Development of high temperature proton exchange membrane water electrolyser for generation of pure hydrogen and oxygen

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DEVELOPMENT OF HIGH TEMPERATURE PROTON EXCHANGE MEMBRANE WATER ELECTROLYSER FOR GENERATION OF PURE

HYDROGEN AND OXYGEN

VARAGUNAPANDIYAN N

DEPARTMENT OF CHEMICAL ENGINEERING INDIAN INSTITUTE OF TECHNOLOGY DELHI

NEW DELHI - 110016

MARCH 2015

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DEVELOPMENT OF HIGH TEMPERATURE PROTON EXCHANGE MEMBRANE WATER ELECTROLYSER FOR GENERATION OF PURE

HYDROGEN AND OXYGEN

by

VARAGUNAPANDIYAN N Department of Chemical Engineering

Submitted

in fulfillment of the requirements of the degree of Doctor of Philosophy

to the

INDIAN INSTITUTE OF TECHNOLOGY DELHI

MARCH 2015

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Dedicated to my family

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CERTIFICATE

This is to certify that thesis entitled “Development of high temperature proton exchange

membrane water electrolyser for generation of pure hydrogen and oxygen” submitted by Mr. Varagunapandiyan N to the Department of Chemical Engineering, Indian Institute of Technology Delhi, New Delhi, for fulfillment of the requirements for the award of Doctor of Philosophy in Chemical Engineering is a record of bonafide work carried out by him. He has worked under my guidance and supervision and has fulfilled the requirements, which to my knowledge, has reached the requisite standard for the submission of the thesis.

The research report and results presented in this thesis have not been submitted, in part or full, to any other university or institute for the award of any degree or diploma.

Suddhasatwa Basu Professor and Head Department of Chemical Engineering Indian Institute of Technology Delhi New Delhi 110016, India

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ACKNOWLEDGEMENTS

First of all, I would like to express my sincere gratitude and heartiest thanks to my guide and mentor Prof. Suddhasatwa Basu for his sincere guidance, keen interest and continuous encouragement. He has always shown immense patience and dedicated interest for rectifying my mistakes and improving my skills through discussions by devoting his invaluable time. I am fortunate enough to work under his supervision. He has influenced me both in academic and personal front.

I wish to thank my committee members, Dr. Anupam Shukla, Prof. A. N. Bhaskarwar and Prof. A. Ramanan, for their valuable suggestion and requisite guidance on technical issues during the research work. Encouragement and constant support from Dr. Anupam Shukla throughout my research work is greatly acknowledged. I am also grateful to all the faculty members for their help and cooperation whenever needed.

I wish to thank Council of Scientific and Industrial Research organization (CSIR) for financial support during the execution of research work. I thank all the non teaching staff of Chemical Engineering Department for their help and support, Centre for Polymer Science and Engineering for providing me SEM and EDX facilities and Department of Physics and Chemistry for TEM and XRD facilities.

It was great pleasure to work in fuel cell laboratory. I am thankful to Dr Debika Basu, Dr.

Anand Singh, Dr. Amit Kumar Gupta, Dr. Rajalekhmi Chockalingam, Mr. Pankaj Kumar Tiwari, Dr. Gurpreet Kaur, Mr. Shaneeth M., Mrs Jyoti Goel, Mr. Amandeep Jindal, Mr.

Harikrishnan N., Dr. Merajul Islam, Mrs. Neetu Kumari, Ms. Ieeba Khan, Mr. Nimai Bhandary, Ms. Garima, Ms. Anu, Mr. Amol, Ms. Criti Mahajan, Mr. Assem Sharma, Mr. Sarthak Nigam,

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Mr. Deepak and all other lab members. I would like to thanks Mr. Sunder Singh for his kind support during entire period.

I wish to express my heartfelt thanks to Mr. Vishesh Kumar for allowing me to use Design Lab and furnaces during my research work. I wish to thank all the laboratory and office staff of Chemical Engineering Department especially Mr. Ashish and Mr. Chandan Singh for their encouragement, help and assistance.

I must express my heartiest thanks to my parents Mr. R. Natarajan and Mrs. Ganambal for their well wishes. I sincerely thank my elder brother Mr. N. Annadurai and his wife Mrs. B.

