Building a Better Redox Flow Battery - Innovative Diagnostics to Visualise Reactant Transport

While the optimization of PEMFCs and RFBs require addressing multiple issues, both systems share an operation mechanism based on pumping a fluid (a gas or a liquid) containing chemically reactive species across the face of an electrode. As a consequence of this characteristic, a significant source of inefficiency is linked to mass transport limitations including high pressure drop or inhomogeneous reactant flow distribution across the electrode. Previously, strategies including infrared mapping, ⁽¹⁾ magnetic resonance imaging ⁽²⁾ or neutron radiography ⁽³⁾ were employed in an attempt to investigate fluid transport phenomena (predominantly for fuel cells). However, although those studies rendered valuable results, the measuring procedures can be considered as expensive and require delicate equipment.

In this contribution, a simple and low cost methodology to study the mass transport processes in RFBs is presented. This approach relies on the instantaneous electrochemiluminescence of Luminol. By simply recording the emitted light with a low cost camera,⁽⁴⁾ concentration profiles at the surface of the electrode were obtained presenting high temporal and spatial resolutions. In addition, modifications on the electrolyte formulation and flow rate permitted identifying turbulent flow areas located at the turn of the flow field (Fig. 1) as well as leading to the design of improved components.

References:

(1) Wang et al., Journal of Power Sources, 157, 181–187 (2006).

(2) Tsushima et al., Magnetic Resonance Imaging, 23, 255-258 (2005).

(3) Trabold et al., International Journal of Heat and Mass Transfer, 49, 4712–4720 (2006).

(4) Lopes et al., Journal of Power Sources, 274, 382–392 (2015).