cross-linked chitosan-sago composite membrane … chitosan-sago composite...ii universiti malaysia...

CROSS-LINKED CHITOSAN-SAGO COMPOSITE MEMBRANE FOR

DIRECT METHANOL FUEL CELL APPLICATION

Hamizan Bin Padiel

Bachelor of Engineering with Honors

(Mechanical and Manufacturing Engineering)

2010

i

CROSS-LINKED CHITOSAN-SAGO COMPOSITE MEMBRANE

FOR DIRECT METHANOL FUEL CELL APPLICATION

HAMIZAN BIN PADIEL

This project is submitted to the

Faculty of Engineering, Universiti Malaysia Sarawak

in partial fulfilment of the requirements for the degree for

Bachelor of Engineering with Honours

(Mechanical and Manufacturing Engineering)

2010

ii

UNIVERSITI MALAYSIA SARAWAK

BORANG PENGESAHAN STATUS TESIS

Judul: CROSS-LINKED CHITOSAN-SAGO COMPOSITE MEMBRANE

FOR DIRECT METHANOL FUEL CELL APPLICATION

SESI PENGAJIAN: 2009/2010

Saya HAMIZAN BIN PADIEL

(HURUF BESAR)

mengaku membenarkan tesis * ini disimpan di Pusat Khidmat Maklumat Akademik, Universiti Malaysia Sarawak

dengan syarat-syarat kegunaan seperti berikut:

1. Tesis adalah hakmilik Universiti Malaysia Sarawak.

2. Pusat Khidmat Maklumat Akademik, Universiti Malaysia Sarawak dibenarkan membuat salinan untuk

tujuan pengajian sahaja.

3. Membuat pendigitan untuk membangunkan Pangkalan Data Kandungan Tempatan.

4. Pusat Khidmat Maklumat Akademik, Universiti Malaysia Sarawak dibenarkan membuat salinan tesis ini

sebagai bahan pertukaran antara institusi pengajian tinggi.

5. ** Sila tandakan ( ) di kotak yang berkenaan

SULIT (Mengandungi maklumat yang berdarjah keselamatan atau kepentingan

Malaysia seperti yang termaktub di dalam AKTA RAHSIA RASMI 1972).

TERHAD (Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/

badan di mana penyelidikan dijalankan).

TIDAK TERHAD

Disahkan oleh

(TANDATANGAN PENULIS) (TANDATANGAN PENYELIA)

Alamat tetap: .

NO 300, LORONG 6A-1

TAMAN MATANG JAYA

93050 KUCHING

CIK NORFAMILA CHE MAT

Nama Penyelia

SARAWAK

Tarikh: Tarikh:

CATATAN * Tesis dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah, Sarjana dan Sarjana Muda.

** Jika tesis ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi

berkenaan dengan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai

SULIT dan TERHAD.

iii

APPROVAL PAGE

The following final year project:

Title : Cross-linked Chitosan-Sago Composite Membrane for Direct Methanol Fuel

Cell Application

Writer : Hamizan Bin Padiel

Matric : 16286

is being read and approved by:

________________________________ _____________________

CIK NORFAMILA CHE MAT DATE

SUPERVISOR

iv

DEDICATION

The research and study of cross-linked Chitosan – Sago composite

membrane used inside the direct methanol fuel cells is dedicated to the

Faculty of Engineering, Universiti Malaysia Sarawak for better

improvement in fuel cells mechanism, performance and research.

v

ACKNOWLEDGEMENT

First of all, thanks to God for giving me the strength and ability to complete

this study. I would like to take this opportunity to thank my supervisor, Miss

Nurfamila bt Che Mat, and my co-supervisor, Mrs. Mahsuri bt Yusof of Mechanical

and Manufacturing Engineering Department, for their guidance and help throughout

the entire project. I also would like to thank my family, friends and fellow course

mates for their support, advice and knowledge shared for me to accomplish this

project successfully. Another express of gratitude and appreciations should be

thrown to Faculty of Engineering, Universiti Malaysia Sarawak for supporting me in

accomplish this project. Thank you everyone, I appreciate the helps with my sincere

gratefulness. May Allah bless you. Thank you.

