Nickel - based electro - oxidation catalysts for urea sensors and urea fuel cells :Doctor of philosophy - Major: Chemical and biological engineering

A thesis for the Degree of Doctor of Philosophy

Nickel – based electro-oxidation catalysts for

urea sensors and urea fuel cells

By

TRAN THAO QUYNH NGAN

Department of Chemical and biological engineering

Graduate School

Gachon University

A thesis for the Degree of Doctor of Philosophy

Nickel – based electro-oxidation catalysts for

urea sensors and urea fuel cells

By

TRAN THAO QUYNH NGAN

Submitted in Fulfillment of the Requirements for the Degree of

Doctor of Philosophy

July, 2018

Department of Chemical and biological engineering

Graduate School

Gachon University

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Thesis for Doctor of Philosophy’s Degree

Nickel – based electro-oxidation catalysts for

urea sensors and urea fuel cells

By

TRAN THAO QUYNH NGAN

Accepted in Fulfillment of the Requirements for the

Degree of Doctor of Philosophy

July 2018

Committee Chairman Young Soo Yoon

Committee Member Hyon Hee Yoon

Committee Member Ho Yu Yong

Committee Member Il Tae Kim

Committee Member Jae Seung Kim

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ACKNOWLEDGEMENTS

Firstly, I would like to express my sincere gratitude to my advisor, Prof.

Hyon Hee Yoon, for his tremendous guidance, support and continuous

encouragement. During my study for Ph.D course, he not only supported

to me the best living and working environment, but also provided his

guidance, with complete patience and motivation in the best condition

for my research process. All my achieved things are direct results of his

nourishment of knowledge bestowed upon me during my study.

Furthermore, his encouragement and advice are the main motivation for me

to overcome the difficulties of being a foreign student in Korea.

Especially, I’d like to give my appreciation to my laboratory members

who are friendly beside me and give their hands to support me during

this period. Sincerely, I would like to thank all the academic and

technical staff of department of Chemical and Biological Engineering,

Gachon University for their support towards me in one way or another.

Finally, I would like to express my heartfelt gratitude to my parents who

gave me a chance to do every incredible thing and always give their

continuous love, uninterrupted support and encouragement throughout

the studying period here. And, many thanks to all my friends who is a

part of my life. I want to you know I deeply cherish you and always will.

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CONTENTS

CHAPTER 1: RESEARCH AMBITION AND SIGNIFICANCE 4

I.1 Urea sensor.........................................................................4

I.2 Direct urea fuel cell. ...........................................................5

I.3 Significance and organization ............................................7

CHAPTER 2: INTRODUCTION ..................................................8

II. 1 Urea sensors .......................................................................8

II. 1.1 Enzymatic urea sensor........................................................8

II. 1.2 Non-enzymatic urea sensor ..............................................10

II. 1.3 Metal-organic frameworks (MOFs). ................................11

II. 1.4 CeO2-modified perovskite oxide (LaNi0.6Fe0.4O3-CeO2) .12

II. 1.5 The role of MWCNT in fabrication of urea sensor..........14

II. 2 Direct urea fuel cell. .........................................................14

II. 2.1 Anode materials................................................................20

II. 2.2 Electrolyte materials.........................................................22

II. 2.3 Cathode materials.............................................................23

II. 3 Modelling of DUFC .........................................................26

II. 3.1 I-V behavior. ....................................................................26

II. 3.2 Basic assumption and model structure. ............................27

II. 3.3 Mathematical model.........................................................32

II.3.3.1Anode side ........................................................................33

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3.3.1.1.Urea transport to gas diffusion layer (GDL):..................33

3.3.1.2.Diffusion layer..................................................................33

3.3.1.3.Catalyst layer ...................................................................35

II.3.3.2Anion exchange membrane (AEM)...................................38

II.3.3.3Ohmic overpotential.........................................................40

II.3.3.4At cathode.........................................................................43

3.3.4.1.Diffusion layer:.................................................................43

3.3.4.2.Catalyst layer:..................................................................44

II.3.3.5Solution procedure............................................................45

3.3.5.1.Anode................................................................................46

3.3.5.2.Cathode ............................................................................48

CHAPTER 3: EXPERIMENTAL SECTION ..............................51

III. 1 Materials processing.........................................................51

III.1.1 LNF-C synthesized and electrode fabrication ..................51

III.1.2 Synthesis of Ni– benzene-1,3,5-tricarboxylic acid metal–

organic framework ...........................................................53

III.1.3 Ni@C, NiO@C synthesis.................................................56

III. 2 Electrical system and single stack cell fabrication...........56

III. 3 Quantitative characterizations. .........................................57

CHAPTER 4: RESULTS AND DISCUSSION ...........................57

IV. 4 Urea sensor.......................................................................57

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IV. 4.1 NiBTC materials...............................................................57

IV. 4.1.1Morphological and structural studies............................57

IV. 4.1.2Electro-catalytic activity of Ni– benzene-1,3,5-

tricarboxylic acid metal–organic framework for urea

electro-oxidation. .............................................................65

IV. 4.1.3Electrochemical performance of urea sensor................70

IV. 4.1.4Interference, reproducibility and shelf life.....................75

IV. 4.1.5Analysis of urea in urine sample....................................78

IV. 4.2 LNF-CeO material............................................................80

IV. 4.2.1Structural and morphological characterization.............80

IV. 4.2.2Electrochemical analysis ...............................................82

IV. 4.2.3Interference, stability, and real sample analysis ...........97

IV. 4.3 Summary ........................................................................100

IV. 5 Ni@C, NiO@C and NiBTC for direct urea fuel cell .....104

IV. 5.1 Characterization and optimization..................................104

IV. 5.2 Catalytic performance of urea electro-oxidation on various

forms of nickel supported-carbon...................................112

IV. 5.3 Performances of DUFC..................................................120

CHAPTER 5: SUMMARY AND CONCLUSIONS .................133

CHAPTER 6: FUTURE WORK................................................135

APPENDICES............................................................................138