Aminopyrene functionalized reduced graphene oxide as a supercapacitor electrode

In this work, we report on the structural and electrochemical properties of aminopyrene functionalized reduced graphene oxide (Ap-rGO) for its suitability as a supercapacitor electrode. The Ap-rGO is prepared by sonicating a suspension of rGO with aminopyrene and the filtered sediment is subjected to spectroscopy studies and electrochemical studies. Spectroscopy studies reveal the successful functionalization of aminopyrene onto Ap-rGO through π–π interactions. Electrochemical analyses of Ap-rGO show a substantial increase in the specific capacitance for Ap-rGO (160 F g−1 at 5 mV s−1) compared to the non-functionalized rGO (118 F g−1 at 5 mV s−1). The enhancement is shown to be the pseudocapacitance arising from the electron donating effect of the amine group and the electron accepting effect of rGO, which enable facile electron transfer between the surface-bound amine group and rGO. The Ap-rGO has desirable charge storage properties such as low series resistance (0.4 Ω) and superior cycling stability (85% after 5000 cycles). Furthermore, the Ap-rGO has 1.5 fold higher energy density than the non-functionalized rGO electrode, thereby making it suitable as a deployable supercapacitor electrode

Graphene functionalized carbon felt/graphite felt fabrication as electrodes for vanadium redox flow batteries (VRBs): A review

The growth in the development of renewable energy sources has led to tremendous attention to the research in energy storage systems. One of the electrochemical energy storage systems that have shown great potential to be used on a large scale is vanadium redox flow batteries (VRBs), as they possess flexible designs, long life cycles, and high energy density. Carbon felts (CF), and graphite felts (GF) have commonly been used as electrodes in VRBs. To improve market penetration using VRB technology, researchers have focused on electrode modifications to increase the power density and rate capabilities of VRBs. One of the carbon-based modifications which have shown significant improvements in the performance of VRBs is the use of graphene, which has outstanding electrochemical and physical characteristics as an electrocatalyst. In this review, electrochemical, physical, and other methods which have been reported in the graphene functionalization of graphite felt/carbon felt are discussed. The working principle and limiting methods were elaborated on and discussed for each method. Finally, recommendations for future developments are also highlighted

One-step production of pyrene-1-boronic acid functionalized graphene for dopamine detection

A facile molecular wedging method is used to exfoliate graphite flakes into graphene sheets, with concurrent functionalization to form pyrene-1-boronic acid functionalized graphene (PBA/G). Different techniques are used to characterize the prepared materials such as field emission scanning electron microscope, energy dispersive X-ray analyzer, Raman, Fourier transformed infrared spectroscopy and fluorescence spectroscopy to evaluate their structural and morphological characteristics. The intercalation of PBA into graphite sheets, followed by exfoliation can be observed under the electron microscope. Elemental analyses show that the PBA acts more than intercalant, it is functionalized onto the graphene sheets upon exfoliation to form PBA/G. Raman analysis indicates PBA/G has a lower number of graphene layers as a result of successful exfoliation by PBA. Electrochemical impedance studies show that the PBA/G possesses high affinity for dopamine through the diol groups interaction, which renders it to have enhanced detection for dopamine

Phenothiazine-functionalized rgo for electrochemical capacitor

The functionalization arose as a technique to improve the physicochemical properties of the reduced graphene oxide (rGO) and consequently enhance the supercapacitor performance. The functionalization compound, phenothiazine (PTZ) introduces nitrogen and sulfur heteroatoms into rGO via the one-pot hydrothermal method. Incorporation of PTZ on the rGO sheets in PTZ-rGO 5 contributes to the high surface area (163.49 m2 g−1) and pore volume (0.3187 cm3 g−1) properties. Contradictory, overloaded PTZ not only shows a lower reduction effect but also reduces the amount of PTZ functionalized in the PTZ-rGO and consequently shows lower electrochemical performance. The excellent properties enable PTZ-rGO 5 enable it to achieve 119.5 F g−1 at 0.5 A g−1 for its specific capacitance and drive it to be the promising electrode material for supercapacitors

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

High Surface Area Activated Carbon from Rice Husk as a High Performance Supercapacitor Electrode