vi

ABSTRACT

Fuel cell is an electro chemical device that combines hydrogen and oxygen to

utilize electricity and produce water and heat. Direct Methanol Fuel Cells (DMFCs)

is one of the potential portable fuel cells mechanisms. The performance of the

DMFC is depending on the Proton Exchange Membrane (PEM) technology. The

research and studies in improving the performance of PEM used inside the DMFC

has long developed. Few factors are still hindering the existing PEM. For example,

Nafion 117 has high methanol crossover, expensive, unrecyclable and short lifespan.

A good PEM should has high proton conductivity, high water uptake, less swelling,

low methanol permeability and crossover, and contribute to a relatively high

efficiency. The fabrications of new composite samples such as chitosan – sago

composite membrane, were developed and compared towards the existing composite

membrane, Nafion 117. Experiments were conducted to determine the water uptake

of the chitosan – sago composite membrane, the methanol permeability, conductivity

of the composite membrane and the efficiency of each composite sample. 10

composite membrane samples were prepared, 5 without cross-linked and another 5

vice versa. The reason for cross-linked is to improve the hydrophilic properties of the

PEM itself. Major outcome of the results in this study should satisfy all the PEM

properties as mentioned above. To conclude, one sample was then suggested as the

most feasible composite membrane that can be applied on the mini DMFC

application.

vii

ABSTRAK

Sel basah merupakan sejenis sel elektro kimia yang menggabungkan hidrogen

dan oksigen untuk menjana elektrik dan menghasilkan air dan haba. Sel basah

berasaskan metanol adalah satu contoh sel basah yang mempunyai potensi untuk

menjadi sel mudah alih. Prestasi sel basah adalah berasaskan metanol bergantung

kepada teknologi membran yang digunakan. Kajian dalam memperbaiki membran

yang digunakan di dalam sel basah telah lama dijalankan. Terdapat beberapa faktor

yang mempengaruhi membran yang sedia ada. Sebagai contoh, Nafion 117

mempunyai kadar penyilangan methanol yang tinggi, mahal, tidak dapat di kitar

semula dan jangka hayat penggunaan yang pendek. Membran yang baik mempunyai

kadar pengaliran proton yang tinggi, kadar penyerapan air yang tinggi, kurang

mengembang, rendah kadar ketertelapan dan penyilangan metanol dan mempunyai

daya kecekapan yang tinggi. Penyediaan membran komposit baru seperti chitosan –

sagu dijalankan dan dibandingkan dengan membran sedia ada Nafion 117.

Experimen dijalankan untuk mengetahui kadar penyerapan air, kadar keterlapan

metanol, kadar pengaliran proton dan kecekapan setiap sampel komposit yang

disediakan. 10 sampel komposit disediakan, 5 tanpa rangkaian silang dan 5

sebaliknya. Tujuan rangkaian silang adalah untuk meningkatkan sifat hidrofili

membran berkenaan. Hasil utama dalam experimen ini harus memuaskan sifat

membran seperti di atas. Kesimpulannya, satu sampel telah dicadangkan untuk

menjadi sampel yang paling sesuai digunakan dalam aplikasi sel basah metanol.

viii

EXTENDED ABSTRACT

Direct Methanol Fuel Cells (DMFCs) is attractive fuel cells on several

applications due to their low weight and volume and applied on small and medium

size application. Proton Exchange Membrane (PEM) is a conductor which provides

any migration of proton between the separations of the anode and cathode electrodes

inside DMFC. Nafion 117 is widely use as PEM in DMFC but due to certain

drawback such as high methanol crossover, expensive and high methanol

permeability limits it usage. Chitosan is a natural product which is derived from an

abundantly available natural biopolymer found in the exo-skeletons of crustacean.

