DO CHI LINH

Transcription

1 MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY OF SCIENCE AND TECNOLOGY GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY DO CHI LINH SYNTHESIS AND CHARACTERIZATION OF CARBON SUPPORTED PT AND PT ALLOY NANOPARTICLES AS ELECTROCATALYSTS MATERIAL FOR PROTON EXCHANGE MEMBRANE FUEL CELL Major: Metal Science Code: SUMMARY OF MATERIALS SCIENCE DOCTORAL THESIS Hanoi 2018

2 PREFACE Proton exchange membrane fuel cell (PEMFC), a potential renewable energy source in the near future, has been considerablely studied in the world. The advantages of the PEMFCs are low temperature operation, high conversion efficiency, fast startup, low temperature operation (<100 C), flexible power scalee and particularly friendly environment. The application of PEMFC focuses on three main areas: transportation, power supply for residential areas and power for portable electronic devices. Platinum is the ideal catalyst material for PEMFC due to its high catalytic activity for hydrogen oxidation (HOR) and oxygen reduction (ORR) reactions as well as high stability in low ph environments at cathode. However, Pt is precious and expensive, so the use of this material will greatly increase the cost of PEMFC. This is one of the major challenges that limit the commercialization of PEMFCs in the world. To reduce the Pt metallic catalyst content, development of nanotechnology has played an important role with research of dispersing Pt metallic particles on carbon supports. To disperse catalyst nano-particles means that the catalyst surface area is increased. In some reports, this area may reach to approcimately 120 m 2 /g. As a result, the activity of the catalyst material has been significantly improved and Pt metallic loading might dropped to 0.4 mg/cm 2 while PEMFC properties change insignificantly. Using Pt alloy catalysts with cheaper metals as electrode material is another effective approche for reducing PEMFC costs. For anodic catalysts, many Pt alloys with alloying metals such as Ru, W, Sn, Pd have been studied. These studies have shown that using

3 catalyst alloys may improve catalytic activity for hydrogen oxidation reaction (HOR) and CO poisoning in PEMFC. For cathode ctalysts, Pt-M catalyst alloys (with M transition metals such as Mn, Cr, Fe, Co and Ni) are the most widely studied due to activity for oxygen reduction reaction (ORR) higher than pure Pt. Alloying catalysts improve ORR activity towards reducing oxygen by direct 4-electron reaction withou H 2 O 2 intermediate stage therefore catalytic activity of these alloys may be higher 3-5 times compared to pure Pt / C catalysts. In Vietnam, research on PEMFC fuel cells has not intensively been considered and there are few research groups being studying on direct methanol fuel cell. With desire to develop PEMFC area using direct hydrogen fuel, research on catalytic materials is essential. Therefore, the topic of the thesis was chosen as: Synthesis and characterization of carbon supported Pt and Pt alloy nanoparticles as electrocatalysts material for proton exchange membrane fuel cell Scope of thesis: - Research and development of Pt/C and Pt-M/C alloys high performence catalysts to apply in proton exchange membrane fuel cells using direct hydrogen fuel. - Research and development of single PEM fuel cell having high power density with active area of 5cm 2. Main contents of thesis: - Introdution of fuel cell and studies on Pt catalysts and Pt alloy catalysts in PEMFC. - Research on synthesis of catalytic materials Pt/C 20% wt. by electroless deposition method and evaluating to influence of

4 experimental parameters such as ph, temperature... in the synthesis process on the properties of catalyst Pt / C 20%wt. - To optimum process for synthesis of Pt/C highly active catalysts as electrode materials in PEMFC. - Research on synthesis of Pt-M/C alloy catalyst 20%wt. (M = Ni, Co and Fe) by electroless deposition method and characterization of alloy catalysts to select a suitable alloy catalyst for ORR at cathode in PEMFC. - Researching, designing, and fabricating components of a single PEM fuel cell with active area of 5cm 2 and study on operating conditions for single fuel cell. CHAPTER 1. INTRODUCTION - Brief introduction on history, configuration, operation principle and application of PEMFC. - Describe the mechanisms and kinetics of hydrogen oxidation reaction and oxygen reduction reaction taking place on Pt / C catalysts in PEMFC - Introduction of history, research and development of catalytic materials serving as anode and cathode in PEMFC. CHAPTER 2. EXPERIMENTAL AND RESEARCH APPROCHES 2.1. Preparation of catalytic materials Pt and Pt 3 M (M = Ni, Co, Fe) on Vulcan XC-72 carbon supports. Pt/C catalyst with metallic content of 20%wt. is synthesized by electroless deposition using ethylene glycol and NaBH 4 assisted ethylene glycol. In ethylene glycol preparation, Pt/C catalysts were synthesized at temperatures of 80 C and 140 C. In addition, the catalysts were synthesized in a mixture of ethylene glycol: water by

