Interfacial Engineering of Porous Electrodes for Redox Flow Cells targeting wettability, reaction selectivity and kinetics
Emre Boz succesfully defended his thesis at the department of Chemical Engineering and Chemistry on May 16th.
Renewable energy sources such as wind and solar are the main alternatives to fossil fuels to reduce our carbon footprint. However, renewable sources are inherently variable and the electrical grid should be robust against their fluctuations. By using batteries, we can reversibly store the electrical energy and balance the energy supply and demand. A special type of battery, called a redox flow battery, is very promising for this use case as it is highly scalable and can store energy for hours. However, the technology is still too expensive for widespread use. In his research, he developed coatings for the electrodes of these batteries to improve their performance and lifetime.
Batteries are energy storage systems where the electrical energy is converted to chemical energy. In a redox flow battery, this conversion takes place in a flow reactor where an electrolyte is pumped through porous electrodes. The electrolyte carries active species (such as metal ions) and can be stored in external tanks for a long time. Thanks to this decoupled design, these batteries can be upscaled to store energy for very long periods.
In his research Emre focused on the electrode and more specifically on the surface of the electrode where the liquid phase meets the solid phase. For example, the electrode surface controls how well the electrode-electrolyte contact is established (wettability), and to improve this he developed coatings with small organic molecules that are very hydrophilic. The challenge here is the porous nature of the electrode, as the coating needs to be uniform throughout the porous network. There are also competing reactions in the battery, which if left unchecked can decrease the lifetime of the device. To tackle this, he developed polymeric coatings that can slow down undesirable reactions without hindering the reaction that we are interested in (reaction selectivity).
Another area that is important is visualizing the movement of electrolyte and active species in the battery. Since the reactor is completely sealed and opaque, it is challenging to ‘see’ what is happening inside during operation. In our group (Electrochemical Materials and Systems) we use state-of-the-art imaging techniques to image the liquid phase within the battery. In his work, he used neutron radiography for this purpose and coupled it with electrochemical diagnostics to study the electrode-electrolyte interactions during the reactor operation. The real-time information gathered through this method can aid in the design of reactor components that are cheaper and perform better.
Emre developed coatings with organic molecules to improve the wettability, reaction kinetics and selectivity of the porous electrodes for flow reactors. Coupled with advancements in electrolyte formulations and electrode design, these results can pave the way for cheaper and more efficient redox flow batteries.Title of PhD thesis: Interfacial Engineering of Porous Electrodes for Redox Flow Cells targeting wettability, reaction selectivity and kinetics, Supervisors: dr. Antoni Forner Cuenca and Professor Kitty Nijmeijer.