Abstract
MXenes are a class of 2D materials with outstanding properties, including high electronic conductivity, hydrophilicity, and high specific capacitance. In particular, Mo 1.33 CT z MXene has a high specific capacitance, whereas films of Ti 3 C 2 T z MXene possess high flexibility and high electronic conductivity. The fabrication of composite materials based on these two MXenes is therefore motivated, taking advantage of combining their good properties. In this article, we introduce a one-step approach to prepare composite MXene films using pristine Mo 1.33 CT z and Ti 3 C 2 T z MXenes. The composite films display superior flexibility and electronic conductivity, as well as high capacitance, up to 1380 F cm −3 (460 F g −1 ), in 1 M H 2 SO 4 . A capacitance retention of 96% is obtained after 17,000 cycles. In addition, the capacitance retentions are about 56% and 25% at scan rates of 200 mV s −1 and 1000 mV s −1 , respectively. A significant rise in the capacitance at high rates, 875 F cm −3 (282 F g −1 ) at a current density of 20 A g −1 , is achieved by using a 3 M H 2 SO 4 solution. The use of composite MXene as negative electrodes for asymmetric supercapacitor devices, as well as lithium-ion batteries, is also discussed. This work suggests new pathways for the use of MXene composites with double transition metals (Mo and Ti) in energy storage devices. • Simple, fast, and robust synthesis approach to fabricate mixed MXene films using Mo 1.33 CT z and Ti 3 C 2 T z pristine MXenes. • The mixed MXene films display good flexibility and high electronic conductivity (up to 140 S cm −1 ). • The mixed MXene films deliver a high capacitance (1380 F cm −3 ) and feature 96% retention after 17,000 cycles in 1 M H 2 SO 4 . • A significant rise in the rate performance is observed in 3 M H 2 SO 4 solution (875 F cm −3 at current density 20 A g −1 ). • Mixed MXene electrodes are employed as negative electrodes for asymmetric supercapacitor devices.
Highlights
Nowadays, rechargeable energy storage devices, such as batteries and supercapacitors, are of great importance in our daily life due to their use in portable devices, electric vehicles, and wearable electronics
Previous studies have shown that the etching of the MAX phase with double transition metals, Mo2TiAlC2, can result in the formation Mo2TiC2Tz MXene with a volumetric capacitance limited to 413 F cm− 3 at 2 mV s− 1.[53] there is motivation to establish an alternative protocol for preparing MXene films contain ing double transition metals, Mo and Ti, while maintaining high capacitance and electronic conductivity
The Mo1.33CTz and Ti3C2Tz MXenes were prepared by selective chemical etching of the corresponding 3D MAX phases
Summary
Rechargeable energy storage devices, such as batteries and supercapacitors, are of great importance in our daily life due to their use in portable devices, electric vehicles, and wearable electronics. MXenes have previously shown outstanding potential for energy storage applications [30], and various approaches have been developed to improve and tune the electrochemical performance of MXenes, including the formation of composite materials with carbon-based ma terials (e.g. graphene, graphene oxide, carbon nanotubes) [31,32,33], transition metal oxides [34], or transition metal chalcogenides.[35]. Previous studies have shown that the etching of the MAX phase with double transition metals, Mo2TiAlC2, can result in the formation Mo2TiC2Tz MXene with a volumetric capacitance limited to 413 F cm− 3 at 2 mV s− 1.[53] there is motivation to establish an alternative protocol for preparing MXene films contain ing double transition metals, Mo and Ti, while maintaining high capacitance and electronic conductivity. The composite MXene films are flexible and feature a high electronic conductivity
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