Kentaro OISHI - Academia.edu (original) (raw)
Papers by Kentaro OISHI
In this work, we investigated the chemical composition, morphology and optical properties of zinc... more In this work, we investigated the chemical composition, morphology and optical properties of zinc oxide thin films deposited from a simple aqueous zinc chloride solution. The ZnO nanorod arrays were prepared and grown on fluorine doped tin dioxide (FTO) substrate at low temperature. The nanostructure images obtained by scanning electron microscopy showed that it had the wurtzite structure or hexagonal grains with rod (needle) like shape perpendicular to the substrate surface. The Xray diffraction patterns indicated that the thin films were almost pure. The preferential orientation of ZnO growth was (002), a direction that matched calculation. These nanoscale metal oxides having ordered distributions are strong electron acceptors with high electron affinity and electron mobility which improves the electric property of photoanode and charge transport due to continuous channeling along the nanorods. In this present research, we additionally developed and optimized a method electrodepos...
Journal of New Materials For Electrochemical Systems, Dec 30, 2019
The integration of photovoltaic (PV) module into the roof or façade of building affects the heat ... more The integration of photovoltaic (PV) module into the roof or façade of building affects the heat flow out of the PV module, thereby elevating its operating temperature. This increases in the module temperature have a major impact on its performances by reducing its power, thereby lowering the efficiency. In addition, higher operating temperatures accelerate the degradation and the failure of the photovoltaic modules. The performance of the photovoltaic module is further affected if the cells within a PV module operate at different temperatures causing mismatching [1-5]. PV modules are rated at 25°C solar cell temperature; however, in field conditions the normal operating cell temperature (NOCT) is 20°C above ambient temperature [6-9] i.e. 45°C. For this case, power output of the PV module decreases by 0.4%/°C; that means the module will deliver 8% lower power when the ambient temperature is 25°C. In warmer climates the solar cells temperature is even higher, say 65°C. In this case the power output of the PV modules may decrease by 16%. Effectively, when the PV modules are integrated in building to form roof or façade, the solar cells temperature is elevated further as the natural cooling from back of the PV module is impeded [6-8]. Then the Installed Normal Operating Cell Temperature (INOCT) increases by an additional 18°C at least. At an ambient temperature of 25°C, the solar cell temperature is denominated as INOCT = NOCT + 18°C = 63°C. Furthermore, in warmer climates or summer months when ambient temperature is higher than 25°C, the INOCT will rise, thereby reducing the power output substantially. On the other hand, commercial PV module manufacturing lines start by sorting solar cells with matching current output to ensure highest output or efficiency and to ensure reliability. If one solar cell connected in series in a solar module delivers lower current than other cells, then the net current output is equal to the lowest output delivered by any solar cell. If one cell's current is lower than the others, then it will
Journal of New Materials For Electrochemical Systems, Dec 30, 2019
This paper discusses concept of a novel Building Integrated Photovoltaic-Thermal (BIPV-T) solar m... more This paper discusses concept of a novel Building Integrated Photovoltaic-Thermal (BIPV-T) solar module (collector). The concept proposes uniform water cooling of individual solar cells in a module to improve performance of photovoltaic (PV) modules. A simulation study was conducted using TRNSYS software that shows much improvement in performance of PV module if individual cells could be cooled separately. Based on our analysis, a novel concept of a cooling pipe layout (heat exchanger) is proposed that will improve the performance of overall energy efficiency of the PV module over conventionally used series cooling of solar cells in BIPV-T modules. This will help to open a new design of BIPV-T technology based on our proposed BIPV-T module.
Journal of electrochemical energy conversion and storage, Mar 20, 2023
MRS Energy & Sustainability
Metals and alloys are among the most technologically important materials for our industrialized s... more Metals and alloys are among the most technologically important materials for our industrialized societies. They are the most common structural materials used in cars, airplanes and buildings, and constitute the technological core of most electronic devices. They allow the transportation of energy over great distances and are exploited in critical parts of renewable energy technologies. Even though primary metal production industries are mature and operate optimized pyrometallurgical processes, they extensively rely on cheap and abundant carbonaceous reactants (fossil fuels, coke), require high power heating units (which are also typically powered by fossil fuels) to calcine, roast, smelt and refine, and they generate many output streams with high residual energy content. Many unit operations also generate hazardous gaseous species on top of large CO2 emissions which require gas-scrubbing and capture strategies for the future. Therefore, there are still many opportunities to lower th...
