Hydrogen-vanadium flow batteries offer a feasible solution for storing electrical energy from the grid or directly from renewable energy sources such as wind and solar. While charging, a hydrogen-vanadium flow battery stores energy in the form of hydrogen and vanadium (V). During discharge, hydrogen is consumed at the negative electrode and vanadium (V) is reduced to vanadium (IV) at the positive electrode. Vanadium systems demonstrate no issues with membrane fouling or metal dendrite formation.¹ Additionally, vanadium solutions have low volatility, low corrosivity, and do not produce toxic vapors.¹ Due to the relatively high cost of vanadium, the hydrogen-vanadium flow battery is attractive over the all-vanadium system due to the 50% reduction in the amount of vanadium solution required. Past research by Yufit et. al. has shown the feasibility of the hydrogen-vanadium flow battery and the importance of vanadium electrode wettability on fuel cell performance.¹ Additionally, studies by Menictas et. al. also revealed crossover of vanadium species during operation of the vanadium-oxygen flow battery, sparking our interest in vanadium’s effect on the hydrogen electrode catalyst.²

In this study, we examine the performance of a hydrogen-vanadium flow battery when using interdigitated flow fields at both electrodes and a high surface area carbon nanotube electrode as the vanadium electrode. With a reference electrode placed in the vanadium side, we separate the cell performance into individual electrode performance.  Using the half-cell results and electrochemical impedance measurements we identify the components and processes that have the greatest influence on the performance of the flow cell during discharge and charge.  Additionally, we explore if crossover of vanadium through the polymer electrolyte membrane results in any negative effect on the platinum catalyst at the hydrogen electrode. This will be determined by employing electrochemical measurement techniques using a platinum rotating disc electrode and a 3-electrode arrangement. In turn, the effect of vanadium crossover to the hydrogen electrode will be investigated by measuring effective exchange current density and electrochemical active surface area (ECSA) of platinum when vanadium (IV) and vanadium (V) are present in the electrolyte.

References:

1. V. Yufit, B. Hale, M. Matian, P. Mazur and N. Brandon, “Development of Regenerative Hydrogen-Vanadium Fuel Cell for Energy Storage Applications,” Journal of the Electrochemical Society, 160(6), A856-A861 (2013).
2. C. Menictas and M. Skyllas-Kazacos, “Performance of vanadium-oxygen redox fuel cell,” Journal of Applied Electrochemistry,  41, 1223-1232 (2011).