5 ratios (EG: W) of 9:1, 7:1, 5:1, and 3:1 (in unit volume). In NaBH 4 assisted ethylene glycol method, catalytic samples are synthesized in mixture solvents with varying ph values of 10; 7; 4 and Preparation of catalyt ink In characterization of catalytic materials and MEA electrodes, catalytic particles were prepared into catalytic inks including Pt/C and Pt 3 M/C catalyst particles with metallic content of 20%wt into a mixture solvent. Catalyst composition includes metallic catalyst of 5mg, absolute ethanol of 4 ml, and Nafion solution 10% of 25 µl MEA preparation The MEA electrodes with a nafion membrane sandwiched between two symmetry diffusion layers coated with catalyst ink were prepared hot-pressing method. Catalysts were prepared by brushing catalyst ink onto a gas diffusion carbon paper with active area of 5 cm Research approches Physical methods Transmission Electron Microscopy TEM is used to evaluate the size and distribution of metallic catalyst particles while X-ray diffraction is used to evaluate the structure and alloying degree of Pt-M/C catalysts. Energy-Dispersive X-Ray Spectroscopy (EDX) were used to determine the purity of the synthesized Pt/C catalysts Electrochemical methods Cyclic Voltammetry (CV) The electrochemical sample is holded into a Teflon mold with a working area of 1 cm 2. The measurements were conducted in a three electrode cell with counter electrode as platinum and the

6 reference electrode as saturated calomel. Electrochemical measurements were done in solution H 2 SO M and apparatus was PARSTAT2273 (EG & G -USA). To study catalytic activity, CV measurements were scanned in potential range of V (NHE) with scanning speed of 50 mv/s at room temperature. For durability test, samples were scanned in potential range of V (NHE) with 1000 cycles and a scanning speed of 50 mv/s. After each 200 durability test cycles of test, the sample is measured by CV for repeating evaluation of catalytic activity Linear scan voltammmetry (LSV) Activity improvements of PtM alloy catalysts for ORR were investigated by measuring LSV scanning. Samples were polarized from open circuit potential value to potential value of 0.7 V in 0.5 M H 2 SO 4 solution with scanning speed of 1mV/s Evaluation of MEA properties by U-I polarization curve In the U-I polarization measurement, voltage of single cell was changed by using an external electric load. Current values were measured by ammeter and were recorded corresponding to each voltage value of single cell. The measurement was done from open circuit voltage to the voltage value of 0.4V. The recorded data of the single cell was used to plot a U-I graph by Excel software. CHAPTER 3. SYNTHESIS OF PT/C CATALYSTS BY ETHYLENE GLYCOL METHOD 3.1. Synthesis of Pt/C catalyst by electroless deposition using ethylene glycol In synthesis process of Pt/C catalysts with EG, temperature has a considerable influence on reduction of forming Pt particles on

7 carbon supports. In this study, Pt/C catalyst was synthesized at 80oC. On TEM image, Pt particles on carbon support were not observed. In addiction, on the CV curve of this sample, there is not electrochemical peaks corresponding to reduction and oxidation of Pt metal. Therefore, at temperature of 80 C, formation of Pt metallic particles from precursor salt occurs slowly due to weak ethylene glycol reduction agent. Increase of temperature to 140oC, the reaction of forming Pt metallic particles becomes better. EDX analysis results confirmed the formation of Pt metal after reduction process. However, in this result presence of oxygen element is also observed. Thus, a small amount of PtO oxide was formed while forming of Pt/C catalysts. Figure 3.6. TEM picture and size distribution histogram of Pt/C catalyst particles synthesized at 1400C The formation of Pt catalyst particles on carbon support is also confirmed by TEM picture. For Pt/C catalysts, on TEM picture balack and small Pt particles appear uniformly on sphere carbon particles. A histogram of Pt particle size distribution measured 100 catalyst particles from TEM picture showed that at this synthesis condition, size of Pt metallic catalyst particles is mainly in the range