Journal of New Materials For Electrochemical Systems, 2019
Resume: Les caracteristiques des modules solaires PV sont determinees dans les conditions normale... more Resume: Les caracteristiques des modules solaires PV sont determinees dans les conditions normales d’essai (STC)avec une temperature ambiante de 25°C. Toutefois, dans les conditions de fonctionnement,la temperature normale d’operation de la cellule (NOCT) est generalement superieure de 20°C audessusde cette temperature ambiante. Ceci fait que dans les conditions reelles le module delivreune puissance inferieure a sa valeur nominale.Cette diminution est generalement de - 0,4% par °C au-dessus des conditions STC. Dans les climats chauds, les temperatures des cellules solaires sont encore plus elevees, reduisant ainsi plus significativement l’energie electrique de sortie des modules PV.----------Abstract: This research work develops the concept and a prototype of a novel Building-Integrated Photovoltaic-Thermal (BIPV-T) solar module (collector). The concept proposes water cooling individual solar cells in a module uniformly to improve performance of photovoltaic (PV) modules. A simulat...
Materials & Design, 2021
• No strong reaction between Al alloys and NaNO 3 up to 720°C in a closed system. • The Al-20%Mg ... more • No strong reaction between Al alloys and NaNO 3 up to 720°C in a closed system. • The Al-20%Mg alloy strongly reacts with NaNO 3 in an open system at 450°C • The Al\ \5%Li alloy reacts with NaNO 3 above its liquidus temperature in an open system • The thermal decomposition of NaNO 3 promotes reactions with Al-based materials. • Reaching the solidus temperature of a material during heat treatment is to be avoided.
Processes, 2020
The discovery of new metallic materials is of prime importance for the development of new technol... more The discovery of new metallic materials is of prime importance for the development of new technologies in many fields such as electronics, aerial and ground transportation as well as construction. These materials require metals which are obtained from various pyrometallurgical processes. Moreover, these materials need to be synthesized under extreme conditions of temperature where liquid solutions are produced and need to be contained. The design and optimization of all these pyrometallurgical processes is a key factor in this development. We present several examples in which computational thermochemistry is used to simulate complex pyrometallurgical processes including the Hall–Heroult process (Al production), the PTVI process (Ni production), and the steel deoxidation from an overall mass balance and energy balance perspective. We also show how computational thermochemistry can assist in the material selection in these extreme operation conditions to select refractory materials in...
Journal of New Materials for Electrochemical Systems, 2019
This paper discusses concept of a novel Building Integrated Photovoltaic-Thermal (BIPV-T) solar m... more This paper discusses concept of a novel Building Integrated Photovoltaic-Thermal (BIPV-T) solar module (collector). The concept proposes uniform water cooling of individual solar cells in a module to improve performance of photovoltaic (PV) modules. A simulation study was conducted using TRNSYS software that shows much improvement in performance of PV module if individual cells could be cooled separately. Based on our analysis, a novel concept of a cooling pipe layout (heat exchanger) is proposed that will improve the performance of overall energy efficiency of the PV module over conventionally used series cooling of solar cells in BIPV-T modules. This will help to open a new design of BIPV-T technology based on our proposed BIPV-T module.
Journal of New Materials for Electrochemical Systems, 2016
The separation of iron from kaolin clay solutions using electro deposition was studied. Electroch... more The separation of iron from kaolin clay solutions using electro deposition was studied. Electrochemical studies of the iron electro-deposition were performed using the techniques of cyclic voltammetry, chronopotentiometry and chronoamperometry on a silver rotating disk electrode (RDE) as a working electrode. The effect of the kaolin solution pretreatment with ultrasonic method on the electrochemical reduction processes was studied. The influence of the disk speed of the electro-deposition performances was also studied. The morphology of the surface of the electro-deposit was observed by SEM. It was found that the ultrasonic pretreatment has an important effect on the reduction processes and on the morphology of the electrodeposited sample. The chemical composition of the electrode-posit was characterized by atomic absorption and ICP-ToFMS. It was shown that Fe2O3 content in the clay was 0.6% (weight). The voltammetric studies revealed that, during the electrochemical reduction proce...
