Co2 by electrolysis

© 2010 Brian A. Rosen

LOW TEMPERATURE ELECTROCATALYTIC REDUCTION OF CARBON DIOXIDE UTILIZING ROOM TEMPERATURE IONIC LIQUIDS

BY BRIAN A. ROSEN

THESIS Submitted in partial fulfillment of the requirements for the degree of Master of Science in Chemical Engineering in the Graduate College of the University of Illinois at Urbana-Champaign, 2010

Urbana, Illinois

Adviser: ProfessorRichard I. Masel

ABSTRACT

Artificial photosynthesis, where one uses electricity from solar, or wind, to convert water and carbon dioxide into a hydrocarbon fuel could provide a viable route to renewable fuels but so far the results have been stymied because of the lack of a CO2 conversion catalyst that operates at low overpotentials. In this study we report a catalyst system that shows CO2conversion at low overpotentials. The system uses two different catalysts to achieve the conversion. First an ionic liquid or ionic salt is used to catalyze the formation of a (CO2) intermediate. Then a transition metal is used to catalyze the conversion of the (CO2) intermediate into useful products. CO formation is first observed at -250mV with respect to a standard hydrogen electrode compared to-800mV in the absence of the ionic liquid. Thus, CO2 conversion to CO can occur without the large energy loss associated with a high overpotential raising the possibility of practical artificial photosynthesis. The reduction of CO2 in 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM BF4) was studied in an H-type electrochemical cell, an in-situ SFG/SERS cell, and a continuous flow CO2electrolysis cell. Results from these experiments suggest that the EMIM BF4 is able to catalyze the reaction in such a way that opens the door for the practical low potential and temperature conversion of CO2.

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I would like to dedicate this Thesis to my family Jordon, Sharon, and Eric

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TABLE OF CONTENTS

LIST OF TABLES............................................................................................................. v LIST OF FIGURES .......................................................................................................... vi CHAPTER 1 INTRODUCTION………………………………………….......................1 CHAPTER 2 BACKGROUND OF CO2 REDUCTION AND IONIC LIQUIDS………………………………………………………………………....5 2.1 Reduction of Carbon Dioxide.......................................................................... 5 2.2 General Physical Properties of Ionic Liquids ................................................ 17 2.3 CO2 Reduction in Ionic Liquids ..................................................................... 24 CHAPTER 3 EXPERIMENTAL..................................................................................... 26 3.1 Materials........................................................................................................ 26 3.2 Methods.......................................................................................................... 29 CHAPTER 4 ELECTROCHEMICAL RESULTS AND DISCUSSION ........................ 48 4.1 CO2 Reduction in EMIM BF4 ........................................................................ 48 4.2 Continuous CO2Reduction in an Electrolyzer .............................................. 77 CHAPTER 5 SPECTROSCOPIC RESULTS AND DISCUSSION ............................... 83 5.1 Sum Frequency Generation (SFG) of CO2 Reduction on a Platinum Cathode …………………………………………………………………............83 CHAPTER 6 CONCLUSIONS ....................................................................................... 92 REFERENCES................................................................................................................ 94 APPENDIX A EXPERIMENTAL PROTOCOL ............................................................ 97 AUTHOR‘S BIOGRAPHY ........................................................................................... 112

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LIST OF TABLES

Table 2.1

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