Ayse Bayrakceken | Ataturk University (original) (raw)

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Papers by Ayse Bayrakceken

Turkish Journal of Chemistry, 2014

International Journal of Hydrogen Energy, 2012

Applied Surface Science, Nov 1, 2014

Microporous and Mesoporous Materials, Jun 1, 2017

International Journal of Hydrogen Energy, Nov 1, 2018

Applied Surface Science, Nov 1, 2014

Abstract CuO structures were synthesized by chemical precipitation method at nanoscale. The effec... more Abstract CuO structures were synthesized by chemical precipitation method at nanoscale. The effects of different reactants including KOH + NH3·H2O, NH3·H2O + KOH, KOH or NaOH in addition to Cu(NO3)2·3H2O on the properties of CuO structures were investigated. Effects of different surfactants including zwitterionic 3-(N,N-dimethyldodecylammonio) propane-sulfonate (SB12), cationic cetyl trimethylammonium bromide (CTAB) and anionic sodium dodecyl sulfate (SDS) were also investigated. Synthesized samples were characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TGA), Fourier Transform Infrared (FTIR) spectra, scanning electron microscopy (SEM) and cyclic voltammetry (CV) techniques. XRD and SEM results showed that the morphologies were significantly changed with respect to the reactant used. The significant effects of different surfactants on the structures were also observed from the experiments. The specific capacitances were changed according to the utilization of different reactants.

International Journal of Hydrogen Energy, Nov 1, 2012

Abstract Polypyrrole (PPy)/Carbon composites were synthesized by in situ chemical oxidative polym... more Abstract Polypyrrole (PPy)/Carbon composites were synthesized by in situ chemical oxidative polymerization of pyrrole monomer on carbon black. Effects of polymerization temperature (either 0 °C or 25 °C) and different dopants including p-toluenesulfonic acid (p-TSA) and sodium dodecyl sulfate (SDS) on the properties of the composites were investigated. The synthesized composites were characterized by XRD, FTIR and TGA. Electrical conductivities of the composites were determined by using four-point probe technique. Electrochemical oxidation characteristics of the synthesized PPy/Carbon composites were investigated by cyclic voltammetry via potential holding experiments. The PPy/Carbon composites synthesized at 0 °C and with p-TSA as dopant showed the best oxidation resistance than carbon and other composites.

Journal of Power Sources, Aug 1, 2009

A significantly active Pd-Pt/carbon electrocatalyst for polymer electrolyte membrane fuel cells w... more A significantly active Pd-Pt/carbon electrocatalyst for polymer electrolyte membrane fuel cells was synthesized by microwave irradiation using a hollow core mesoporous shell (HCMS) carbon as catalyst support that was prepared by template replication of core/shell spherical silica particles and two different carbon precursors. Pt/Pd percent weight ratios on carbon support were varied as 20/0, 15/5, 10/10, 5/15 to 0/20. As the average pore diameter of the carbon support was increased from 3.02nm to 3.90nm by changing the type of the carbon precursor, fuel cell performances of the HCMS carbon based Pd-Pt bimetallic catalysts were improved significantly.

Gazi university journal of science, Sep 28, 2022

International Journal of Hydrogen Energy, 2016

In this study, we compared two facile and effective approaches which are supercritical carbon dio... more In this study, we compared two facile and effective approaches which are supercritical carbon dioxide (scCO2) deposition and microwave irradiation methods to synthesize Pt nanoparticles uniformly dispersed on graphene nanoplatelets (G) having 750 m2/g surface area as the support material. The prepared catalysts were characterized by using XRD, TGA, TEM, CV and PEM fuel cell performance tests. Microwave irradiation (Pt/G1) and scCO2 deposition (Pt/G2) methods resulted in the particle sizes of 3.1–3.4 nm and 1.5–1.6 nm, respectively. Higher electrochemically active surface area and PEM fuel cell performance were obtained for the Pt/G2 catalyst. An accelerated aging test, carbon corrosion, is also applied to the catalysts and Tafel slope losses were determined. Pt/G1 catalyst resulted in 50 mV Tafel slope loss whereas no significant loss was observed for Pt/G2 catalyst after carbon corrosion test.

International Journal of Hydrogen Energy, 2012

International Journal of Hydrogen Energy, 2016

Abstract In the last years new carbon and/or composite materials have been suggested as support f... more Abstract In the last years new carbon and/or composite materials have been suggested as support for PEM fuel cell catalysts to improve the stability of the catalysts. In the present study, polypyrrole (PPy) was used as conducting polymer and PPy/carbon composites having different carbon ratios were synthesized by in situ chemical oxidative polymerization of pyrrole on carbon black. Platinum (Pt) nanoparticles over these composites were achieved by using microwave irradiation technique. Physicochemical characterizations of the composites were carried out by using BET, TEM, XRD and TGA techniques. Cyclic voltammetry (CV) measurements were used to determine the ex-situ electrocatalytic activity and also the degradation behaviors of the prepared catalysts. In situ PEM fuel cell performance tests were used to evaluate the effect of carbon ratio in composite material on PEM fuel cell performance. PEM fuel cell performance was increased as the carbon ratio in the composite was increased.

