Lenihan, C;Oboroceanu, D;Quill, N;Eidhin, DN;Bourke, A;Lynch, RP;Buckley, DN

SELECTED PROCEEDINGS FROM THE 233RD ECS MEETING

Water Affinity of Vanadium Electrolytes

2018

January

Published

1

3 ()

REDOX FLOW BATTERY IV-V-V CATHOLYTE STABILITY EXCHANGE MEMBRANES KINETICS CARBON CHARGE STATE PRECIPITATION PRETREATMENT

175

189

Rates of water transfer across a Nafion membrane between vanadium electrolytes (V-V, V-IV, V-III and V-II) and H2SO4 solutions of various concentrations were measured and the H2SO4 concentration corresponding to a zero-transfer rate was thus estimated. The difference in sulfate concentration between an electrolyte and the equivalent H2SO4 solution varies considerably with the oxidation state of the vanadium. The value is close to zero for V-IV but has a large positive value for V-V and large negative values for V-III and V-II. Both the water affinity, defined in terms of the chemical potential of water, and the thermodynamic activity of water was estimated for vanadium electrolytes at 25 degrees C from the measured values of equivalent H2SO4 concentration. The water affinity increases in the order V-II approximate to V-III < V-IV < V-V and the activity of water in the order V-V < V-IV < V-III approximate to V-II < H2O.

10.1149/08513.0175ecst