Here we report the experimental and theoretical study of two TiO2–graphene oxide (TG) and TiO2–re... more Here we report the experimental and theoretical study of two TiO2–graphene oxide (TG) and TiO2–reduced graphene oxide (TR) composites synthesized by a facile and ecological route, for enhanced visible light (470 nm) photocatalytic degradation of Methylene Blue (MB) (99% efficiency), with high rate constant values (1800% over bare TiO2). TG couples TiO2 nanopowder with Graphene Oxide (GO) while TR couples it with reduced graphene oxide (RGO). The present study, unlike previous reports, discusses never-before-reported double absorption edges obtained for both TG (3.51 eV and 2.51 eV) and TR (3.42 eV and 2.39 eV) composites, which represents the reason behind feasible visible light (2.56 eV) induced photocatalysis. TiO2 domains in the composites dominate the higher band edge, while GO/RGO domains explain the lower band edge. Formation of Ti–O–C bonds in both TG and TR drives the shifting upwards of the valence band edge and reduction in band gap. Further, these bonds provide a conductive pathway for charge carriers from TiO2 nanopowder to the degraded species via the GO/RGO matrix, resulting in decreased charge carrier recombination in TiO2 and enhanced efficiency. To attest that the developed theory is correct, density function theory (DFT) calculations were performed. DFT obtained energetics and electronic structures support experimental findings by demonstrating the role of the Ti–O–C bond, which results in double band edge phenomenon in composites. Finally, the mechanism behind MB degradation is discussed comprehensively and the effect of the weight percent of GO/RGO in the composite on the rate constant and photodegradation efficiency has been studied experimentally and explained by developing analytical equations.
Ti-based bulk metallic glass (BMGs) and their bimodal composites are linked with the pronounced s... more Ti-based bulk metallic glass (BMGs) and their bimodal composites are linked with the pronounced strain hardening after yielding but with much low value of strength. Therefore, developing Ti-based alloys with high yield strength and high plasticity is the current challenge. Here, we report the synthesis of ultra-fine grained bulk (UFG) Ti0.705Fe0.295)100xGax (0 6 x 6 2) bimodal eutectic composites with not only high strength and larger plasticity but also with high yield strength which is one of the important mechanical property for structural application. Reasonably high strength, high yield strength, strain to failure ratio, and enhanced plasticity of 7 ± 0.8% was observed in (Ti70.5Fe29.5)98Ga2 composite which is superior than Ti-based BMGs and bimodal composites. Modification of degree of eutectic structure refinement and volume fraction of constituent phases with the addition of Ga are the crucial factors in enhancing the mechanical properties of Ti–Fi–(Ga) composites.
Titanium Dioxide (TiO2 has been used as a working electrode of Dye sensitized solar cells (DSSC)... more Titanium Dioxide (TiO2 has been used as a working electrode of Dye sensitized solar cells (DSSC) for a long time. Their porous nature results in high surface area that ensures efficient light absorption. Apart from other advantages the porous nature of TiO2 results in a large number of surface states that trap carriers and promote recombination because of which efficiency goes down. In the present work, we have synthesized nanoparticles of PbS and develop a nanocomposite paste of TiO2–PbS. We have tested our nanocomposite paste for working electrode in DSSC. The samples were characterized using XRD, UV-VIS absorbance spectroscopy, FT-IR and SEM. PbS nanoparticles serve as surface state depressors, which reduces the surface states of TiO2 films. This further reduces recombination rate and increases the conversion efficiency of DSSC. The mechanism of charge transport on photovoltaic response and other parameters of the DSSC using PbS–TiO2 nanocomposite are also presented in detail.
The structural and ion transport studies of PVAx:NH4SCN solid polymer electrolytes (SPEs) with th... more The structural and ion transport studies of PVAx:NH4SCN solid polymer electrolytes (SPEs) with the aim of developing suitable ion conducting electrolytes for solid state ionic devices have been reported. DSC, XRD and IR analysis of as synthesized films have been carried out to study morphology and complexation behavior of PVA with NH4SCN. A possible structure of PVA complex has been proposed on the basis of IR spectroscopy. The electrical characterization which comprises of I - t, coulometery, TIC measurements and impedance spectroscopy has been carried out to assess ion transport behaviour of these complexes. The electrical measurement evidenced cationic transport with maximum in electrical conductivity of 7.0x10-5 S cm-1 for x = 0.15 in the system. The compositional variation of ionic conductivity has been correlated to morphology and concentration of charge carriers.
