Rizwan Raza | COMSATS Institute of Information Technology Lahore (original) (raw)
Papers by Rizwan Raza
Microelectronic Engineering
In this study, equilibrium geometry and band structure of oxygen-doped diamond have been investig... more In this study, equilibrium geometry and band structure of oxygen-doped diamond have been investigated based on density function theory (DFT) using VASP code. These calculations have shown that the highest occupied molecular orbital is localized at the oxygen atom. Moreover, C 4 AO bond lengths are equivalent to those of CAC bonds leading to no lattice distortions. Doping of oxygen into diamond seems to be thermodynamically favorable due to negative formation energy. Band structure calculations lead to the semiconducting behavior of oxygen-doped diamonds due to the creation of defects states inside the band gap extending to conduction band minimum. The spin projected density of states calculations illustrates significant contributions of O 2p states at the Fermi level without the appearance of appreciable magnetic moments on oxygen or on carbon atoms (for all C 1 -C 4 ) leading to its non-magnetic semi-conducting behavior with zero density of carriers at the Fermi level for both spin projections; O;"(E F ) = 0. Present DFT results verify our experimental findings that addition of oxygen into diamond lattice increases its conductivity so that oxygen-doped diamond films behave like a good semiconductor.
Our recent developments have been made on the single layer or electrolyte-free fuel cells using a... more Our recent developments have been made on the single layer or electrolyte-free fuel cells using a homogeneous mixed semi- and ion conducting layer which can function as the electrodes, anode and cathode, and electrolyte simultaneously. We have achieved near 800 mW/cm2 at 550oC. A number of material groups have also been developed for advanced SLFCs. This radical new invention has made this nice concept of SLFC into practical application and also opens a new fuel cell R&D strategy.
RSC Advances
We report a new energy conversion technology joining electrochemical and physical principles. Thi... more We report a new energy conversion technology joining electrochemical and physical principles. This technology can realize the fuel cell function but built on a different scientific principle. The device consists of a single component which is a homogenous mixture of ceria composite with semiconducting materials, e.g. LiNiCuZn-based oxides. The test devices with hydrogen and air operation delivered a power density of 760 mW cm−2 at 550 °C. The device has demonstrated a multi-fuel flexibility and direct alcohol and biogas operations have delivered 300–500 mW cm−2 at the same temperature. Device physics reveal a key principle similar to solar cells realizing the function based on an effective separation of electronic and ionic conductions and phases within the single-component. The component material multi-functionalities: ion and semi-conductions and bi-catalysis to H2 or alcohol (methanol and ethanol) and air (O2) enable this device realized as a fuel cell.
International Journal of Hydrogen Energy
This paper reports the effects of sintering temperature on structure, particle size and conductiv... more This paper reports the effects of sintering temperature on structure, particle size and conductivity of electrodes (Sn0.2Zn0.8Fe0.2O & Sn0.8Zn0.2Fe0.2O). The electrode material was prepared by the chemical method combining a solid state reaction. Structural analyses were performed using X-ray diffraction and scanning electron microscopy. The particle size of the material obtained using Scherrer's formula was 50-60 nm and the nanostructure's surface was studied using electrochemical characterisations tools. Electrical conductivity was determined using the 4-probe DC method, which was compared with the 4-probe AC method. These results suggest a promising substitute for the conventional electrodes of solid oxide fuel cells (SOFCs). It is known that a sintering temperature above 1000 degrees C causes an increase in density and a reduction of porosity. Therefore, we optimised the sintering temperature at 1000 degrees C and obtained electrical conductivity of about 5 S Thus, this ...