The Oxygen Reduction Reaction (ORR) activity in acid medium on Pd-Co was studied in this work. Th... more The Oxygen Reduction Reaction (ORR) activity in acid medium on Pd-Co was studied in this work. The catalysts were synthesized by two techniques; physical vapor deposition technique and ultrasonic spray reaction technique. The last technique was developed for the first time in our laboratory for the supported electro catalyst preparation and direct deposition onto the carbon paper or gas diffusion electrode the for PEMFC applications. The electrochemical properties such as the amount of hydrogen adsorption/desorption, the oxide formation/reduction of Pd-Co alloy catalyst have not been sufficiently studied before. Therefore these electrochemical properties were investigated by using the Pd-Co thin films prepared by sputtering method. A thin film catalyst cannot be directly used as an electrode of working PEMFCs, however the sputtering method is very useful since the chemical composition of alloy and surface area of the electrode can be controlled easily. Thus the fundamental electrochemical properties such as the amount of hydrogen adsorption/desorption, oxide formation/reduction and oxide reduction peak position on thin films of Pd-Co alloy, Pd and Pt catalysts were determined and their correlations to ORR catalytic activities in acid medium were studied. Enhancements of the catalytic activities for ORR by Pd-Co binary alloys were found to be in agreement with results obtained in previous studies. The electro catalytic performance of the ORR on the various electrodes studied here is: in the order Pd 16 Co 84 < Pd 42 Co 58 < Pd < Pd 50 Co 50 < Pd 75 Co 25 < Pd 65 Co 35. This result clearly shows that alloying Pd with a specific composition of Co enhances significantly the electro-catalytic properties of the ORR on Pd-Co alloys in comparison to Pd alone. Pd 65 Co 35 alloy exhibited the highest ORR activity followed by Pd 75 Co 25 and Pd 50 Co 50 alloys. No obvious activity enhancements were found for Pd 42 Co 58 and Pd 16 Co 84 , which have higher Co content. A linear correlation between hydrogen charges and ORR catalytic activities on Pd-Co alloys was obtained. Catalysts having more Co content have lower ORR activities. With regard to the correlation between the amount of oxide formation/reduction and ORR activities, no linier correlation was found. However the results of this work indicated that the optimized atomic ratio between Pd and Co for ORR in acid medium was found to be around Pd:Co = 3:1. Ultrasonic spray reaction method was developed for the first time in our laboratory for carbon supported nano-scale catalyst for PEMFC application. Fine catalyst particles supported on high surface area carbon powder are required to apply the catalyst as the PEMFC cathode materials for x the commercialization, but none of the studies done before were able to successfully obtain the Pd-Co fine particles which are comparable with the existing carbon supported platinum catalyst (φ2-4nm). Therefore the establishment of the catalyst synthesis method for Pd-Co fine particles are required to use the catalyst for PEMFCs. By using this method established in this study, carbon supported Pt, Pd and Pd-Co catalysts were synthesized and characterised for ORR activity. TEM images indicate that this technique is very useful for preparing carbon supported nano-scale catalysts having the dominant particle size of 2.5-4.5 nm. XRD showed diffraction peaks consistent with face-centered cubic (fcc) structure for Pt. XRD of the synthesized Pd and Pd-Co catalysts by ultrasonic spray reaction also indicated fcc crystal system. All diffractograms of the samples are similar to the structure of fcc Pd, but the Co-origin peaks cannot be found. The Pd-Co system is substitutional solid solutions where some Pd atoms are replaced by Co atoms. The solid solution system is considered to be stable in acid media [1]. We developed this new technique of the ultrasonic spray reaction method not only for nano-scale carbon supported catalyst synthesis but also fabricate directly