Study of Loss Mechanisms in a Regenerative Hydrogen Vanadium Fuel Cell

Development of renewable energies such as solar and wind power have received a great deal of attention. However, in order to utilise efficiently the power generated, it is essential to introduce energy storage systems at the grid level scale. Redox flow batteries are excellent candidates for this purpose as they present many potential advantages such as: decoupling of power and energy; modularity (kilowatts to megawatts systems); site independence; long cycle life and minimal maintenance.

But there remains scope to reduce the cost and improve the performance of current systems, and in this context a novel regenerative fuel cell, utilising an aqueous vanadium electrolyte and hydrogen gas has recently been reported¹. The advantages offered by this approach are fast hydrogen kinetics, use of half of vanadium electrolyte in comparison to the conventional all vanadium flow battery and the absence of cross-contamination between the positive and negative half-cells.

The first generation of this vanadium-hydrogen cell assembled with commercial MEAs demonstrated a maximum power density of 107 mW/cm² in a 1M V(IV)/V(V) solution. In this work we report improved performance to achieve a maximum power density of 229 mW/cm² through cell design modification. Half-cell measurements have been used to gain a better understanding of the loss mechanisms in the cathode and anode. Additionally, the authors have implemented the use of 3D tomography to study the structural changes of carbon based electrodes over different numbers of experimental conditions (Figure 1). The latest results from these studies will be presented.

¹ V. Yufit, B. Hale, M. Matian, P. Mazur and N.P. Brandon, Development of a Regenerative Hydrogen-Vanadium Fuel Cell for energy storage applications, Journal of The Electrochemical Society, 160 (2013), A856-A861.

Figure 1: 3D reconstructed image of a used SGL 10AA carbon electrode acquired using x-ray tomography. The volume represents a size of 211 x 749 x 914 μm³.