Preparation of Montmorillonite Nanosheets with a High Aspect Ratio through Heating/Rehydrating and Gas-Pushing Exfoliation

Montmorillonite (MMT) is an abundant silicate mineral with ultrahigh stability. The exfoliation of stacked MMT into high-aspect-ratio nanosheets is of crucial importance for various applications such as toxic gas suppression, barrier property enhancement, flame retardancy, and ion conduction. In this work, we develop a new heating/rehydrating and gas-pushing method that can successfully exfoliate MMT into nanosheets with aspect ratios (600-5000) far higher than the currently reported values (1-120). The MMT first goes through a starvation pretreatment under different heating temperatures to improve its hydrophilicity and is then rehydrated in a hydrogen peroxide solution. The hydrogen peroxide in the MMT interlayer space can decompose into water and oxygen bubbles, thus finally leading to the exfoliation via gas-pushing while preserving the large lateral size (mainly in the range of 1-6 mu m) of the nanosheets. By changing the pretreatment temperature and pH value of the hydrogen peroxide solution, the exfoliation performance can be tuned. This simple and low-cost exfoliation method is promising to achieve the mass production of MMT nanosheets with a high aspect ratio and may promote its application in various fields such as energy conversion, drug delivery, and photocatalysis.

Automated summary

In this work, a new heating/rehydrating and gas-pushing method is developed to successfully exfoliate Montmorillonite (MMT) into nanosheets with high aspect ratios. The exfoliation performance can be tuned by changing the pretreatment temperature and pH value of the hydrogen peroxide solution. This simple and low-cost method holds promise for mass production of high aspect ratio MMT nanosheets and can promote their application in various fields.