catalyzed GDE. By using carbon paper as a filter of ultrasonic spray reaction method as described above, carbon supported catalyst are directly deposited onto the carbon paper. It directly forms catalyzed GDE. This technique saves some step of the GDE fabrication and will leads lower cost of PEMFC. Catalytic activity enhancements of ORR for the synthesized Pd-Co catalysts by ultrasonic spray reaction method are confirmed. This result has good agreement with the ORR activity enhancement of the thin film synthesized by PVD. For a given potential, the ORR current of Pd 3 Co 1 /C and Pd 2 Co 1 /C were almost the same and show the highest values among the values of all the other alloys. After, the value of the current decreases from Pd 5 Co 1 /C to Pd 1 Co 1 /C and Pd/C. All Pd based catalysts have around 45mV/dec of tafel slope and Pd mass corrected exchange current around 10-11 mA mg-1. It is assumed that the ORR kinetics in this potential region are the same among the Pd and Pd based catalysts and the addition of Co into Pd have small effect on the ORR kinetics. We conclude that ultrasonic spray reaction method with piezoelectric transducer is applicable for Pd-Co binary alloy catalyst synthesis and the activity enhancement effect caused by alloying with Co was confirmed on the synthesized catalyst by this technique. xi This study contributes to the advancement of the knowledge of fundamental properties of Pd-Co alloy catalysts and their correlations to the oxygen reduction reaction activities. In addition, the ultrasonic spray reaction method developed for the first time in this study introduces a new easy and low cost Membrane Electrode Assembly preparation significantly to an industrial fabrication process of method of preparation of catalyzed gas diffusion electrodes for PEMFCs. The synthesis method of small particle size (φ2-4nm) Pd-Co alloy catalysts were not possible to be obtained by using the existing conventional methods. However this work has achieved the synthesis of the fine particle catalysts supported on carbons by using the ultrasonic spray reaction method. These results will contribute significantly in the development of PEMFCs based on Pd-Co alloy catalysts in the future. xii
Journal of Electroanalytical Chemistry, 2013
Please cite this article as: K. Oishi, O. Savadogo, Electrochemical investigation of Pd-Co thin f... more Please cite this article as: K. Oishi, O. Savadogo, Electrochemical investigation of Pd-Co thin films binary alloy for the oxygen reduction reaction in acid medium,
Electrochemistry Communications, 2004
Extremely active palladium-based alloys catalysts without platinum for the oxygen reduction react... more Extremely active palladium-based alloys catalysts without platinum for the oxygen reduction reaction (ORR) in an acid medium were shown for the first time. The palladium alloys were prepared by sputtering under a vacuum of less than 10− 4 Pa from a palladium target and ...
Journal of Alloys and Compounds
In this work, we investigated the chemical composition, morphology and optical properties of zinc... more In this work, we investigated the chemical composition, morphology and optical properties of zinc oxide thin films deposited from a simple aqueous zinc chloride solution. The ZnO nanorod arrays were prepared and grown on fluorine doped tin dioxide (FTO) substrate at low temperature. The nanostructure images obtained by scanning electron microscopy showed that it had the wurtzite structure or hexagonal grains with rod (needle) like shape perpendicular to the substrate surface. The Xray diffraction patterns indicated that the thin films were almost pure. The preferential orientation of ZnO growth was (002), a direction that matched calculation. These nanoscale metal oxides having ordered distributions are strong electron acceptors with high electron affinity and electron mobility which improves the electric property of photoanode and charge transport due to continuous channeling along the nanorods. In this present research, we additionally developed and optimized a method electrodepos...
