Operando spectroscopic methods to study electrochemical processes

Fossil resources are being depleted, while the concentration of CO2 in the atmosphere rises. There clearly is a strong and immediate need for a radical energy transition. Renewable energy is growing strongly as supplier of fossil-free electricity, but it needs large-scale and long-term storage options in order to be able to make a real impact on our total energy market. Petroleum is not only a feedstock for energy resources such as kerosene and gasoline, but also for many materials and chemicals that are being used in everyday life. A technology called electrochemical CO2 reduction (CO2R) can provide a solution to both these issues: renewably generated electricity is converted in any carbon-based energy containing molecule. The purpose (large-scale energy storage, mobile energy carrier or chemical) determines the molecule that should be produced. Electrochemical CO2 reduction is demonstrated at the lab scale. In order for it to become economically feasible and scalable to use in industry, additional research is needed to find better catalysts, understand the reactions and to improve cell design. The need for research includes a need for operando studies to investigate the exact physical and structural state of the catalyst under operating conditions. Also, relevant reaction intermediates cannot be studied without operando experiments. This thesis therefore focusses on the question how we can use existing operando characterisation techniques to study electrochemical systems. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy is used to study reaction mechanisms on silver electrodes. A front-irradiation, surface-sensitive cell design for an electrochemical cell enabling operando X-ray absorption spectroscopy (XAS) studies on modified silver electrodes during CO2 reduction is presented. A guide on how to conduct operando XAS experiments on gas diffusion electrode-based CO2 reduction catalysts and its results are demonstrated. Oxygen and vanadium are studied with X-ray Raman scattering (XRS) in order to elucidate the electronic effect of photocharging on bismuth vanadate photoelectrodes for solar water splitting.