| 1. |
- Ahmed, Heba, et al.
(författare)
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Recovery of oxidized two-dimensional MXenes through high frequency nanoscale electromechanical vibration
- 2023
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Ingår i: Nature Communications. - : NATURE PORTFOLIO. - 2041-1723. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- MXenes hold immense potential given their superior electrical properties. The practical adoption of these promising materials is, however, severely constrained by their oxidative susceptibility, leading to significant performance deterioration and lifespan limitations. Attempts to preserve MXenes have been limited, and it has not been possible thus far to reverse the materials performance. In this work, we show that subjecting oxidized micron or nanometer thickness dry MXene films-even those constructed from nanometer-order solution-dispersed oxidized flakes-to just one minute of 10 MHz nanoscale electromechanical vibration leads to considerable removal of its surface oxide layer, whilst preserving its structure and characteristics. Importantly, electrochemical performance is recovered close to that of their original state: the pseudocapacitance, which decreased by almost 50% due to its oxidation, reverses to approximately 98% of its original value, with good capacitance retention ( approximate to 93%) following 10,000 charge-discharge cycles at 10 A g(-1). These promising results allude to the exciting possibility for rejuvenating the material for reuse, therefore offering a more economical and sustainable route that improves its potential for practical translation. Despite their vast potential, the practical deployment of MXenes has been hampered by their tendency to be oxidized. Here, the authors show that simply vibrating MXene films in just a minute can remove the oxide layer formed and restore their electrochemical performance close to its original state.
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| 2. |
- Alijani, Hossein, et al.
(författare)
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Acoustomicrofluidic Synthesis of Pristine Ultrathin Ti3C2Tz MXene Nanosheets and Quantum Dots
- 2021
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Ingår i: ACS Nano. - : AMER CHEMICAL SOC. - 1936-0851 .- 1936-086X. ; 15:7, s. 12099-12108
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Tidskriftsartikel (refereegranskat)abstract
- The conversion of layered transition metal carbides and/or nitrides (MXenes) into zero-dimensional structures with thicknesses and lateral dimensions of a few nanometers allows these recently discovered materials with exceptional electronic properties to exploit the additional benefits of quantum confinement, edge effects, and large surface area. Conventional methods for the conversion of MXene nanosheets and quantum dots, however, involve extreme conditions such as high temperatures and/or harsh chemicals that, among other disadvantages, lead to significant degradation of the material as a consequence of their oxidation. Herein, we show that the large surface acceleration.on the order of 10 million gs.produced by high-frequency (10 MHz) nanometer-order electromechanical vibrations on a chipscale piezoelectric substrate is capable of efficiently nebulizing, and consequently dimensionally reducing, a suspension of multilayer Ti3C2Tz (MXene) into predominantly monolayer nanosheets and quantum dots while, importantly, preserving the material from any appreciable oxidation. As an example application, we show that the high-purity MXene quantum dots produced using this room-temperature chemical-free synthesis method exhibit superior performance as electrode materials for electrochemical sensing of hydrogen peroxide compared to the highly oxidized samples obtained through conventional hydrothermal synthesis. The ability to detect concentrations as low as 5 nM is a 10-fold improvement to the best reported performance of Ti3C2Tz MXene electrochemical sensors to date.
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