Meenakshi. I should not forget my in-laws Mr. V. Sadhasivam and Mrs. R. Siraivani and brother-in-law Mr. S. Stalin who supported me in these years and help me to take challenges through devotion and hard work.

The research would not have been possible without the support of my wife S. Ezhilarasi. I will always be thankful to her for tremendous patience and encouragement to generate positive thoughts and strength inside me to accomplish the ultimate goal.

Varagunapandiyan N

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ABSTRACT

Proton exchange membrane water electrolyser (PEMWE) splits water into oxygen and pure hydrogen by oxygen evolution reaction (OER) at anode and hydrogen evolution reaction (HER) at cathode. Water splitting may be more efficient in high temperature PEMWE because of the higher kinetics of electrocatalyst and conductivity of membrane. Although the work on high temperature PEM fuel cell is reported in literature, the same is not true for high temperature PEMWE. To reduce energy consumption in PEMWE, RuO2 and RuO2-Ta2O5

electrocatalysts are tried as anode electrocatalyst in high temperature PEMWE. The anode electrocatalysts are prepared by sol-gel procedure with different compositions and at different calcination temperatures for oxygen evolution reaction. The catalysts are characterized by physical and electrochemical characterization techniques. Physical characterizations are carried out to study the thermal stability, oxygen-metal bond formation, crystalline phase and size, particle size, surface morphology, elemental analysis and elemental mapping by thermogravimetry analysis (TGA), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) pattern, transmission electron microscope (TEM), scanning electron microscope (SEM) and energy dispersive X-ray (EDX), respectively. Electrochemical characterization is carried out to study the OER on prepared electrocatalyst by cyclic voltammetry (CV), chronoamperometry (CA) in 1.0 M H3PO4 and 0.5 M H2SO4 electrolyte.

Additionally, the effect of electrolyte temperature (25-90 °C) on oxygen evolution reaction is studied and apparent activation energy is estimated from chronoamperogram. The maximum current density (17.27 mA cm^-2) at 1.2 V is achieved for 90%RuO2-10%Ta2O5 anode electrocatalyst calcined at 500 °C in CV experiment using 1.0 M H3PO4 electrolyte at 90 °C.

LSV is carried out to understand the OER electron pathway mechanism using rotating ring disk electrode (RRDE) with different rotations (800 to 2000 rpm). LSV of RuO2 and 90%RuO2-10%Ta2O5 electrocatalyst calcined at 500 ^oC follows 3.8 and 2.68 electron

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pathway mechanism for OER. Since proton exchange membrane, Nafion 117, dry up at high temperature (>100 ^oC) leading to severe loss in ionic conductivity, phosphoric acid doped polybenzimidazole (PBI) membrane is used as electrolyte in the present work. The measured conductivity of 14 M H3PO4 acid doped PBI membrane is 0.012 S/cm at 150 ^oC. RuO2 and RuO2-Ta2O5 electrocatalysts are tested in PEMWE for splitting of water using 14 M H3PO4

acid doped PBI membrane as proton exchange electrolyte and Pt black as cathode catalyst.

Gold plated titanium mesh is used as current collector and gold plated titanium monopolar plate (TMP) is used as an end plate and water vapour delivery system at the anode. PEMWE showed best performance for 90%RuO2-10%Ta2O5 electrocatalyst calcined at 500 °C and operating at 150 °C with current density of 1.1 A cm^-2 at 1.8 V. However, RuO2 used as anode electrocatalyst in PEMWE (at 80 °C) gave lower current density of 0.875 A cm^-2 at 1.8 V and its performance dipped after 2.8 h. The stability of PEMWE is improved by the addition of tantalum oxide to ruthenium oxide as 90%RuO2-10%Ta2O5 anode electrocatalyst showed the stable current density of 1.1 A cm^-2 at 1.8 V up to 5.3 h. The product analysis are carried out in gas chromatography using molecular sieve 5A and Propak Q column, which confirms the presence of hydrogen and oxygen with purity of 99.68% and 95.5% respectively The energy efficiency of PEMWE is estimated as 35.31%. Moreover 90%RuO2-10%Ta2O5

anode catalyst found to be more stable compared to RuO2 in 5 h operation of PEMWE at 150

°C and, further, PEMWE anolyte, membrane electrode assembly after PEMWE operation are investigated by FTIR and X-ray photoelectron spectroscopies (XPS) to evaluate degradation.

