Guodong Zou

Synthesis of MXene/Ag Composites for Extraordinary Long Cycle Lifetime Lithium Storage at High Rates

A new MXene/Ag composite was synthesized by direct reduction of a AgNO3 aqueous solution in the presence of MXene (Ti3C2(OH)0.8F1.2). The as-received MXene/Ag composite can be deemed as an excellent anode material for lithium-ion batteries, exhibiting an extraordinary long cycle lifetime with a large capacity at high charge-discharge rates. The results show that Ag self-reduction in MXene solution is related to the existence of low-valence Ti. Reversible capacities of 310 mAh·g(-1) at 1 C (theoretical value being ∼320 mAh·g(-1)), 260 mAh·g(-1) at 10 C, and 150 mAh·g(-1) at 50 C were achieved. Remarkably, the composite withstands more than 5000 cycles without capacity decay at 1-50 C. The main reasons for the long cycle life with high capacity are relevant to the reduced interface resistance and the occurrence of Ti(II) to Ti(III) during the cycle process.

Synthesis of urchin-like rutile titania carbon nanocomposites by iron-facilitated phase transformation of MXene for environmental remediation

Self-assembling has been confirmed as an effective pathway to achieve some unique properties. The recently developed two-dimensional transition metal carbides (termed MXene) provide more potential opportunities to modify the surfaces of layered materials relative to simple graphene. Here we describe a one-step method for preparing an urchin-like rutile TiO2–C (u-RTC) nano-composite with a high amount of (110) facets by in situ phase transformation of MXene (Ti3C2(OH)0.8F1.2) under FeCl3 conditions. A layered anatase TiO2–C (l-ATC) nano-composite with a high percentage of (001) facets first forms, and then it changes into u-RTC due to the Fe(III) ion induction. The u-RTC displays a high Cr(VI) adsorption capacity of ∼225 mg g−1, which is higher than that of the primitive MXene (∼62 mg g−1) and the l-ATC precursor (∼11 mg g−1), owing to the inhibition of H2O molecule adsorption by bridging oxo groups in terms of the first principles calculations. Apart from the fact that the finding leads to a desirable aligned oxide-carbon material, this approach may set up a new trajectory to self-assemble functional surfaces of other MXene derivatives.

Fabrication of tunable hierarchical MXene@AuNPs nanocomposites constructed by self-reduction reactions with enhanced catalytic performances

MXene, a new type of two-dimensional layered transition metal carbide material differing from graphene, demonstrates intriguing chemical/physical properties and wide applications in recent years. Here, the preparation of the self-assembled MXene-gold nanoparticles (MXene@AuNPs) nanocomposites with tunable sizes is reported. The nanocomposites are obtained via the self-reduction reactions of MXene material in a HAuCl4 solution at room temperature. The sizes of the Au particles can be well-controlled by regulating the self-reduction reaction time. They can greatly influence the catalytic behaviors of the MXene@AuNPs composites. MXene@AuNPs composites with optimized reduction time show high catalytic performances and good cycle stability for model catalytic reactions of nitro-compounds, such as 2-nitrophenol and 4-nitrophenol. This work demonstrates a new approach for the preparation of tunable MXene-based self-assembled composites.摘要MXene是一种不同于石墨烯的新型层状二维过渡金属碳化物材料, 近年来表现出有趣的化学、 物理性能并被广泛应用. 本文报道了结构新颖且尺寸可调的自组装层状MXene@AuNPs纳米复合材料的制备方法. 在室温下MXene@AuNPs纳米复合材料可通过MXene材料在HAuCl4溶液中的自还原反应制备. 控制自还原反应的时间可精确地调节Au粒子的颗粒尺寸. 而金纳米颗粒的粒径对MXene@AuNPs复合材料的催化性能具有很大的影响. 适当自还原时间下得到的MXene@AuNPs复合材料表现出对模型硝基化合物(如4-NP和2-NA)催化反应很高的催化性能和良好的循环稳定性. 本研究工作为基于MXene自组装复合材料的制备与调控提供了新方法.

Synthesis of Nanoflower-Shaped MXene Derivative with Unexpected Catalytic Activity for Dehydrogenation of Sodium Alanates

Surface group modification and functionalization of two-dimensional materials in many cases are deemed as effective approaches to achieve some distinctive properties. Herein, we present a new nanoflower-shaped TiO2/C composite which was synthesized by in situ alcoholysis of two-dimensional layered MXene (Ti3C2(OHxF1-x)2) in a dilute HF solution (0.5 wt %) for the first time. Furthermore, it is demonstrated that it bestows a strong catalytic activity for the dehydrogenation of NaAlH4. The results show that the NaAlH4 containing 10 wt % A0.9R0.1-TiO2/C (containing 90% anatase TiO2 and 10% rutile TiO2) composite merely took ∼85 min to reach a stable and maximum dehydrogenation capacity of ∼3.08 wt % at 100 °C, and it maintains stable after ten cycles, which is the best Ti-based catalyst for the dehydrogenation of NaAlH4 reported so far. Theoretical calculation confirms that this C-doping TiO2 crystals remarkably decreases desorption energy barrier of Al-H bonding in NaAlH4, accelerating the breakdown of Al-H bonding. This finding raises the potential for development and application of new fuel cells.