GR/C 3 N 4 /CDots in comparison with other counterparts. The synergism effect between organic contaminants and heavy metals also contributed to the efficient performance of GR/C 3 N 4 /CDots, wherein the O 2− and OH were the main active species in the photoredox reactions. This metals-free heterostructure shows favorable photostability in cyclic experiments. We anticipate that our work could provide a classical paradigm for rational design of efficient and visible-light-driven photocatalysts for their sustainable applications in wastewater treatment. [ABSTRACT FROM AUTHOR]

In order to enhance the luminescent thermal stability and water resistance of K 2 SiF 6 :Mn4+, we proposed a simple hydrothermal method to synthesize K 2 SiF 6 :0.06Mn4+@GE-GQD S (6 mg/mol) (GE-GQDs: green emission graphene quantum dots) red emitting phosphor with outstanding water resistance. The emission intensity of the sample coated with the GE-GQDs still maintains 87.74% of the initial one after immersion for 360 min, while the uncoated K 2 SiF 6 :0.06Mn4+ sharply decreases to 11.26%. Another impressive phenomenon is that due to the negative thermal quenching (NTQ) effect, the luminescent thermal stability of the coated sample is also significantly improved, and the integrated photoluminescence (PL) intensity at 180 °C is 238% of that at 25 °C. In the meantime, the integrated PL intensity of the coated samples is 2.55 times that of K 2 SiF 6 :0.06Mn4+ under room temperature. Based on experimental results, it is suggested that after coating with GE-GQDs, a surface protective layer is formed on the surface of the sample, which improves the water resistance, room temperature emission intensity, and luminescent thermal stability of the coated sample. Finally, the improvement mechanism of the above multiple enhancements on luminescent properties is discussed and proposed. The above multiple enhancement effects make the sample have broad application for blue light-based warm and high-power WLEDs (white light-emitting diodes). • K 2 SiF 6 : Mn4+@GE-GQD S has been synthesized. • Sample has high water resistance, thermal stability and luminescent intensity. • Water resistance, thermal stability and emission intensity are enhanced by GE-GQDs. • The high water resistance is attributed to formation of coordination polymer. [ABSTRACT FROM AUTHOR]

Nitrogen-doped 3D graphene frameworks (N-3D GFs) were synthesized by a facile two-step method: Polystyrene (PS) encapsulated in graphene oxide (GO) composites (denoted as PS@GO) are first synthesized, followed by a post–thermal annealing in ammonia step to get N-doped 3D GFs. The resulting N-3D GFs inherit the advantages of graphene, which possesses high electrical conductivity and high specific surface area. Furthermore, the well-defined 3D interconnected structure can facilitate the access of the electrolyte to the electrode surface, thus shortening the diffusion length of both Li + /e − , keeping the overall electrode highly conductive and active in lithium storage. Simultaneously, the in-situ formation of pyridinic N and pyrrolic N in 3D GFs provide high electronic conductivity and structure stability for lithium storage. The designed N-3D GFs electrode delivers a high specific capacity of 1094 mAhg −1 after 100 cycles at 200 mAg −1 and superior rate capability (691 mAhg −1 after 500 cycles at 1000 mAg −1 ) when used as anode for LIBs. We believe that such an inherently inexpensive, scalable, facile method can significantly increase the feasibility of building high performance energy storage system. [ABSTRACT FROM AUTHOR]

A facile, time-saving and one-step process to prepare graphene-based materials with excellent comprehensive capacitive performance is very promising for practical applications. Here, porous nitrogen-doped graphene/carbon nanotubes composite (PNGC) with loosened structure was prepared by pyrolysis method and the porous structure of PNGC was controlled by combined action of urea and low-cost lignosulfonate. PNGC is equipped with porous structure and thin graphene nanosheets, and meanwhile possess numerous active sites and high surface areas. Importantly, PNGC exhibits a high specific capacitance of 246.6 F g −1 at a current density of 0.5 A g −1 and high stability of 96.5% capacitance retention ratio after 2000 cycles at 100 mV s −1 , indicating an excellent performance of PNGC. Furthermore, the corresponding mechanism of pore formation in PNGC is hence proposed. This work of obtaining PNGC is of paramount importance for the future practical application of electrode materials for supercapacitor application. [ABSTRACT FROM AUTHOR]