Results in Physics

Abstract In this investigation, Al/PEDOT/C/p-Si structure has been fabricated by synthesizing PED... more Abstract In this investigation, Al/PEDOT/C/p-Si structure has been fabricated by synthesizing PEDOT/C composites on the p-Si substrate. The thickness and surface morphology of PEDOT/C on p-Si have been investigated by using the scanning electron microscope. The optical characterization of PEDOT/C solution indicated a strong optical absorbance peak located at 267 nm. The electrical characterization of Al/PEDOT/C/p-Si structure was made under dark and illumination conditions at the room temperature. The ideality factor, and barrier height were identified to be 1.28, 1.12 and 0.80 eV, 0.83 eV from current–voltage (I–V) measurements for dark and illuminated conditions, respectively. The results show that the Al/PEDOT/C/p-Si structure may be utilized to be a photodiode in optoelectronic implementations.

International Journal of Hydrogen Energy

In the last years new carbon and/or composite materials have been suggested as support for PEM fu... more In the last years new carbon and/or composite materials have been suggested as support for PEM fuel cell catalysts to improve the stability of the catalysts. In the present study, polypyrrole (PPy) was used as conducting polymer and PPy/carbon composites having different carbon ratios were synthesized by in situ chemical oxidative polymerization of pyrrole on carbon black. Platinum (Pt) nanoparticles over these composites were achieved by using microwave irradiation technique. Physicochemical characterizations of the composites were carried out by using BET, TEM, XRD and TGA techniques. Cyclic voltammetry (CV) measurements were used to determine the ex-situ electrocatalytic activity and also the degradation behaviors of the prepared catalysts. In situ PEM fuel cell performance tests were used to evaluate the effect of carbon ratio in composite material on PEM fuel cell performance. PEM fuel cell performance was increased as the carbon ratio in the composite was increased.

In this study, we compared two facile and effective approaches which are supercritical carbon dio... more In this study, we compared two facile and effective approaches which are supercritical carbon dioxide (scCO2) deposition and microwave irradiation methods to synthesize Pt nanoparticles uniformly dispersed on graphene nanoplatelets (G) having 750 m2/g surface
area as the support material. The prepared catalysts were characterized by using XRD, TGA, TEM, CV and PEM fuel cell performance tests. Microwave irradiation (Pt/G1) and scCO2 deposition (Pt/G2) methods resulted in the particle sizes of 3.1e3.4 nm and 1.5e1.6 nm, respectively. Higher electrochemically active surface area and PEM fuel cell performance were obtained for the Pt/G2 catalyst. An accelerated aging test, carbon corrosion, is also applied to the catalysts and Tafel slope losses were determined. Pt/G1 catalyst resulted in 50 mV Tafel slope loss whereas no significant loss was observed for Pt/G2 catalyst after carbon corrosion test.

Fuel Cells, 2015

ABSTRACT Cathode electrodes of proton exchange membrane fuel cells were fabricated by using Pt sp... more ABSTRACT Cathode electrodes of proton exchange membrane fuel cells were fabricated by using Pt sputter deposition to increase the gravimetric power density (W mgPt−1) with reduced Pt loading. Ultra low Pt-based electrodes having Pt loading in between 0.0011 and 0.06 mgPt cm−2 were prepared by a radio frequency (RF) sputter deposition method on the surface of a non-catalyzed gas diffusion layer (GDL) substrate by changing the sputtering time (20, 90, 180, 1050 s). The effect of cathode Pt loading on the performance of membrane electrode assembly were investigated using polarization curve, impedance, H2 crossover and cyclic voltammetry techniques. The effect of backpressure on PEMFC performance was also investigated. Sputter1050 (0.06 mgPt cm−2) exhibited the best power density at 80 °C cell temperature and without backpressure for H2/O2, 100 %RH (297 mW cm−2 and 5 W mgPt−1 at 0.6 V). On the other hand sputter90 (0.005 mgPt cm−2) showed the peak gravimetric power density (15 W mgPt−1 and 75 mW cm−2 at 0.6 V). The Pt utilization efficiency increased as the Pt loading decreased. Sputter20 and sputter90 electrodes yielded insufficient electrochemical surface area (ECSA), higher charge transfer and ohmic resistance, but sputter180 and sputter1050 yielded sufficient ECSA and lower charge transfer and ohmic resistance.