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LIST OF FIGURES

Figure No. Title Page

No.

Fig. 1.1 Schematic diagram showing working principle of PEMWE 5

Fig. 1.2 Polarization curve of PEMWE 7

Fig. 3.1 TGA/DTA curve of RuCl3.xH2O and RuO2 calcined at 400 °C 44 Fig. 3.2 Schematic diagram of three electrode cell assembly connected to

potentiostat-galvanostat 47

Fig. 3.3 Schematic diagram of rotating ring disk electrode 48

Fig. 3.4 Structure of phosphoric acid doped PBI 49

Fig. 3.5 PBI membrane conductivity measurement setup 49 Fig. 3.6 Apparent activation energy of PBI membrane 50 Fig. 3.7 Schematic representation of gold coating (a) TMP flow channel (b)

Titanium mesh 51

Fig. 3.8 Photograph of gold coating setup for TMP flow channel 52 Fig. 3.9 Photograph of gold coated (a) TMP flow channel (b)Titanium mesh 52 Fig. 3.10 Schematic representation of fabrication of membrane electrode

assembly (MEA) for PEMWE 53

Fig. 3.11 Photograph of (a) RuO2 coated on PBI membrane (b) Pt black coated on carbon

54

Fig. 3.12 (a) Schematic diagram of PEMWE 55

Fig. 3.12 (b) Schematic diagram of high temperature PEMWE experimental setup 55 Fig. 3.12 (c) Photograph of high temperature PEMWE experimental setup 56

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Fig. 4.1 XRD of RuO2 calcined at three temperatures (a) 400 °C, (b) 500 °C

and (c) 600 °C 60

Fig. 4.2 FTIR of RuO2 calcined at three temperatures (a) 400 °C, (b) 500 °C

and (c) 600 °C 61

Fig. 4.3 TEM of RuO2 calcined at three temperatures (a) 400 °C, (b) 500 °C

and (c) 600 °C 62

Fig. 4.4 EDX of RuO2 calcined at three temperatures (a) 400 °C, (b) 500 °C

and (c) 600 °C 63

Fig. 4.5 SEM of RuO2 calcined at three temperatures (a) 400 °C, (b) 500 °C

and (c) 600 °C 64

Fig. 4.6 Cyclic voltammetry at different temperatures of electrolyte for RuO2

calcined at 400 °C, 500 °C, 600 °C (a) 1.0 H3PO4 (b) H2SO4 66 Fig. 4.7 Chronoampertometry of RuO2 calcined at 500 °C at different

electrolyte (1.0 H3PO4) temperatures 66

Fig. 4.8 Apparent activation energy plot for RuO2 calcined at 400 °C, 500 °C,

and 600 °C (a) 1.0 M H3PO4 (b) 0.5 M H2SO4 68 Fig. 4.9 Linear sweep voltammetry using rotating ring disk electrode for

RuO2 catalyst calcined at 500 °C in 1.0 M H3PO4 electrolyte at 50 °C

with different rotation speeds 69

Fig. 4.10 Linear sweep voltammetry using rotating ring disk electrode for RuO2 catalyst calcined at 500 °C in 1.0 H3PO4 electrolyte at 90 °C

with different rotation speeds 70

Fig. 4.11 Koutecky-Levich plot for RuO₂ catalyst calcined at 500 °C 71 Fig. 4.12 i-V curve of PEMWE with RuO2 and IrO2 as anode catalyst for

PEMWE with different operating temperatures

73

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Fig. 4.13 Performance of PEMWE with Pt black as anode and cathode catalyst 74 Fig. 4.14 Performance of PEMWE with RuO2 as anode catalyst calcined at 400

