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Design of an Electrochemical Cell for In-Situ Infrared Spectroscopy of The Design of an electrochemical cell for In-Situ infrared spectroscopy of the carbon dioxide reduction reaction Jorrit Kroes Sustainable Technology Energy 24 January 2018 Design of an electrochemical cell for In- Situ infrared spectroscopy of the carbon dioxide reduction reaction By J.H. Kroes in partial fulfilment of the requirements for the degree of Master of Science in Sustainable Energy Technology at the Delft University of Technology, to be defended publicly on Thursday March 1, 2018 at 10:00 AM. Supervisors: Dr. W.A. Smith (MECS, TU Delft) N.J. Firet (MECS, TU Delft) Thesis committee: Prof. Dr. B. Dam (MECS, TU Delft) Dr. W.A. Smith (MECS, TU Delft) Dr. R. Kortlever (P&E, TU Delft) An electronic version of this thesis is available at http://repository.tudelft.nl/. Abstract The Worlds energy demand is increasing hoWever, the majority of the energy supply is still based on fossil fuels. The consumption of fossil fuels results in the emission of carbon diox- ide Which is one of the main greenhouse gases responsible for the ongoing climate change. In order to reduce the carbon dioxide emissions, more and more energy is produced in a reneWable Way. Mainly from solar and Wind energy. This energy is hoWever intermittent in character and comes in the form of electricity. To overcome the intermittency, the excess produced electricity has to be stored in an efficient reversible Way, so that the energy can released again When it is needed. One possible solution that tackles both problems is the electrochemical reduction of carbon dioxide in aqueous electrolytes into highly valuable chemicals, or so called solar fuels. In this study, a neW infrared spectroelectrochemical cell With an easy exchangeable electrocatalyst is developed to study the reaction mechanism on a silver catalyst in 0.1 M KCl and 0.1 M KHCO3 electrolytes at applied potentials of -1.4, -1.6 and -1.8 V vs a Ag/AgCl reference electrode. The performance of the neW developed cell is compared to the already proven ATR cell configuration. Investigation of the infrared signal strength shoWed high infrared signals at angles of incidence of the infrared beam betWeen 30° and 45°. The measured infrared absorption spectra in the thin layer floW cell shoW three absorption bands Which are also present in the obtained infrared absorption spectra of the ATR cell. In the ATR spectra hoWever, three further infrared absorption bands can be ob- served. Due to the loWer number of absorption bands present in the FTIR spectra measured in the neW designed thin layer floW cell, it can be concluded that despite the high IR signal no neW insights on the reaction mechanism of the carbon dioxide reduction reaction can be ac- quired. Acknowledgements I Would like to thank Wilson Smith of the MECS group for giving me the opportunity to per- form my graduation research project in the field of energy conversion. Further, I Would like to express my gratitude to my daily supervisor Nienke Firet for her guidance during this project, helping me With the interpretation of the IR absorption spectra, the provision of the XRD and AFM data and the critical feedback on my report. I Would also like to thank Bernard Dam and Ruud Kortlever for being part of the MSc thesis committee and their time and effort for as- sessing my report. Last but not least, I Would like to thank Joost Middelkoop and Herman Schreuders for converting my ideas for the neW spectroelectrochemical cell in a technical drawing, so that the neW cell could be fabricated, and teaching me hoW to operate the AJA and PREVAC magnetron sputtering systems, to produce the silver and platinum electrodes, respectively. As both, the fabrication of the neW spectroelectrochemical cell and the produc- tion of the electrodes Were key parts in this study, the performed research Would not have been possible Without their help. 1 2 List of abbreviations Abbreviation Definition AFM Atomic force microscopy ATR Attenuated total reflection CE Counter electrode FT Fourier-transform HER Hydrogen evolution reaction IR Infrared OC Open circuit RE Reference electrode RHE Reversible hydrogen electrode RPM Rounds per minute SEIRA Surface enhanced infrared absorption SERS Surface enhanced Raman scattering SHE Standard hydrogen electrode WE Working electrode XRD X-ray diffraction List of symbols Symbol Name Unit dp Penetration depth of the evanescent Wave [nm] E Applied potential [V] 0 Ecell Standard cell potential [V] Eanode Potential of the half reaction at the anode [V] Ecathode Potential of the half reaction at the cathode [V] Ecell Theoretical cell potential [V] ERHE Potential With respect to the reversible hydrogen electrode [V] f Frequency [Hz] I Current [mA] J Current density [mA cm-2] n1 Refractive index of the ATR crystal [-] n2 Refractive index of the sample [-] Q FloW rate [mL min-1] t Time [s] θe Effective angle of incidence [°] θf Face angle of the ATR crystal [°] θs Set angle on the ATR accessory [°] λ Wavelength [nm] ν Wavenumber [cm-1] 3 4 Table of Contents Abstract .................................................................................................................................. 1 AcknoWledgements ................................................................................................................ 1 List of abbreviations ............................................................................................................... 3 List of symbols ....................................................................................................................... 3 1. Introduction ..................................................................................................................... 9 2. Literature revieW ............................................................................................................ 11 2.1. Reduction of atmospheric carbon dioxide.............................................................. 11 2.2. Electrochemical reduction of CO2 .......................................................................... 12 2.2.1. Required electric potential ............................................................................. 12 2.2.2. Hydrogen evolution reaction .......................................................................... 13 2.2.3. Electrolytes for the CO2 reduction reaction .................................................... 14 2.2.4. Sustainable and economic viable CO2 reduction products ............................. 15 2.2.5. The effect of the used electrocatalyst on the CO2 reduction products ............ 16 2.2.6. Electrochemical reduction of CO2 on a silver electrode ................................. 17 2.3. Vibrational spectroscopy ....................................................................................... 18 2.3.1. Theory ........................................................................................................... 18 2.3.2. Infrared spectroscopy .................................................................................... 19 2.3.3. Raman spectroscopy ..................................................................................... 20 2.3.4. Surface enhanced vibrational spectroscopy .................................................. 21 2.4. In-Situ infrared spectroelectrochemical cells ......................................................... 22 2.4.1. Internal reflection cell configuration ............................................................... 23 2.4.2. External reflection cell configuration .............................................................. 25 2.4.3. Alternative cell configurations ........................................................................ 27 2.4.4. Results of studies using the introduced cell configurations ............................ 28 2.5. Infrared absorption bands in the CO2 reduction reaction on silver ......................... 30 3. Limitations of the current and requirements for the neW spectroelectrochemical cell ..... 35 3.1. Limitations of the current spectroelectrochemical cell ........................................... 35 3.2. Requirements for the neW spectroelectrochemical cell .......................................... 36 4. Design of the neW In-Situ IR spectroelectrochemical cell............................................... 39 5 5. Experimental ................................................................................................................. 41 5.1. Setup .................................................................................................................... 41 5.1.1. ATR cell ........................................................................................................ 41 5.1.2. Thin layer floW cell ......................................................................................... 42 5.2. Electrode preparation ............................................................................................ 43 5.2.1. ATR cell ........................................................................................................ 44 5.2.2. Thin layer floW cell ......................................................................................... 44 5.3. Experiments .......................................................................................................... 45 5.3.1. ATR cell ........................................................................................................ 45 5.3.2. Thin layer floW cell ......................................................................................... 47 6. Results and
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