Enhanced vanadium redox flow battery performance using graphene nanoplatelets to decorate carbon electrodes

• Published in: Journal of power sources Vol. 387; pp. 91 - 100
• Main Authors: Sankar, Abhinandh, Michos, Ioannis, Dutta, Indrajit, Dong, Junhang, Angelopoulos, Anastasios P.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 31.05.2018
• Subjects: Decoration; Electrocatalysis; Graphene; Redox flow battery; Electrocatalysis; Graphene; Redox flow battery; Decoration
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2018.03.045

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+ redox reaction can be substantially enhanced by using electrostatic layer-by-layer assembly (LbL) to decorate their surface with graphene nanoplatelets (GNPs). An exchange current density, i0, is obtained that is more than two orders of magnitude greater than that observed with standard carbon supported Pt nanocatalyst with the deposition of only 20 GNP layers. 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 GNPs and associated edge sites the can attenuate activity gains with increasing number of layers. Practical implementation to existing Vanadium Redox Flow Battery (VRFB) configurations was demonstrated through the application of a 370 nm (20 layer) LbL GNP coating on carbon felt (CF). The GNP coating yielded a 5% increase relative in voltage and overall efficiency of charge discharge curves obtained under typical VRFB cell operating conditions at 40 mA cm−2. Furthermore, a substantial increase in the discharge time is observed with this GNP coating on CF. [Display omitted] •Electrostatic assembly is used to decorate electrodes with graphene nanoplatelets.•Significant enhancement of VO2+/VO2+ redox kinetics with number of layers.•Tafel slope and edge site density increase with number of layers.•Decoration of carbon felt (CF) enhances operating battery performance.