Y. Ramprakash - Academia.edu (original) (raw)
Papers by Y. Ramprakash
Optical Materials Technology for Energy Efficiency and Solar Energy Conversion IV, 1985
Fourth E.C. Photovoltaic Solar Energy Conference, 1982
The photovoltaic performance characteristics of a photoelectrochemical cell composed of a 25-micr... more The photovoltaic performance characteristics of a photoelectrochemical cell composed of a 25-micron-thick CdS layer deposited by spray pyrolysis on an n-InP single-crystal electrode are presented and analyzed. The combination was chosen as a theoretically effective way of protecting the InP anode from photoanodic dissolution in the alkaline electrolyte (5M KOH with 0.1M sulfide/polysulfide redox system, pH = 10). The preparation
Surface Science, 1984
ABSTRACT The transient photovoltaic response of single crystal n-InP electrodes in a PEC cell has... more ABSTRACT The transient photovoltaic response of single crystal n-InP electrodes in a PEC cell has been studied at different frequencies using a light chopper. The variables were light intensity, chopping frequency and redox species. The nature of the response and time constants were found to be sensitive to modification of the InP surface using ruthenium ions. The capture cross-section and density of traps at the semiconductor-electrolyte interfaces have thus been determined.
Solid State Ionics, 1999
ABSTRACT The polarisation behaviour of Ni/3 mol % Y2O3–ZrO2 (Ni/Y–TZP) cermet electrodes for H2 o... more ABSTRACT The polarisation behaviour of Ni/3 mol % Y2O3–ZrO2 (Ni/Y–TZP) cermet electrodes for H2 oxidation reaction has been investigated by the galvanostatic current interruption (GCI) over a wide range of H2O content and temperature in both undiluted and diluted H2 fuel. The electrode performance increases with H2O content with a maximum at 14% H2O. The reaction orders with respect to partial pressure of H2O and H2 are 0.5 and 0.1, respectively. The activation energy for the reaction is about 70 kJmol−1 in the H2O content range between 4 to 14% in undiluted H2 and in the H2 content range between 14 to 96% in diluted H2. The polarisation behaviour was analysed by fitting the measured data with the Nernst-type concentration equation and an empirical rate equation. The results have demonstrated that charge transfer process may play an very important role in the polarisation behaviour for H2 oxidation reaction on Ni/Y–TZP cermet electrodes. The deviation of the calculated data according to the empirical rate equation from the measured polarisation data at high current densities and low H2 contents indicates that the reaction is limited by at least two electrode processes.
Solid State Ionics, 1999
Reaction order and activation energy for H2 oxidation on Ni/3 mol.% Y2O3–ZrO2 (Ni/Y-TZP) cermet e... more Reaction order and activation energy for H2 oxidation on Ni/3 mol.% Y2O3–ZrO2 (Ni/Y-TZP) cermet electrodes have been evaluated by galvanostatic current interruption (GCI) and electrochemical impedance spectroscopy (EIS) techniques. GCI data show a reaction order in PH2O of 0.4 and activation energy of 76 kJ mol−1. In contrast, a first order with respect to PH2O and an activation energy of
Journal of Materials Science - J MATER SCI, 2000
The shelf-life of Sr doped LaMnO3 (LSM) materials of varying stoichiometric compositions prepared... more The shelf-life of Sr doped LaMnO3 (LSM) materials of varying stoichiometric compositions prepared by wet chemical synthesis was investigated under storage conditions of low and high humidity at ambient temperature for ~350 days. It has been found that the adhesion, chemical stability and stability of the electrode performance of LSM materials are critically dependent on the A-site stoichiometry (i.e., (La+Sr)/Mn ratio) of the LSM materials and much less dependent on storage conditions (humidity level and storage time) over the period investigated. In this respect, LSM materials with stoichiometric and sub-stoichiometric compositions where (La+Sr)/Mn=1 are stable and LSM with A-site sub-stoichiometry ((La+Sr)/Mn=~0.9) is effective in achieving good adherence, high chemical stability and high stability of electrode performance.
Materials Letters, 1989
ABSTRACT Modification of n-InP photoelectrode surfaces by matte etching followed by RuCl3 treatme... more ABSTRACT Modification of n-InP photoelectrode surfaces by matte etching followed by RuCl3 treatment has been shown to enhance the performance and stability of PEC solar cells. The unmodified and modified surfaces have been examined by SIMS, Auger and Raman spectroscopy. These experiments indicate the formation of a thin oxide layer due to modification which results in reduced sub-band gap response and increased Schottky barrier height.
