A Particle-Bonded Catalyst-Modified Electrode for Flow Batteries: Extending a Two-Phase Interface toward Stable Mass Transport and Efficient Redox Reaction

One of the targets associated with developing high-performance flow batteries is to enhance the activity and retain the durability of electrodes. Herein, a particle-bonded catalyst-modified electrode was proposed from the insight into interface behaviors of flow batteries, matching the demands of redox reactions and mass transports in the electrode. In this uniquely developed electrode, not only does the particle-form binder bond the catalyst and electrode base with powerful force against electrolyte scouring, but also the point-to-point bonding structure enlarges the reactant-catalyst interface and prolongs the reactant-ion transport pathway. Thanks to the completely emerged reaction interface, the particle-bonded electrode exhibits a redox peak current density of 9.54 mA cm^-2 in the cyclic voltammetry measurements, twice higher than that of a traditional film-bonded electrode. More impressively, the mass transport resistance of a particle-bonded electrode is proved obviously lower than traditional electrodes, owing to the generated porous structure from binder particles. In battery charge-discharge measurements, the developed electrode enables an energy efficiency as high as 78.05% at a current density of 200 mA cm^-2, obviously higher than that of film-bonded electrodes. The particle-bonded electrode enables a maximum current density of 2300 mA cm^-2 and a considerably high peak power density of 1165 mW cm^-2 in the polarization test, much higher than flow batteries with traditional electrodes, and even higher than most reported fuel cells. Moreover, the polarization curve of a flow battery assembled with the particle-bonded electrode shows no degradation after cycling electrolyte more than 20 h, exhibiting inspiring stability.