Impact of Thermally Reducing Temperature on Graphene Oxide Thin Films and Microsupercapacitor Performance.

In this work, a thermally reduced graphene oxide (TRGO) thin film on microscopic glass was prepared using spray coating and atmospheric pressure chemical vapour deposition. The structure of TRGO was analysed using X-ray diffraction (XRD) spectroscopy, scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible spectroscopy (UV-Vis) suggesting a decrease in oxygen functional groups (OFGs), leading to the restacking, change in colour, and transparency of the graphene sheets. Raman spectrum deconvolution detailed the film's parameters, such as the crystallite size, degree of defect, degree of amorphousness, and type of defect.

Binary vanadium pentoxide carbon-graphene foam composites derived from dark red hibiscus sabdariffa for advanced asymmetric supercapacitor.

The development of advanced electrode materials derived from biomass for the next generation of energy storage devices, such as supercapacitors with high specific energy and specific power coupled with a good cycle stability, is required to meet the high demand for electric vehicles and portable devices. In this study, sustainable binary vanadium pentoxide carbon-graphene foam composites (VO@C-RHS/GF) were synthesized using a solvothermal method. The X-ray diffraction, Raman and FTIR techniques were used to study the structural properties of the composites (VO@C-RHS/20 mg GF and VO@C-RHS/40 mg GF).

Novel Thermally Reduced Graphene Oxide Microsupercapacitor Fabricated via Mask-Free AxiDraw Direct Writing.

We demonstrate a simple method to fabricate all solid state, thermally reduced graphene oxide (TRGO) microsupercapacitors (µ-SCs) prepared using the atmospheric pressure chemical vapor deposition (APCVD) and a mask-free axiDraw sketching apparatus. The Fourier transform infrared spectroscopy (FTIR) shows the extermination of oxygen functional groups as the reducing temperature (RT) increases, while the Raman shows the presence of the defect and graphitic peaks. The electrochemical performance of the µ-SCs showed cyclic voltammetry (CV) potential window of 0-0.

Enhanced Electrochemical Behavior of Peanut-Shell Activated Carbon/Molybdenum Oxide/Molybdenum Carbide Ternary Composites.

Biomass-waste activated carbon/molybdenum oxide/molybdenum carbide ternary composites are prepared using a facile in-situ pyrolysis process in argon ambient with varying mass ratios of ammonium molybdate tetrahydrate to porous peanut shell activated carbon (PAC). The formation of MoO and MoC nanostructures embedded in the porous carbon framework is confirmed by extensive structural characterization and elemental mapping analysis. The best composite when used as electrodes in a symmetric supercapacitor (PAC/MoO/MoC-1//PAC/MoO/MoC-1) exhibited a good cell capacitance of 115 F g with an associated high specific energy of 51.

Tuning the Nanoporous Structure of Carbons Derived from the Composite of Cross-Linked Polymers for Charge Storage Applications.

Controlling the porosity of carbon-based electrodes is key toward performance improvement of charge storage devices, e.g., supercapacitors, which deliver high power via fast charge/discharge of ions at the electrical double layer (EDL).

Onion-derived activated carbons with enhanced surface area for improved hydrogen storage and electrochemical energy application.

High surface area activated carbons (ACs) were prepared from a hydrochar derived from waste onion peels. The resulting ACs had a unique graphene-like nanosheet morphology. The presence of N (0.

Bullet-like microstructured nickel ammonium phosphate/graphene foam composite as positive electrode for asymmetric supercapacitors.

Unique microstructured nickel ammonium phosphate Ni(NH)(PO)·4HO and Ni(NH)(PO)·4HO/GF composite were successfully synthesized through the hydrothermal method with different graphene foam (GF) mass loading of 30, 60 and 90 mg as a positive electrode for asymmetric supercapacitors. The crystal structure, vibrational mode, texture and morphology of the samples were studied with X-ray diffraction (XRD), Raman spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis and scanning electron microscopy (SEM). The prepared materials were tested in both 3-and 2-electrode measurements using 6 M KOH electrolyte.

Ex-situ nitrogen-doped porous carbons as electrode materials for high performance supercapacitor.

Nitrogen (N) doping of porous carbon materials is an effective strategy for enhancing the electrochemical performance of electrode materials. Herein, we report on ex-situ (post) nitrogen-doped porous carbons prepared using a biomass waste, peanut shell (PS) as a carbon source and melamine as the nitrogen source. The synthesis method involved a two-step mechanism, initial chemical activation of the PS using KOH and post N-doping of the activated carbon.

Nitridation Temperature Effect on Carbon Vanadium Oxynitrides for a Symmetric Supercapacitor.