The present paper deals with ion transport studies on a new proton conducting composite
polymer e... more The present paper deals with ion transport studies on a new proton conducting composite polymer electrolyte - (PVAx:NH4SCN)y:PVAc system. Complexation and morphology of the composite electrolyte films are discussed on the basis of X-ray diffraction and differential scanning calorimetry data. Coulometry and transient ionic current measurements revealed charge transport through protons. The maximum ion conductivity was found to be 7.4.10 -4 S.cm -1 for the composition: x = 0.15, y = 0.12. The observed conductivity behaviour is correlated to the morphology of the films. The temperature dependence of the electrical conductivity exhibits Arrhenius characteristics in two different temperature ranges separated by a plateau region related to morphological changes occurring in the electrolyte.
The dielectric behaviour of polyvinyl alcohol (PVA) films complexed with ammonium thiocyanate
(NH... more The dielectric behaviour of polyvinyl alcohol (PVA) films complexed with ammonium thiocyanate (NH4SCN) have been investigated at various frequencies (from 100 Hz to 10 kHz) in the temperature range from 303 to 383 K. The relative permittivity (e0), loss tangent (tan d) and relaxation time (t) were found to be temperature and dopant concentration dependent. The experimental results reveal a, ab and b-types of relaxation processes for PVA±NH4SCN complexes.
In the present work, the attempt has been made to explain the influence of filler concentration o... more In the present work, the attempt has been made to explain the influence of filler concentration on the conductivity response of PVA-based composite polymer electrolytes following the Effective Medium Theory (EMT) approach. In the present investigation, the variation in the thickness of the highly amorphous space charge layer (responsible for enhancement in conductivity), covering the dispersed grains, has been taken into account while interpreting the conductivity data. During the estimation of the surface layer conductivity the role of glass transition temperature and degree of crystallinity were also considered. The simulated conductivity data incorporating these parameters in the EMT model show a better fit to the experimental conductivity response.
This paper reports the investigations on the optimization of nanostructured TiO2 with respect to ... more This paper reports the investigations on the optimization of nanostructured TiO2 with respect to optimum photoelectrode area for modular design of photoelectrolysis cell. This was done for determining the electrode area for optimum electrical output and hydrogen production rate. The nanostructured TiO2 has been formed by hydrolysis of titanium tetraisopropoxide Ti[OCH(CH3)2]4 followed by the deposition with spin on technique. The photoelectrochemical cell having nanostructured TiO2 photoanode of several geometricareas, namely, 0.21, 0.50, 0.72, 1.47 and 1:85 cm2, were fabricated and characterized. It has been found that the photoanode area corresponding to optimum electrical output and hydrogen production rate corresponds to ∼ 0:5 c m2.
We report the formation of polycrystalline TiO2 3lm (rutile phase; tetragonal: a=4:593 8A and c=2... more We report the formation of polycrystalline TiO2 3lm (rutile phase; tetragonal: a=4:593 8A and c=2:959 A8 ) by anodic oxidation of titanium sheet. The microstructural characterization revealed the porous nature of the 3lm consisting of randomly oriented microcrystals. The photoelectrochemical (PEC) characterization of TiO2 3lms has been carried out by employing standard electrochemical techniques. The investigations being reported involve I–V and C–V measurements, besides the use of PEC cell for hydrogen production by employing photovoltaic power as external biasing source. The open circuit voltage and short circuit current for the cell were found to be 780 mV and 9:27 mA cm−2, respectively. The observed frequency dispersion in Mott–Schottky plots was related to the presence of interface states participating in the charge exchange with bulk electrolyte. The hydrogen production rates were found to be 37.4 and 24:6 l h−1 m−2, respectively, for PV biased PEC and PV (stand-alone) driven electrolysis modes. ? 2001 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.
