Taurine electrografting onto porous electrodes improves redox flow battery performance

The surface properties of porous carbonaceous electrodes govern the performance, durability, and ultimately the cost of redox flow batteries. As prepared, commercially available carbon fiber electrode interfaces suffer from limited kinetic activity and incomplete wettability, fundamentally limiting the performance. Here, we propose electrografting as a versatile and facile technique to enable task-specific functionalization of the ubiquitous carbon fiber-based porous electrodes. We elect to investigate taurine as a model molecule as the sulfonic acid group is anticipated to provide hydrophilic and active interfaces whereas the amine group allowing covalent attachment to the carbon surface would enhance stability. We perform hydrodynamic voltammetry and find enhanced kinetic rates of taurine treated model electrodes and flow cell experiments reveal superior mass-transport properties of taurine treated porous cloth electrodes. Additionally, we perform operando neutron radiography to visualize electrolyte infiltration within the electrode in a flow cell setup and find superior wettability of porous electrodes functionalized with taurine. Electrografting emerges as a promising technique to functionalize three-dimensional porous electrodes for redox flow batteries and other electrochemical technologies for energy conversion and storage.