In situ growth of redox-active iron-centered nanoparticles on graphene sheets for specific capacitance enhancement

AbstractA fast and facile approach is proposed to enhance the specific capacitance of N-Methyl-2-pyrrolidone (NMP)-exfoliated graphene. Redox-active nickel ferricyanide (NiFeCN) nanoparticles were grown on the surface of graphene sheets using a simple co-precipitation method. Apart from the synergetic effect of graphene as double layer capacitance and NiFeCN as pseudocapacitance in specific capacitance enhancement, the NiFeCN nanoparticles served as the spacer to prevent the graphene sheets agglomeration. The NiFeCN/graphene exhibited specific capacitance of 113.5Fg−1, which was 2 times higher than the NMP-exfoliated graphene (52Fg−1) and 6times higher than the pure NiFeCN (18Fg−1). The findings suggested the NiFeCN/graphene could be the potential candidate for supercapacitor electrode

Removal of cadmium from aqueous solution by dried water hyacinth, (Eichhornia crassipes)

Water hyacinth (E. crassipes) approaches being a scourge in many parts of the world, choking waterways and hindering transport upon them. At the same time it is known to readily abstract heavy metal ions from water and, thus, aids in the removal of heavy metals found in such waters. This study considers the possibility of using dried parts of the plant as an inexpensive adsorbent for the removal of heavy metals from cadmium solution. Water hyacinth is dried and used as biosorbent as removal of cadmium in aqueous solution. Parameters that are used for these studies are dosage of biosorbent, contact time, pH and temperature. The analysis was done by using Atomic Absorption Spectroscopy where initial concentration was 20 mg/L; the amount of biosorbent was from 0.4 to 4 g/L, pH range between 2 to 10, contact time between 10 until 50 min, and temperature range between 25 until 60 degree celcius. The best conditions were found to be biosorbent at dose of 2 g/L, pH of 7, and contact time of 40 min and 35oC for temperature. The results obtained show that the dried Water Hyacinth performed well for the removal of cadmium as heavy metals. As a low cost adsorbent, Water Hyacinth can preferable for removal of heavy metals from wastewaters

IN SITU growth redox-active iron-centered particles on graphene sheets for specific capacitance enhancement

Graphene is a unique two-dimensional carbon material having good conductivity, stable chemical properties, and good mechanical properties with large surface area (- 2600 M2 g). Due to the outstanding mechanical and electrical properties, graphene is proposed as an electrode material for supercapacitor applications. Nevertheless, graphene has issues where in the dry state it is tends to agglomerate which hindering its full capability in electrochemical performance. Therefore, an improvement is needed in order to resolve the re-stacking issue. In this study, a facile approach is proposed to enhance the specific capacitance of (N-methylpyrrolidone) NMP-exfoliated graphene. Redox-active nickel hexacyanoferrate (NiFeCN) nanoparticles were grown on the surface of graphene sheets using a co-precipitation method. Apart from the synergetic effect of graphene and NiFeCN in the specific capacitance enhancement, the NiFeCN nanoparticles served as the spacer for graphene sheets to prevent the agglomeration between graphene sheets. This combination performed as a hybrid composite nanomaterial which possessed both electrochemical double layer capacitor (EDLC) and pseudo capacitance. With the above motivation, a graphene-based nanocomposite material has been extensively studied in this thesis. All the materials examined were prepared via simple co-precipitation synthesis techniques with different range of composite ratios (NiFeCN/G-10, NiFeCNIG-25, NiFeCN/G-50, NiFeCNIG-75 and NiFeCNIG-90). Characterization has been done using Fourier transform infrared spectroscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy and field emission scanning electron microscope. Their electrochemical properties were evaluated for supercapacitors using three electrode system configurations. From this experiment, a nanocomposite at a ratio of 25: 75 (NiFeCN/G-25) is shown to have a very high specific capacitance of 113.5 F g-iwhich is 2 times higher than the NMP-exfoliated graphene (52 F g-i) and 6 times higher than the pure NiFeCN (18 F g-i). The findings suggest that the NiFeCN/graphene could be the potential candidate for supercapacitors electrode. The enhanced electrochemical performance of these nanocomposite materials could be attributed to the dual contributions of graphene and nanoparticles. The results of this study indicated the graphene nanocomposite has great potential for application to practical energy storage devices

