Sulfonated tryptanthrin anolyte increases performance in pH neutral aqueous redox flow batteries

Climate changes have led to the emergence of environmental questions in the top group of concerns for mankind. Clean and sustainable energy sources are becoming more attractive as power generation moves away from combustion-based technology.

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The demand for solar energy is in a counter-cycle with the supply of sunlight. So, how can we directly convert solar energy into storable energy? Energy storage is an emerging sector in constant development that is reshaping the renewable energy market. However, the development of environmentally friendly ways of store clean energy is urgently needed.

Redox flow batteries (RFBs) are currently being considered to be one of the most promising technologies for storage of electrical energy. Commercial RFBs are vanadium-based which show problems in solar energy capture and storage in form of chemical energy. Thus, the development of organic redox flow batteries, in particular those that work in aqueous media (AORFBs)  based on trypthatrin derivatives, constitutes not only a sustainable alternative for vanadium based technology, but also to the current organic RFB which is still strongly focused on anthraquinone derivatives.

We report the synthesis of a new electrolyte material, a water soluble form of tryptanthrin (TRYP), to be used as the anolyte in two types of RFBs: aqueous organometallic and all-organic. A lab prototype was used to test the RFB, showing promising values of efficiencies and storage capacities. Moreover,  this RFB operates at neutral pH values, thus avoiding extreme conditions of strongly acidic and alkaline media, which are not only corrosive (decreasing the lifetime of the battery) but also more environmentally friendly. This is relevant in terms of sustainability.

This new family of water soluble molecules (based on TRYP) paves the way for the use of this core structure for the successful development of new active materials for aqueous RFBs.

In our photochemistry group we investigate new molecular systems for capture and storage of energy. You can have a glance of our group and what we are presently doing at Photochemistry @ UC.

If you are interested to find more information our new active material and this attractive energy storage technology (RFBs), check out our paper (with Daniela Pinheiro and Marta Pineiro)  here  DOI: 10.1038/s42004-021-00523-0.

References

[1] Pinheiro D, Pineiro M, de Melo JSS (2021) Sulfonated tryptanthrin anolyte increases performance in pH neutral aqueous redox flow batteries. Communications Chemistry 4 (1):89. doi:10.1038/s42004-021-00523-0

[2] Lima ARF, Pereira RC, Azevedo J, Mendes A, Sérgio Seixas de Melo J (2021) On the path to aqueous organic redox flow batteries: Alizarin red S alkaline negolyte. Performance evaluation and photochemical studies. Journal of Molecular Liquids 336:116364. doi:https://doi.org/10.1016/j.molliq.2021.116364

Sergio Seixas de Melo

Professor, University of Coimbra

A photochemist from Portugal, that moved from Lisbon to Coimbra 28 years ago.  

Group Leader of the Photochemistry @UC Group

Senior member of the  Coimbra Laser Lab (which is part of LaserLab Europe)