Many electrochemical energy storage and conversion devices employ porous media as electrodes, gas diffusion layers or separators. Recently, electrospinning has received significant attention as a way to generate nano‐fibers of polymers with controlled morphology and properties that, once carbonised, can act as conductive and porous media for electrochemical energy devices. The recent advances in X‐ray computed tomography have led the technique to be widely used in the characterisation of energy technologies and porous media as it offers a uniquely non‐destructive insight into the 3D microstructure of materials. Here we present electrospun fibrous mats with uncontrolled, controlled and aligned morphology for use as redox flow battery electrodes and, for the first time, obtain ultra‐high resolution nano‐tomographic X‐ray imaging of the materials using a lab source. The virtual 3D volumes enable extraction of parameters that would not be possible via other characterisation routes.
Salvinia leaf and sharkskin are prime examples of nature's marvel. Salvinia leaf‐inspired superhydrophobic surfaces keep themselves clean and reduce drag in fluid flow. Sharkskin also reduces drag in turbulent flow and inhibits biofouling. Therefore, the prospect of having a drag‐reducing surface with both salvinia leaf and sharkskin properties is attractive. However, fabricating such a surface is difficult, and the current fabrication methods require at least two separate steps. In addition, the mechanisms of drag reduction of salvinia leaf and sharkskin are different, and their combined effect on the flow field is not well understood. In this study, we produced a PTFE surface that mimics sharkskin in its surface pattern and copies the superhydrophobic nature of the salvinia leaf in its microstructure. This surface was fabricated by laser machining and tested in a closed channel under turbulent flow conditions. We measured the pressure drop at different Reynolds numbers on this surface both in pre‐wet and non‐pre‐wet conditions and compared the result with pressure drop data on four other PTFE samples: two types of non‐superhydrophobic sharkskin inspired surface (riblets), a superhydrophobic surface, and a non‐machined surface. Both the non‐superhydrophobic riblets and the superhydrophobic sample reduced drag compared to the non‐machined surface. However, we observed a lack of drag reduction by the superhydrophobic riblets sample. We presented a qualitative explanation for the lack of drag reduction and concluded that the modifications of the flow field by the two drag reduction mechanisms are not beneficial for overall drag reduction in our experiment.
Characterisation of Electrospun Electrodes for Redox Flow Batteries: Redox flow batteries represent a possible grid‐scale energy storage solution, having the ability to decouple power and energy and suffering from less extreme degradation issues compared to other technologies such as lithium ion batteries. Currently, they employ woven carbon fibre felts as electrodes that provide the surface on which redox reactions take place, as well as a 3D microstructure through which the electrolyte containing the redox active species flows. The flow characteristics of such electrodes are intrinsically linked to their microstructure and a significant parasitic power loss can occur due to the pumping of the electrolyte through unoptimized structures. In the Full Paper by Rhodri Jervis et al., an electrospinning technique is employed to create highly tunable microstructure, fibre size and alignment in novel electrodes with varying degrees of anisotropy. Lab‐based x‐ray nano‐computed tomography allows, for the first time, highly resolved 3D imaging of electrospun fibres with diameters below 0.5 μm. Obtaining virtual 3D structures of the electrodes with sufficient detail allows the accurate computational extraction of various parameters pertaining to the performance of redox flow batteries, giving guidance to a more thoughtful design of next generation materials. More details can be found in the Full Paper by Rhodri Jervis et al. on page 2488 in Issue 12, 2018 (10.1002/ente.201800338).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.