8 of nm and average particle size is about 3.8 nm (seeing on figure 3.6). Meanwhile, with the commercial catalyst sample, size of Pt catalyst particles is in range of nm with average particle size of 3.1nm. Figure 3.9. CV curves of Vulcan XC-72 carbon, commercial catalyst and synthesized catalyst Pt/C 20%wt. Figure 3.9 shows the CV curves of Vulcan XC-72 carbon commercial catalyst and synthesized catalyst Pt/C 20%wt. samples in 0.5M H 2 SO 4 solution. By integrating, ESA values are calculated from H 2 desorb/absorb peaks in the V potential range. ESA value of commercial and synthesized catalyst samples reach to and m 2 / g, respectively. Figure 3.11 shows changes in ESA values of Pt/C commercial and synthesized catalyst samples after durability test. In general, after every 200 durability cycles, activity of catalyts decreases. After 1000 cycles, deacreses in ESA values of synthesized and commercial catalyst samples are and 32.33%. Thus, compared with commercial sample, synthesized catalyst sample is more durable.

9 Figure Graph of changes in ESA values of commercial and synthesized catalyst samples after the durability test To reduce particle size and increase the surface area of Pt metallic catalyst particles, studies using solvent mixtures in synthesis of Pt/C catalyst were conducted. Pt/C catalysts were synthesized at 140 C with mixture solvents having different EG:W ratios of 9:1, 7:1, 5:1 and 3:1. The Pt/C catalysts synthesized with EG:W ratios of 9:1 and 7:1 have ESA values of about 72m 2 /g while the JM sample is about 64,91 m 2 /g. In addition, after 1000 cycles of durability test, these synthesized catalysts exhibite high durability. Therefore, Pt/C catalysts synthesized with EG:W ratios of 9:1 and 7:1 have high activity and durability Synthesis of Pt/C catalysts by NaBH 4 assisted ethylene glycol In order to reduce temperature of synthesis process as well as to improve properties of Pt / C catalyst material, study on synthesis of Pt/C catalysts by NaBH 4 assisted ethylene glycol method was conducted. Catalyst samples were synthesized with ph values of 2, 4, 7, 10 and 12. Table 3.5 summarizes average size values of the synthesized Pt catalyst particles at these ph values. From the

10 obtained results, it is clear that when ph of mixture solvent decreases, size of the synthesized catalyst particles also decreases. With ph value of 4, the synthesized catalyst sample have the highest ESA value of m 2 /g. The Pt/C synthesized catalyst at ph of 4 has also moderate durability with a decrease in ESA value after 1000 cycles of test only of 15.58%. Table 3.5. Average particle size of Pt/C catalyst samples synthesized at different ph values ph Average size (nm) Synthesis procedure of Pt/C catalyst Figure Synthesis procedure of catalyst Pt/C 20 %wt