°C and Pt black as cathode catalyst 74

Fig. 4.15 Performance of PEMWE with RuO2 as anode catalyst calcined at 500

Fig. 4.16 Performance of PEMWE with RuO2 as anode catalyst calcined at 600

Fig. 4.17 Stability test of RuO2 in PEMWE operated at 150 °C 77 Fig. 5.1 XRD of RuO2-Ta2O5 with different compositions calcined at 400 °C 83 Fig. 5.2 XRD of RuO2-Ta2O5 with different compositions calcined at 500 °C 83 Fig. 5.3 XRD of RuO2-Ta2O5 with different compositions calcined at 600 °C 84 Fig. 5.4 FTIR of RuO2-Ta2O5 with different compositions calcined at 400 °C 85 Fig. 5.5 FTIR of RuO2-Ta2O5 with different compositions calcined at 500 °C 86 Fig. 5.6 FTIR of RuO2-Ta2O5 with different compositions calcined at 600 °C 86 Fig. 5.7 TEM of RuO2-Ta2O5 with different compositions calcined at 400 °C

(a) 90% RuO2-10%Ta2O5 (b) 80% RuO2-20%Ta2O5 (c) 70% RuO2-

30%Ta2O5 87

Fig. 5.8 TEM of RuO2-Ta2O5 with different compositions calcined at 500 °C (a) 90% RuO2-10%Ta2O5 (b) 80% RuO2-20%Ta2O5 (c) 70% RuO2-

30%Ta2O5 87

Fig. 5.9 TEM of RuO2-Ta2O5 with different compositions calcined at 600 °C

(a) 90% RuO2-10%Ta2O5 (b) 80% RuO2-20%Ta2O5 88 Fig. 5.10 EDX of RuO₂-Ta₂O₅ with different compositions calcined 400 °C (a)

90%RuO2-10%Ta2O5 (b) 80%RuO2-20%Ta2O5 (c) 70%RuO2-

30%Ta2O5 (d) 60%RuO2-40%Ta2O5 89

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Fig. 5.11(a) Elemental mapping of 90%RuO2-10%Ta2O5 calcined at 400 °C 89 Fig. 5.11(b) Elemental mapping of 80%RuO2-20%Ta2O5 calcined at 400 °C 90 Fig. 5.11(c) Elemental mapping of 70%RuO2-30%Ta2O5 calcined at 400 °C 90 Fig. 5.11(d) Elemental mapping of 60%RuO2-40%Ta2O5 calcined at 400 °C 91 Fig. 5.12 SEM of RuO2-Ta2O5 with different compositions calcined at 400 °C

(a) 90%RuO2-10%Ta2O5 (b) 80%RuO2-20%Ta2O5 (c) 70%RuO2-

30%Ta2O5 (d) 60%RuO2-40%Ta2O5 91

Fig. 5.13 SEM of RuO2-Ta2O5 with different compositions calcined at 500 °C (a) 90%RuO2-10%Ta2O5 (b) 80%RuO2-20%Ta2O5 (c) 70%RuO2-

30%Ta2O5 (d) 60%RuO2-40%Ta2O5 92

Fig. 5.14 SEM of RuO2-Ta2O5 with different compositions calcined at 600 °C (a) 90%RuO2-10%Ta2O5 (b) 80%RuO2-20%Ta2O5 (c) 70%RuO2-

30%Ta2O5 (d) 60%RuO2-40%Ta2O5 92

Fig. 5.15 Cyclic voltammetry of RuO2-Ta2O5 calcined at 400 °C with different

compositions in 1.0 M H3PO4 with 20 mV s^-1 at 50 °C 93 Fig. 5.16 Cyclic voltammetry of RuO2-Ta2O5 calcined at 500 °C with different

compositions in 1.0 M H3PO4 with 20 mV s^-1 at 50 °C 94 Fig. 5.17 Cyclic voltammetry of RuO2-Ta2O5 calcined at 600 °C with different

compositions in 1.0 M H3PO4 with 20 mV s^-1 at 50 °C 95 Fig. 5.18 Cyclic voltammetry of 90%RuO2-10%Ta2O5 calcined at different

calcination temperatures and electrolyte (1.0 M H3PO4) temperatures

with 20 mV s^-1 98

Fig. 5.19 Cyclic voltammetry of 80%RuO₂-20%Ta₂O₅ calcined at different calcination temperatures and electrolyte (1.0 M H3PO4) temperatures

with 20 mV s^-1 99

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Fig. 5.20 Cyclic voltammetry of 70%RuO2-30%Ta2O5 calcined at different calcination temperatures and electrolyte (1.0 M H3PO4) temperatures