Journal of Fuel Cell Science and Technology, 2011
Wiley Interdisciplinary Reviews: Energy and Environment, 2012
In this article, a planar, low-temperature, solid-oxide fuel cell based on nanocomposite material... more In this article, a planar, low-temperature, solid-oxide fuel cell based on nanocomposite materials is developed by cost-effective tape casting and hot-pressing methods. First, a single cell with active area of 6 × 6 cm 2 was manufactured and tested to determine the cell performance. The power density of 0.4 and 0.7 W cm −2 were achieved at stable open-circuit voltages at operating temperature of 550 • C using the syngas and hydrogen, respectively. Based on these experimental results, a 5-kW low-temperature, solid-oxide fuel cell polygeneration system is designed and analyzed. This system can provide electrical power and heating concurrently from a single source of fuel. The system design and the energy and mass balance are presented and a simulation based on syngas is performed. Finally, effects of fuel utilization factor, fuel cell operating temperature, and air temperature at cathode inlet on performance of polygeneration system is investigated. C 2012 John
Advanced Energy Materials, 2011
Page 1. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim FULL P APER 1 wileyonli... more Page 1. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim FULL P APER 1 wileyonlinelibrary.com Adv. Energy Mater. 2011, XX, 19 www.MaterialsViews. com www.advenergymat.de 1. Introduction In recent decades ...
Nanoscience and Nanotechnology Letters, 2012
Composite electrodes of Cu 0 16 Ni 0 27 Zn 0 37 Ce 0 16 Gd 0 04 (CNZGC) oxides have been successf... more Composite electrodes of Cu 0 16 Ni 0 27 Zn 0 37 Ce 0 16 Gd 0 04 (CNZGC) oxides have been successfully synthesized by solid state reaction method as anode material for low temperature solid oxide fuel cell (LTSOFC). These electrodes are characterized by XRD followed by sintering at various time periods and temperatures. Particle size of optimized composition was calculated 40-85 nm and sintered at 800 C for 4 hours. Electrical conductivity of 4.14 S/cm was obtained at a temperature of 550 C by the 4-prob DC method. The activation energy was calculated 4 × 10 −2 eV at 550 C. Hydrogen was used as fuel and air as oxidant at anode and cathode sides respectively. I-V/I-P curves were obtained in the temperature range of 400-550 C. The maximum power density was achieved for 570 mW/cm 2 at 550 C.
Advanced Energy Materials, 2015
BHJ) structure. The BHJ requires delicate tailoring of n-and p-particles in order to avoid the el... more BHJ) structure. The BHJ requires delicate tailoring of n-and p-particles in order to avoid the electronic short-circuit problem and make fuel cell function properly. Hereby, we introduce the different Schottky junction type FC confi guration by means of combined nano and composite approach that is even simpler and more effective than EFFC.
Rsc Advances, 2012
Recently, a fuel cell device constructed with only one layer composited of ceria based nanocompos... more Recently, a fuel cell device constructed with only one layer composited of ceria based nanocomposites (typically, lithium nickel oxide and gadolinium doped ceria (LiNiO2-GDC) composite materials), name electrolyte free fuel cell (EFFC) was realized for energy conversion by Zhu et al. 1-3 The maxium power density of this single component fuel cell is 450 mW cm −2 at 550 o C using hygrogen fuel. In this study, a model is developed to evaluate the performance of an EFFC. The kinetics of anodic and cathodic 10 reactions are modeled based on electrochemical impedance spectroscopy (EIS) measurement. The results show that both of the anodic and cathodic reactions are kinetically fast processes at 500 o C. The safety issues of an EFFC using oxidant and fuels at the same time without gas−tight separator is analyzed under open circuit and normal operation states, respectively. The reaction depth of anodic and cathodic processes dominates the competition between surface electrochemical and gas−phase reactions which are 15 effected by the catalytic activity and porosity of the materials. The voltage and power output of an EFFC are calculated based on the model and compared with the experimental results.
Nano Energy, 2013
Electrolyte-separator-free fuel cell (EFFC) is a new emerging energy conversion technology. The E... more Electrolyte-separator-free fuel cell (EFFC) is a new emerging energy conversion technology. The EFFC consists of a single-component of nanocomposite material which works as a one-layer fuel cell device contrary to the traditional three-layer anode-electrolyte-cathode structure, in which an electrolyte layer plays a critical role. The nanocomposite of a single homogenous layer consists of a mixture of semiconducting and ionic materials that provides the necessary electrochemical reaction sites and charge transport paths for a fuel cell. These can be accomplished through tailoring ionic and electronic (n, p) conductivities and catalyst activities, which enable redox reactions to occur on nano-particles and finally accomplish a fuel cell function.