Chitosan is cheap, inert, hydrophilic, insoluble and less swollen. Sago is a food

starch that prepared from carbohydrate material stored in the trunks of several palms

and well known as almost a pure starch. When two particles is bond into one

polymer chain to another and to ensure the stability of the composite membrane is

called cross-linked. The preparation of chitosan are carried out using crab shells and

consist of 4 steps; deprotenization (remove protein), demineralization (remove

minerals), decoloration (remove colours) and deacetylation (remove acetyl group).

The fabrications of chitosan - sago membrane are as follow. Chitosan flakes were

dissolved completely into acetic acid solution. Then it is filtered and cast on glass

plate to dry (24 hours) and then dried out inside an oven (24 hours, 60oC). The dried

membrane then neutralized into NaOH (5 min) and washed thoroughly. The process

repeated by adding various proportion of sago starches (2.5%, 5.0%, 7.5% and

10.0% respectively) and then divided into two portions (5 without cross-linked, 5

FYP%20Slide/2.pptx

ix

cross-linked). Cross-linked process then carried out by immersing the samples into

0.5M H2SO4 for 24 hours. The electro catalyst ink is prepared by mixing small

amount of carbon black, wet Pt, de-ionized water and then adding small amount of

methanol and Nafion 117 solution and stirred for 10 minutes. After the catalyst ink

had been prepared, it then coated onto the carbon paper and the attach samples were

heat press (4 – 7 min, 130oC). Results obtained from experiment conducted compares

on both cross-linked and without cross-linked samples. For water uptake, without

cross-linked samples shows better results compare with cross-linked samples.

Without cross-linked samples absorb more water compare with cross-linked samples.

High water uptake lead to high proton conductivity, which is good for the PEM

applications. Without cross-linked samples produces a lower permeability compare

with the cross-linked samples. The addition of sago helps to reduce methanol

permeability and also leads to low methanol crossover. The proton conductivity test

were carried out determine which samples contribute the highest conductivity.

Without cross-linked samples gives higher conductivity than cross-linked samples

due to its higher water uptake. The thermodynamics analysis was conducted to

determine the efficiency of the DMFC using the chitosan –sago as PEM. Without

cross-linked samples gives low efficiency with the higher methanol concentration.

Cross-linked samples give much lower efficiency than without cross-linked samples

might due to low water uptake and less absorbing. Overall, it concludes that without

cross-linked samples perform better than cross-linked samples. The samples still

cannot match Nafion 117 as it was used as comparison with all samples tested and

still the best composite membrane used inside fuel cells application. Therefore

without cross-linked samples (92.5% chitosan + 7.5% sago, 0.5M, 40oC) is the

feasible composite samples for the mini DMFC operation.

