Structural Design And Quantum Chemistry Simulation For Org Anic Electroactive Molecules

With the development of the global economy,fossil fuels such as petroleum,coal and natural gas are exploited and consumed in large quantities,accompanied by severe environmental pollution.In this context,clean renewable energy has received extensive attention and developed rapidly.To overcome the challenges such as intermittency in large-scale utlizations of renewable energy,it is urgent to develop efficient,safe,and low-cost electrochemical energy storage systems.Due to high designability,potential low-cost,safety,and environmental friendliness of organic electrolyte materials,aqueous organic flow batteries have become one of the most promising candidates in various electrochemical energy storage technologies.In this work,we first design several phenazine-based active electrolyte materials that are expected to be used in aqueous organic flow batteries by combining quantum chemical theoretical simulation calculations and thermodynamic Born-Haber cycle.Then two kinds of phenazine electroactive molecules were obtained by chemical synthesis routes.Their physicochemical properties such as electrochemical properties and solubility were preliminarily studied.In addition,we also explored an aqueous organic battery composed of an organic solid-state anode combined with a metal-organic framework(MOF)cathode.The main contents of this work are as follows:(1)Using density functional theory(DFT)combined with the thermodynamic Born-Haber cycle,a theoretical calculation method was established to calculate the redox potential and solvation free energy.The effects of substituents and conjugated rings of phenazine derivatives on the redox potential and solvation free energy were further investigated.According to the requirements of alkaline aqueous organic flow battery(AAOFB)for the redox potential and aqueous-solubility of redox electrolytes,several promising organic active electrolyte candidates were screened,including three low-potential anolyte materials and one high-potential catholyte material.(2)Two redox-active organic conjugated molecules,2,3-dihydroxyphenazine(2,3-DHPZ)and2,3-dihydroxy-6,9-dibromophene(DHDBPZ),were synthesized by simple Schiff-base condensation reaction.The chemical structure of these materials was characterized by the nuclear magnetic resonance(NMR)spectroscopy and their electrochemical properties in aqueous systems were further studied by cyclic voltammetry(CV).The results show that2,3-DHPZ and DHDBPZ have reversible electrochemical reactions and lower redox potentials in strongly acidic and strongly alkaline aqueous solutions.Therefore,it is expected to be used as electroactive materials for aqueous organic batteries.(3)An aqueous secondary battery was designed and constructed with the above phenazine derivatives as the negative electrode material and copper Prussian blue(Cu HCF)as the positive electrode material.The exprimental results show that the 2,3-DHPZ//Cu HCF aqueous secondary battery exhibit better rate capability and excellent charge-discharge cycling stability.