Preparation Of Ti₃C₂T_x MXene By Hydrothermal Method And Its Application In Zinc-air Battery

MXene is used in many fields due to its good properties such as hydrophilicity and high conductivity.The commonly used preparation methods of MXene usually involve high HF concentration and are prone to stacking,which restricts their further application.ZABs have attracted extensive concern because of their high energy density and low expense.In this paper,Ti₃C₂T_xMXene was prepared by a mild and environmentally friendly hydrothermal method and compounded with a material with high catalytic activity as a cathode oxygen reduction catalyst for zinc-air battery.The main research contents of this paper are as follows:1.Preparation of Ti₃C₂T_xby hydrothermal method.Ti₃C₂T_xwas prepared by hydrothermal method using HCl and Li F as etchants,and its morphology was studied.The effects of reaction temperature,MAX/Li F mass ratio,reaction time and concentration of hydrochloric acid on the structure of Ti₃C₂T_xwere investigated.The effect of hydrothermal method and HF etching method on the structure of Ti₃C₂T_xwas studied.Compared with HF etching method,the layer spacing of Ti₃C₂T_xprepared by hydrothermal method is larger,the lamellar distribution is more uniform,the specific surface area increases by 36 m²/g,and the electrical conductivity increases by more than two times,indicating that hydrothermal method has a great advantage in the preparation of Ti₃C₂T_x.In addition,the hydrothermal method is also suitable for the preparation of V₂CT_xMXene.This method provides a general,safe and efficient way for the preparation of MXene.2.Preparation of Iron phthalocyanine-Ti₃C₂T_x-reduced graphene oxide composites（FePc-M-rGO）and application of zinc-air batteries.Based on Ti₃C₂T_xprepared by hydrothermal method,FePc-M-rGO was prepared by self-assembly method,and its morphology,structure and composition were characterized and analyzed.FePc is evenly attached to the surface of MXene and rGO,O₂is easier to adsorb and reduce at the active site of Fe N₄,accelerating the rate of electron transfer,and rGO insertion reduces the stacking of MXene between layers.The oxygen reduction（ORR）performance of FePc-M-rGO was studied.The half-wave voltage of FePc-M-rGO is 0.9 V,and it shows better ORR activity than Pt-C catalyst.The specific capacitance of the zinc-air battery using FePc-M-rGO as cathode catalyst is 676.65 m Ah/g,and it can maintain 1.08 V discharge voltage and 9.05 h discharge time at the current density of 10 m A/cm².3.In order to reduce the cost,Ti₃C₂T_xwas grafted with sulfonic group and polyaniline-Ti₃C₂T_X-reduced graphene oxide（PANI-M-rGO）composites were prepared by hydrothermal method.The morphology,structure and composition of PANI were characterized and analyzed.PANI is uniformly attached to the surface of Ti₃C₂T_xand rGO.The half-wave voltage of the composite is 0.88 V,which is equivalent to that of Pt-C catalyst,and the number of transferred electrons is 3.9.O₂can be directly reduced to OH^-by one-step four-electron reaction.The sulfonic group can improve the protonation degree of PANI,and PANI improved the selectivity of the composites to O₂.The specific capacitance of PANI-M-rGO-based zinc air battery is 625.31 m Ah/g,and it can maintain 1.13 V discharge voltage and8.95 h discharge time at the current density of 10 m A/cm².It has good stability and reversibility.It is proved that Ti₃C₂T_xhas a good application prospect in cathode oxygen reduction catalyst of zinc-air battery.