x

TABLE OF CONTENTS

CONTENTS PAGE

TITLE i

CERTIFICATION FORM OF THESIS STATUS ii

APPROVAL PAGE iii

DEDICATION iv

ACKNOWLEDGEMENT v

ABSTRACT vi

ABSTRAK vii

EXTENDED ABSTRACT viii

LIST OF FIGURES xiv

LIST OF TABLES xvii

LIST OF ABBREVIATIONS xviii

CHAPTER 1: INTRODUCTION

1.1 Fuel Cells 1

1.2 Types of Fuel Cells 2

1.2.1 Alkaline fuel cell (AFC) 2

1.2.2 Molten Carbonate fuel cell (MCFC) 3

1.2.3 Phosphoric Acid fuel cell (PAFC) 4

1.2.4 Solid Oxide fuel cell (SOFC) 4

1.2.5 Zinc Air fuel cell (ZAFC) 5

1.2.6 Proton Exchange Membrane fuel cell (PEMFC) 6

xi

1.2.7 Direct Methanol fuel cell (DMFC) 7

1.3 Proton Exchange Membrane 9

1.3.1 Nafion 9

1.3.2 Chitosan 10

1.3.3 Sago 11

1.3.4 Cross-linked 12

1.3.5 Sol Gel Method 13

1.4 Problem Statements 14

1.5 Objective 15

1.6 Outline of Thesis 16

CHAPTER 2: LITERATURE REVIEW

2.1 Direct Methanol Fuel Cells (DMFC) Development 17

2.2 Proton Exchange Membrane (PEM) 20

2.3 Nafion 22

2.3.1 Effect of the methanol crossover on DMFC

performance using Nafion membranes 23

2.4 Composite Membrane for Direct Methanol Fuel Cell Applications 26

2.4.1 Chitosan 26

2.4.2 Sago Starch 29

2.4.3 Cross-Linked Composite Membrane 32

2.4.4 Sol Gel Method 35

xii

CHAPTER 3: METHODOLOGY

3.1 Material 38

3.2 Chitosan-Sago membrane synthesis and fabrication method 39

3.3 Cross-linked method 41

3.4 Membrane thickness 42

3.5 Mini Direct Methanol Fuel Cell 42

3.6 Preparation of membrane electrode assembly (MEA) 44

3.7 Measurement of mechanical properties and testing 46

3.7.1 Water uptake measurement 46

3.7.2 Methanol permeability studies 47

3.7.3 Electro-osmotic 48

3.7.4 Proton conductivity test 49

3.7.5 Nafion 117 pretreatment 50

3.8 Thermodynamics Analysis 51

CHAPTER 4: RESULTS & DISCUSSIONS

4.1 Introduction 54

4.2 Effect of Methanol Feed Concentration on Mini DMFC Performance 55

4.2.1 Nafion 117 56

4.2.2 Chitosan – Sago Composite Without Cross-linked 57

4.2.3 Chitosan – Sago Composite With Cross-linked 60

4.3 Effect of Sago Content on Mini DMFC Performance 63



xiii

4.4 Water Uptake Measurement 68



4.4.3 Nafion 117 75

4.5 Methanol Permeability Studies 76



4.6 Proton Conductivity Test 80



4.6.3 Nafion 117 83

4.7 Thermodynamic Analysis 84



CHAPTER 5: CONCLUSIONS & RECOMMENDATIONS

5.1 Introduction 90

5.2 Conclusion 91

5.3 Recommendations 95

REFERENCES 97

APPENDICES 105

xiv

LIST OF FIGURES

Figures Pages

Figure 1.1 Direct Methanol Fuel Cell (DMFC) 8

Figure 2.1 Direct Methanol Fuel Cell Schematics 19

Figure 2.2 DMFCs overall chemical reaction 19

Figure 2.3 Chemical structures and physical schematic representation of

(a) amylase starch and (b) amylopectin starch 31

Figure 2.4 Chemical structure of cross-linked Chitosan 33

Figure 2.5 Enhanced properties for various polymers that are possible by

means of polymer in sire sol-get processes for inorganic

alkoxides or/and organoalkoxysilanes 37

Figure 3.1 Preparation process of raw Chitosan 39

Figure 3.2 Mini DMFCs 43

Figure 3.3 Hydrogen and oxygen molecules combine into water (schematic) 43

Figure 3.4 Exploded View of the Membrane Electrode Assembly 45

Figure 3.5 Schematic Diagram of the Experimental Setup 45

Figure 4.1 Effect of Methanol Feed Concentration on Nafion 117

Membrane at 85oC 56

Figure 4.2 Effect of Methanol Feed Concentration on 100.0% Chitosan

+ 0.0% Sago Membrane at 40°C 57





xv















Figure 4.12 Effects of Sago Content at 40oC and 0.5M Methanol Concentration 63








xvi

Figure 4.20 Water uptakes for without cross-linked composite at temperature

30oC 69


40oC 69


50oC 70

Figure 4.23 Water uptakes for cross-linked composite at temperature 30oC 72



Figure 4.26 Water uptakes for Nafion 117 composite at temperature 30oC,

