Simonkolleite-graphene foam composites and their superior electrochemical performance

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. The effect of the activating agent/precursor ratio and the ex-situ N-doping on the structural, textural, electrochemical properties of the porous carbons was studied. The ex-situ N-doped porous carbon with an optimum amount of KOH to PS exhibited the best capacitance performance with a specific surface area (SSA) of 1442 m² g^-1 and an enriched nitrogen content (3.2 at %). The fabricated symmetric device exhibited a 251.2 F g^-1 specific capacitance per electrode at a gravimetric current of 1 A g^-1 in aqueous electrolyte (2.5 M KNO₃) at a wide cell voltage of 2.0 V. A specific energy of 35 Wh kg^-1 with a corresponding specific power of 1 kW kg^-1 at 1 A g^-1 was delivered with the device still retaining up to 22 Wh kg^-1 and a 20 kW kg^-1 specific power even at 20 A g^-1. Moreover, long term device stability was exhibited with an 83.2% capacity retention over 20 000 charge/discharge cycles and also a good rate capability after 180 h of floating at 5 A g^-1. This great performance of the symmetric supercapacitor can be correlated to the surface porosity and post nitrogen-doping effect which increased the electrochemically-active sites resulting in a remarkable charge storage capability.

Electron paramagnetic resonance and microstructural insights into the thermal behavior of simonkolleite nanoplatelets

The thermal decomposition process of simonkolleite, at 500 °C was monitored by EPR and electron microscopy. The experimental data indicate that after an 1 h at 500 °C, three morphologies can be observed from the thermal decomposition of ZHC.

Potential anti-cancer and anti-Candida activity of Zn-derived foams

Zinc (Zn)-derived foams have been prepared from an alkaline electrolyte solution by galvanostatic electrodeposition under different conditions. A detailed physico-chemical characterization was performed by Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). A pioneer application of these foams in medical implant-related applications was investigated. The in vitro behaviour of these Zn-derived foams in simulated physiological conditions was studied. The results revealed that the presence of zinc oxide was important enough to change the in vitro behaviour of these materials. The potential of these Zn-derived foams in inhibiting bone cancer cell proliferation - osteoscarcoma cells - and important pathogenic fungi responsible for implant-related infections -Candida albicans- was examined. Furthermore, the foams were evaluated for cytocompatibility with normal human osteoblasts. The results obtained allowed us to conclude that Zn-derived foams have an interesting potential for anti-cancer and anti-Candida activity, targeted for bone-related implant applications, suggesting that this novel material may have potential for further clinical studies.

Ag Nanoparticles-Modified 3D Graphene Foam for Binder-Free Electrodes of Electrochemical Sensors

Ag nanoparticles-modified 3D graphene foam was synthesized through a one-step in-situ approach and then directly applied as the electrode of an electrochemical sensor. The composite foam electrode exhibited electrocatalytic activity towards Hg(II) oxidation with high limit of detection and sensitivity of 0.11 μM and 8.0 μA/μM, respectively. Moreover, the composite foam electrode for the sensor exhibited high cycling stability, long-term durability and reproducibility. These results were attributed to the unique porous structure of the composite foam electrode, which enabled the surface of Ag nanoparticles modified reduced graphene oxide (Ag NPs modified rGO) foam to become highly accessible to the metal ion and provided more void volume for the reaction with metal ion. This work not only proved that the composite foam has great potential application in heavy metal ions sensors, but also provided a facile method of gram scale synthesis 3D electrode materials based on rGO foam and other electrical active materials for various applications.

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

Manganese phosphate (Mn₃(PO₄)₂ hexagonal micro-rods and (Mn₃(PO₄)₂ 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 Mn₃(PO₄)₂ hexagonal micro-rods and Mn₃(PO₄)₂/GF composites. It was observed that the specific capacitance of Mn₃(PO₄)₂/GF composites with different GF mass loading increases with mass loading up to 100mg, and then decreases with increasing mass loading up to 150mg. The specific capacitance of Mn₃(PO₄)₂/100mg GF electrode was calculated to be 270Fg^-1 as compared to 41Fg^-1 of the pristine sample at a current density of 0.5Ag^-1 in a three-electrode cell configuration using 6M KOH. Furthermore, the electrochemical performance of the Mn₃(PO₄)₂/100mg GF electrode was evaluated in a two-electrode asymmetric cell device where Mn₃(PO₄)₂/100mg GF electrode was used as a positive electrode and activated carbon (AC) from coconut shell as a negative electrode. AC//Mn₃(PO₄)₂/100mg GF asymmetric cell device was tested within the potential window of 0.0-1.4V, and showed excellent cycling stability with 96% capacitance retention over 10,000 galvanostatic charge-discharge cycles at a current density of 2Ag^-1.

Enhanced electrochemical response of activated carbon nanostructures from tree-bark biomass waste in polymer-gel active electrolytes

The enhancement in current response and operating voltage is observed based on the nature of the electrolyte and conductive additive used. This serves to enhance ion penetration and transport across the pores within the AC nanostructure network.

High performance asymmetric supercapacitor based on CoAl-LDH/GF and activated carbon from expanded graphite

An asymmetric supercapacitor based on CoAl-LDH/GF composite and activated carbon from expanded graphite (AEG) in aqueous 6 M KOH electrolyte is reported with excellent electrochemical properties.

Effect of additives on the corrosion mechanism of nanocrystalline zinc–nickel alloys in an alkaline bath

Bright Zn–Ni alloys can be obtained from the bath with additives. The mechanism of better corrosion resistance of bright Zn–Ni alloys compared to dull Zn–Ni alloys was analyzed by XPS and EIS.