ABSTRACT Lignin, the second most abundant component after cellulose in biomass, has been examined... more ABSTRACT Lignin, the second most abundant component after cellulose in biomass, has been examined in this study as a fuel for direct conversion into electricity using direct carbon fuel cells (DCFC). Two different types of industrial lignins were investigated: Lignosulfonate (LS) and Kraft lignin (KL), in their commercial forms, after their blending with commercial active carbon (AC) or after alteration of their structures by a pH adjustment to pH 10. It was found that the open circuit voltage (OCV) of the DCFC could reach around 0.7 V in most of the trials. Addition of active carbon increased the maximum current density from 43–57 to 83–101 mA cm−2. The pH adjustment not only increased the maximum current density but also reduced the differences between the two types of lignins, resulting in an OCV of 0.68–0.69 V and a maximum current density of 74–79 mA cm−2 from both lignins. Typical power density was 12 (for KL + AC) and 24 mW cm−2 (for LS + AC). It is concluded that a direct lignin fuel cell is feasible and the lignin hydrophilicity is critical for the cell performance.
Nano, 2014
ABSTRACT Zinc oxide (ZnO) nanowire (NW) films were synthesized at low temperature (95 degrees C) ... more ABSTRACT Zinc oxide (ZnO) nanowire (NW) films were synthesized at low temperature (95 degrees C) through amine-assisted solution process and used as photoanode for the fabrication of dye-sensitized solar cells (DSSCs). It was found that with the addition of polyethyleneimine (PEI) and ammonium hydroxide (NH4OH) in growth solution, the NWs were smaller in diameter and longer in length by prolonging the growth time without refreshing the growth solution. A reasonable overall conversion efficiency of 1.25% was achieved with photoanode based on ZnO NWs containing PEI and NH4OH. However, DSSC fabricated with ZnO NWs not containing PEI and NH4OH showed low conversion efficiency of 0.58%. All the DSSCs exhibited almost similar values of open circuit voltage (V-OC) and fill factor (FF). Interestingly, DSSC based on ZnO NWs with PEI and NH4OH obtained two times higher short circuit current density (J(SC)) compared to ZnO NWs photoanode without PEI and NH4OH. The increase in efficiency and J(SC) with the length of NWs is attributed to the increase in internal surface area for sufficient dye loading and light harvesting.
Energy & Environment, 2009
... 3. P. Akhtar, "Challenges for the Promotion of Renewable-Energy Technologies in Pakistan... more ... 3. P. Akhtar, "Challenges for the Promotion of Renewable-Energy Technologies in Pakistan" Renewable Energy Technologies and Sustainable Development, Proceedings ... T. Abe, H. Shima, K. Wantanbe and Y. Ito "A study of Polymer Electrolyte Fuel Cells by the Measurement ...
Progress in Natural Science: Materials International, 2014
Electromagnetic signals in deep reservoir are very weak so that it is difficult to predict about ... more Electromagnetic signals in deep reservoir are very weak so that it is difficult to predict about the presence of hydrocarbon in seabed logging (SBL) environment. In the present work, Mn 0.8 Zn 0.2 Fe 2 O 4 nanoferrites were prepared by a sol-gel technique at different sintering temperatures of 450 1C, 650 1C and 850 1C to increase the strength of electromagnetic (EM) antenna. XRD, FESEM, Raman spectroscopy and HRTEM were used to analyze the phase, surface morphology and size of the nanoferrites. Magnetic properties of the nanoferrites were also measured using an impedance network analyzer. However, nanoferrites sintered at 850 1C with initial permeability of 200 and Q factor of 50 were used as magnetic feeders with the EM antenna. Lab scale experiments were performed to investigate the effect of magnetic field strength in scale tank. SPSS and MATLAB softwares were also used to confirm the oil presence in scale tank. It was observed that the magnitude of the EM waves for the antenna was increased up to 233%. Finally, the correlation values also show 208% increase in the magnetic field strength with the presence of the oil. Therefore, antenna with Mn 0.8 Zn 0.2 Fe 2 O 4 nanoferrites based magnetic feeders can be used for deep water and deep target hydrocarbon exploration.