In this work, zinc sulfide (ZnS) nanoparticles have been synthesized by simple chemical precipita... more In this work, zinc sulfide (ZnS) nanoparticles have been synthesized by simple chemical precipitation method without using any capping agent. The synthesized nanoparticles were characterized using XRD, optical microscopy, UV-Vis, FTIR, and impedance spectroscopy. The X-ray diffraction shows that ZnS particles have cubic sphalerite structure with the crystallite size of 10-20 nm. SEM images of nanopowder samples reveal the presence of nanoflakes and agglomerated nanoparticles. Formation of ZnS has been confirmed through the appearance of 714 cm-1 absorption peak. The thermal stability of synthesized nanoparticles has been checked by annealing the material at different temperatures. Transformation of ZnS into ZnO subsequent to annealing has been evidenced from XRD and FTIR studies. UV-Vis spectra exhibited a red shift in the optical absorption on increase in annealing temperature. Variation in electrical conductivity obtained from impedance measurements at different temperatures has been suitably correlated to Davis- Mott model
This report is aimed at the development of modular PEC solar cells for hydrogen production. For f... more This report is aimed at the development of modular PEC solar cells for hydrogen production. For fabrication of cell, photoelectrodes in the from of nanostructured TiO 2 film over Ti-metal base have been synthesized by alkoxide sol-gel method using Ti[OCH(CH 3 ) 2 ] 4 as precursor followed by deposition using spin on technique. Crystalline phase and microstructure of the deposited film have investigated with the help of X-ray diffraction and TEM techniques. The photoelectrochemical response of the individual film electrodes of different area as well as parallel combination of two and four electrodes have been recorded and compared using conventional three electrode configuration and 1 M-NaOH as electrolyte. The photoconversion efficiencies have also been determined and compared for both the configurations. The rates of hydrogen production have been determined by measuring volume of the gas evolved over cathode. It has been found that the optimum area of the photoelectrode for modular PEC solar cell design in the present study corresponds to ∼ 0.40 cm 2 . ᭧
Here we report the experimental and theoretical study of two TiO2–graphene oxide (TG) and TiO2–re... more Here we report the experimental and theoretical study of two TiO2–graphene oxide (TG) and TiO2–reduced graphene oxide (TR) composites synthesized by a facile and ecological route, for enhanced visible light (470 nm) photocatalytic degradation of Methylene Blue (MB) (99% efficiency), with high rate constant values (1800% over bare TiO2). TG couples TiO2 nanopowder with Graphene Oxide (GO) while TR couples it with reduced graphene oxide (RGO). The present study, unlike previous reports, discusses never-before-reported double absorption edges obtained for both TG (3.51 eV and 2.51 eV) and TR (3.42 eV and 2.39 eV) composites, which represents the reason behind feasible visible light (2.56 eV) induced photocatalysis. TiO2 domains in the composites dominate the higher band edge, while GO/RGO domains explain the lower band edge. Formation of Ti–O–C bonds in both TG and TR drives the shifting upwards of the valence band edge and reduction in band gap. Further, these bonds provide a conductive pathway for charge carriers from TiO2 nanopowder to the degraded species via the GO/RGO matrix, resulting in decreased charge carrier recombination in TiO2 and enhanced efficiency. To attest that the developed theory is correct, density function theory (DFT) calculations were performed. DFT obtained energetics and electronic structures support experimental findings by demonstrating the role of the Ti–O–C bond, which results in double band edge phenomenon in composites. Finally, the mechanism behind MB degradation is discussed comprehensively and the effect of the weight percent of GO/RGO in the composite on the rate constant and photodegradation efficiency has been studied experimentally and explained by developing analytical equations.
Ti-based bulk metallic glass (BMGs) and their bimodal composites are linked with the pronounced s... more Ti-based bulk metallic glass (BMGs) and their bimodal composites are linked with the pronounced strain hardening after yielding but with much low value of strength. Therefore, developing Ti-based alloys with high yield strength and high plasticity is the current challenge. Here, we report the synthesis of ultra-fine grained bulk (UFG) Ti0.705Fe0.295)100xGax (0 6 x 6 2) bimodal eutectic composites with not only high strength and larger plasticity but also with high yield strength which is one of the important mechanical property for structural application. Reasonably high strength, high yield strength, strain to failure ratio, and enhanced plasticity of 7 ± 0.8% was observed in (Ti70.5Fe29.5)98Ga2 composite which is superior than Ti-based BMGs and bimodal composites. Modification of degree of eutectic structure refinement and volume fraction of constituent phases with the addition of Ga are the crucial factors in enhancing the mechanical properties of Ti–Fi–(Ga) composites.
