Synthesis of Mo_(2)C MXene with high electrochemical performance by alkali hydrothermal etching

Two-dimensional MXenes are generally prepared by the etching of acid solutions.The as-synthesized MXenes are terminated by acid group anions(F^(–),Cl^(–),etc.),which affect the electrochemical performance of MXenes.Here,we report a novel method to prepare Mo_(2)C MXene from Mo_(2)Ga_(2)C by the hydrothermal etching of alkali solutions.Highly pure Mo_(2)C MXene was successfully synthesized by the etching of NaOH,while the etchings of LiOH and KOH were failed.The concentration of NaOH,temperature,and time strongly affect the purity of as-prepared MXene.Pure Mo_(2)C MXene could be synthesized by the etching of 20 M NaOH at 180 for 24 h.After℃intercalation by hexadecyl trimethyl ammonium bromide at 90 for 96 h,few℃-layer Mo_(2)C MXene was obtained.The Mo_(2)C MXene made by NaOH etching after intercalation exhibited excellent performance as anode of lithium-ion battery,compared with general Mo_(2)C MXene made by HF etching and the Mo_(2)C MXene reported in literature.The final discharge specific capacity was 266.73 mAh·g^(−1)at 0.8 A·g^(−1),which is 52%higher than that Mo_(2)C made by HF etching(175.77 mAh·g^(−1)).This is because Mo_(2)C MXene made by NaOH etching has lager specific surface area,lower resistance,and pure O/OH termination without acid anion termination.This is the first report to make Mo_(2)C MXene by alkali etching and the samples made by this method exhibited significantly better electrochemical performance than the samples made by general HF etching.