Synthesis Of Two Dimensional Nitrogen-doped Ordered Mesoporous Carbon And The Electrocatalytic Performance Of Low-dimensional Materials In Zinc-Bromine Flow Battery

Flow batteries have become an important candidate in the field of large-scale energy storage,because they can charge and discharge to a deep state of charge,tune power and energy modules independently,and set up the equipment without the geographical consideration.The application of them is that they can be used in smoothing the output of fluctuated new energy and establishing the separated electric grid.The zinc-bromine flow battery is one of the promising battery system because it owns the characters of affordable price of raw materials and high energy capacity density.However,currently,the low energy efficiency is still the obstacle of developing the zinc-bromine flow battery.Synthesizing advanced positive electrode catalysts is the method to solve this problem.In this essay,the low battery performance is addressed by reducing the polarization problem of positive electrode via developing positive electrode materials with the feature of high catalytic performance.The advanced bromine catalysts were synthesized by using different dimensional SiO₂ templates to control their morphology.And then,they were characterized by contemporary physical chemistry methods,including TEM,XRD,nitrogen ad/desorption isotherm,XPS,etc.,and evaluated by electrochemistry measurements,for instance,CV,LSV and EIS to reveal the structure-property relationship of them.Furthermore,the materials were applied in the single flow battery test and the battery operation data were obtained.First,the two-and three-dimensional SiO₂ templates were synthesized with different components of inducing agents（with or without graphene oxide）.And then the SiO₂ templates were used to synthesize different dimensional nitrogen-doped ordered mesoporous carbon materials（NOMC-2D and NOMC-3D）via nano-casting method.Different nitrogen compositions of two materials were found by XPS because of the nano-confinement effect.And NOMC-2D has higher specific area and larger pore width than NOMC-3D as the result of using different templates.Second,the better performance towards bromine redox was observed in NOMC-2D by CV test and the spatial resistance effect of NOMC-3D can also been observed by it.To be specific,it can be found that the bromine was trapped in the long meso-channel of NOMC-3D via CV test.And the calculation results of the electrode kinetics show that NOMC-2D has larger exchange current and kinetic coefficient than NOMC-3D.Third,single flow batteries were assembled with two as-synthesized catalysts modified carbon felt and the other critical materials such as membrane and electrolyte were optimized as well,in order to increase the battery’s durability and lower the internal resistance.By using the NOMC-2D,the polarization reduced,the difference value of charging-discharging plateau minimized,finally,the energy efficiency can be increased to 84.3%at the current density of 80mA cm^-2.