11 CHAPTER 4 SYNTHESIS AND CHARACTERIZATION OF PT-M/C ALLOY CATALYSTS (M = NI, CO, FE) Alloy catalysts in research have a molar ratio Pt: M of 3: 1 (with M as Ni, Co and Fe transition metals). Precursors of M metals include NiCl 2, CoCl 2 and FeCl 2 corresponding to the Pt 3 Ni 1 /C, Pt 3 Co 1 /C and Pt 3 Fe 1 /C catalysts. The reduction process for deposition of metals to form alloys is done with NaBH 4 reduction agent Characterization of Pt 3 M 1 /C synthesized alloy catalysts Figure 4.2 expresses X-ray diffraction patterns of Pt/C, Pt 3 Ni 1 /C, Pt 3 Co 1 /C and Pt 3 Fe 1 /C catalyst samples. On diffraction pattern of Pt/C sample, there are reflection peaks at different angle values (Fig. 4.2a). For Pt metal, from standard atlas, X-ray result confirms that Pt structure is face centred cubic. The diffraction peaks of the Pt/C catalyst are wide and low intensity. This proves that Pt synthesized catalyst particles are very small size and therefore can have a very large active surface area. With presence of M metals, diffraction peaks of Pt 3 M 1 alloy particles change considerably. On the diffraction patterns of Pt 3 Ni 1, Pt 3 Co 1 and Pt 3 Fe 1 alloys, structure of Pt-M alloys are still face centred cubic (Fig. 4.2b, Fig. 4.2c and Fig. 4.2d). The reflection peaks of (111) and (200) faces still appear with large peak root, but angle value 2θ is slightly shifted in compared to peaks of Pt/C catalyst. Specific peaks of Ni, Co and Fe metals and their oxides are not found. Therefore, after deposition, alloying of Pt with M metals happends to form a solid solution. Atoms of M metals have entered Pt crysstall and randomly replaced to some positions of Pt atom and caused Pt lattice deformation. This deformation may shorten Pt-Pt bond in the lattice. As a result, reflection peaks on X-ray diffraction patterns are slightly shifted.

12 File: Thai VKHVL mau 41.raw - Type: 2Th/Th locked - Start: End: Step: Step time: 1. s - Temp.: 25 C (Room) - Time Started: 12 s - 2-Theta: Theta: Chi: (D) - Platinum - Pt - Y: %- d x by: 1. - WL: Cubic - a b c alpha beta gamma Face-centered - Fm-3m (225) Different types of M metals lead to different shifts of angle 2θ. The shift is more clear for lattice of the Pt-Ni alloy catalyst. Thus, Pt 3 Ni 1 /C alloy catalyst may have the highest alloying degree of three synthesized alloy catalysts. Faculty of Chemistry, HUS, VNU, D8 ADVANCE-Bruker - Sample M d= Lin (Cps) d= d= Lin (Cps) Faculty of Chemistry, HUS, VNU, D8 ADVANCE-Bruker - Sample Theta - Scale File: Thai VKHVL mau M38.raw - Type: 2Th/Th locked - Start: End: Step: Step time: 1. s - Temp.: 25 C (Room) - Time Started: 17 s - 2-Theta: Theta: Chi: (D) - Platinum - Pt - Y: %- d x by: 1. - WL: Cubic - a b c alpha beta gamma Face-centered - Fm-3m (225) a. Pt/C b. Pt 3 Ni 1 /C d=2.257 d=1.932 Lin (Cps) Theta - Scale File: Thai VKHVL mau 33.raw - Type: 2Th/Th locked - Start: End: Step: Step time: 1. s - Temp.: 25 C (Room) - Time Started: 12 s - 2-Theta: Theta: Chi: (D) - Platinum - Pt - Y: %- d x by: 1. - WL: Cubic - a b c alpha beta gamma Face-centered - Fm-3m (225) d=1.402 Faculty of Chemistry, HUS, VNU, D8 ADVANCE-Bruker - Sample 41 d=2.261 d=1.972 d= Theta - Scale c. Pt 3 Co 1 /C d. Pt 3 Fe 1 /C Figure 4.2. X ray diffraction pattern of catalyst samples (a) Pt/C, (b) Pt 3 Ni 1 /C, (c) Pt 3 Co 1 /C and (d) Pt 3 Fe 1 /C Figure 4.2 is LSV graph of Pt 3 Ni 1 /C, Pt 3 Co 1 /C and Pt 3 Fe 1 /C alloy catalyst samples in H 2 SO 4 0.5M. The LSV curves of the alloy catalyst samples are shifted to the left of the LSV curve of the Pt/C sample meaning increase of current density. This may be due to the higher ORR reaction rates taking place on the alloy catalyst samples

