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Anastasios Angelopoulos1 Junhang Dong1 Abhinandh Sankar1

1, University of Cincinnati, Cincinnati, Ohio, United States

Rotating Disk Electrode (RDE) measurements on model glassy carbon (GC) substrates and Cyclic Voltammetry on more practical commercial carbon supports are used to demonstrate that the kinetics of the positive VO2+/VO2+ and negative V3+/V2+ redox reactions can be substantially enhanced by using electrostatic layer-by-layer assembly (LbL) to decorate their surface with graphene and bismuth nanoplatelets (NPs). Substantial increases in exchange current densities, i0, are observed relative to standard carbon electrodes. Tafel slope analysis is compared to electron microscopy imaging to conclude that while faster redox kinetics is associated with an increase in the available active area, the prevalence of smaller NPs and associated edge sites the can attenuate activity gains with increasing number of layers. Practical implementation to existing VRFB configurations was demonstrated through the application of NP coatings on carbon felt (CF). The NP coatings yielded a significant increase relative in voltage and overall efficiency of charge discharge curves obtained under typical VRFB cell operating conditions. Furthermore, a substantial increase in the discharge time is observed.

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