with 20 mV s^-1 99

Fig. 5.21 In-situ FTIR of 90%RuO2-10%Ta2O5 anode catalyst at different

voltages in 1.0 M H3PO4 electrolyte at 25 °C 101 Fig. 5.22 Chronoamperometry of 90%RuO2-10%Ta2O5 calcined at different

calcination temperatures and electrolyte (1.0 M H3PO4) temperatures 102 Fig. 5.23 Chroamperometry of 80%RuO2-20%Ta2O5 calcined at different

calcination temperatures and electrolyte (1.0 M H3PO4) temperatures 103 Fig. 5.24 Chronoamperometry of 70%RuO2-30%Ta2O5 calcined at different

calcination temperatures and electrolyte (1.0 M H3PO4) temperatures 103 Fig. 5.25 Linear sweep voltammetry using rotating ring disk electrode for

90%RuO2-10%Ta2O5 catalyst calcined at 500 °C in 1.0 M H3PO4

electrolyte at 90 °C with different rotation speeds 105 Fig. 5.26 Linear sweep voltammetry using rotating ring disk electrode for

80%RuO2-20%Ta2O5 catalyst calcined at 500 °C in 1.0 M H3PO4

electrolyte at 90 °C with different rotation speeds 106 Fig. 5.27 Koutecky-Levich plot at different voltages for 90%RuO2-10%Ta2O5

catalyst calcined at 500 °C 107

Fig. 5.28 Linear sweep voltammetry using rotating ring disk electrode for 90%RuO2-10%Ta2O5 catalyst calcined at 500 °C at different

electrolyte (1.0 M H3PO4) temperatures at 2000 rpm 108 Fig. 5.29 i-V curve of PEMWE with different compositions of RuO₂-Ta₂O₅ as

anode catalyst calcined at 400 °C 110

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Fig. 5.30 i-V curve of PEMWE with different compositions of RuO2-Ta2O5 as

Fig. 5.31 i-V curve of PEMWE with different compositions of RuO2-Ta2O5 as

Fig. 5.32 i-V curve of PEMWE of 90%RuO2-10%Ta2O5 as anode catalyst calcined at 500 °C using Celazole PBI membrane with different

operating temperatures 112

Fig. 5.33 i-V curve of PEMWE of 90%RuO2-10%Ta2O5 as anode catalyst calcined at 500 °Cusing NCL PBI membrane with different

operating temperatures 112

Fig. 5.34 Stability of different anode catalysts in high temperature PEMWE 114 Fig. 5.35 FTIR of 90%RuO2-10%Ta2O5 electrocatalyst before and after

PEMWE operation 115

Fig. 5.36 Core level peaks for 90%RuO2-10%Ta2O5 before and after PEMWE

operation (a) Ru 3d (b) Ta 4f and (c) O 1s 117 Fig. 5.37 FTIR of H3PO4 doped PBI membrane before and after experiment 118 Fig. 5.38 SEM of catalyst coated PBI membrane (a) before (b) after PEMWE

operation 119

Fig. 5.39 EDX of catalyst coated PBI membrane (a) before (b) after PEMWE

operation 119

Fig. 5.40 PEMWE anolyte analysis using UV spectrometry 120 Fig. A.1 Flow chart for electrocatalyst synthesis by polyol method 131 Fig. A.2 XRD pattern of RuO2 and IrO2 catalyst prepared by polyol method 132

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Fig. A.3(a) Cyclic voltammetry of RuO2 with different electrolyte (0.5 M H2SO4)

temperature with scan rate of 20 mV sec^-1 133 Fig. A.3(b) Cyclic voltammetry of RuO2 with different electrolyte (1.0 M H3PO4)

temperature with scan rate of 20 mV sec^-1 133

Fig. A.4(a) Cyclic voltammetry of IrO2 with different electrolyte (0.5 M H2SO4)

Fig. A.4(b) Cyclic voltammetry of IrO2 with different electrolyte (1.0 M H3PO4)

Fig. B.1 Stability of 90%RuO2-10%Ta2O5 electrocatalyst in different

electrolyte (1.0 M H3PO4) temperatures and calcination temperatures 136 Fig. C.1 Apparent activation energy for Nafion composite membranes 137 Fig. C.2 i-V curve of PEMWE with different composite membranes operating

at 70 °C and 80 °C

138

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LIST OF TABLES

Table No. Title Page No.