Titanium Dioxide (TiO2 has been used as a working electrode of Dye sensitized solar cells (DSSC)... more Titanium Dioxide (TiO2 has been used as a working electrode of Dye sensitized solar cells (DSSC) for a long time. Their porous nature results in high surface area that ensures efficient light absorption. Apart from other advantages the porous nature of TiO2 results in a large number of surface states that trap carriers and promote recombination because of which efficiency goes down. In the present work, we have synthesized nanoparticles of PbS and develop a nanocomposite paste of TiO2–PbS. We have tested our nanocomposite paste for working electrode in DSSC. The samples were characterized using XRD, UV-VIS absorbance spectroscopy, FT-IR and SEM. PbS nanoparticles serve as surface state depressors, which reduces the surface states of TiO2 films. This further reduces recombination rate and increases the conversion efficiency of DSSC. The mechanism of charge transport on photovoltaic response and other parameters of the DSSC using PbS–TiO2 nanocomposite are also presented in detail.
The structural and ion transport studies of PVAx:NH4SCN solid polymer electrolytes (SPEs) with th... more The structural and ion transport studies of PVAx:NH4SCN solid polymer electrolytes (SPEs) with the aim of developing suitable ion conducting electrolytes for solid state ionic devices have been reported. DSC, XRD and IR analysis of as synthesized films have been carried out to study morphology and complexation behavior of PVA with NH4SCN. A possible structure of PVA complex has been proposed on the basis of IR spectroscopy. The electrical characterization which comprises of I - t, coulometery, TIC measurements and impedance spectroscopy has been carried out to assess ion transport behaviour of these complexes. The electrical measurement evidenced cationic transport with maximum in electrical conductivity of 7.0x10-5 S cm-1 for x = 0.15 in the system. The compositional variation of ionic conductivity has been correlated to morphology and concentration of charge carriers.
The present paper deals with ion transport studies on a new proton conducting composite
polymer e... more The present paper deals with ion transport studies on a new proton conducting composite polymer electrolyte - (PVAx:NH4SCN)y:PVAc system. Complexation and morphology of the composite electrolyte films are discussed on the basis of X-ray diffraction and differential scanning calorimetry data. Coulometry and transient ionic current measurements revealed charge transport through protons. The maximum ion conductivity was found to be 7.4.10 -4 S.cm -1 for the composition: x = 0.15, y = 0.12. The observed conductivity behaviour is correlated to the morphology of the films. The temperature dependence of the electrical conductivity exhibits Arrhenius characteristics in two different temperature ranges separated by a plateau region related to morphological changes occurring in the electrolyte.
The dielectric behaviour of polyvinyl alcohol (PVA) films complexed with ammonium thiocyanate
(NH... more The dielectric behaviour of polyvinyl alcohol (PVA) films complexed with ammonium thiocyanate (NH4SCN) have been investigated at various frequencies (from 100 Hz to 10 kHz) in the temperature range from 303 to 383 K. The relative permittivity (e0), loss tangent (tan d) and relaxation time (t) were found to be temperature and dopant concentration dependent. The experimental results reveal a, ab and b-types of relaxation processes for PVA±NH4SCN complexes.
In the present work, the attempt has been made to explain the influence of filler concentration o... more In the present work, the attempt has been made to explain the influence of filler concentration on the conductivity response of PVA-based composite polymer electrolytes following the Effective Medium Theory (EMT) approach. In the present investigation, the variation in the thickness of the highly amorphous space charge layer (responsible for enhancement in conductivity), covering the dispersed grains, has been taken into account while interpreting the conductivity data. During the estimation of the surface layer conductivity the role of glass transition temperature and degree of crystallinity were also considered. The simulated conductivity data incorporating these parameters in the EMT model show a better fit to the experimental conductivity response.
This paper reports the investigations on the optimization of nanostructured TiO2 with respect to ... more This paper reports the investigations on the optimization of nanostructured TiO2 with respect to optimum photoelectrode area for modular design of photoelectrolysis cell. This was done for determining the electrode area for optimum electrical output and hydrogen production rate. The nanostructured TiO2 has been formed by hydrolysis of titanium tetraisopropoxide Ti[OCH(CH3)2]4 followed by the deposition with spin on technique. The photoelectrochemical cell having nanostructured TiO2 photoanode of several geometricareas, namely, 0.21, 0.50, 0.72, 1.47 and 1:85 cm2, were fabricated and characterized. It has been found that the photoanode area corresponding to optimum electrical output and hydrogen production rate corresponds to ∼ 0:5 c m2.
