Ahmed Abd El-Moneim

MnO2/carbon nanowall electrode for future energy storage application: effect of carbon nanowall growth period and MnO2 mass loading

Nanostructured MnO2 films with 50 and 100 μg cm−2 mass loadings supported on two dimensional (2D) stand-free carbon nanowalls (CNWs) were synthesized by anodic electrodeposition and investigated for supercapacitor application. The underlying CNW films of different growth periods, 12–24 s, were grown first by microwave plasma enhanced chemical vapor deposition on three dimensional (3D) nickel foam substrate. Tailoring the MnO2/CNW/Ni hybrid nanocomposite electrode with an optimized CNW growth period of 18 s and a MnO2 loading of 50 μg cm−2 achieves the best capacitive performance; it exhibits a specific capacitance of 1170 F g−1 at a galvanostatic charging–discharging current density of 1 mA cm−2 and retains 110% of its initial capacitance after 2000 cycles at a current density of 3 mA cm−2. The high density of atomic scale graphitic edges, large surface area with optimized defects and degree of crystallinity of CNWs in conjunction with an efficient utilization of MnO2 nanoparticles facilitated rapid electron and ion transport and electrochemical cyclic stability, hence offering the potential of unique capacitive behavior. These results demonstrate an exciting commercial potential for high performance, environmentally friendly and low-cost electrical energy storage devices based on the MnO2/CNW/Ni hybrid electrode.

Investigation of a New High Sensitive Micro-Electromechanical Strain Gauge Sensor Based on Graphene Piezoresistivity

A new strain gauge based on graphene piezoresistivity was fabricated by a novel low cost technique which suits mass production of micro piezoresistor sensors. The strain gauge consists of a monolayer graphene film made by chemical vapor deposition on a copper foil surface, and transferred to Si/SiO2 surface by using a polymethyl-methacrylate (PMMA) assisted transfer method. The film is shaped by laser machine to work as a conductive-piezoresistive material between two deposited electrical silver electrodes. This method of fabrication provides a high productivity due to the homogeneous distribution of the graphene monolayer all over the Si/SiO2 surface. The experimentally measured gauge factor of graphene based device is 255, which promises a new strain gauge sensor of high sensitivity.

One-step fabrication of copper sulfide nanoparticles decorated on graphene sheets as highly stable and efficient counter electrode for CdS-sensitized solar cells

Quantum-dot-sensitized solar cells (QDSSCs) are thin-film photovoltaics and highly promising as next-generation solar cells owing to their high theoretical efficiency, easy fabrication process, and low production cost. However, the practical photoconversion efficiencies (PCEs) of QDSSCs are still far below the theoretically estimated value owing to the lack of an applicable design of the materials and electrodes. In this work, we developed a highly stable and efficient counter electrode (CE) from copper sulfide nanocrystals and reduced graphene oxide (Cu x S@RGO) for QDSSC applications. The Cu x S@RGO electrocatalyst was successfully prepared by a facile one-pot hydrothermal method, then directly applied to a fluorine-doped tin oxide (FTO)-coated glass substrate by the simple drop-casting technique. Owing to the synergistic effect between Cu x S nanocrystals and conductive RGO sheets, the Cu x S@RGO CE showed high electrocatalytic activity for polysulfide electrolyte reduction. A CdS QDSSC based on the Cu x S@RGO CE yielded a high and reproducible PCE of 2.36%, exceeding those of 1.57 and 1.33% obtained with the commonly used Cu2S/brass and Pt CEs, respectively. Moreover, the QDSSC with the Cu x S@RGO CE showed excellent photostability in a light-soaking test without any obvious decay in the photocurrent, whereas the cell based on the Cu2S/brass CE was severely degraded.

Graphene film development on flexible substrate using a new technique: temperature dependency of gauge factor for graphene-based strain sensors

Purpose – The purpose of this paper is to develop a new simple technique to synthesize graphene film on a flexible polyethylene terephthalate (PET) substrate and applied as a strain sensor. Design/methodology/approach – Graphene film was synthesized using laser treatment of graphene oxide (GO) film deposited on PET substrate. A universal laser system was used to simultaneously reduce and pattern the GO film into laser reduced graphene oxide (LRGO) film. Findings – The laser treatment synthesizes a multilayer graphene film with overlapped flakes, which shows structure integrity, mechanical flexibility and electrical conductivity of 1,330 S/m. The developed LRGO/PET film was used to fabricate a high sensitivity strain sensor. The sensitivity and temperature dependency of its gauge factor (GF) was examined at applied strains up to 0.25 per cent and operating temperatures up to 80°C. The fabricated sensor shows stable GF of approximately 78 up to 60°C with standard error of the mean not exceeding approximatel...

Improving the stability of CdS quantum dot sensitized solar cell using highly efficient and porous CuS counter electrode

Thin films from copper sulfide (CuxS) are the most commonly used electrocatalyst counter electrodes (CEs) for high-efficiency quantum dot sensitized solar cells (QDSSCs) because of its superior electrocatalytic activity in the presence of polysulfide electrolytes. In addition to the stability issues, the CuxS CEs are usually prepared by complicated, costly, time consuming, and less productive methods, which are inadequate for practical applications of QDSSCs. In this work, we present a simple approach for fabricating an efficient and stable CE for QDSSCs using pure covellite phase CuS nanoparticles (NPs) pre-prepared via a cheap, fast, and scalable chemical method. The catalyst ink was obtained by mixing the as-prepared CuS NPs with polyvinylidene fluoride, as a polymeric binder, which was then directly applied to a conductive fluorine-doped tin oxide substrate without any further high temperature post treatment. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and Tafel polarization...