Journal of New Materials For Electrochemical Systems, Dec 30, 2019
The integration of photovoltaic (PV) module into the roof or façade of building affects the heat ... more The integration of photovoltaic (PV) module into the roof or façade of building affects the heat flow out of the PV module, thereby elevating its operating temperature. This increases in the module temperature have a major impact on its performances by reducing its power, thereby lowering the efficiency. In addition, higher operating temperatures accelerate the degradation and the failure of the photovoltaic modules. The performance of the photovoltaic module is further affected if the cells within a PV module operate at different temperatures causing mismatching [1-5]. PV modules are rated at 25°C solar cell temperature; however, in field conditions the normal operating cell temperature (NOCT) is 20°C above ambient temperature [6-9] i.e. 45°C. For this case, power output of the PV module decreases by 0.4%/°C; that means the module will deliver 8% lower power when the ambient temperature is 25°C. In warmer climates the solar cells temperature is even higher, say 65°C. In this case the power output of the PV modules may decrease by 16%. Effectively, when the PV modules are integrated in building to form roof or façade, the solar cells temperature is elevated further as the natural cooling from back of the PV module is impeded [6-8]. Then the Installed Normal Operating Cell Temperature (INOCT) increases by an additional 18°C at least. At an ambient temperature of 25°C, the solar cell temperature is denominated as INOCT = NOCT + 18°C = 63°C. Furthermore, in warmer climates or summer months when ambient temperature is higher than 25°C, the INOCT will rise, thereby reducing the power output substantially. On the other hand, commercial PV module manufacturing lines start by sorting solar cells with matching current output to ensure highest output or efficiency and to ensure reliability. If one solar cell connected in series in a solar module delivers lower current than other cells, then the net current output is equal to the lowest output delivered by any solar cell. If one cell's current is lower than the others, then it will
Journal of New Materials For Electrochemical Systems, Dec 30, 2019
This paper discusses concept of a novel Building Integrated Photovoltaic-Thermal (BIPV-T) solar m... more This paper discusses concept of a novel Building Integrated Photovoltaic-Thermal (BIPV-T) solar module (collector). The concept proposes uniform water cooling of individual solar cells in a module to improve performance of photovoltaic (PV) modules. A simulation study was conducted using TRNSYS software that shows much improvement in performance of PV module if individual cells could be cooled separately. Based on our analysis, a novel concept of a cooling pipe layout (heat exchanger) is proposed that will improve the performance of overall energy efficiency of the PV module over conventionally used series cooling of solar cells in BIPV-T modules. This will help to open a new design of BIPV-T technology based on our proposed BIPV-T module.
Journal of electrochemical energy conversion and storage, Mar 20, 2023
MRS Energy & Sustainability
Metals and alloys are among the most technologically important materials for our industrialized s... more Metals and alloys are among the most technologically important materials for our industrialized societies. They are the most common structural materials used in cars, airplanes and buildings, and constitute the technological core of most electronic devices. They allow the transportation of energy over great distances and are exploited in critical parts of renewable energy technologies. Even though primary metal production industries are mature and operate optimized pyrometallurgical processes, they extensively rely on cheap and abundant carbonaceous reactants (fossil fuels, coke), require high power heating units (which are also typically powered by fossil fuels) to calcine, roast, smelt and refine, and they generate many output streams with high residual energy content. Many unit operations also generate hazardous gaseous species on top of large CO2 emissions which require gas-scrubbing and capture strategies for the future. Therefore, there are still many opportunities to lower th...
Journal of New Materials For Electrochemical Systems, 2019
Resume: Les caracteristiques des modules solaires PV sont determinees dans les conditions normale... more Resume: Les caracteristiques des modules solaires PV sont determinees dans les conditions normales d’essai (STC)avec une temperature ambiante de 25°C. Toutefois, dans les conditions de fonctionnement,la temperature normale d’operation de la cellule (NOCT) est generalement superieure de 20°C audessusde cette temperature ambiante. Ceci fait que dans les conditions reelles le module delivreune puissance inferieure a sa valeur nominale.Cette diminution est generalement de - 0,4% par °C au-dessus des conditions STC. Dans les climats chauds, les temperatures des cellules solaires sont encore plus elevees, reduisant ainsi plus significativement l’energie electrique de sortie des modules PV.----------Abstract: This research work develops the concept and a prototype of a novel Building-Integrated Photovoltaic-Thermal (BIPV-T) solar module (collector). The concept proposes water cooling individual solar cells in a module uniformly to improve performance of photovoltaic (PV) modules. A simulat...
Materials & Design, 2021
• No strong reaction between Al alloys and NaNO 3 up to 720°C in a closed system. • The Al-20%Mg ... more • No strong reaction between Al alloys and NaNO 3 up to 720°C in a closed system. • The Al-20%Mg alloy strongly reacts with NaNO 3 in an open system at 450°C • The Al\ \5%Li alloy reacts with NaNO 3 above its liquidus temperature in an open system • The thermal decomposition of NaNO 3 promotes reactions with Al-based materials. • Reaching the solidus temperature of a material during heat treatment is to be avoided.