Applied Surface Science, 2014
Structural and photovoltaic characteristics of hierarchical ZnO nanostructures solar cell have be... more Structural and photovoltaic characteristics of hierarchical ZnO nanostructures solar cell have been studied in relation to growth reaction temperature. It is found that the hierarchical ZnO nanostructures network to act not only as large surface area substrates but also as a transport medium for electrons injected from the dye molecules. The incident photon-to-current conversion efficiency is decreased by increasing the growth reaction temperature of ZnO electrodes. The best conversion efficiency of a 0.25 cm 2 cell is measured to be 1.24% under 100 mW cm −2 irradiation.
International Journal of Hydrogen Energy, 2015
Alkali stability Guanidine derivative
Journal of Magnetism and Magnetic Materials, 2014
The effects of synthesis methods such as sol-gel (SG), self combustion (SC) and modified conventi... more The effects of synthesis methods such as sol-gel (SG), self combustion (SC) and modified conventional mixed oxide (MCMO) on the structure, morphology and magnetic properties of the (Y 3 Fe 5 O 12 ) garnet ferrites have been studied in the present work. The samples of Y 3 Fe 5 O 12 were sintered at 950 1C and 1150 1C (by SG and SC methods). For MCMO route the sintering was done at 1350 1C for 6 h. Synthesized samples prepared by various routes were investigated using X-ray diffraction (XRD) analysis, Field emission scanning electron microscopy (FESEM), Impedance network analyzer and transmission electron microscopy (TEM). The structural analysis reveals that the samples are of single phase structure and shows variations in the particle sizes and cells volumes, prepared by various routes. FESEM and TEM images depict that grain size increases with the increase of sintering temperature from 40 nm to 100 nm. Magnetic measurements reveal that garnet ferrite synthesized by sol gel method has high initial permeability (60.22) and low magnetic loss (0.0004) as compared to other garnet ferrite samples, which were synthesized by self combustion and MCMO methods. The M-H loops exhibit very low coercivity which enables the use of these materials in relays and switching devices fabrications. Thus, the garnet nanoferrites with low magnetic loss prepared by different methods may open new horizon for electronic industry for their use in high frequency applications.
Solid State Ionics, 2011
The purpose of this study is to develop new oxide ionic conductors based on nanocomposite materia... more The purpose of this study is to develop new oxide ionic conductors based on nanocomposite materials for an advanced fuel cell (NANOCOFC) approach. The novel two phase nanocomposite oxide ionic conductors, Ce 0.8 Sm 0.2 O 2 − δ (SDC)-Y 2 O 3 were synthesized by a co-precipitation method. The structure and morphology of the prepared electrolyte were investigated by means of X-ray diffraction (XRD) and high resolution scanning electron microscopy (HRSEM). XRD results showed a two phase composite consisting of yttrium oxide and samaria doped ceria and SEM results exhibited a nanostructure form of the sample. The yttrium oxide was used on the SDC as a second phase. The interface between two constituent phases and the ionic conductivities were studied with electrochemical impedance spectroscopy (EIS). An electrochemical study showed high oxide ion mobility and conductivity of the Y 2 O 3 -SDC two phase nanocomposite electrolytes at a low temperature (300-600°C). Maximum conductivity (about 1.0 S cm −1 ) was obtained for the optimized Y 2 O 3 -SDC composite electrolyte at 600°C. It is found that the nanocomposite electrolytes show higher conductivities with the increased concentration of yttrium oxides but decreases after reaching a certain level. A high fuel cell performance, 0.75 W cm −2 , was achieved at 580°C.
