Preparation Of Riboflavin Derivatives And Application In Flow Batteries

Redox flow battery is one of the new energy storage technologies.It has the characteristics of independent energy and power,low cost and long cycle life,which can meet specific energy storage requirements.At the same time,it has the functions of amplitude and frequency modulation and smooth output,which can ensure the normal operation of the power grid.Among them,the core of the aqueous organic redox flow battery is the aqueous redox-active electrolyte.Given its structural diversity,customizability and potential low cost,redox-active organic molecules have jumped to a more important electrolyte than traditional inorganic substances.At present,the research on anode electrolytes has made some achievements,but there is still a lack of new organic molecules.In this paper,two anode electrolytes were prepared based on riboflavin and their basic properties and various performances in batteries were explored.The potential of these two active materials as active materials for aqueous organic flow batteries was demonstrated.The specific research contents are as follows:Firstly,carboxymethylflavin（CMF）,a negative electrolyte,was successfully prepared by two-step oxidation reaction with low-cost riboflavin as a single raw material.It was characterized and analyzed by infrared spectroscopy and nuclear magnetic resonance spectroscopy.The physical and chemical properties of CMF were explored by combining ultraviolet spectroscopy and electrochemical analysis techniques.The results found that CMF has good solubility and electrochemical properties and the diffusion coefficient is also comparable to that of other organic molecules.Under alkaline conditions,CMF and K₄[Fe（CN）₆]were used as negative and positive electrolyte respectively to construct the battery system.The theoretical voltage is up to 1.04 V and the battery could operate stably under constant current.At the same time,the cyclic voltammetry curve of negative electrolyte before and after test has no obvious deviation.The preparation and properties of CMF in this chapter can further broaden the research on riboflavin-based flow batteries,and can also provide novel ideas for the development of anode electrolytes.Secondly,based on the matrix of riboflavin,the water-soluble carboxyl group was modified and the negative electrolyte 3-carboxymethylriboflavin was successfully prepared and characterized by nuclear magnetic resonance spectroscopy.Solubility measurements show that the existence of hydroxyl and carboxyl groups in electrolyte molecules improves the solubility and lays a foundation for increasing the energy density of the battery.In addition,the electrochemical method shows that it has good redox reversibility and the reaction on the electrode surface is controlled by diffusion.Under neutral conditions,it was assembled with4-OH-TEMPO to form a battery and the battery operates stably under constant current.After300 times of charge and discharge,the average coulombic efficiency is 83.97%.Under different currents,the charge-discharge curve of the battery has good symmetry.In conclusion,this work provides a new platform for exploring and designing more riboflavin derivatives to facilitate the development of high-performance flow batteries.