Determination of Rate Constants and Reaction Orders of Vanadium‐Ion Kinetics on Carbon Fiber Electrodes.

Abstract

In the present work, the kinetic behavior of vanadiumion reactions on novel single carbon-fiber electrodes is investigated. The theory of reaction orders and charge-transfer coefficients is reviewed and typical sources of error due to incorrectly determined electrochemically active surface area, inhomogeneous current density distributions, mass transfer resistances, and aging are highlighted. The measured rate constants are in a range of 2.5 • 10 À 7-1.1 • 10 À 5 s À 1 for the positive and 7.0 • 10 À 8-2.6 • 10 À 6 s À 1 for the negative electrolyte. Despite these different activities of individual fibers, the reaction orders of V 2 + , V 3 + , VO 2 + and VO 2 + species are precisely determined as a function of the concentration and the state of charge. Moreover, charge-transfer coefficients are calculated with two different approaches based on Tafel slopes and through adjustment of the Butler-Volmer equation.

Electron‐Deficient Sites for Improving V2+/V3+ Redox Kinetics in Vanadium Redox Flow Batteries

“…To better explore the fundamentals of the catalytic effect of TiB 2 toward V 2+ /V 3+ , we have conducted Tafel plots to investigate its reaction mechanism and the structure of the vanadium ion complexes in the electrolyte. [ 6 ] The reaction order of V 3+ () and V 2+ () was measured to probe the fundamental electrocatalytic behavior of TiB 2 for V 2+ /V 3+ , [ 4a,19 ] which is essential to explore the reaction mechanisms. To mitigate the influence of hydrogen evolution reaction (HER), a relatively low concentration of H + is chosen for the electrolyte (Figure S17, Supporting Information).…”

Flow field designs developed by comprehensive CFD model decrease system costs of vanadium redox-flow batteries

“…From the cell voltage U cell and the current density i, the power density p for charging and discharging results according to Eqs. ( 31) and (32).…”

The impact of overpotential on the enthalpy of activation and pre-exponential factor of electrochemical redox reactions

“…At higher Z (480 mV), the sum of a H and Ta S is 41, which is not reasonable, perhaps due to the temperature-dependent precipitation/overpotential-dependent surface coverage of the electrode by the adsorbed species; a is also reported to be potential-dependent. 69,70 From the above discussions, it can be concluded that the temperature dependent i-V curve can be studied either by the Eyring equation (eqn ( 8)), where the potential dependence of DH # and DS # can be evaluated or from eqn (15) to evaluate the contributions of DH # and DS # to a.…”