Three dye-functionalized graphene oxide/polyaniline (GAP) composites were first prepared by optimizing acid blue 74 (AB74) feed content, and then dye-functionalized graphene/polyaniline (rGAP) nanocomposites were obtained from the GAP composites through reducing and re-protonating treatments. The AB74 dye molecules with negatively charged sulfonic groups can effectively prevent aggregation of graphene sheets during the reduction process of graphene oxide, and can be used as a bridge to attach polyaniline nanorods via π–π conjunction and electrostatic attraction. Furthermore, when rGAP5 (the AB74 feed content of 5 wt.%) was used as a supercapacitor electrode material, it achieved a high specific capacitance of 579 F g −1 at a current density of 0.5 A g −1 , good cycling stability and rate capacity. [ABSTRACT FROM AUTHOR]

Composites consisting of graphene nanosheets (GNSs) decorated with amorphous TiO 2 thin films were synthesized by an atomic layer deposition (ALD) technique. It was revealed that the TiO 2 thin films were uniformly deposited onto the worm-like GNSs. When used as anode materials in lithium ion batteries (LIBs), the TiO 2 –GNS composites deliver a stable capacity of ~ 140 mAh g − 1 after 100 cycles at a specific current of 100 mA g − 1 as well as superior rate capability, accounting for a sustainable 95 mAh g − 1 capacity at a specific current of 1200 mA g − 1 . It is believed that the remarkable electrochemical performance lied in the unique features of the composites, i.e., the amorphous nature of the TiO 2 films and the large surface area of GNSs. The former rendered short Li + diffusion pathways in TiO 2 thin film, while the latter offered excellent electronic conductivity as well as a large intimate contact area between the electrolyte and TiO 2 . This work laid a venue for designing new electrodes for high-performance LIBs. [ABSTRACT FROM AUTHOR]

The gram-scale synthesis of graphene based mesoporous SnO 2 composite (G-M-SnO 2 ) has been successfully realized based on kirkendall effect. When used as anode for lithium ion batteries, it delivers a high reversible capacity of 1354 mAhg −1 after 50 cycles at 100 mAg −1 and excellent rate capability of 664 mAhg −1 at 2 Ag −1 . The outstanding lithium storage performance mainly results from the synergistic effect of the ultrasmall SnO 2 and conductive graphene nanoparticles, which not only enhanced the conductivity of the whole electrode but also provide buffer matrix for the expansion of SnO 2 nanoparticles during charge-discharge process. Furthermore, the ultra-small size of SnO 2 shortens the diffusion length of Li + /e − in SnO 2 . [ABSTRACT FROM AUTHOR]

• A novel double heterojunction of CdS-SnS-SnS 2 supported on rGO was synthesized. • CdS-SnS-SnS 2 /rGO showed enhanced photocatalytic activity and durability. • rGO as an electron carrier facilitated the migration of photogenerated charge. • The double heterojunction efficiently suppressed fast electron-hole recombination. In this work, a novel CdS-SnS-SnS 2 /rGO photocatalyst with two tin valence states (Ⅱ and IV) was successfully synthesized by a one-pot solvothermal method. For comparison, CdS-SnS 2 /rGO (GCS2) with tin in only the IV valence state was made by the same method. Based on a series of characterizations, CdS, SnS and SnS 2 were shown to be successfully loaded onto the rGO surface. The introduction of rGO may increase charge carrier separation. The degradation efficiency increased gradually with increasing rGO loading content, and the optimum photocatalytic activity was observed at 6.0 wt% rGO loading content (GCS1), which achieved the efficient removal (84.46%) of ibuprofen over 60 min. Compared with GCS2, the CdS-SnS-SnS 2 /rGO composite exhibited significantly improved photocatalytic performance, which can be ascribed to the formation of a double heterostructure. rGO worked as a transfer mediator to transfer electrons from the conduction band (CB) of SnS to the CB of SnS 2 at the heterointerface, which then flowed to the CB of CdS because of another heterojunction, further enhancing the separation efficiency of photogenerated carriers. Therefore, this study highlights a novel double heterojunction system with a facial preparation method, visible light response and good recyclability, which is beneficial for environmental remediation. [ABSTRACT FROM AUTHOR]