In this study, we report on the application of high surface area activated carbon (AC) derived from rice husks as a supercapacitor electrode. The prepared AC was free from Brønsted or Lewis acid sites, thus making the electrical double layer capacitance as the main charge storage mechanism. Three samples of AC with different surface areas were prepared at different activation temperatures and studied electrochemically using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. All AC samples exhibited good electrochemical performance as supercapacitor electrode. The maximum specific capacitance (147 F g−1) was obtained by the AC sample (surface area of 2696 m2 g−1) which was prepared at an activation temperature of 850 °C. Detailed impedance studies revealed the low resistivity (0.23 Ω) of AC sample and the fast frequency response (0.11 s) of the supercapacitor electrode

Pseudocapacitive performance of phenothiazine functionalized graphene aerogel

This study utilizes light adsorbing molecule, phenothiazine (PTZ) to reduce graphene oxide (GO) and functionalize into PTZ-rGO aerogel (PTZ-rGO). The UV excited PTZ reduces GO via electron transfer while PTZ is simultaneously oxidized and functionalized onto rGO to produce PTZ-rGO aerogel. The optimum incorporation of PTZ on rGO sheets renders good electrochemical active surface area of 495.71 m2 g−1 and enhances the diffusion behavior up to 41.92%. This pseudocapacitive effect and the excellent surface property provide promising charge storage results of 235.5 F g−1 at 0.5 A g−1. Furthermore, the stable charge-discharge cycles with 92% capacitance retention after 10,000 cycles render it an excellent electrode material for supercapacitor fabrication

Design and construction of a small open-air wind tunnel without contraction and diffuser

This paper presents the design and construction of a small open jet wind tunnel without the contraction and diffuser. The wind tunnel is intended for experimental testing of models in a controlled airflow environment and its design offers an affordable and practical solution for researchers and students to conduct their aerodynamic experiments on small-scale models. The paper outlines key considerations for designing and constructing the wind tunnel, including selected blower fan and design of the fan holder structure. The wind tunnel is successfully constructed and tested, and the results have shown that the airflow with an average of 4 m/s and turbulence intensity of 15%. Through its capacity to provide a wide range of turbulence intensities (i.e. 15% - 89%), this wind tunnel empowers researchers to explore an extensive spectrum of real-world conditions, ensuring that the experimental data more authentically mirrors the dynamic characteristics of outdoor environments. This enhanced versatility in turbulence intensity is of particular importance, especially given the marked variations in turbulence levels that have been evident across the different urban locales. Consequently, this study not only furnishes the practical guidance for constructing small open jet wind tunnels but also highlights the critical significance of regulating turbulence intensity, varying between 89% at a distance of 200 mm and 15% at 2000 mm from the outlet to ensure precise experimental fidelity

1-Pyrenebutyric Acid Functionalized Reduced Graphene Oxide (1-Pb-Rgo) Energy Storage

Supercapacitors are a class of energy storage device which has high energy density and high power density. As a material with unique 2D structure as well as outstanding physical properties such as high electrical conductivity and large surface area, graphene demonstrates great potential to be the electrode material for supercapacitors. Despite graphene showing theoretical surface area as high as 2630 m2/g, results acquired showed that not all the surface area were utilized. This could be due to the tendency of the graphene layers to restack. In this work, 1-pyrenebutyric acid (1-PB) was anchored to graphene with the pyrenyl group via π-π stacking to prevent the restacking of graphene layers. The successful functionalization of 1-PB on the hydrophobic surface of rGO was characterized with UV-Vis Spectroscopy and Fourier Transformed Infrared Spectroscopy (FTIR). The electrochemical performance of 1-PB-rGO was studied through cyclic voltammetry (CV), galvanostatic charge-discharge (CD) and electrochemical impedance spectroscopy (EIS). Using 6 M KOH as the electrolyte, we obtained an enhanced specific capacitance for 1-PB-rGO. These findings indicates that the non-covalent functionalization of 1-PB on rGO enhances the capacitive storage ability and it show potential as an electrode material in the energy storage application

Current trend in small scale solar updraft tower designs: a review

Solar updraft tower is a renewable energy technology which harvest heat generated from the sun. This technology has great potential in locations where sun is available around the year. The main components for this technology are chimney, collector and turbine. The chimney will guide the wind from collector flow upward where the wind will flow through turbine. As carbon footprint becoming more concerning, a small-scale solar tower updraft is one of great solution to alleviate this conundrum. Hence the chimney and collector design play important roles in solar updraft tower performance. Additionally, types of collector ground used and turbine blade technology for harvesting energy can further improve the performance of small-scale solar updraft tower. This paper review current small-scale design solar updraft tower