Increasing Charge Transfer at the Liquid−Solid Interface Using Electrodes Modified with Redox Mediators

Abstract

The power density of redox flow batteries (RFBs) utilized on iron‐containing electrolytes is improved by incorporating iron particle redox mediators into the electrodes. Nonpurified carbon nanotube (CNT) electrodes containing iron nanoparticles, formed during the synthesis of CNTs using the ferrocene−xylene process, are activated to create “hotspots” for faradaic energy storage that reduces losses associated with kinetical, ohmic, and mass transfer resistances. CNT electrodes are activated through cyclic voltammetry to initiate charge transfer interactions between redox electrolytes and iron nanoparticles in the electrode. RFBs with modified electrodes experience a 140% increase in power density and a 57% increase in energy density in coin‐cell configurations. Economic value and ready availability of iron paired with enhanced performance make iron RFBs a viable option for future RFB research. Herein, the highest peak power density yet reported for an iron‐based RFB at 180 mW cm−2 with iron‐modified electrodes under no electrolyte flow is demonstrated.

Keywords

• carbon nanotubes
• electrochemistry
• heterogeneous catalysis
• power densities
• redox flow batteries