Renewable and Sustainable Energy Reviews, 2009
Microelectronic Engineering
In this study, equilibrium geometry and band structure of oxygen-doped diamond have been investig... more In this study, equilibrium geometry and band structure of oxygen-doped diamond have been investigated based on density function theory (DFT) using VASP code. These calculations have shown that the highest occupied molecular orbital is localized at the oxygen atom. Moreover, C 4 AO bond lengths are equivalent to those of CAC bonds leading to no lattice distortions. Doping of oxygen into diamond seems to be thermodynamically favorable due to negative formation energy. Band structure calculations lead to the semiconducting behavior of oxygen-doped diamonds due to the creation of defects states inside the band gap extending to conduction band minimum. The spin projected density of states calculations illustrates significant contributions of O 2p states at the Fermi level without the appearance of appreciable magnetic moments on oxygen or on carbon atoms (for all C 1 -C 4 ) leading to its non-magnetic semi-conducting behavior with zero density of carriers at the Fermi level for both spin projections; O;"(E F ) = 0. Present DFT results verify our experimental findings that addition of oxygen into diamond lattice increases its conductivity so that oxygen-doped diamond films behave like a good semiconductor.
Our recent developments have been made on the single layer or electrolyte-free fuel cells using a... more Our recent developments have been made on the single layer or electrolyte-free fuel cells using a homogeneous mixed semi- and ion conducting layer which can function as the electrodes, anode and cathode, and electrolyte simultaneously. We have achieved near 800 mW/cm2 at 550oC. A number of material groups have also been developed for advanced SLFCs. This radical new invention has made this nice concept of SLFC into practical application and also opens a new fuel cell R&D strategy.
RSC Advances
We report a new energy conversion technology joining electrochemical and physical principles. Thi... more We report a new energy conversion technology joining electrochemical and physical principles. This technology can realize the fuel cell function but built on a different scientific principle. The device consists of a single component which is a homogenous mixture of ceria composite with semiconducting materials, e.g. LiNiCuZn-based oxides. The test devices with hydrogen and air operation delivered a power density of 760 mW cm−2 at 550 °C. The device has demonstrated a multi-fuel flexibility and direct alcohol and biogas operations have delivered 300–500 mW cm−2 at the same temperature. Device physics reveal a key principle similar to solar cells realizing the function based on an effective separation of electronic and ionic conductions and phases within the single-component. The component material multi-functionalities: ion and semi-conductions and bi-catalysis to H2 or alcohol (methanol and ethanol) and air (O2) enable this device realized as a fuel cell.
International Journal of Hydrogen Energy
This paper reports the effects of sintering temperature on structure, particle size and conductiv... more This paper reports the effects of sintering temperature on structure, particle size and conductivity of electrodes (Sn0.2Zn0.8Fe0.2O & Sn0.8Zn0.2Fe0.2O). The electrode material was prepared by the chemical method combining a solid state reaction. Structural analyses were performed using X-ray diffraction and scanning electron microscopy. The particle size of the material obtained using Scherrer's formula was 50-60 nm and the nanostructure's surface was studied using electrochemical characterisations tools. Electrical conductivity was determined using the 4-probe DC method, which was compared with the 4-probe AC method. These results suggest a promising substitute for the conventional electrodes of solid oxide fuel cells (SOFCs). It is known that a sintering temperature above 1000 degrees C causes an increase in density and a reduction of porosity. Therefore, we optimised the sintering temperature at 1000 degrees C and obtained electrical conductivity of about 5 S Thus, this ...