International Journal of Hydrogen Energy, 2015

Applied Mechanics and Materials, 2015

Turkish Journal of Chemistry, 2014

International Journal of Hydrogen Energy, 2012

Applied Surface Science, Nov 1, 2014

Microporous and Mesoporous Materials, Jun 1, 2017

International Journal of Hydrogen Energy, Nov 1, 2018

Applied Surface Science, Nov 1, 2014

Abstract CuO structures were synthesized by chemical precipitation method at nanoscale. The effec... more Abstract CuO structures were synthesized by chemical precipitation method at nanoscale. The effects of different reactants including KOH + NH3·H2O, NH3·H2O + KOH, KOH or NaOH in addition to Cu(NO3)2·3H2O on the properties of CuO structures were investigated. Effects of different surfactants including zwitterionic 3-(N,N-dimethyldodecylammonio) propane-sulfonate (SB12), cationic cetyl trimethylammonium bromide (CTAB) and anionic sodium dodecyl sulfate (SDS) were also investigated. Synthesized samples were characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TGA), Fourier Transform Infrared (FTIR) spectra, scanning electron microscopy (SEM) and cyclic voltammetry (CV) techniques. XRD and SEM results showed that the morphologies were significantly changed with respect to the reactant used. The significant effects of different surfactants on the structures were also observed from the experiments. The specific capacitances were changed according to the utilization of different reactants.

International Journal of Hydrogen Energy, Nov 1, 2012

Abstract Polypyrrole (PPy)/Carbon composites were synthesized by in situ chemical oxidative polym... more Abstract Polypyrrole (PPy)/Carbon composites were synthesized by in situ chemical oxidative polymerization of pyrrole monomer on carbon black. Effects of polymerization temperature (either 0 °C or 25 °C) and different dopants including p-toluenesulfonic acid (p-TSA) and sodium dodecyl sulfate (SDS) on the properties of the composites were investigated. The synthesized composites were characterized by XRD, FTIR and TGA. Electrical conductivities of the composites were determined by using four-point probe technique. Electrochemical oxidation characteristics of the synthesized PPy/Carbon composites were investigated by cyclic voltammetry via potential holding experiments. The PPy/Carbon composites synthesized at 0 °C and with p-TSA as dopant showed the best oxidation resistance than carbon and other composites.

Journal of Power Sources, Aug 1, 2009

A significantly active Pd-Pt/carbon electrocatalyst for polymer electrolyte membrane fuel cells w... more A significantly active Pd-Pt/carbon electrocatalyst for polymer electrolyte membrane fuel cells was synthesized by microwave irradiation using a hollow core mesoporous shell (HCMS) carbon as catalyst support that was prepared by template replication of core/shell spherical silica particles and two different carbon precursors. Pt/Pd percent weight ratios on carbon support were varied as 20/0, 15/5, 10/10, 5/15 to 0/20. As the average pore diameter of the carbon support was increased from 3.02nm to 3.90nm by changing the type of the carbon precursor, fuel cell performances of the HCMS carbon based Pd-Pt bimetallic catalysts were improved significantly.

Gazi university journal of science, Sep 28, 2022

International Journal of Hydrogen Energy, 2016

In this study, we compared two facile and effective approaches which are supercritical carbon dio... more In this study, we compared two facile and effective approaches which are supercritical carbon dioxide (scCO2) deposition and microwave irradiation methods to synthesize Pt nanoparticles uniformly dispersed on graphene nanoplatelets (G) having 750 m2/g surface area as the support material. The prepared catalysts were characterized by using XRD, TGA, TEM, CV and PEM fuel cell performance tests. Microwave irradiation (Pt/G1) and scCO2 deposition (Pt/G2) methods resulted in the particle sizes of 3.1–3.4 nm and 1.5–1.6 nm, respectively. Higher electrochemically active surface area and PEM fuel cell performance were obtained for the Pt/G2 catalyst. An accelerated aging test, carbon corrosion, is also applied to the catalysts and Tafel slope losses were determined. Pt/G1 catalyst resulted in 50 mV Tafel slope loss whereas no significant loss was observed for Pt/G2 catalyst after carbon corrosion test.

International Journal of Hydrogen Energy, 2012

International Journal of Hydrogen Energy, 2016

Abstract In the last years new carbon and/or composite materials have been suggested as support f... more Abstract In the last years new carbon and/or composite materials have been suggested as support for PEM fuel cell catalysts to improve the stability of the catalysts. In the present study, polypyrrole (PPy) was used as conducting polymer and PPy/carbon composites having different carbon ratios were synthesized by in situ chemical oxidative polymerization of pyrrole on carbon black. Platinum (Pt) nanoparticles over these composites were achieved by using microwave irradiation technique. Physicochemical characterizations of the composites were carried out by using BET, TEM, XRD and TGA techniques. Cyclic voltammetry (CV) measurements were used to determine the ex-situ electrocatalytic activity and also the degradation behaviors of the prepared catalysts. In situ PEM fuel cell performance tests were used to evaluate the effect of carbon ratio in composite material on PEM fuel cell performance. PEM fuel cell performance was increased as the carbon ratio in the composite was increased.