In this work, porous carbon-vanadium oxynitride (C-VNO) nanostructures were obtained at different nitridation temperature of 700, 800 and 900 °C using a thermal decomposition process. The X-ray diffraction (XRD) pattern of all the nanomaterials showed a C-VNO single-phase cubic structure. The C-VNO obtained at 700 °C had a low surface area (91.

Effect of porosity enhancing agents on the electrochemical performance of high-energy ultracapacitor electrodes derived from peanut shell waste.

In this study, the synthesis of porous activated carbon nanostructures from peanut (Arachis hypogea) shell waste (PSW) was described using different porosity enhancing agents (PEA) at various mass concentrations via a two-step process. The textural properties obtained were depicted with relatively high specific surface area values of 1457 m g, 1625 m g and 2547 m g for KHCO KCO and KOH respectively at a mass concentration of 1 to 4 which were complemented by the presence of a blend of micropores, mesopores and macropores. The structural analyses confirmed the successful transformation of the carbon-containing waste into an amorphous and disordered carbonaceous material.

Electrochemical analysis of Na-Ni bimetallic phosphate electrodes for supercapacitor applications.

Bimetallic sodium-nickel phosphate/graphene foam composite (NaNi(PO)/GF) was successfully synthesized using a direct and simple precipitation method. The hierarchically structured composite material was observed to have demonstrated a synergistic effect between the conductive metallic cations and the graphene foam that made up the composite. The graphene served as a base-material for the growth of NaNi(PO) particles, resulting in highly conductive composite material as compared to the pristine material.

Deciphering the Structural, Textural, and Electrochemical Properties of Activated BN-Doped Spherical Carbons.

In this study, the effect of K₂CO₃ activation on the structural, textural, and electrochemical properties of carbon spheres (CSs) and boron and nitrogen co-doped carbon spheres (BN-CSs) was evaluated. Activation of the CSs and BN-CSs by K₂CO₃ resulted in increased specific surface areas and I/I ratios. From the X-ray photoelectron spectroscopy (XPS) results, the BN-CSs comprised of 64% pyridinic-N, 24% pyrrolic-N and 7% graphitic-N whereas the activated BN-CSs had 19% pyridinic-N, 40% pyrrolic-N and 22% graphitic-N displaying the effect of activation on the type of N configurations in BN-CSs.

Malathion-filled trilayer polyolefin film for malaria vector control.

The emergence of pyrethroid resistance in mosquitoes is complicating malaria elimination efforts in Africa and alternative insecticides have to be considered for indoor residual spray. Unfortunately, the high volatility of WHO-approved organophosphate alternatives, e.g.

Green and scalable synthesis of 3D porous carbons microstructures as electrode materials for high rate capability supercapacitors.

Porous carbon nanostructures have long been studied because of their importance in many natural phenomena and their use in numerous applications. A more recent development is the ability to produce porous carbon materials with tuneable properties for electrochemical applications, which has enabled new research directions towards the production of suitable carbon materials for energy storage applications. Thus, this work explores the activation of carbon from polyaniline (PANI) using a less-corrosive potassium carbonate (KCO) salt, with different mass ratios of PANI and the activating agent (KCO as compared to commonly used KOH).

Three dimensional vanadium pentoxide/graphene foam composite as positive electrode for high performance asymmetric electrochemical supercapacitor.

The electrochemical performance of hydrothermal synthesized three dimensional (3D) orthorhombic vanadium pentoxide (VO) nanosheets and vanadium pentoxide/graphene foam (VO/GF) composites at different mass loading of GF were successfully studied. The optimized VO/GF-150 mg composite provided a high specific capacity of 73 mA h g, which was much higher than that the pristine VO (60 mA h g) nanosheets at a specific current of 1 A g. A hybrid capacitor was also fabricated by adopting a carbon-based negative electrode obtained from the pyrolysis of an iron-PANI polymer (C-Fe/PANI) mixture and the 3D VO/GF-150 mg composite as the positive electrode in 6 M KOH electrolyte.

Preparation of carbon nanofibers/tubes using waste tyres pyrolysis oil and coal fly ash derived catalyst.

In this study, two waste materials namely; coal fly ash (CFA) and waste tyres pyrolysis oil, were successfuly utilized in the synthesis of carbon nanofibers/tubes (CNF/Ts). In addition, Fe-rich CFA magnetic fraction (Mag-CFA) and ethylene gas were also used for comparison purposes. The carbons obtained from CFA were found to be anchored on the surface of the cenosphere and consisted of both CNTs and CNFs, whereas those obtained from Mag-CFA consisted of only multi-walled carbon nanotubes (MWCNTs).

Utilization of waste tyres pyrolysis oil vapour in the synthesis of Zeolite Templated Carbons (ZTCs) for hydrogen storage application.