Functionalized Graphene as Energy Storage Supercapacitor

Supercapacitor is an energy storage device that store energy via accumulation of electrical charges at the electrode double layer. It received much attention in scientific community due to its high power density (higher than battery and fuel cell) and high energy density (higher than conventional capacitor). Commercial available supercapacitors mostly focus on activated carbon as the electrode material due to its cost efficient and large surface area with good conductivity. The booming of graphene in research community has drawn the attention of supercapacitor manufacturers to look into this Nobel Prize winning nanomaterials, as it possesses superb conductivity and enhanced surface area. Numerous works on the graphene as supercapacitor electrode had been published. However, graphene itself could not store much energy as it solely relies on double layer capacitance. The incorporation of pseudocapacitance material to make the hybrid supercapacitor is a solution to increase the charge storage ability. The synergetic effect of double layer capacitance and pseudocapacitance could provide the enhancement of capacitance whilst maintaining the long term cyclability. In this work, we report a simple co-precipitation method to produce graphene/Ni3(Fe(CN)6)2 composite as hydrid supercapacitor electrode. Ni3(Fe(CN) is a good candidate to replace costly ruthenium in enhancing pseudocapacitance. With sonication and coprecipitation,Ni3(Fe(CN)6) nanoparticles were intercalated between graphene interlayer sheets, as confirmed by microscopic and spectroscopic analysis. The electrode was tested electrochemically and results show that graphene extended the operating voltage of Ni23(Fe(CN)6) and the specific capacitance was enhanced by Ni3(Fe(CN)6)2. The energy density of graphene/Ni was found to be increased by at least 2 folds as compared to Ni3(Fe(CN)6)alone. The works suggest that the graphene/Ni 3(Fe(CN)6)22 is a good electrode material for high energy supercapacitor

In Situ Growth of Redox-Active Iron-Centered Particles On Graphene Sheets for Specific Capacitance Enhancement

A fast and facile approach is proposed to enhance the specific capacitance of N-Methyl-2-pyrrolidone (NMP)–exfoliated graphene. Redox–active nickel ferricyanide (NiFeCN) nanoparticles were grown on the surface of graphene sheets using a simple co–precipitation method. Apart from the synergetic effect of graphene as double layer capacitance and NiFeCN as pseudocapacitance in specific capacitance enhancement, the NiFeCN nanoparticles served as the spacer to prevent the graphene sheets agglomeration. The NiFeCN/graphene exhibited specific capacitance of 113.5 F g-1, which was 2 times higher than the NMP–exfoliated graphene (52 F g-1) and 6 times higher than the pure NiFeCN (18 F g-1). The findings suggested the NiFeCN/graphene could be the potential candidate for supercapacitors electrode

In situ growth of redox-active iron-centered nanoparticles on graphene sheets for specific capacitance enhancement

A fast and facile approach is proposed to enhance the specific capacitance of N-Methyl-2-pyrrolidone (NMP)-exfoliated graphene. Redox-active nickel ferricyanide (NiFeCN) nanoparticles were grown on the surface of graphene sheets using a simple co-precipitation method. Apart from the synergetic effect of graphene as double layer capacitance and NiFeCN as pseudocapacitance in specific capacitance enhancement, the NiFeCN nanoparticles served as the spacer to prevent the graphene sheets agglomeration. The NiFeCN/graphene exhibited specific capacitance of 113.5 F g−1, which was 2 times higher than the NMP-exfoliated graphene (52 F g−1) and 6 times higher than the pure NiFeCN (18 F g−1). The findings suggested the NiFeCN/graphene could be the potential candidate for supercapacitor electrode