Processes, 2020
The discovery of new metallic materials is of prime importance for the development of new technol... more The discovery of new metallic materials is of prime importance for the development of new technologies in many fields such as electronics, aerial and ground transportation as well as construction. These materials require metals which are obtained from various pyrometallurgical processes. Moreover, these materials need to be synthesized under extreme conditions of temperature where liquid solutions are produced and need to be contained. The design and optimization of all these pyrometallurgical processes is a key factor in this development. We present several examples in which computational thermochemistry is used to simulate complex pyrometallurgical processes including the Hall–Heroult process (Al production), the PTVI process (Ni production), and the steel deoxidation from an overall mass balance and energy balance perspective. We also show how computational thermochemistry can assist in the material selection in these extreme operation conditions to select refractory materials in...
Journal of New Materials for Electrochemical Systems, 2019
This paper discusses concept of a novel Building Integrated Photovoltaic-Thermal (BIPV-T) solar m... more This paper discusses concept of a novel Building Integrated Photovoltaic-Thermal (BIPV-T) solar module (collector). The concept proposes uniform water cooling of individual solar cells in a module to improve performance of photovoltaic (PV) modules. A simulation study was conducted using TRNSYS software that shows much improvement in performance of PV module if individual cells could be cooled separately. Based on our analysis, a novel concept of a cooling pipe layout (heat exchanger) is proposed that will improve the performance of overall energy efficiency of the PV module over conventionally used series cooling of solar cells in BIPV-T modules. This will help to open a new design of BIPV-T technology based on our proposed BIPV-T module.
Journal of New Materials for Electrochemical Systems, 2016
The separation of iron from kaolin clay solutions using electro deposition was studied. Electroch... more The separation of iron from kaolin clay solutions using electro deposition was studied. Electrochemical studies of the iron electro-deposition were performed using the techniques of cyclic voltammetry, chronopotentiometry and chronoamperometry on a silver rotating disk electrode (RDE) as a working electrode. The effect of the kaolin solution pretreatment with ultrasonic method on the electrochemical reduction processes was studied. The influence of the disk speed of the electro-deposition performances was also studied. The morphology of the surface of the electro-deposit was observed by SEM. It was found that the ultrasonic pretreatment has an important effect on the reduction processes and on the morphology of the electrodeposited sample. The chemical composition of the electrode-posit was characterized by atomic absorption and ICP-ToFMS. It was shown that Fe2O3 content in the clay was 0.6% (weight). The voltammetric studies revealed that, during the electrochemical reduction proce...
The Oxygen Reduction Reaction (ORR) activity in acid medium on Pd-Co was studied in this work. Th... more The Oxygen Reduction Reaction (ORR) activity in acid medium on Pd-Co was studied in this work. The catalysts were synthesized by two techniques; physical vapor deposition technique and ultrasonic spray reaction technique. The last technique was developed for the first time in our laboratory for the supported electro catalyst preparation and direct deposition onto the carbon paper or gas diffusion electrode the for PEMFC applications. The electrochemical properties such as the amount of hydrogen adsorption/desorption, the oxide formation/reduction of Pd-Co alloy catalyst have not been sufficiently studied before. Therefore these electrochemical properties were investigated by using the Pd-Co thin films prepared by sputtering method. A thin film catalyst cannot be directly used as an electrode of working PEMFCs, however the sputtering method is very useful since the chemical composition of alloy and surface area of the electrode can be controlled easily. Thus the fundamental electrochemical properties such as the amount of hydrogen adsorption/desorption, oxide formation/reduction and oxide reduction peak position on thin films of Pd-Co alloy, Pd and Pt catalysts were determined and their correlations to ORR catalytic activities in acid medium were studied. Enhancements of the catalytic activities for ORR by Pd-Co binary alloys were found to be in agreement with results obtained in previous studies. The electro catalytic performance of the ORR on the various electrodes studied here is: in the order Pd 16 Co 84 < Pd 42 Co 58 < Pd < Pd 50 Co 50 < Pd 75 Co 25 < Pd 65 Co 35. This result clearly shows that alloying Pd with a specific composition of Co enhances significantly the electro-catalytic properties of the ORR on Pd-Co alloys in comparison to Pd alone. Pd 65 Co 35 alloy exhibited the highest ORR activity followed