60oC and 80

oC 75

Figure 4.27 Average graph of conductivity vs. Sago content samples 81

Figure 4.28 Average graph of conductivity vs. Sago content samples 82

Figure 4.29 Efficiency of methanol concentration to fuel cells without

cross-linked sample 86

Figure 4.30 Efficiency of methanol concentration to fuel cells with

cross-linked sample 88

xvii

LIST OF TABLES

Table Pages

Table 2.1 Influence of increasing different operating parameters in the

methanol crossover and in the fuel cell performance 25

Table 2.2 Literature survey on using chitosan composites for fuel cell

applications 28

Table 3.1 Composite membrane without cross-linked 41

Table 3.2 Composite membrane with cross-linked 41

Table 4.1 Keys of samples 55

Table 4.5 Methanol permeability for without cross-linked samples 76

Table 4.6 Methanol permeability for cross-linked samples 78

Table 4.7 Average conductivity produce by the difference of Sago content 80

Table 4.8 Average conductivity produce by the difference of Sago content 82

Table 4.9 Conductivity produce by Nafion 117 at various concentrations 83

Table 4.10 Efficiency of without cross-linked sample with different

methanol concentration 85

Table 4.11 Efficiency of with cross-linked sample with different

methanol concentration 87

xviii

LIST OF ABBREVIATIONS

oC - Unit temperature (Degree celcius)

% - Percentage

Wt - Weight/Wet

mV - Mili-Volt

h - Time (Hour)

g - Weight (Gram)

H - Hydrogen

O - Oxygen

CH3OH - Methanol

C7HF13O5S.C2F4 - Nafion

NaOH - Natrium Hydroxide

H2SO4 - Sulfuric Acid

DMFC - Direct Methanol Fuel Cell

PEM - Proton Exchange Membrane

MEA - Membrane Electrode Assembly

σ - Conductivity

η - Efficiency

µ - Micro

M - Molarity

1

CHAPTER 1

INTRODUCTION

1.1 Fuel Cells

The highly demand of fossil fuel especially for the energy intensive in industries

trigger severe energy crisis. Moreover the usage of this fossil fuel can emit a significant

amount of carbon dioxide, carbon monoxide and other harmful gases, thus causing more

pollution and aggregating the green house effects. [1]. Two major world crisis; the

depletion of fossil fuel and the green house effect need to be diverse the solution in order

to reserve and protected in the future.

One of the alternative ways to reduce dependency on fossil fuel usage and also

the green house effect is by using fuel cells. Fuel cells are an electrochemical device that

combines hydrogen and oxygen to utilizing electricity, from continuous chemical

reaction and produce water and heat [2]. The supplied fuel will make the fuel cell to

2

continuing to works and generate power. Since the conversion of the fuel to energy takes

place via an electrochemical process rather than combustion process, the process is

reported to be cleaner, less noise generated and have a relatively high efficiency. Fuel

cells are also reported to have a relatively low carbon dioxide emission [2]. The

utilization of fuel cells as an alternative source of energy has been reported to be the

most promising ways for the energy sustainability for the present and the future.

1.2 Types of Fuel Cells

Fuel cells are classified based on the electrolyte and the electrochemical reaction.

Each takes place in each type of fuel cells, what catalyst required the temperature range,

types of electrolyte required and much more factors [3]. There are several types of fuel

cells currently under development, each with its own advantages, limitations, and

potential applications. There are Alkaline Fuel Cells (AFC), Molten Carbonate Fuel

Cells (MCFC), Phosphoric Acid Fuel Cells (PAFC), Solid Oxide Fuel Cells (SOFC) and

Zinc Air Fuel Cells (ZAFC), Proton Exchange Membrane Fuel Cells (PEMFC) and

Direct Methanol Fuel Cells (DMFC) [3].