We report the formation of polycrystalline TiO2 3lm (rutile phase; tetragonal: a=4:593 8A and c=2... more We report the formation of polycrystalline TiO2 3lm (rutile phase; tetragonal: a=4:593 8A and c=2:959 A8 ) by anodic oxidation of titanium sheet. The microstructural characterization revealed the porous nature of the 3lm consisting of randomly oriented microcrystals. The photoelectrochemical (PEC) characterization of TiO2 3lms has been carried out by employing standard electrochemical techniques. The investigations being reported involve I–V and C–V measurements, besides the use of PEC cell for hydrogen production by employing photovoltaic power as external biasing source. The open circuit voltage and short circuit current for the cell were found to be 780 mV and 9:27 mA cm−2, respectively. The observed frequency dispersion in Mott–Schottky plots was related to the presence of interface states participating in the charge exchange with bulk electrolyte. The hydrogen production rates were found to be 37.4 and 24:6 l h−1 m−2, respectively, for PV biased PEC and PV (stand-alone) driven electrolysis modes. ? 2001 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.
In this work, zinc sulfide (ZnS) nanoparticles have been synthesized by simple chemical precipita... more In this work, zinc sulfide (ZnS) nanoparticles have been synthesized by simple chemical precipitation method without using any capping agent. The synthesized nanoparticles were characterized using XRD, optical microscopy, UV-Vis, FTIR, and impedance spectroscopy. The X-ray diffraction shows that ZnS particles have cubic sphalerite structure with the crystallite size of 10-20 nm. SEM images of nanopowder samples reveal the presence of nanoflakes and agglomerated nanoparticles. Formation of ZnS has been confirmed through the appearance of 714 cm-1 absorption peak. The thermal stability of synthesized nanoparticles has been checked by annealing the material at different temperatures. Transformation of ZnS into ZnO subsequent to annealing has been evidenced from XRD and FTIR studies. UV-Vis spectra exhibited a red shift in the optical absorption on increase in annealing temperature. Variation in electrical conductivity obtained from impedance measurements at different temperatures has been suitably correlated to Davis- Mott model
This report is aimed at the development of modular PEC solar cells for hydrogen production. For f... more This report is aimed at the development of modular PEC solar cells for hydrogen production. For fabrication of cell, photoelectrodes in the from of nanostructured TiO 2 film over Ti-metal base have been synthesized by alkoxide sol-gel method using Ti[OCH(CH 3 ) 2 ] 4 as precursor followed by deposition using spin on technique. Crystalline phase and microstructure of the deposited film have investigated with the help of X-ray diffraction and TEM techniques. The photoelectrochemical response of the individual film electrodes of different area as well as parallel combination of two and four electrodes have been recorded and compared using conventional three electrode configuration and 1 M-NaOH as electrolyte. The photoconversion efficiencies have also been determined and compared for both the configurations. The rates of hydrogen production have been determined by measuring volume of the gas evolved over cathode. It has been found that the optimum area of the photoelectrode for modular PEC solar cell design in the present study corresponds to ∼ 0.40 cm 2 . ᭧
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Papers by PK Shukla
graphene oxide (TR) composites synthesized by a facile and ecological route, for enhanced visible light
(470 nm) photocatalytic degradation of Methylene Blue (MB) (99% efficiency), with high rate constant
values (1800% over bare TiO2). TG couples TiO2 nanopowder with Graphene Oxide (GO) while TR
couples it with reduced graphene oxide (RGO). The present study, unlike previous reports, discusses
never-before-reported double absorption edges obtained for both TG (3.51 eV and 2.51 eV) and TR
(3.42 eV and 2.39 eV) composites, which represents the reason behind feasible visible light (2.56 eV)
induced photocatalysis. TiO2 domains in the composites dominate the higher band edge, while GO/RGO
domains explain the lower band edge. Formation of Ti–O–C bonds in both TG and TR drives the shifting
upwards of the valence band edge and reduction in band gap. Further, these bonds provide a conductive
pathway for charge carriers from TiO2 nanopowder to the degraded species via the GO/RGO matrix,
resulting in decreased charge carrier recombination in TiO2 and enhanced efficiency. To attest that the
developed theory is correct, density function theory (DFT) calculations were performed. DFT obtained
energetics and electronic structures support experimental findings by demonstrating the role of the
Ti–O–C bond, which results in double band edge phenomenon in composites. Finally, the mechanism
behind MB degradation is discussed comprehensively and the effect of the weight percent of GO/RGO
in the composite on the rate constant and photodegradation efficiency has been studied experimentally
and explained by developing analytical equations.
