Enhanced mass transfer in nanofluid electrolytes for aqueous flow batteries: The mechanism of nanoparticles as catalysts for redox reactions

Carbon-based nanoparticles are introduced into the electrolytes of vanadium redox flow batteries and their impact on the electrochemical performance of these batteries is experimentally investigated. Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy characterizations reveal defects in the nanoparticles that act as active sites for electrochemical reactions. Cyclic voltammetry analysis reveals that the nanofluidic electrolytes exhibits higher oxidation/reduction kinetics and mass transfers than those of pristine electrolytes. The mass transfers of the VO2+/VO2+ electrolyte ions during oxidation/reduction reactions are 17.2% and 59.8%, respectively, while those of the V2+/V3+ electrolyte ions are 5.6 times and 1.2 times higher than those of the VO2+ and VO2+ electrolytes, respectively. Overall, these nanofluidic electrolytes enhance electron and mass transfers at the active region interface. According to the redox mechanism, the VO2+/VO2+ electrolytes have an increased active area, while the V2+/V3+ electrolytes demonstrate excellent performance by acting as a catalyst to reduce the redox reaction activation energy.

Automated summary

Introducing carbon-based nanoparticles into the electrolytes of vanadium redox flow batteries enhances electrochemical performance by improving oxidation/reduction kinetics and mass transfers. The defects in nanoparticles in nanofluidic electrolytes act as active sites for electrochemical reactions, enhancing electron and mass transfers at the active region interface to boost battery performance. The redox mechanism shows that the VO2+/VO2+ electrolytes have increased active area, while V2+/V3+ electrolytes act as catalysts to reduce the activation energy of redox reactions.