1.2.1 Alkaline fuel cell (AFC)

AFCs can achieve power generating efficiencies of up to 70% and used widely

on space technology such as NASA. They were used on spacecraft to provide both

electricity and drinking water. Alkaline fuel cells use potassium hydroxide as the

3

electrolyte and operate at 71.11°C. However, they are very susceptible to carbon

contamination, so require pure hydrogen and oxygen [3, 4]. Chemical reaction occurs on

each side of the electrode:

Anode Reaction: 2 H2 + 4 OH- → 4 H2O + 4 e

-

Cathode Reaction: O2 + 2 H2O + 4 e- → 4 OH

-

Overall Net Reaction: 2 H2 + O2 → 2 H2O

1.2.2 Molten Carbonate fuel cell (MCFC)

MCFCs use an electrolyte composed of a molten carbonate salt mixture

suspended in a porous, chemically inert matrix, and operate at high temperatures

(approximate 648.89ºC). MCFC require carbon dioxide, CO2 and oxygen, O2 to be

delivered to the cathode. To date, MCFCs have been operated on hydrogen, H2, carbon

monoxide, CO, natural gas, propane, landfill gas, marine diesel, and simulated coal

gasification products [3, 4]. Chemical reaction occurs on each side of the electrode:

Anode Reaction: CH3OH + H2O → CO2 + 6H+ + 6e

-

Cathode Reaction: 3/2 O2 + 6 H+ + 6e

- → 3 H2O

Overall Cell Reaction: CH3OH + 3/2 O2 → CO2 + 2 H2O

4

1.2.3 Phosphoric Acid fuel cell (PAFC)

PAFCs are used commercially nowadays and have been installed in various

places such as hospitals, nursing homes, hotels, office buildings, schools, utility power

plants, landfills and waste water treatment plants. PAFCs use liquid phosphoric acid as

the electrolyte and operate at about 232.22°C. One of the main advantages beside it

cogeneration efficiency, it can use impure hydrogen as fuel. PAFCs can tolerate a CO

concentration of about 1.5%, which broadens the choice of fuels they can use [3, 4].

Chemical reaction occurs on each side of the electrode:

Anode Reaction: 2 H2 → 4 H+ + 4 e

-

Cathode Reaction: O2 + 4 H+ + 4 e

- → 2 H2O

Overall Cell Reaction: 2 H2 + O2 → 2 H2O

1.2.4 Solid Oxide fuel cell (SOFC)

SOFCs use a hard, non-porous ceramic compound as the electrolyte, and operate

at very high temperatures (around 982.22°C). SOFCs generate among the highest

efficiency that is about 60% and can achieve the potential efficiency over 70% if

combining a high-temperature fuel cell with a turbine into a hybrid fuel cell. SOFCs are

suitable for stationary applications as well as for auxiliary power units (APUs) used in

vehicles to power electronics [3, 4]. Chemical reaction occurs on each side of the

electrode:

Anode Reaction: 2 H2 + 2 O2-

→ 2 H2O + 4 e-

Cathode Reaction: O2 + 4 e- → 2 O

2-

Overall Cell Reaction: 2 H2 + O2 → 2 H2O

5

1.2.5 Zinc Air fuel cell (ZAFC)

ZAFCs have a high operating temperature that enables internal reforming of

hydrocarbons and generate hydrogen. Due to this advantage, the by-product heat can be

used to generate high-pressure steam for industrial and commercial applications. The

electrolyte for the ZAFC has some advantages; it cannot dry out, eliminating the need to

carefully monitor and control anode and cathode moisture levels. Additionally, as a

solid, no leakage of the electrolyte will occur. Due to the consumption of the zinc anode,

this component requires replacing at intervals [3, 4]. Chemical reaction occurs on each

side of the electrode:

Anode Reaction: CH4 + H2O → CO2 + 6H+ + 6e

-

Zn + OH- → ZnO + H + e

-

Cathode Reaction: O2 + 2H+ + 2e

- → 2 OH

-

O2 + 4H+

+ 4e- → 2 H2O

Overall Cell Reaction: CH4 + 2 O2 → CO2 + 2 H2O

cross-linked chitosan-sago composite membrane … chitosan-sago composite...ii universiti malaysia...

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