Materials Chemistry and Physics, 1987
The technique of spray pyrolysis which is a simple and inexpensive method for preparing thin film... more The technique of spray pyrolysis which is a simple and inexpensive method for preparing thin films is reviewed with reference to a number of compounds.
Journal of Power Sources, 2002
The electrode behaviour of strontium (Sr)-doped LaMnO 3 (LSM) electrodes is investigated by an el... more The electrode behaviour of strontium (Sr)-doped LaMnO 3 (LSM) electrodes is investigated by an electrochemical impedance spectroscopy technique over the temperature range 850-1000 8C and the oxygen partial pressure range 0.01-0.21 atm. The electrodes are screen-printed on 50 mm  50 mm 3 mol% Y 2 O 3 -ZrO 2 electrolyte cells with an electrode surface area of 10 cm 2 . The impedance responses show two separable arcs and are analysed in terms of two different equivalent circuits with comparable information on the electrode processes at high and low frequencies. The electrode process associated with the high-frequency arc is essentially independent of O 2 partial pressure with an activation energy of 74kJmolAˋ1,whilethatatthelow−frequencyarchasanactivationenergyof74 kJ mol À1 , while that at the low-frequency arc has an activation energy of 74kJmolAˋ1,whilethatatthelow−frequencyarchasanactivationenergyof202 kJ mol À1 and a reaction order with respect to O 2 partial pressure of 0.5atlowtemperaturesand0.5 at low temperatures and 0.5atlowtemperaturesand0.85 at high temperatures. The electrode processes associated with the low-and highfrequency arcs are discussed. #
Journal of Power Sources, 1988
Thin films of CdS have been prepared by the screen-printing technique. Optical absorption studies... more Thin films of CdS have been prepared by the screen-printing technique. Optical absorption studies reveal a band gap of 2.42 eV. Current-voltage studies at the CdS-(1 M NaOH-0.1 M NazS-0.1 M S) interface yield an exchange current density of 6 X 10m6 A cmm2 and a junction ideality factor of 2.8. Mott-Schottky plots at 0.4, 1.0, 2.0 and 4.0 kHz show a flat-band potential of -1.07 V (SCE). At 84.5 mW cmw2 tungsten-halogen illumination, the photoelectrochemical cell gives an open-circuit voltage of 0.32 V, a short-circuit current density of 0.23 mA cme2, and a fill-factor of 0.42. 0378-7753/88/$3.50 0 Elsevier Sequoia/Printed in The Netherlands
Journal of Power Sources, 1988
... Chem. Soc., 98 (1976) 6855. 24 Y. Ramprakash, V. Subramanian, R, Krishnakumar, AS Lakshmanan ... more ... Chem. Soc., 98 (1976) 6855. 24 Y. Ramprakash, V. Subramanian, R, Krishnakumar, AS Lakshmanan and VK Venkatesan, SESI J., 1 (1987 ) 41. ... Phys. Lett., 38 (1981) 458. 27 VP Singh, Proc. 13th IEEE Photovoltaic Specialists Conf., Washington, DC, 1978, p. 507. ...
Journal of Materials Science Letters, 1988
Journal of Applied Electrochemistry, 1991
ABSTRACT The development of iron oxide films on pyrite has been investigated using linear potenti... more ABSTRACT The development of iron oxide films on pyrite has been investigated using linear potential sweep voltammetry. Voltammograms for a fresh pyrite surface indicated the presence of an iron(II) hydroxyoxide. After brief exposure to air, the surface layer oxidized to iron(III) hydroxy-oxide. Immersion in iron(II) solutions containing small amounts of iron(III) resulted in an increase in the thickness of the oxide layer to a limiting value; the oxide was present mainly in the iron(III) state. An iron hydroxy-oxide also developed on gold during immersion in iron(II) solution. A pyrite surface abraded on iron powder in deoxygenated water also became coated with iron hydroxy-oxide. Immersion of pyrite in cyanide solution resulted in a decrease in the quantity of oxide on the surface.
Solid State Ionics, 1999
The adhesion and the electrochemical performance of Sr doped LaMnO 3 (LSM) electrode with zirconi... more The adhesion and the electrochemical performance of Sr doped LaMnO 3 (LSM) electrode with zirconia-yttria electrolyte has been investigated as a function of the A-site non-stoichiometry. In addition the effect of cathodic current treatment on the electrode resistance and the mechanism of oxygen reduction have been carefully studied. The LSM/electrolyte interface region was examined by SEM/EDS and XRD.
