Zusammenfassung
A novel photocatalytic mechanism at the Liquid-Liquid Interface (LLI) is proposed in this thesis. In order to proof this proposed concept, there are a few crucial prerequisites such as stabilization of a photocatalytic particles at the LLI, preparation of conducting oil-like electrolytes, and characterization of LLIs must be achieved in the first hand. Therefore, achieving these pre-steps are the primary aim of this work.
First, photocatalytic TiO2 nanoparticles were stabilized at the LLIs using Pickering emulsion approaches. TiO2-nanoparticles-stabilized Pickering emulsions are highly interesting for photocatalysis as they are promising candidates for such purpose. In this regard, a highly stable Pickering emulsions using TiO2 nanoparticles were successfully prepared which are stable over months. Also, a modified TiO2 nanoparticles based asymmetric patchy particles were successfully prepared within our group with the aim of using in photocatalytic investigations. Notably, preliminary results show that N719 dye sensitized TiO2 nanoparticles can form a stable Pickering emulsion which is very useful for extending spectral response of the photocatalyst.
Secondly, a conducting oil-like phase which is immiscible with aqueous phase is another crucial requirement in the proposed photocatalytic mechanism. 1-octanol based conducting oil-like phase have been successfully prepared for this purpose. Interestingly, conductivity of the prepared oil-like phase shows a wider range of conductivities with as high as 1 mS/cm. Further, the conductivity of the oil-like phase could be tuned by modifying 1-octanol with n-hexadecane which is enhancing the immiscibility of the oil-like phase with aqueous phase. In addition, Pickering emulsions using conducting oil-like phase is another requirement which has been achieved in this step.
Finally, electrochemical properties of the LLIs were investigated using electrochemical impedance spectroscopy (EIS) technique. As this is the most important step in my research, greater time and effort have been dedicated for this step. In general, the charge transport across the LLI is an interesting phenomenon which is not fully understood yet. Here, we employed LLIs prepared using redox-type (I−/I3−) electrolytes. In this system, electron transport was found to be largely dominating over the ion transport. In addition, surprisingly, we realized a novel charge transport phenomenon across this investigated interface system using the EIS analysis.
In this transport phenomenon, there is a temporal delay in the current flow across the interface with respect to the applied voltage signal. To best of our knowledge, such transport concept seemed to be previously unknown in the field. A model that explains this is developed and called as exponential delayed current (EDC) model. However, further investigation is necessary to fully understand and explain the electrochemical behavior of the system and eventually test the proposed photocatalytic mechanism.