13 than the Pt pure metal. Thus, activity for the ORR of Pt 3 M 1 /C alloy samples is much higher than that of Pt/C sample. From LSV measurements, the current density values at the 0.9V (i@0.9v) of the catalyst samples are summarized in Table 4.5 which show that activity of Pt 3 Ni 1 /C catalyst is the highest. Figure 4.8. LSV curves of alloying catalysts: Pt 3 Ni 1 /C, Pt 3 Co 1 /C and Pt 3 Fe 1 /C Table 4.5. Current density at potential of 0.9V (NHE) of Pt-M/C alloying catalyst samples Samples Pt/C Pt 3 Ni 1 /C Pt 3 Co 1 /C Pt 3 Fe 1 /C Current density i@0.9v (ma/cm 2 ) Influence of Ni content on performance of PtNi/C alloy catalysts In order to find optimal composition of PtNi/C alloy catalyst materials, research on effect of Ni content in alloy catalyst materials were conducted. PtNi/C alloy catalysts with different atomic ratios of

14 Pt:Ni of 3:1; 2:1; 1:1; 1:2 and 1:3 was synthesized by electroless deposition. The results from CV curves show that activity of alloy catalyst samples decreases when Ni metallic content in sample increases. This decrease may be explained by comparison of activity for ORR of various metals. As increasing Ni content, amount of Ni metal on catalyst surface increases meaning that amount of Pt metallic catalysts decreases. Because activity of Pt metal for ORR is much higher than that of Ni metal, on whole surface of catalytic particle the rate for ORR may be decreased. In addition, at equilibrium potential, a strong bond of Ni metal with O and the group containing OH adsorbed on the surface slows down the rate of proton exchange steps in mechanism of ORR. Therefore, the rate for ORR on Ni surface would be decreased meaning that rate for ORR on PtNi/C is also decreased. When increasing Ni content, durability of PtNi/C alloy catalysts is considerably influenced. To be optimum between activity and economy effectiveness, Pt 1 Ni 1 /C particles may be potential catalysts served as cathode electrode in PEMFC. Table 4.6. ESA values of PtNi/C catalyst samples with different composition Sample Pt:Ni 3:1 2:1 1:1 1:2 1:3 ESA (m 2 /g) Influence of heat treatment on performance of PtNi/C alloy catalysts. In synthesis of alloy catalysts for ORR, heat treatment is an important stage needed to be investigated for improving properties of catalytic material. To investigate the effect of heat treatment on

15 properties of catalysts, Pt 1 Ni 1 /C alloys were selected for sintering at temperatures of 300, 500, 700 and C in a gas mixture of Ar and 5% H 2. Change in structure of alloy catalyst material was evaluated by X-ray diffraction. Figure 4.15 shows X-ray diffraction pattern of the Pt 1 Ni 1 /C catalyst samples treated at various temperatures. When temperature increases, the diffraction peaks of the alloys become sharper and narrower. This may be caused by transition of metal particles from amorphous to crystall and increase of particle size due to sintering. In addition, shifts of diffraction peaks are also increased which may be explained because of increasing Ni metallic content in solid solutions by heat diffusion. Figure XRD patterns of Pt/C and Pt 1 Ni 1 /C catalyst samples without and with heat treatment at various temperatures. Changes in particle sizes are also observed in TEM picture of catalyst samples. Withou heat treatment, size of alloy catalyst particles is typically in the range of 2-3 nm. With heat treatment, the size of PtNi catalyst particles increases by alloying phenomenon. The size of the alloy catalyst particles increased and ranged from 4 to 6nm when heat treated at 300 C. With heat treatment at 500 and

16 700 0 C, the catalytic particle size increased to 5-7nm and 5-9nm, respectively. Table 4.8. Changes in ESA values after durability test of Pt 1 Ni 1 /C catalysts without and with heat treatment at various temperature. Temperature 25 o C 300 o C 500 o C 700 o C 900 o C ESA (m 2 /g) Change in ESA values (%) Changes in structure and size affect on activity and durability of PtNi alloy catalysts. Table 4.8 shows ESA values and changes of these values after 1000 durability test cycles. From the table, ESA values of alloy catalyst samples decrease when sintering temperature increases. However, percentage of change after durability test is significantly improved. ESA change of heat-treated catalysts at 500 and 700 C decrease to 33% compared to that of untreated sample approximately 40%. Therefore, durability of alloy catalysts has been significantly improved by heat treatment. CHAPTER 5. FABRICATION AND CHARACTERIZATION OF PEMFC SINGLE CELL In this chapter, fabrication of MEA electrode and a PEMFC single cell having active area of 5cm 2 will be discussed. Subsequently, the properties of synthesized Pt/C catalyst materials will be measured in PEMFC single cell to compare the effectiveness between synthesized and commercial catalysts.