Optical Materials Technology for Energy Efficiency and Solar Energy Conversion IV, 1985
Fourth E.C. Photovoltaic Solar Energy Conference, 1982
The photovoltaic performance characteristics of a photoelectrochemical cell composed of a 25-micr... more The photovoltaic performance characteristics of a photoelectrochemical cell composed of a 25-micron-thick CdS layer deposited by spray pyrolysis on an n-InP single-crystal electrode are presented and analyzed. The combination was chosen as a theoretically effective way of protecting the InP anode from photoanodic dissolution in the alkaline electrolyte (5M KOH with 0.1M sulfide/polysulfide redox system, pH = 10). The preparation
Surface Science, 1984
ABSTRACT The transient photovoltaic response of single crystal n-InP electrodes in a PEC cell has... more ABSTRACT The transient photovoltaic response of single crystal n-InP electrodes in a PEC cell has been studied at different frequencies using a light chopper. The variables were light intensity, chopping frequency and redox species. The nature of the response and time constants were found to be sensitive to modification of the InP surface using ruthenium ions. The capture cross-section and density of traps at the semiconductor-electrolyte interfaces have thus been determined.
Solid State Ionics, 1999
ABSTRACT The polarisation behaviour of Ni/3 mol % Y2O3–ZrO2 (Ni/Y–TZP) cermet electrodes for H2 o... more ABSTRACT The polarisation behaviour of Ni/3 mol % Y2O3–ZrO2 (Ni/Y–TZP) cermet electrodes for H2 oxidation reaction has been investigated by the galvanostatic current interruption (GCI) over a wide range of H2O content and temperature in both undiluted and diluted H2 fuel. The electrode performance increases with H2O content with a maximum at 14% H2O. The reaction orders with respect to partial pressure of H2O and H2 are 0.5 and 0.1, respectively. The activation energy for the reaction is about 70 kJmol−1 in the H2O content range between 4 to 14% in undiluted H2 and in the H2 content range between 14 to 96% in diluted H2. The polarisation behaviour was analysed by fitting the measured data with the Nernst-type concentration equation and an empirical rate equation. The results have demonstrated that charge transfer process may play an very important role in the polarisation behaviour for H2 oxidation reaction on Ni/Y–TZP cermet electrodes. The deviation of the calculated data according to the empirical rate equation from the measured polarisation data at high current densities and low H2 contents indicates that the reaction is limited by at least two electrode processes.
Solid State Ionics, 1999
Reaction order and activation energy for H2 oxidation on Ni/3 mol.% Y2O3–ZrO2 (Ni/Y-TZP) cermet e... more Reaction order and activation energy for H2 oxidation on Ni/3 mol.% Y2O3–ZrO2 (Ni/Y-TZP) cermet electrodes have been evaluated by galvanostatic current interruption (GCI) and electrochemical impedance spectroscopy (EIS) techniques. GCI data show a reaction order in PH2O of 0.4 and activation energy of 76 kJ mol−1. In contrast, a first order with respect to PH2O and an activation energy of
Journal of Materials Science - J MATER SCI, 2000
The shelf-life of Sr doped LaMnO3 (LSM) materials of varying stoichiometric compositions prepared... more The shelf-life of Sr doped LaMnO3 (LSM) materials of varying stoichiometric compositions prepared by wet chemical synthesis was investigated under storage conditions of low and high humidity at ambient temperature for ~350 days. It has been found that the adhesion, chemical stability and stability of the electrode performance of LSM materials are critically dependent on the A-site stoichiometry (i.e., (La+Sr)/Mn ratio) of the LSM materials and much less dependent on storage conditions (humidity level and storage time) over the period investigated. In this respect, LSM materials with stoichiometric and sub-stoichiometric compositions where (La+Sr)/Mn=1 are stable and LSM with A-site sub-stoichiometry ((La+Sr)/Mn=~0.9) is effective in achieving good adherence, high chemical stability and high stability of electrode performance.
Materials Letters, 1989
ABSTRACT Modification of n-InP photoelectrode surfaces by matte etching followed by RuCl3 treatme... more ABSTRACT Modification of n-InP photoelectrode surfaces by matte etching followed by RuCl3 treatment has been shown to enhance the performance and stability of PEC solar cells. The unmodified and modified surfaces have been examined by SIMS, Auger and Raman spectroscopy. These experiments indicate the formation of a thin oxide layer due to modification which results in reduced sub-band gap response and increased Schottky barrier height.
