【Research Background】

      As an emerging two-dimensional (2D) material, MXenes has received extensive attention in the fields of energy storage systems, catalytic fields, and wastewater treatment. It is well known that Ti3C2Tx MXenes is particularly attractive for use in alkaline ion (ie Li+ and Na+) batteries [Lithium Ion Batteries and Sodium Ion Batteries (LIBs/SIBs)] due to their metallic conductivity compared to other 2D materials. However, due to its lower theoretical capacity of 320 mA h/g, its further application in rechargeable batteries is hindered. Compared with MXenes, phosphorus (P) has an advantage in theoretical capacity (2595 mA h/g) and can compete with high-capacity Si and Sn. Among the three allotropes of phosphorus (red, black, and white P), red phosphorus is considered to be one of the attractive candidates because of its non-toxicity, good stability in air, and low cost. 

[Introduction]
      The team of Zhejiang University Han Weiqiang and the team of the Sydney University of Science and Technology Wang Guoxiu team found that the combination of red phosphorus and MXene by ball milling has excellent performance in alkaline ion batteries.
     MXenes synthesized from MAX is a new energy storage material with good metal conductivity and rich surface chemistry. The currently reported MXenes are mainly synthesized by Al-based MAX. The synthesis of MXenes from silicon-based MAX is still a big challenge because of the strong Ti-Si bond. Here, we report for the first time a high-energy ultrasonic cell disruption extraction method, successfully prepared Ti3C2Tx MXenes from silicon-based MAX, using a single low-concentration etchant. The method has the advantages of high extraction efficiency, short preparation time and short time, and can be used for selective etching of silicon. In addition, the red phosphorus nanodot / Ti3C2Tx (PTCT) composite was successfully prepared by high energy ball milling technology, and has excellent electrochemical properties in lithium ion and sodium ion. This new method for synthesizing Ti3C2TxMXenes from Si-based MAX and the unique P-O-Ti bonded PTCT composite opens a new door for the preparation of high-performance MXenes-based materials and is developed for next-generation energy storage. The low cost MXenes and other 2D materials provide convenience.

      The article was published in the well-known journal ACS Appl. Mater. Interfaces entitled: NovelSynthesis of Red Phosphorus Nanodot/Ti3C2Tx MXenes from Low-Cost Ti3SiC2 MAX Phases for Superior Lithium- and Sodium-Ion Batteries.

[Graphic introduction]

Figure 1. Flow chart of synthesis of red phosphorus nanodot / Ti3C2Tx (PTCT) composite.

Figure 2 Comparison of XRD and Raman before and after etching.

Figure 3 SEM and TEM characterization after etching.

Figure 4. Red phosphorus nanodot /Ti3C2Tx (PTCT) composite lithium battery performance test chart.

[Summary of this article]
     In summary, this paper successfully demonstrates a new strategy, using a large number of Ti3SiC2 MAX phases, through high-energy ultrasonic cell disruption sonication, using a single low-concentration etchant to destroy the Ti-Si bond of the MAX phase. Multilayer Ti3C2Tx nanoflakes were prepared. In particular, we have carefully selected high-capacity red phosphorus combined with Ti3C2Tx MXenes to form a unique P-O-Ti-bonded red phosphorus nanodot/Ti3C2Tx (PTCT) composite, which fully combines the high capacity of red phosphorus with the excellent electrical conductivity of Ti3C2Tx MXenes. . When the PTCT electrode is used for LIBs or SIBs, the PTCT electrode exhibits good cycle stability in 1000 cycles. By increasing the P content, the capacity of LIBs can be increased to 818.2 mA h/g after 200 cycles. When sodium is stored, the initial capacity is 863.8 mA h/g, the current density is 50 mA/g, and it can maintain 370.2 mA h/g after 200 cycles, showing good sodium storage performance of MXenes-based materials. More importantly, the efficient, low-cost, and scalable strategy for preparing MXenes and MXenes-based high-capacity materials can be extended to other MXenes and high-capacity composites for energy storage and conversion. The high capacity of red phosphorus and the excellent conductivity of Ti3C2Tx MXenes are fully integrated.

Document connection:
DOI: 10.1021/acsami.9b13308
Source: WeChat public account  MXene Frontier