17 5.1. Design and fabrication of components in a PEMFC single cell a. Bipolars b. Collectors c. End plates d. PEMFC single cell Figure 5.2. Pictures of components of a PEMFC single cell with active area of 5cm 2 The PEMFC single cell in research and has working area of about 5cm 2. Figure 5.2 expresses images of the fabricated components in a single cell. Configuration of the single cell consists of a MEA electrode, bipolar plates, rubber gaskets, collector and end plates Effect of operating conditions on the properties of PEMFC single cell Properties of PEMFC single cell are considerably affected by

18 operating conditions. A MEA electrode with Pt/C commercial catalyst loading of 0.4mg/cm 2 was prepared by hot-pressing at pressure of 19 kg/cm 2, temperature of 130 o C and hold time of 180s in order to study the effect of operating conditions on the properties of PEMFC single cell. The effect of fuel gas flow and operating temperature on the properties of single cell are presented and discussed Effect of operation temperature In general, electrochemical reactions will be accelerated when temperature of fuel cell is high. The maximum power density values calculated from the U-I curves are summarized in Table 5.1. Under laboratory conditions, the operating temperature of a PEMFC single cell should be kept between 60 and 65 C. Table 5.1. Maximum power density of single cell operated at different temperature Temperature ( o C) Pmax@0.4V (mw/cm 2 ) Influence of fuel gas flow Based on the calculated formulas, effect of fuel gas flow on properties of single cell was inxestigated. A MEA electrode was used to operate with different stoichiometry of H 2 and O 2 gas flows. Fuel consumption coefficients and maximum power Pmax of working conditions are summarized in Table 5.3. When increasing the fuel gas flow, the maximum power density of single cell increases. Single

19 cells operates well with S coefficients being higher than 1.5 and 2 for H 2 and O 2 respectively. Table 5.3. Maximum power density of single cell operated with different stoichiometry of fuel gas flow Maximum power density Pmax (mw/cm 2 ) O 2 S H Evaluation of MEA property prepared with synthesized catalysts. Figure 5.5. U-I and P-I curves of MEA electrode used the synthesized catalysts

20 After finding out optimum operating conditions for PEMFC single cell, a MEA using the synthesized catalyst materials was prepared. Figure 5.5 shows U-I and P-I curves of MEA using synthesized. Compared to commercial catalyst, the electrical properties of this MEA are significantly better. Maximum power density of this MEA is about 624 mw/cm 2 compared to MEA using commercial catalyst reaching about 534 mw/cm 2. Improvement of electrical properties when using synthesized catalysts may be due to smaller size and higher activity than that of commercial catalysts. CONCLUTION 1. Catalyst particles Pt/C 20%wt. were synthesized by electroless deposition using mixture solvents of ethylene glycol and water and NaBH 4 assisted mixture solvent. The best synthesized catalyst had size of approximately 2.5 nm and electrochemical surface area ESA of m 2 /g. 2. A synthesis procedure of catalyst materials Pt/C 20%wt. in scale of 200mg/batch was suggested with parameters: EG:W of 9:1, temperature 80 o C and ph of 4. The synthesized catalysts had high activity and durability being suitable to serve as anode and cathode electrode material in PEM fuel cell. 3. Alloy catalysts Pt 3 M/C 20%wt. (with M = Ni, Co and Fe) were synthesized by electroless deposition using NaBH 4 assisted mixture solvent of ethylene glycol and water. The results show that activity of alloy catalysts for ORR decreased in direction of Pt 3 Ni 1 /C ~ Pt 3 Co 1 /C> Pt 3 Fe 1 /C> Pt/C. The best catalyst Pt 3 Ni 1 /C had high performance with particle size of about 2.8nm and ESA electrochemical surface area of m 2 /g. The current density value of Pt 3 Ni 1 /C alloy catalyst at 0.9V achieved about