Materials Chemistry and Physics, 1987
The technique of spray pyrolysis which is a simple and inexpensive method for preparing thin film... more The technique of spray pyrolysis which is a simple and inexpensive method for preparing thin films is reviewed with reference to a number of compounds.
Journal of Power Sources, 2002
The electrode behaviour of strontium (Sr)-doped LaMnO 3 (LSM) electrodes is investigated by an el... more The electrode behaviour of strontium (Sr)-doped LaMnO 3 (LSM) electrodes is investigated by an electrochemical impedance spectroscopy technique over the temperature range 850-1000 8C and the oxygen partial pressure range 0.01-0.21 atm. The electrodes are screen-printed on 50 mm  50 mm 3 mol% Y 2 O 3 -ZrO 2 electrolyte cells with an electrode surface area of 10 cm 2 . The impedance responses show two separable arcs and are analysed in terms of two different equivalent circuits with comparable information on the electrode processes at high and low frequencies. The electrode process associated with the high-frequency arc is essentially independent of O 2 partial pressure with an activation energy of 74kJmolAˋ1,whilethatatthelow−frequencyarchasanactivationenergyof74 kJ mol À1 , while that at the low-frequency arc has an activation energy of 74kJmolAˋ1,whilethatatthelow−frequencyarchasanactivationenergyof202 kJ mol À1 and a reaction order with respect to O 2 partial pressure of 0.5atlowtemperaturesand0.5 at low temperatures and 0.5atlowtemperaturesand0.85 at high temperatures. The electrode processes associated with the low-and highfrequency arcs are discussed. #
Journal of Power Sources, 1988
Thin films of CdS have been prepared by the screen-printing technique. Optical absorption studies... more Thin films of CdS have been prepared by the screen-printing technique. Optical absorption studies reveal a band gap of 2.42 eV. Current-voltage studies at the CdS-(1 M NaOH-0.1 M NazS-0.1 M S) interface yield an exchange current density of 6 X 10m6 A cmm2 and a junction ideality factor of 2.8. Mott-Schottky plots at 0.4, 1.0, 2.0 and 4.0 kHz show a flat-band potential of -1.07 V (SCE). At 84.5 mW cmw2 tungsten-halogen illumination, the photoelectrochemical cell gives an open-circuit voltage of 0.32 V, a short-circuit current density of 0.23 mA cme2, and a fill-factor of 0.42. 0378-7753/88/$3.50 0 Elsevier Sequoia/Printed in The Netherlands
Journal of Power Sources, 1988
... Chem. Soc., 98 (1976) 6855. 24 Y. Ramprakash, V. Subramanian, R, Krishnakumar, AS Lakshmanan ... more ... Chem. Soc., 98 (1976) 6855. 24 Y. Ramprakash, V. Subramanian, R, Krishnakumar, AS Lakshmanan and VK Venkatesan, SESI J., 1 (1987 ) 41. ... Phys. Lett., 38 (1981) 458. 27 VP Singh, Proc. 13th IEEE Photovoltaic Specialists Conf., Washington, DC, 1978, p. 507. ...
Journal of Materials Science Letters, 1988
Journal of Applied Electrochemistry, 1991
ABSTRACT The development of iron oxide films on pyrite has been investigated using linear potenti... more ABSTRACT The development of iron oxide films on pyrite has been investigated using linear potential sweep voltammetry. Voltammograms for a fresh pyrite surface indicated the presence of an iron(II) hydroxyoxide. After brief exposure to air, the surface layer oxidized to iron(III) hydroxy-oxide. Immersion in iron(II) solutions containing small amounts of iron(III) resulted in an increase in the thickness of the oxide layer to a limiting value; the oxide was present mainly in the iron(III) state. An iron hydroxy-oxide also developed on gold during immersion in iron(II) solution. A pyrite surface abraded on iron powder in deoxygenated water also became coated with iron hydroxy-oxide. Immersion of pyrite in cyanide solution resulted in a decrease in the quantity of oxide on the surface.
Solid State Ionics, 1999
The adhesion and the electrochemical performance of Sr doped LaMnO 3 (LSM) electrode with zirconi... more The adhesion and the electrochemical performance of Sr doped LaMnO 3 (LSM) electrode with zirconia-yttria electrolyte has been investigated as a function of the A-site non-stoichiometry. In addition the effect of cathodic current treatment on the electrode resistance and the mechanism of oxygen reduction have been carefully studied. The LSM/electrolyte interface region was examined by SEM/EDS and XRD.