Investigating The Preparation And Reactive Mechanism Of Graphite Felt Composite Electrodes For Vanadium Redox Flow Batteries

It has been an inevitable trend for renewable energies to replace the fossil fuels in the fields of energy storage in recent years.Renewable energies such as wind,solar and tidal energy due to the intermittent characteristic and low-efficiency utilization are difficult to meet the needs of daily life.It is urgent for us to find high-efficiency strategy to solve above-mentioned issues.Vanadium redox flow batteries play a vital role in the storage and transformation of renewable energies because of their cost-effective,long life-spans,excellent cycle stability and eco-friendly.However,the inferior catalytic activity and redox kinetic reversibility have severely restricted their application in large scale.The electrode materials are designed and fabricated in this article aiming at the issues that vanadium redox flow batteries face.The main contents are as follows:?1?High Electro-Catalytic Graphite Felt/MnO₂ Composite Electrodes for Vanadium Redox Flow BatteriesA graphite felt/MnO₂?GF-MNOs?composite electrodes with excellent electro-catalytic activity towards VO²⁺/VO₂⁺redox couples in the VRFB was synthesized by a one-step hydrothermal process.The resulting GF-MNOs electrodes possess an improved electrochemical kinetic reversibility to the vanadium redox reactions compared to the pristine GF,the corresponding energy efficiency and discharge capacity are increased by 12.5%and 40%at 150 mA cm^-2,respectively.The discharge capacity maintains 4.8 Ah L^-1 at the ultra-high current density of 250 mA cm^-2.Especially,the energy efficiency of GF-MNOs composite electrodes retained 80%after 120 charging-discharging cycles at 150 mA cm^-2.Furthermore,it demonstrated that more catalytic active sites were provided by the MnO₂ particles.The proposed synthesis rote is facile,and the raw materials is low-cost and eco-friendly,Therefore,the novel GF-MNOs hold a great promise in the large-scale vanadium redox flow battery energy storage.?2?Designing High-Performance Composite Electrodes for Vanadium Redox Flow Batteries Based on Experimental and Computational Collaborative InvestigationsThe graphitic carbon nitride granules decorated graphite felt electrode?GF@CN?were constructed via facile urea pyrolysis.By virtue of computational investigations,it was demonstrated that the catalytic activity sites concentrated on the electro-rich pyridinic N within the modifying CN granules cladding layer.Therefore,the GF composed with CN granules dramatically improves the cycling stability of VRFBs with energy efficiency more than 75%after 800 cycles at current density(150 mA cm^-2).The cost-effective route simplifies the preparation process for the high performance composite electrodes,and the computational result sheds light on future design of the electrodes materials for other high-power flow batteries.