Table 1.1 Classification of electrolyser and its features 2 Table 1.2 Application areas for hydrogen energy 3 Table 2.1 Literature review on anode catalyst for PEMWE and its

performance

22

Table 3.1 Composition and properties of Nafion^® dispersion 42

Table 3.2 Properties of carbon paper 42

Table 3.3 Properties of PBI electrolyte membrane 43 Table 4.1 Apparent activation energy of RuO2 at different calcination

temperature 67

Table 5.1 Onset potential and current density at 1.2 V for OER on RuO₂-Ta₂O₅ catalyst with different compositions calcined at 400 °C

95

Table 5.2 Onset potential and current density at 1.2 V for OER on RuO2-Ta2O5 catalyst with different compositions calcined at 500 °C

95

Table 5.3 Onset potential and current density at 1.2 V for OER on RuO2-Ta2O5 catalyst with different compositions calcined at 600 °C

96

Table 5.4 Anodic peak charge density (qF) of RuO2-Ta2O5 96 Table 5.5 Capacitive charge density (qdl) of RuO2-Ta2O5 97

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Table 5.6 Onset potential and current density at 1.2 V with different electrolyte temperature for OER on 90%RuO2-10%Ta2O5

calcined at 400 °C, 500 °C and 600 °C 100

Table 5.9 Apparent activation energy of RuO2-Ta2O5 anode

electrocatalyst 104

Table 5.10 Performance of RuO2-Ta2O5 with different compositions

and calcination temperatures at 1.8 V 113 Table 5.11 Energy efficiency of PEMWE operated at 150 °C with

90%RuO2-10%Ta2O5 anode catalyst calcined at 500 °C 121

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NOMENCLATURE

Symbol

Meaning

IC Internal combustion

PEMWE Proton exchange membrane water electrolyser

PEM Proton exchange membrane

OER Oxygen evolution reaction

HER Hydrogen evolution reaction

MEA Membrane electrode assembly

HHV High heating value of hydrogen = 3.55 kWh/Nm³ RRDE Rotating ring disk electrode

EC Energy consumption (Wh/Nm³)

En Nernst potential (V)

H2

P Partial pressure of hydrogen

O2

P Partial pressure of oxygen

H O2

P Partial pressure of water

Go

' Free energy change for the reaction (kJ mol^-1) Volume of hydrogen measured (m³) Volume of hydrogen theoretically calculated (m³) R Universal gas constant (8.314 J/mol K)

I Current (A)

T Temperature (K)

t Time (s)

F Faraday’s constant (96485 C/mol)

p Pressure (Pa)

n Number of electrons

H mea2

V

H theo2

V

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ηf Faraday efficiency (%)

V Voltage (V)

Hydrogen production rate (Nm³/h),

Q Total charge (C)

ηE Energy efficiency (%)

Etn Thermoneutral voltage (V)

R Universal rate constant (8.314 J/ mol K) RH

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Development of high temperature proton exchange membrane water electrolyser for generation of pure hydrogen and oxygen

DEVELOPMENT OF HIGH TEMPERATURE PROTON EXCHANGE MEMBRANE WATER ELECTROLYSER FOR GENERATION OF PURE

HYDROGEN AND OXYGEN

VARAGUNAPANDIYAN N

DEPARTMENT OF CHEMICAL ENGINEERING INDIAN INSTITUTE OF TECHNOLOGY DELHI

NEW DELHI - 110016

MARCH 2015

DEVELOPMENT OF HIGH TEMPERATURE PROTON EXCHANGE MEMBRANE WATER ELECTROLYSER FOR GENERATION OF PURE

HYDROGEN AND OXYGEN

by

VARAGUNAPANDIYAN N Department of Chemical Engineering

Submitted

in fulfillment of the requirements of the degree of Doctor of Philosophy

to the

INDIAN INSTITUTE OF TECHNOLOGY DELHI

MARCH 2015

Dedicated to my family

CERTIFICATE

ACKNOWLEDGEMENTS

ABSTRACT

CONTENTS

LIST OF FIGURES

LIST OF TABLES

NOMENCLATURE

Symbol

Meaning