Integrating renewables like solar and wind to meet the growing electricity demand has led to a search for low-cost electricity storage technologies. Vanadium redox flow batteries (VRFBs) are a promising technology to store electricity, but they suffer from high costs in part arising from the slow kinetics of the V2+/V3+ reaction at the negative electrode, preventing VRFBs from large scale deployment. The lack of fundamental understanding of the V2+/V3+ reaction has hindered the design of electrolytes and electrocatalysts to increase the reaction rate. In this talk, I will discuss our efforts in understanding V2+/V3+ reaction mechanism by a combination of kinetic measurements, microkinetic modeling, and spectroscopic techniques. We measure V2+/V3+ reaction kinetics in carefully chosen electrolytes on different electrocatalysts under controlled conditions (electrochemically active surface area, mass transfer, etc.) to develop a simplistic microkinetic model explaining the observed behavior We identify the structure of the reacting species in solution by Extended X-Ray Absorption and UV-Vis Spectroscopy, and detect the structure of adsorbed intermediate by Surface Enhanced Raman Spectroscopy. Finally, we show that the V2+/V3+ reaction kinetics is correlated to energy of the identified adsorbed vanadium intermediate. This work can be utilized to engineer the electrolyte and electrocatalysts with optimum vanadium intermediate adsorption energy to enhance V2+/V3+ charge transfer, aiding to the development of cheaper and more efficient VRFBs for large scale energy storage.
All seminars begin at 11:00 a.m. Eastern Daylight Time (UTC-04:00).