Current distribution in a rectangular flow channel manufactured by 3‐D printing

Abstract

The characterization and improvement of a rectangular channel electrolyte flow compartment used in an iron-air flow battery was carried out by using an arrangement of copper electrodes to measure the current density distribution employing the limiting current technique. The present work addresses the hydrodynamics and mass transport distribution in the compartment and their improvement by an improved electrolyte compartment that results in a more uniform current distribution. The current distribution was evaluated as the ratio between the local and the averaged limiting current densities during the reduction of copper ions over a range of mean linear flow velocity across the electrode surface (2-30 cm s -1 ).The initial compartment, showed larger differences between the minimum and maximum currents than the electrolyte compartment that resulted as part of the design process and showed a higher pressure drop at a given mean linear flow velocity.Keywords: 3D printing, current distribution, electrolyte compartment, mass transport, pressure drop * Author for correspondence: E-mail: capla@soton.ac.uk 2 IntroductionThe energy demands of modern society, together with its supply and distribution, pose challenging problems. Finding a solution without compromising future generations will require our energy infrastructure to be transformed by allowing a greater, more managed contribution from renewable energy sources. At the same time, the present energy conversion systems should adopt new technologies to become more versatile and efficient. These crucial issues, together with the need of the automotive industry to develop electric and hybrid vehicles, have triggered new research approaches in energy storage technologies.Fuel cells, redox flow batteries and metal-air batteries have been highlighted due to their potential to deliver a high specific energy at moderate cost. In particular, metal air batteries, such as zinc-aluminium-and iron-air batteries, have received increasing attention due to the low cost and natural abundance of the metals and air together with their ease of electrical recharging. Iron-air batteries have advantages during the recharging cycle compared to zinc-air batteries, which have a tendency to form zinc dendrites at the negative electrode upon repeated cycling 1 . Figure 1 shows that the specific energy and theoretical capacity of the iron-air battery compare well with zincair batteries 2,3 . There remain many challenges for the development of the iron-air battery, including the low cell voltage due to slow reduction and passivation of the iron electrode due to the formation of insoluble and non-conductive oxides on discharge and slow evolution of oxygen on charge. Recent advances in nanotechnology have enabled lower oxygen reaction overpotentials by the use of catalytic nanostructured materials and improvements in the reversibility of iron 4,5,6 . 3When designing an electrochemical iron-air battery, it is important to consider that having an even current distribution is essential for effic...

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