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INVESTIGATIONS ON REDOX FLOW CELLS AND PHOTOGALVANIC CELLS

BY

TANUJA RAVJNDRA KUMAR

Department of Chemistry

THESIS SUBMITTED

IN FULFILMENT OF THE REQUIREMENTS OF THE DEGREE OF

DOCTOR OF PHILOSOPHY

to the

INDIAN INSTITUTE OF TECHNOLOGY, DELHI

JANUARY, 1991

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-

T-H

5

Lit. lb

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LIBRARY

40u.

Ns 907

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T (.7) RA V I

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CERTIFICATE

This is to certify that thesis entitled

"INVESTIGATIONS ON REDOX FLOW CELLS AND PHOTOGALVANIC CELLS"

being submitted by Mrs. Tanuja Ravindra Kumar for the award of the degree of "Doctor of Philosophy" in Chemistry is a record of bonafide research work 'carried out by her.

Mrs. Tanuja R. Kumar has worked under our guidance one supervision and has fulfilled the requirements fox submission of the thesis, which to our knowledge, has reached the requisite standard.

The results contained in this thesis have not beer submitted, in part or in full, to any other University ox Institute for the award of any degree.

1 (G.N."RAO) Professor

Department of Chemistry Indian Institute of

Technology, New Delhi - 16

(A.S.N. MURTHY1 Professor & Head

Department of Chemistry Indian Institute of

Technology, New Delhi - 1(

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ACKNOWLEDGEMENTS

It is my pleasure and duty to express my deep sense of gratit to Prof. A.S.N.Murthy for his inspiring guidance and critJ supervision without which the thesis would not have taken this she I am also thankful to Prof. G.N. Rao for his valuable suggestions guidance from time to time.

My sincere thanks are also due to Prof. A.K. Mukher:

Department of Textile Technology for providing ion select membranes.

I wish to express my indebtedness to Swarita Kapur and Lat Singh for cheerfully coming to my assistance on countless occassior I am also thankful to Dr. M. Bhatnagar, Physics Department, M.P. Singh, Mr. R.K. Gupta and my colleagues and friends Balvinc Aprna, Kiran, Nupur, Anjali, Sunita, Anita and Mr. A.K. Gupta understanding and cooperation extended by them.

Financial assistance provided by Department of Non-conventic Energy Sources and Indian Institute of Technology, Delhi is grateft acknowledged.

Care has been taken to give proper credit for the work of of authors in the literature. The author would like to apologise for unintentional omissions which might have occurred by oversight.

And last but not the least, my sincere thanks go to Mr. Jagd Lohia and Ms. Amarjit Kaur for typing the manuscript.

KkA tAe`ar

(TANUJA R. KUMAR)

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ABSTRACT

The thesis has been divided into three parts.

The first part of the thesis deals with the investigations on redox flow cells. Various complexes of iron viz. Fe-ethylenediamine-tetraacetic acid, Fe- diethylenetriamine-pentaacetic acid and Fe-nitrilotriacetic acid have been identified as potential redox couples for their use in positive half of an all iron redox cell.

Performance characteristics of two all-iron redox cells consisting of iron-EDTA complex and/or iron-DTPA complex as the positive half cell and iron-phenanthroline complex as the negative half cell have been investigated. It has been found that the performance of the cell is constrained due to high overvoltages in both the half cells.

The second part of the thesis reports the results on photogalvanic (PG) cells. Cyclic voltammetric studies have been carried out in order to determine the kinetics of reaction between reduced dyes (thionine, methylene blue and new methylene blue) and Fe3+. For improving the performance of the new methylene blue (NMB) based photogalvanic cell, NMB coated platinum electrode was prepared. The NMB modified platinum electrode was characterized by cyclic voltammetric and spectroscopic technique. It has been observed that the NMB modified electrode improves the performance of the PG cell containing NMB and Fel+.

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Results on photogalvanic effect arising out of chlorophyll and chloroplast coated electrodes in solution containing substituted quinones and a ferrocene derivative is reported in the last part of the thesis. Chlorophyll and chloroplast coated pyrolytic graphite (basal plane) electrodes have been found to be negative with respect tc quinones and positive with respect to a substituted ferrocene.

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CONTENTS

Pa CERTIFICATE

ACKNOWLEDGEMENT ABSTRACT

LIST OF FIGURES

CHAPTER I INTRODUCTION

I.1 Redox Flow Systems

1.2 Photogalvanic Cells 1

1.3 Photosynthetic Photoelectrochemical Cells 1 1.4 Scope of the Present Work 2

References 2

CHAPTER II MATERIALS AND METHODS

II.1 Materials 3

11.2 Cell Design

11.3 Electrode Preparation 4.

11.4 Measurement Technique 4!

References 51

CHAPTER III ELECTROCHEMICAL STUDY OF Fe(III)/Fe(II)- LIGAND SYSTEMS FOR USE AS POSITIVE HALF CELLS IN REDOX FLOW CELLS

III.1 Introduction 6(

111.2 Experimental 6(

111.3 Cyclic Voltammetric Study of Various

Complexes of Iron 6

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111.4 Variation of Formal Potentials with pH 7;

111.5 Electron Transfer Kinetics 7:

111.6 Controlled Potential Coulometric (CPC)

Measurement 8:

111.7 D.C. Linear Polarization Studies 81

111.8 Conclusion 9*

References 91

CHAPTER IV OPERATING PERFORMANCE OF AN ALL IRON STATIONARY REDOX CELL

IV.1 Introduction 101

Iv.2 Experimental 10

IV.3 Charge-discharge Curves 10 IV.4 Discharge Characteristics 10,

1V.5 Conclusion 12'

References 13

CHAPTER V A KINETIC STUDY OF THE REACTION BETWEEN LEUCODYE AND Fe(III) BY CYCLIC VOLTAMMETRY

V.1 Introduction 13

V.2 Experimental 13

V.3 Results and Discussion 13

V.4 Conclusion 15

References 15

CHAPTER VI NEW METHYLENE BLUE COATED SELECTIVE ELECTRODE FOR IRON-NMB PHOTOGALVANIC CELL

VI.1 Introduction 15

VI.2 Experimental 16

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VI.3 Cyclic Voltammetric Study of Reversible Adsorption of NMB

VI.4 Adsorption Isotherm of NMB on Bare Platinum Electrode

VI.5 Chronocoulometric Study of Adsorption Behaviour of NMB

VI.6 NMB MOdified Electrode

VI.7 Behaviour of Fe(III)/Fe(II) at NMB Coated Platinum Electrode

VI.8 Study of PG Cell Containing NMB Coated Pt Electrode

VI.9 Conclusion References

CHAPTER VII EXPLORATORY INVESTIGATIONS ON PHOTO- SYNTHETIC PHOTOGALVANIC CELL

VII.1 Introduction 18

VII.2 Experimental 181

VII.3 Results and Discussion 19(

VII.4 Spectral Response 191

VII.5 Cyclic Voltammetric Studies 19!

VII.6 Conclusion 20:

References

SUMMARY •

LIST OF PUBLICATIONS.

16

16

17 17

17

18 18 18

References

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