Synthesis And Optimization Of Two-dimensional Layered Ti₃C₂ As Supercapacitor Electrode Material

Supercapacitors are promising energy storage devices due to their high power densities,short charging time,and good cycle stability.As an energy storage device,the supercapacitor's ability to store energy depends largely on the performance of the electrode material.Ti₃C₂Tx?Tx is a surface active group?,as a new type of two-dimensional transition metal carbon / nitride layered material,has been proved to be an intercalated pseudocapacitor supercapacitor electrode material with excellent electrochemical performance.However,at present,Ti₃C₂ Tx is synthesized by HF and various etchants such as fluorine-containing salts.Therefore,surface groups such as-F are inevitably present during the etching process.Studies have shown that the agglomeration of these groups on the surface of Ti₃C₂ Tx limits its electrochemical performance,so that it does not reach the theoretical specific capacity.In this experiment,Ti₃C₂ Tx with abundant surface groups was first prepared.After XRD,SEM,and EDS characterization,it was found that the content of-F groups in HCl-6M is lower than that of HF-48,HF-72 and HCl-9M.The distance between floors is larger.Electrochemical performance of electrode materials was studied using electrochemical methods testing such as cyclic voltammetry?CV?,constant current charge / discharge?GCD?and electrochemical impedance?EIS?.The specific capacity of HCl-6M in 1M H2SO4 electrolyte reaches 303 F g-1,which was significantly higher than that of HF-48,HF-72 and HCl-6M?respectively: 112 F g-1,198 F g-1,143 F g-1?.At the same time,the rate performance and cycle stability of HCl-6M are also the best,mainly because the-F content in HCl-6M is low,the layer spacing is large,which is conducive to the rapid transmission of ions and the reversibility of its redox reaction Strong.These results indicate that the electrochemical performance of Ti₃C₂ Tx is mainly affected by the content of the indicated groups and the size of the interlayer spacing.This article also explores the effect of electrolyte on the electrochemical performance of Ti₃C₂ Tx.The experimental results show that the specific capacity in H2SO4 electrolyte is much higher than that in KOH or Na2SO4 electrolyte.This is because Ti₃C₂ Tx in H2SO4 electrolytePseudo-capacitance is generated,which is a typical interlayer pseudo-capacitor material.The above research results laid the foundation for the subsequent modification of Ti₃C₂ Tx.In this experiment,by modifying the surface structure of Ti₃C₂ Tx and increasing the interlayer distance to further optimize its electrochemical performance.After alkali treatment and heat treatment,the KOH-400-Ti₃C₂ layer spacing increases and the-F content is greatly reduced.Its specific capacity reaches 405 F g-1,which is much higher than that of unmodified Ti₃C₂ Tx.After the second charge and discharge cycle,the specific capacity retention rate of KOH-400-Ti₃C₂ was 96.1%,much higher than the specific capacity retention rate of HCl-6M electrode 79.7%,and the electrochemical performance was significantly improved.This is due to the reduction of the surface-F group content,which reduced group reunion.Moreover,the interlayer spacing becomes larger,and the interlayer becomes uniform and stable,which facilitates the entry of ions into the interlayer.This paper discusses many factors that affect the performance of Ti₃C₂ Tx supercapacitor electrode materials.It is concluded that increasing the layer spacing and reducing the surface-F group content can effectively improve the performance of Ti₃C₂ Tx electrodes.This paper broadens the research field of Ti₃C₂ Tx supercapacitor electrode materials,provides some experience for the surface modification of Ti₃C₂ Tx materials,and increases the possibility of applying Ti₃C₂ Tx electrode materials to supercapacitors.