by Pd 75 Co 25 and Pd 50 Co 50 alloys. No obvious activity enhancements were found for Pd 42 Co 58 and Pd 16 Co 84 , which have higher Co content. A linear correlation between hydrogen charges and ORR catalytic activities on Pd-Co alloys was obtained. Catalysts having more Co content have lower ORR activities. With regard to the correlation between the amount of oxide formation/reduction and ORR activities, no linier correlation was found. However the results of this work indicated that the optimized atomic ratio between Pd and Co for ORR in acid medium was found to be around Pd:Co = 3:1. Ultrasonic spray reaction method was developed for the first time in our laboratory for carbon supported nano-scale catalyst for PEMFC application. Fine catalyst particles supported on high surface area carbon powder are required to apply the catalyst as the PEMFC cathode materials for x the commercialization, but none of the studies done before were able to successfully obtain the Pd-Co fine particles which are comparable with the existing carbon supported platinum catalyst (φ2-4nm). Therefore the establishment of the catalyst synthesis method for Pd-Co fine particles are required to use the catalyst for PEMFCs. By using this method established in this study, carbon supported Pt, Pd and Pd-Co catalysts were synthesized and characterised for ORR activity. TEM images indicate that this technique is very useful for preparing carbon supported nano-scale catalysts having the dominant particle size of 2.5-4.5 nm. XRD showed diffraction peaks consistent with face-centered cubic (fcc) structure for Pt. XRD of the synthesized Pd and Pd-Co catalysts by ultrasonic spray reaction also indicated fcc crystal system. All diffractograms of the samples are similar to the structure of fcc Pd, but the Co-origin peaks cannot be found. The Pd-Co system is substitutional solid solutions where some Pd atoms are replaced by Co atoms. The solid solution system is considered to be stable in acid media [1]. We developed this new technique of the ultrasonic spray reaction method not only for nano-scale carbon supported catalyst synthesis but also fabricate directly catalyzed GDE. By using carbon paper as a filter of ultrasonic spray reaction method as described above, carbon supported catalyst are directly deposited onto the carbon paper. It directly forms catalyzed GDE. This technique saves some step of the GDE fabrication and will leads lower cost of PEMFC. Catalytic activity enhancements of ORR for the synthesized Pd-Co catalysts by ultrasonic spray reaction method are confirmed. This result has good agreement with the ORR activity enhancement of the thin film synthesized by PVD. For a given potential, the ORR current of Pd 3 Co 1 /C and Pd 2 Co 1 /C were almost the same and show the highest values among the values of all the other alloys. After, the value of the current decreases from Pd 5 Co 1 /C to Pd 1 Co 1 /C and Pd/C. All Pd based catalysts have around 45mV/dec of tafel slope and Pd mass corrected exchange current around 10-11 mA mg-1. It is assumed that the ORR kinetics in this potential region are the same among the Pd and Pd based catalysts and the addition of Co into Pd have small effect on the ORR kinetics. We conclude that ultrasonic spray reaction method with piezoelectric transducer is applicable for Pd-Co binary alloy catalyst synthesis and the activity enhancement effect caused by alloying with Co was confirmed on the synthesized catalyst by this technique. xi This study contributes to the advancement of the knowledge of fundamental properties of Pd-Co alloy catalysts and their correlations to the oxygen reduction reaction activities. In addition, the ultrasonic spray reaction method developed for the first time in this study introduces a new easy and low cost Membrane Electrode Assembly preparation significantly to an industrial fabrication process of method of preparation of catalyzed gas diffusion electrodes for PEMFCs. The synthesis method of small particle size (φ2-4nm) Pd-Co alloy catalysts were not possible to be obtained by using the existing conventional methods. However this work has achieved the synthesis of the fine particle catalysts supported on carbons by using the ultrasonic spray reaction method. These results will contribute significantly in the development of PEMFCs based on Pd-Co alloy catalysts in the future. xii
Journal of Electroanalytical Chemistry, 2013
Please cite this article as: K. Oishi, O. Savadogo, Electrochemical investigation of Pd-Co thin f... more Please cite this article as: K. Oishi, O. Savadogo, Electrochemical investigation of Pd-Co thin films binary alloy for the oxygen reduction reaction in acid medium,
Electrochemistry Communications, 2004
Extremely active palladium-based alloys catalysts without platinum for the oxygen reduction react... more Extremely active palladium-based alloys catalysts without platinum for the oxygen reduction reaction (ORR) in an acid medium were shown for the first time. The palladium alloys were prepared by sputtering under a vacuum of less than 10− 4 Pa from a palladium target and ...
Journal of Alloys and Compounds