were characterized using XRD, UV-VIS absorbance spectroscopy, FT-IR and SEM. PbS nanoparticles serve as surface state depressors, which reduces the surface states of TiO2 films. This further reduces recombination rate and increases the conversion efficiency of DSSC. The mechanism of charge transport on photovoltaic response and other parameters of the DSSC using PbS–TiO2 nanocomposite are also presented in detail.
polymer electrolyte - (PVAx:NH4SCN)y:PVAc system. Complexation and morphology of
the composite electrolyte films are discussed on the basis of X-ray diffraction and differential
scanning calorimetry data. Coulometry and transient ionic current measurements revealed charge
transport through protons. The maximum ion conductivity was found to be 7.4.10 -4 S.cm -1 for the
composition: x = 0.15, y = 0.12. The observed conductivity behaviour is correlated to the morphology
of the films. The temperature dependence of the electrical conductivity exhibits Arrhenius
characteristics in two different temperature ranges separated by a plateau region related to morphological
changes occurring in the electrolyte.
(NH4SCN) have been investigated at various frequencies (from 100 Hz to 10 kHz) in the temperature
range from 303 to 383 K. The relative permittivity (e0), loss tangent (tan d) and relaxation
time (t) were found to be temperature and dopant concentration dependent. The experimental results
reveal a, ab and b-types of relaxation processes for PVA±NH4SCN complexes.
the conductivity response of PVA-based composite polymer electrolytes following the Effective
Medium Theory (EMT) approach. In the present investigation, the variation in the thickness
of the highly amorphous space charge layer (responsible for enhancement in conductivity),
covering the dispersed grains, has been taken into account while interpreting the conductivity
data. During the estimation of the surface layer conductivity the role of glass transition temperature
and degree of crystallinity were also considered. The simulated conductivity data incorporating
these parameters in the EMT model show a better fit to the experimental conductivity
response.
area for modular design of photoelectrolysis cell. This was done for determining the electrode area for optimum electrical
output and hydrogen production rate. The nanostructured TiO2 has been formed by hydrolysis of titanium tetraisopropoxide
Ti[OCH(CH3)2]4 followed by the deposition with spin on technique. The photoelectrochemical cell having nanostructured
TiO2 photoanode of several geometricareas, namely, 0.21, 0.50, 0.72, 1.47 and 1:85 cm2, were fabricated and characterized. It
has been found that the photoanode area corresponding to optimum electrical output and hydrogen production rate corresponds
to ∼ 0:5 c m2.
oxidation of titanium sheet. The microstructural characterization revealed the porous nature of the 3lm consisting of randomly
oriented microcrystals. The photoelectrochemical (PEC) characterization of TiO2 3lms has been carried out by employing
standard electrochemical techniques. The investigations being reported involve I–V and C–V measurements, besides the use
of PEC cell for hydrogen production by employing photovoltaic power as external biasing source. The open circuit voltage
and short circuit current for the cell were found to be 780 mV and 9:27 mA cm−2, respectively. The observed frequency
dispersion in Mott–Schottky plots was related to the presence of interface states participating in the charge exchange with bulk
electrolyte. The hydrogen production rates were found to be 37.4 and 24:6 l h−1 m−2, respectively, for PV biased PEC and
PV (stand-alone) driven electrolysis modes. ? 2001 International Association for Hydrogen Energy. Published by Elsevier
Science Ltd. All rights reserved.
