Abstract
GUITAR (Graphene from the University of Idaho Thermolyzed Asphalt Reaction) has the classical basal and edge plane morphology of graphites and thin layer graphenes with similar X-ray photoelectron spectroscopy (XPS), Raman and IR characteristics. However previous investigations indicated GUITAR is different electrochemically from graphenes and classical graphites. GUITAR has faster heterogeneous electron transfer across its basal plane and an electrochemical window that exceeds graphitic materials by 1 V. These beneficial properties are examined for application in the negative electrode of the vanadium redox flow battery (VRFB). Graphitic materials in this application suffer from hydrogen gassing and slow electron transfer kinetics for the V2+/3+ redox couple. Cyclic voltammetry of the V2+/3+ redox couple (0.05 M V3+ in 1 M H2SO4) on bare KFD graphite felt gives an estimated standard rate constant (k0) of 8.2 × 10−7 cm/s. The GUITAR-coated KFD graphite felt improves that quantity to 8.6 × 10−6 cm/s. The total contribution of the cyclic voltammetric currents at −1.0 V vs. Ag/AgCl to hydrogen evolution is 3% on GUITAR-coated KFD graphite felt. On bare KFD graphite felt, this is 22%. These results establish GUITAR as an excellent alternative material for the negative electrode in the vanadium redox flow battery.
Highlights
GUITAR (Graphene from the University of Idaho Thermolyzed Asphalt Reaction) is a hypothesized new allotrope of carbon that offers many advantages over other conventional carbon-based materials in electrochemical applications [1,2]
We demonstrate that the kinetics of both the edges as well as the planar surfaces of GUITAR are fast in Fe(CN)6 4 ́/3 ́, which is one of several properties which gives GUITAR a significant advantage over other carbon electrode materials in electrochemical applications [1]
Electrode materials used in the vanadium redox flow battery (VRFB) are often carbon and graphite felts, which have relatively high surface area and allow for electrolyte flow through the fibers [20,31,32,33]
Summary
GUITAR (Graphene from the University of Idaho Thermolyzed Asphalt Reaction) is a hypothesized new allotrope of carbon that offers many advantages over other conventional carbon-based materials in electrochemical applications [1,2]. Graphene and other planar lamellar carbon materials, GUITAR possesses significantly faster electron transfer kinetics on the basal plane (BP), which serves as the most practical electrode surface in most applications [1]. Electron transfer at the surface of graphite is seen to be more favored at the terminating edges and grain boundaries as compared to the basal plane. We demonstrate that the kinetics of both the edges as well as the planar surfaces of GUITAR are fast in Fe(CN)6 4 ́/3 ́ , which is one of several properties which gives GUITAR a significant advantage over other carbon electrode materials in electrochemical applications [1]. The facile heterogeneous electron transfer (HET) rate of Basal Plane-GUITAR (BP-GUITAR) is attributed to increased density of electronic states (DOS) from the structural defects
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