Journal of Fuel Cell Science and Technology, 2011
Wiley Interdisciplinary Reviews: Energy and Environment, 2012
In this article, a planar, low-temperature, solid-oxide fuel cell based on nanocomposite material... more In this article, a planar, low-temperature, solid-oxide fuel cell based on nanocomposite materials is developed by cost-effective tape casting and hot-pressing methods. First, a single cell with active area of 6 × 6 cm 2 was manufactured and tested to determine the cell performance. The power density of 0.4 and 0.7 W cm −2 were achieved at stable open-circuit voltages at operating temperature of 550 • C using the syngas and hydrogen, respectively. Based on these experimental results, a 5-kW low-temperature, solid-oxide fuel cell polygeneration system is designed and analyzed. This system can provide electrical power and heating concurrently from a single source of fuel. The system design and the energy and mass balance are presented and a simulation based on syngas is performed. Finally, effects of fuel utilization factor, fuel cell operating temperature, and air temperature at cathode inlet on performance of polygeneration system is investigated. C 2012 John
Advanced Energy Materials, 2011
Page 1. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim FULL P APER 1 wileyonli... more Page 1. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim FULL P APER 1 wileyonlinelibrary.com Adv. Energy Mater. 2011, XX, 19 www.MaterialsViews. com www.advenergymat.de 1. Introduction In recent decades ...
Nanoscience and Nanotechnology Letters, 2012
Composite electrodes of Cu 0 16 Ni 0 27 Zn 0 37 Ce 0 16 Gd 0 04 (CNZGC) oxides have been successf... more Composite electrodes of Cu 0 16 Ni 0 27 Zn 0 37 Ce 0 16 Gd 0 04 (CNZGC) oxides have been successfully synthesized by solid state reaction method as anode material for low temperature solid oxide fuel cell (LTSOFC). These electrodes are characterized by XRD followed by sintering at various time periods and temperatures. Particle size of optimized composition was calculated 40-85 nm and sintered at 800 C for 4 hours. Electrical conductivity of 4.14 S/cm was obtained at a temperature of 550 C by the 4-prob DC method. The activation energy was calculated 4 × 10 −2 eV at 550 C. Hydrogen was used as fuel and air as oxidant at anode and cathode sides respectively. I-V/I-P curves were obtained in the temperature range of 400-550 C. The maximum power density was achieved for 570 mW/cm 2 at 550 C.
Advanced Energy Materials, 2015
BHJ) structure. The BHJ requires delicate tailoring of n-and p-particles in order to avoid the el... more BHJ) structure. The BHJ requires delicate tailoring of n-and p-particles in order to avoid the electronic short-circuit problem and make fuel cell function properly. Hereby, we introduce the different Schottky junction type FC confi guration by means of combined nano and composite approach that is even simpler and more effective than EFFC.
Rsc Advances, 2012
Recently, a fuel cell device constructed with only one layer composited of ceria based nanocompos... more Recently, a fuel cell device constructed with only one layer composited of ceria based nanocomposites (typically, lithium nickel oxide and gadolinium doped ceria (LiNiO2-GDC) composite materials), name electrolyte free fuel cell (EFFC) was realized for energy conversion by Zhu et al. 1-3 The maxium power density of this single component fuel cell is 450 mW cm −2 at 550 o C using hygrogen fuel. In this study, a model is developed to evaluate the performance of an EFFC. The kinetics of anodic and cathodic 10 reactions are modeled based on electrochemical impedance spectroscopy (EIS) measurement. The results show that both of the anodic and cathodic reactions are kinetically fast processes at 500 o C. The safety issues of an EFFC using oxidant and fuels at the same time without gas−tight separator is analyzed under open circuit and normal operation states, respectively. The reaction depth of anodic and cathodic processes dominates the competition between surface electrochemical and gas−phase reactions which are 15 effected by the catalytic activity and porosity of the materials. The voltage and power output of an EFFC are calculated based on the model and compared with the experimental results.
Nano Energy, 2013
Electrolyte-separator-free fuel cell (EFFC) is a new emerging energy conversion technology. The E... more Electrolyte-separator-free fuel cell (EFFC) is a new emerging energy conversion technology. The EFFC consists of a single-component of nanocomposite material which works as a one-layer fuel cell device contrary to the traditional three-layer anode-electrolyte-cathode structure, in which an electrolyte layer plays a critical role. The nanocomposite of a single homogenous layer consists of a mixture of semiconducting and ionic materials that provides the necessary electrochemical reaction sites and charge transport paths for a fuel cell. These can be accomplished through tailoring ionic and electronic (n, p) conductivities and catalyst activities, which enable redox reactions to occur on nano-particles and finally accomplish a fuel cell function.