A Study of Promoters Effect on Fe on Reduced Graphene Oxide Catalyst Performance in Fischer-Tropsch Synthesis System

In this work the Fischer-Tropsch synthesis reaction was catalyzed by reduced graphene oxide supported Fe nanoparticles catalysts in a fixed bed reactor. Also the influence of promotion by K and Mn on the catalytic activity of Fe nanoparticles was investigated. The systems showed acceptable CO conversions reaching as high as 96.2%. The selectivities of the C1-5 ranged from 38 to 62%. There was a very high CO2 selectivity which was explained by incomplete reduction of the catalysts. The Anderson-Schultz-Flory parameter was calculated and varied between 0.25 and 0.3. The strongest promoting effect was achieved by the K promoter which tended to reduce light product selectivities and CO2 production the most.

Flexible Interdigital In-Plane Supercapacitor Based on Laser Reduced Graphene Oxide (LRGO)

We Demonstrated and Verified the Use Of laser Reduced Graphene Oxide (LRGO) Supported on Polyethylene Terephthalate (PET) Substrate for Flexible Supercapacitor Applications. we Compared the Interdigitated in-Plan Structure with the Conventionally Stacked Structure Supercapacitor. To understand the Role of Increasing the Number of Sub-Electrodes per Unit Area, Three electrode Architecture of 2, 4, and 6 Sub-Electrodes were Studied. Polymeric Gel electrolyte of Poly (vinyl Alcohol) and Phosphoric Acid (PVA-H3PO4)was Selected for the Realization of the Cells. the Interdigital in – Planesupercapacitor with 6 Sub-Electrodes I-PS(6) Showed a Volumetric Capacitance Of9.3 Fcm-3 Opposed to 3.6, 0.6, 0.5 Fcm-3 for I-PS(4), I-PS(2), and conventional Structure Supercapacitor, Respectively at 0.1 Ma Cm-2 Current Density. the Maximum Stated Energy Density of 0.409 Mwh.cm-3and Power Density of 994.6 W.cm-3 were for I-PS(6). our Results clearly Showed that the LRGO can Hold much Promise for Low-Cost, Easy, and Scalablesupercapacitor Fabrication.

LASER Reduced Graphene on Flexible Substrate for Strain Sensing Applications: Temperature Effect on Gauge Factor

New technique is developed to synthesize graphene film on flexible substrate for strain sensing applications. A flexible graphene/Poly-ethylene Terephthalate (PET) strain sensor based on graphene piezoresistivity is produced by a new simple low cost technique. Graphene oxide film on PET substrate is reduced and patterned simultaneously using 2 Watt CO2 LASER beam. The synthesized graphene film is characterized by XRD, FT-IR, SEM, and Raman techniques. Commercial strain gauges are used to predict experimentally the gauge factor (GF) of the graphene film at different values of applied strain. The stability of the graphene film and its GF are studied at different operating temperatures. The fabricated sensor showed high GF of 78 with great linearity and stability up to 60 °C.

Nanocomposite Multilayer Fibrous Membrane for Sustained Drug Release

Building on the success of the many earlier studies on electrospun nanofibers technique which provide a non woven web to the order of nanometers introducing superior properties such as large surface area, superior mechanical properties and ease of implementation in many fields of applications, elctrospun nanofibers became an important issue for many researchers in various fields. Using elctrospun fibers as a drug carrier, is showing a huge promising potential for the future of biomedical application. Our work in this research is focusing on engineering a system to control the drug release profile rate especially for wound dressing. Nanocomposite multilayer fibrous membranes, using electrospinning method, have been developed for drug release in form of sandwich structure of three layers. Inner layer which is kept Polycaprolactane (PCL) loaded with drug. The two outer layers have been changed with different blend ratios between Chitosan (Cs) and PCL as follow [0%:100% Cs:PCL, 30%:70% Cs:PCL, 50%:50% Cs:PCL, 70%:30% Cs:PCL]. The results showed that the release rate has been affected dramatically by the outer layer composition. SEM images showed changing in the morphology due to the different in the composition of outer layer.

Effect of chitosan addition on the structure and capacitive characteristics of electrodeposited manganese oxides

Nano-structured MnO2-chitosan hybrid composite electrodes containing low and high chitosans Mw were synthesized by one-step cathodic electrodeposition on nickel foam substrate for electrochemical capacitors (ECs) application. The effect of chitosan molecular weight (Mw) on the structure and capacitive behaviour of the tailored electrodes was examined. The electrodes have been characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. The presence of CH promotes both ion and electron transport in the matrix of MnO2. Furthermore, the use of CH with its inherent binding properties allowed the formation of adherent and cracks free deposits. The MnO2-chitosan hybrid nanocomposite electrodes showed better specific capacitance and rate capability than MnO2 electrode. The highest specific capacitance of 424 F/g was obtained for the MnO2-chitosan composite electrode with low chitosans Mw at a current density of 1 mA/cm2. The electrode retained a very stable capacitance over 400 cycles by charging and discharging at 3 mA/cm2, as the capacity loss is only 3%, indicative of long term electrochemical cycling stability.