In this study, we investigated the potential for use of waste tyre pyrolysis oil vapour as a carbon precursor in the synthesis of zeolite templated carbons (ZTC). With Zeolite 13X as the template, the ZTCs were synthesised using two methods namely: 1-step process which involved the carbonization of gaseous carbon precursor in the zeolite template (in this case, ethylene and pyrolysis oil vapour) and the 2-step synthesis method involved the impregnation of zeolite pores with furfural alcohol prior to carbonization of the gaseous carbon precursor. The replication of the zeolite 13X structural ordering was successful using both methods.

Correction: A high energy density asymmetric supercapacitor utilizing a nickel phosphate/graphene foam composite as the cathode and carbonized iron cations adsorbed onto polyaniline as the anode.

[This corrects the article DOI: 10.1039/C7RA12028A.].

A high energy density asymmetric supercapacitor utilizing a nickel phosphate/graphene foam composite as the cathode and carbonized iron cations adsorbed onto polyaniline as the anode.

This work presents the effect of different contents of graphene foam (GF) on the electrochemical capacitance of nickel phosphate Ni(PO) nano-rods as an electrode material for hybrid electrochemical energy storage device applications. Pristine Ni(PO) nano-rods and Ni(PO)/GF composites with different GF mass loadings of 30, 60, 90 and 120 mg were synthesised a hydrothermal method. The electrochemical behavior of pristine Ni(PO) and Ni(PO)/GF composites were analysed in a three-electrode cell configuration using 6 M KOH electrolyte.

Hydrothermal synthesis of manganese phosphate/graphene foam composite for electrochemical supercapacitor applications.

Manganese phosphate (Mn(PO) hexagonal micro-rods and (Mn(PO) with different graphene foam (GF) mass loading up to 150mg were prepared by facile hydrothermal method. The characterization of the as-prepared samples proved the successful synthesis of Mn(PO) hexagonal micro-rods and Mn(PO)/GF composites. It was observed that the specific capacitance of Mn(PO)/GF composites with different GF mass loading increases with mass loading up to 100mg, and then decreases with increasing mass loading up to 150mg.

High performance asymmetric supercapacitor based on molybdenum disulphide/graphene foam and activated carbon from expanded graphite.

Molybdenum disulphide which has a graphene-like single layer structure has excellent mechanical and electrical properties and unique morphology, which might be used with graphene foam as composite in supercapacitor applications. In this work, Molybdenum disulphide (MoS)/graphene foam (GF) composites with different graphene foam loading were synthesized by the hydrothermal process to improve on specific capacitance of the composites. Asymmetric supercapacitor device was fabricated using the best performing MoS/GF composite and activated carbon derived from expanded graphite (AEG) as positive and negative electrodes, respectively, in 6M KOH electrolyte.

High electrochemical performance of hybrid cobalt oxyhydroxide/nickel foam graphene.

In this study, we report the in-situ hydrothermal synthesis of mesoporous nanosheets of cobalt oxyhydroxide (CoOOH) on nickel foam graphene (Ni-FG) substrate, obtained via atmospheric pressure chemical vapour deposition (AP-CVD). The produced composite were closely interlinked with Ni-FG, which enhances the synergistic effect between graphene and the metal hydroxide, CoOOH. It is motivating that the synthesized CoOOH on the Ni-FG substrate showed a homogenous coating of well-ordered intersected nanosheets with porous structure.

Microwave-assisted synthesis of high-voltage nanostructured LiMn1.5Ni0.5O4 spinel: tuning the Mn3+ content and electrochemical performance.

The LiMn1.5Ni0.5O4 spinel is an important lithium ion battery cathode material that has continued to receive major research attention because of its high operating voltage (∼4.

Doping a semiconductor to create an unconventional metal.

Landau-Fermi liquid theory, with its pivotal assertion that electrons in metals can be simply understood as independent particles with effective masses replacing the free electron mass, has been astonishingly successful. This is true despite the Coulomb interactions an electron experiences from the host crystal lattice, lattice defects and the other approximately 10(22) cm(-3) electrons. An important extension to the theory accounts for the behaviour of doped semiconductors.

Large anomalous Hall effect in a silicon-based magnetic semiconductor.

Magnetic semiconductors are attracting great interest because of their potential use for spintronics, a new technology that merges electronics with the manipulation of conduction electron spins. (GaMn)As and (GaMn)N have recently emerged as the most popular materials for this new technology, and although their Curie temperatures are rising towards room temperature, these materials can only be fabricated in thin-film form, are heavily defective, and are not obviously compatible with Si. We show here that it is productive to consider transition metal monosilicides as potential alternatives.