ABSTRACT Lignin, the second most abundant component after cellulose in biomass, has been examined... more ABSTRACT Lignin, the second most abundant component after cellulose in biomass, has been examined in this study as a fuel for direct conversion into electricity using direct carbon fuel cells (DCFC). Two different types of industrial lignins were investigated: Lignosulfonate (LS) and Kraft lignin (KL), in their commercial forms, after their blending with commercial active carbon (AC) or after alteration of their structures by a pH adjustment to pH 10. It was found that the open circuit voltage (OCV) of the DCFC could reach around 0.7 V in most of the trials. Addition of active carbon increased the maximum current density from 43–57 to 83–101 mA cm−2. The pH adjustment not only increased the maximum current density but also reduced the differences between the two types of lignins, resulting in an OCV of 0.68–0.69 V and a maximum current density of 74–79 mA cm−2 from both lignins. Typical power density was 12 (for KL + AC) and 24 mW cm−2 (for LS + AC). It is concluded that a direct lignin fuel cell is feasible and the lignin hydrophilicity is critical for the cell performance.
Nano, 2014
ABSTRACT Zinc oxide (ZnO) nanowire (NW) films were synthesized at low temperature (95 degrees C) ... more ABSTRACT Zinc oxide (ZnO) nanowire (NW) films were synthesized at low temperature (95 degrees C) through amine-assisted solution process and used as photoanode for the fabrication of dye-sensitized solar cells (DSSCs). It was found that with the addition of polyethyleneimine (PEI) and ammonium hydroxide (NH4OH) in growth solution, the NWs were smaller in diameter and longer in length by prolonging the growth time without refreshing the growth solution. A reasonable overall conversion efficiency of 1.25% was achieved with photoanode based on ZnO NWs containing PEI and NH4OH. However, DSSC fabricated with ZnO NWs not containing PEI and NH4OH showed low conversion efficiency of 0.58%. All the DSSCs exhibited almost similar values of open circuit voltage (V-OC) and fill factor (FF). Interestingly, DSSC based on ZnO NWs with PEI and NH4OH obtained two times higher short circuit current density (J(SC)) compared to ZnO NWs photoanode without PEI and NH4OH. The increase in efficiency and J(SC) with the length of NWs is attributed to the increase in internal surface area for sufficient dye loading and light harvesting.
Energy & Environment, 2009
... 3. P. Akhtar, "Challenges for the Promotion of Renewable-Energy Technologies in Pakistan... more ... 3. P. Akhtar, "Challenges for the Promotion of Renewable-Energy Technologies in Pakistan" Renewable Energy Technologies and Sustainable Development, Proceedings ... T. Abe, H. Shima, K. Wantanbe and Y. Ito "A study of Polymer Electrolyte Fuel Cells by the Measurement ...
Progress in Natural Science: Materials International, 2014
Electromagnetic signals in deep reservoir are very weak so that it is difficult to predict about ... more Electromagnetic signals in deep reservoir are very weak so that it is difficult to predict about the presence of hydrocarbon in seabed logging (SBL) environment. In the present work, Mn 0.8 Zn 0.2 Fe 2 O 4 nanoferrites were prepared by a sol-gel technique at different sintering temperatures of 450 1C, 650 1C and 850 1C to increase the strength of electromagnetic (EM) antenna. XRD, FESEM, Raman spectroscopy and HRTEM were used to analyze the phase, surface morphology and size of the nanoferrites. Magnetic properties of the nanoferrites were also measured using an impedance network analyzer. However, nanoferrites sintered at 850 1C with initial permeability of 200 and Q factor of 50 were used as magnetic feeders with the EM antenna. Lab scale experiments were performed to investigate the effect of magnetic field strength in scale tank. SPSS and MATLAB softwares were also used to confirm the oil presence in scale tank. It was observed that the magnitude of the EM waves for the antenna was increased up to 233%. Finally, the correlation values also show 208% increase in the magnetic field strength with the presence of the oil. Therefore, antenna with Mn 0.8 Zn 0.2 Fe 2 O 4 nanoferrites based magnetic feeders can be used for deep water and deep target hydrocarbon exploration.