graphene oxide (TR) composites synthesized by a facile and ecological route, for enhanced visible light
(470 nm) photocatalytic degradation of Methylene Blue (MB) (99% efficiency), with high rate constant
values (1800% over bare TiO2). TG couples TiO2 nanopowder with Graphene Oxide (GO) while TR
couples it with reduced graphene oxide (RGO). The present study, unlike previous reports, discusses
never-before-reported double absorption edges obtained for both TG (3.51 eV and 2.51 eV) and TR
(3.42 eV and 2.39 eV) composites, which represents the reason behind feasible visible light (2.56 eV)
induced photocatalysis. TiO2 domains in the composites dominate the higher band edge, while GO/RGO
domains explain the lower band edge. Formation of Ti–O–C bonds in both TG and TR drives the shifting
upwards of the valence band edge and reduction in band gap. Further, these bonds provide a conductive
pathway for charge carriers from TiO2 nanopowder to the degraded species via the GO/RGO matrix,
resulting in decreased charge carrier recombination in TiO2 and enhanced efficiency. To attest that the
developed theory is correct, density function theory (DFT) calculations were performed. DFT obtained
energetics and electronic structures support experimental findings by demonstrating the role of the
Ti–O–C bond, which results in double band edge phenomenon in composites. Finally, the mechanism
behind MB degradation is discussed comprehensively and the effect of the weight percent of GO/RGO
in the composite on the rate constant and photodegradation efficiency has been studied experimentally
and explained by developing analytical equations.
were characterized using XRD, UV-VIS absorbance spectroscopy, FT-IR and SEM. PbS nanoparticles serve as surface state depressors, which reduces the surface states of TiO2 films. This further reduces recombination rate and increases the conversion efficiency of DSSC. The mechanism of charge transport on photovoltaic response and other parameters of the DSSC using PbS–TiO2 nanocomposite are also presented in detail.
polymer electrolyte - (PVAx:NH4SCN)y:PVAc system. Complexation and morphology of
the composite electrolyte films are discussed on the basis of X-ray diffraction and differential
scanning calorimetry data. Coulometry and transient ionic current measurements revealed charge
transport through protons. The maximum ion conductivity was found to be 7.4.10 -4 S.cm -1 for the
composition: x = 0.15, y = 0.12. The observed conductivity behaviour is correlated to the morphology
of the films. The temperature dependence of the electrical conductivity exhibits Arrhenius
characteristics in two different temperature ranges separated by a plateau region related to morphological
changes occurring in the electrolyte.
(NH4SCN) have been investigated at various frequencies (from 100 Hz to 10 kHz) in the temperature
range from 303 to 383 K. The relative permittivity (e0), loss tangent (tan d) and relaxation
time (t) were found to be temperature and dopant concentration dependent. The experimental results
reveal a, ab and b-types of relaxation processes for PVA±NH4SCN complexes.
the conductivity response of PVA-based composite polymer electrolytes following the Effective
Medium Theory (EMT) approach. In the present investigation, the variation in the thickness
of the highly amorphous space charge layer (responsible for enhancement in conductivity),
covering the dispersed grains, has been taken into account while interpreting the conductivity
data. During the estimation of the surface layer conductivity the role of glass transition temperature
and degree of crystallinity were also considered. The simulated conductivity data incorporating
these parameters in the EMT model show a better fit to the experimental conductivity
response.
area for modular design of photoelectrolysis cell. This was done for determining the electrode area for optimum electrical
output and hydrogen production rate. The nanostructured TiO2 has been formed by hydrolysis of titanium tetraisopropoxide
Ti[OCH(CH3)2]4 followed by the deposition with spin on technique. The photoelectrochemical cell having nanostructured
TiO2 photoanode of several geometricareas, namely, 0.21, 0.50, 0.72, 1.47 and 1:85 cm2, were fabricated and characterized. It
has been found that the photoanode area corresponding to optimum electrical output and hydrogen production rate corresponds
to ∼ 0:5 c m2.
oxidation of titanium sheet. The microstructural characterization revealed the porous nature of the 3lm consisting of randomly
oriented microcrystals. The photoelectrochemical (PEC) characterization of TiO2 3lms has been carried out by employing
standard electrochemical techniques. The investigations being reported involve I–V and C–V measurements, besides the use
of PEC cell for hydrogen production by employing photovoltaic power as external biasing source. The open circuit voltage
and short circuit current for the cell were found to be 780 mV and 9:27 mA cm−2, respectively. The observed frequency
dispersion in Mott–Schottky plots was related to the presence of interface states participating in the charge exchange with bulk
electrolyte. The hydrogen production rates were found to be 37.4 and 24:6 l h−1 m−2, respectively, for PV biased PEC and
PV (stand-alone) driven electrolysis modes. ? 2001 International Association for Hydrogen Energy. Published by Elsevier
Science Ltd. All rights reserved.