Recently, a large family of 2D materials called MXenes have attracted much attention in the field of supercapacitors, thanks to the excellent performance demonstrated by Ti3C2 MXene-based electrodes. However, research on MXenes for supercapacitor applications has been primarily focused on Ti3C2, even though there are more than 20 other members of this large family of materials already available. Studies on other MXenes are emerging, with promising results already achieved by Ti2C, Mo2C, and Mo1.33C in aqueous electrolytes. Yet, many other MXenes remain unexplored in aqueous supercapacitor applications. In this work, we report on the electrochemical behavior of a vanadium carbide MXene, V2C, in three aqueous electrolytes. Excellent specific capacitances were achieved, specifically 487 F/g in 1 M H2SO4, 225 F/g in 1 M MgSO4, and 184 F/g in 1 M KOH, which are higher than previously reported values for few micrometer-thick delaminated MXene electrodes. This work shows the promise of V2C MXene for energy storage using aqueous electrolytes.

Electrochemical actuators are devices that convert electrical energy into mechanical energy via electrochemical processes. They are used in soft robotics, artificial muscles, micropumps, sensors and other fields. The design of flexible and stable electrode materials remains a major challenge. MXenes, an emerging family of 2D materials, have found applications in energy storage. Here, we report an actuator device using MXene (Ti3C2Tx) as a flexible electrode material. The electrode in 1 M H2SO4 electrolyte exhibits a curvature's change up to 0.083 mm-1 and strain of 0.29%. Meanwhile, the MXene-based actuator with a symmetric configuration separated by gel electrolyte (PVA-H2SO4) has curvature and strain changes up to 0.038 mm-1 and 0.26% with excellent retention after 10,000 cycles. In-situ X-ray diffraction analysis demonstrates that the actuation mechanism is due to the expansion and shrinkage of the interlayer spacing of MXenes. This research shows promise of this new family of materials for electrochemical actuators.

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