Abstract
Biological redox reactions inspire us to design sustainable and environmentally safe energy storage systems. Flavins have been demonstrated as solid-state electroactive materials for Li-metal batteries. [1,2] The concentration of flavin in those composite electrodes was no more than 50 wt%, however, due to the high content of conductive carbon necessary to complement the low electronic conductivity of flavin. In nature, flavins are often found dissolved in water or fat, such as in biological systems. As they are commonly more useful in this state, so may it be in batteries as well. Interestingly, flavins have yet to be reported as an active material for any redox flow batteries (RFBs). Here we explore the use of riboflavin-5’-phosphate sodium salt (FMN-Na) for RFBs. A diffusion coefficient and a kinetic rate constant of FMN in a strongly alkaline aqueous solution are determined and shown to be comparable to those of vanadium ions used for industrially utilized RFBs. Nicotinamide (known as vitamin B3) is used as a hydrotropic agent to enhance the water-solubility of FMN-Na, and therefore, its energy density in a RFB by as much as 15 times. A RFB using strongly basic FMN-based anolyte and ferrocyanide/ferricyanide-based catholyte shows highly stable cycling performance over the course of 200 cycles. The oxidized and reduced FMN can be stabilized by a variety of resonance structures, leading to the stable cycling performance. This work shows that biological redox centers are shown to be promising materials for environmentally friendly energy storage systems and warrant future exploration in this field.
Highlights
The versatility in design of redox flow batteries makes them apt to efficiently store energy in large-scale applications at low cost
We propose that the superior performance of flavin mononucleotide (FMN)/Fe Redox flow batteries (RFBs) is enabled by resonance structures, which can stabilize oxidized and reduced forms of FMN-Na
For reasons described we mainly explore the use of FMN in flow batteries under these strongly basic conditions
Summary
The versatility in design of redox flow batteries makes them apt to efficiently store energy in large-scale applications at low cost. A redox flow battery using flavin mononucleotide negative and ferrocyanide positive electrolytes in strong base shows stable cycling performance, with over 99% capacity retention over the course of 100 cycles. We hypothesize that this is enabled due to the oxidized and reduced forms of FMN-Na being stabilized by resonance structures. The large fraction of FMN combines with a second molecule of ATP to form FAD catalysed by FAD synthetase Inspired by these biochemicals, flavins, such as riboflavin and lumichrome, have been demonstrated as solidstate electroactive materials for Li-metal batteries[22,23]. This study provides a promising strategy to design energy storage system using organic active materials
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