21 µa/cm 2 while the current density value of pure metal catalyst Pt/C is just µa/cm 2. This material was suitable to serve as cathode electrode material in PEM fuel cell. 4. Content of Ni metal and heat treatment process affect considerably on properties of PtNi/C alloy catalyst material. As increasing the Ni content, structure of alloy is changed and the rate of ORR on PtNi/C alloy catalyst surface decreased. In sintering process, as increasing temperature, durability of alloy catalyst increased and the best temperature for sintering process was 700 C. Based on the balance between the economy and activity, the Pt 1 Ni 1 /C alloy catalyst was potential material serving as cathode electrode material for PEMFC. 5. A single PEMFC fuel cell with active area of 5cm 2 was designed and fabricated. Use of Pt/C 20wt. and Pt 3 Ni 1 /C 20%wt. catalysts serving as anode and cathode materials respectively, the maximum power density of a single PEMFC fuel cell reached about 624 mw/cm 2 while with commercial catalysts, the single cell reached just maximum power density of 543 mw/cm 2. NEW DISTRIBUTIONS OF THESIS 1. The Pt/C catalysts nanoparticles with high performance were synthesized by ethylene glycol method and NaBH 4 assisted ethylene glycol method. Under experimental condition, an optimum procedure to synthesis the catalysts Pt/C 20%wt. was suggested in scale of 200mg/batch. 2. The alloy catalyst nanoparticles Pt-M/C (with M = Ni. Co and Fe) was synthesized by NaBH 4 assisted ethylene glycol method. The catalysts PtNi/C expressed high activity for oxygen reduction reaction and therefore this catalyst was high potential to serve as cathode electrode in PEMFC.

22 3. Used the synthesized catalysts, the first time in Vietnam, a PEMFC single cell having active area of 5cm 2 was designed, fabricated and assembled with maximum power density of approximately 624mW/cm 2. PUBLICATIONS 1. Chi Linh Do, Thy San Pham, Ngoc Phong Nguyen and Viet Quan Tran. Properties of Pt/C nanoparticle catalysts synthesized by electroless deposition for proton exchange membrane fuel cel.l Adv. Nat. Sci.: Nanosci. Nanotechnol. 4 (2013) (5pp) 2. Đỗ Chí Linh, Phạm Thy San, Giang Hồng Thái, Nguyễn Ngọc Phong, Trần Việt Quân. Nghiên cứu đánh giá tính chất vật liệu xúc tác Pt/C dùng trong pin nhiên liệu màng trao đổi proton. Tạp chí Hóa học số 2AB51,2013, trang Đỗ Chí Linh, Phạm Thy San, Nguyễn Ngọc Phong, Phạm Hồng Hạnh, Trần Việt Quân. Nghiên cứu đánh giá vật liệu xúc tác hợp kim PtNi/C cho phản ứng khử ôxy trong pin nhiên liệu màng trao đổi proton. Tạp chí Hóa học T.51 3AB, 2013, trang Đỗ Chí Linh, Phạm Thy San Nguyễn Ngọc Phong, Giang Hồng Thái, Trần Việt Quân. Sythesis and characterization of electrocatalysts nano particles Pt/MWCNT for PEMFC application. Journal of science and technology, Vol 52(3C) (2014), Pham Thy San, Vu Dinh Lam, Nguyen Ngoc Phong, Do Chi Linh, Research and development PEM fuel cell at institute of materials science, Proc. Of the first VAST-BAS workshop on science and technology, HaLong, November 20 th 21 st /2014, Chi Linh Do, Thy San Pham, Ngoc Phong Nguyen, Viet Quan Tran and Hong Hanh Pham. Synthesis and characterization of alloy catalyst nanoparticles PtNi/C for oxygen reduction reaction in proton exchange membrane fuel cell. Adv. Nat. Sci.: Nanosci. Nanotechnol. 6 (2015) (6pp)