Results in Physics

Abstract In this investigation, Al/PEDOT/C/p-Si structure has been fabricated by synthesizing PED... more Abstract In this investigation, Al/PEDOT/C/p-Si structure has been fabricated by synthesizing PEDOT/C composites on the p-Si substrate. The thickness and surface morphology of PEDOT/C on p-Si have been investigated by using the scanning electron microscope. The optical characterization of PEDOT/C solution indicated a strong optical absorbance peak located at 267 nm. The electrical characterization of Al/PEDOT/C/p-Si structure was made under dark and illumination conditions at the room temperature. The ideality factor, and barrier height were identified to be 1.28, 1.12 and 0.80 eV, 0.83 eV from current–voltage (I–V) measurements for dark and illuminated conditions, respectively. The results show that the Al/PEDOT/C/p-Si structure may be utilized to be a photodiode in optoelectronic implementations.

International Journal of Hydrogen Energy

In the last years new carbon and/or composite materials have been suggested as support for PEM fu... more In the last years new carbon and/or composite materials have been suggested as support for PEM fuel cell catalysts to improve the stability of the catalysts. In the present study, polypyrrole (PPy) was used as conducting polymer and PPy/carbon composites having different carbon ratios were synthesized by in situ chemical oxidative polymerization of pyrrole on carbon black. Platinum (Pt) nanoparticles over these composites were achieved by using microwave irradiation technique. Physicochemical characterizations of the composites were carried out by using BET, TEM, XRD and TGA techniques. Cyclic voltammetry (CV) measurements were used to determine the ex-situ electrocatalytic activity and also the degradation behaviors of the prepared catalysts. In situ PEM fuel cell performance tests were used to evaluate the effect of carbon ratio in composite material on PEM fuel cell performance. PEM fuel cell performance was increased as the carbon ratio in the composite was increased.

In this study, we compared two facile and effective approaches which are supercritical carbon dio... more In this study, we compared two facile and effective approaches which are supercritical carbon dioxide (scCO2) deposition and microwave irradiation methods to synthesize Pt nanoparticles uniformly dispersed on graphene nanoplatelets (G) having 750 m2/g surface
area as the support material. The prepared catalysts were characterized by using XRD, TGA, TEM, CV and PEM fuel cell performance tests. Microwave irradiation (Pt/G1) and scCO2 deposition (Pt/G2) methods resulted in the particle sizes of 3.1e3.4 nm and 1.5e1.6 nm, respectively. Higher electrochemically active surface area and PEM fuel cell performance were obtained for the Pt/G2 catalyst. An accelerated aging test, carbon corrosion, is also applied to the catalysts and Tafel slope losses were determined. Pt/G1 catalyst resulted in 50 mV Tafel slope loss whereas no significant loss was observed for Pt/G2 catalyst after carbon corrosion test.

Fuel Cells, 2015

ABSTRACT Cathode electrodes of proton exchange membrane fuel cells were fabricated by using Pt sp... more ABSTRACT Cathode electrodes of proton exchange membrane fuel cells were fabricated by using Pt sputter deposition to increase the gravimetric power density (W mgPt−1) with reduced Pt loading. Ultra low Pt-based electrodes having Pt loading in between 0.0011 and 0.06 mgPt cm−2 were prepared by a radio frequency (RF) sputter deposition method on the surface of a non-catalyzed gas diffusion layer (GDL) substrate by changing the sputtering time (20, 90, 180, 1050 s). The effect of cathode Pt loading on the performance of membrane electrode assembly were investigated using polarization curve, impedance, H2 crossover and cyclic voltammetry techniques. The effect of backpressure on PEMFC performance was also investigated. Sputter1050 (0.06 mgPt cm−2) exhibited the best power density at 80 °C cell temperature and without backpressure for H2/O2, 100 %RH (297 mW cm−2 and 5 W mgPt−1 at 0.6 V). On the other hand sputter90 (0.005 mgPt cm−2) showed the peak gravimetric power density (15 W mgPt−1 and 75 mW cm−2 at 0.6 V). The Pt utilization efficiency increased as the Pt loading decreased. Sputter20 and sputter90 electrodes yielded insufficient electrochemical surface area (ECSA), higher charge transfer and ohmic resistance, but sputter180 and sputter1050 yielded sufficient ECSA and lower charge transfer and ohmic resistance.

International Journal of Hydrogen Energy, 2015

Applied Mechanics and Materials, 2015