Applied Surface Science, 2014
Structural and photovoltaic characteristics of hierarchical ZnO nanostructures solar cell have be... more Structural and photovoltaic characteristics of hierarchical ZnO nanostructures solar cell have been studied in relation to growth reaction temperature. It is found that the hierarchical ZnO nanostructures network to act not only as large surface area substrates but also as a transport medium for electrons injected from the dye molecules. The incident photon-to-current conversion efficiency is decreased by increasing the growth reaction temperature of ZnO electrodes. The best conversion efficiency of a 0.25 cm 2 cell is measured to be 1.24% under 100 mW cm −2 irradiation.
International Journal of Hydrogen Energy, 2015
Alkali stability Guanidine derivative
Journal of Magnetism and Magnetic Materials, 2014
The effects of synthesis methods such as sol-gel (SG), self combustion (SC) and modified conventi... more The effects of synthesis methods such as sol-gel (SG), self combustion (SC) and modified conventional mixed oxide (MCMO) on the structure, morphology and magnetic properties of the (Y 3 Fe 5 O 12 ) garnet ferrites have been studied in the present work. The samples of Y 3 Fe 5 O 12 were sintered at 950 1C and 1150 1C (by SG and SC methods). For MCMO route the sintering was done at 1350 1C for 6 h. Synthesized samples prepared by various routes were investigated using X-ray diffraction (XRD) analysis, Field emission scanning electron microscopy (FESEM), Impedance network analyzer and transmission electron microscopy (TEM). The structural analysis reveals that the samples are of single phase structure and shows variations in the particle sizes and cells volumes, prepared by various routes. FESEM and TEM images depict that grain size increases with the increase of sintering temperature from 40 nm to 100 nm. Magnetic measurements reveal that garnet ferrite synthesized by sol gel method has high initial permeability (60.22) and low magnetic loss (0.0004) as compared to other garnet ferrite samples, which were synthesized by self combustion and MCMO methods. The M-H loops exhibit very low coercivity which enables the use of these materials in relays and switching devices fabrications. Thus, the garnet nanoferrites with low magnetic loss prepared by different methods may open new horizon for electronic industry for their use in high frequency applications.
Solid State Ionics, 2011
The purpose of this study is to develop new oxide ionic conductors based on nanocomposite materia... more The purpose of this study is to develop new oxide ionic conductors based on nanocomposite materials for an advanced fuel cell (NANOCOFC) approach. The novel two phase nanocomposite oxide ionic conductors, Ce 0.8 Sm 0.2 O 2 − δ (SDC)-Y 2 O 3 were synthesized by a co-precipitation method. The structure and morphology of the prepared electrolyte were investigated by means of X-ray diffraction (XRD) and high resolution scanning electron microscopy (HRSEM). XRD results showed a two phase composite consisting of yttrium oxide and samaria doped ceria and SEM results exhibited a nanostructure form of the sample. The yttrium oxide was used on the SDC as a second phase. The interface between two constituent phases and the ionic conductivities were studied with electrochemical impedance spectroscopy (EIS). An electrochemical study showed high oxide ion mobility and conductivity of the Y 2 O 3 -SDC two phase nanocomposite electrolytes at a low temperature (300-600°C). Maximum conductivity (about 1.0 S cm −1 ) was obtained for the optimized Y 2 O 3 -SDC composite electrolyte at 600°C. It is found that the nanocomposite electrolytes show higher conductivities with the increased concentration of yttrium oxides but decreases after reaching a certain level. A high fuel cell performance, 0.75 W cm −2 , was achieved at 580°C.
Renewable and Sustainable Energy Reviews, 2009