The research group led by Prof. ZHU Yanwu from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences and his collaborators realized efficient and intrinsically safe graphite oxidation, by utilizing customized chip microreactors with characteristics of continuous flow. This work was published in Advanced Materials.

As significant precursors for the batch-style preparation of graphene, graphite oxide and its exfoliated counterpart graphene oxide (GO) are promising materials for many technologies.

Hummers’ method to oxidize graphite was first reported in 1958 and has been updated many times in recent years, but the oxidation of graphite was still hindered by challenges of long reaction time, safety concern, and quality control. Therefore, it is a compelling task to develop an efficient, safe, and large-scale technology of GO preparation.

The efficiency of mass transfer and energy exchange was significantly boosted in microchannels. Thus, the graphite could be oxidized within two minutes via enhanced microfluidic reaction to the degree which would be obtained in hours in traditional reactors. By changing the configuration of microchannels and the fluidic parameter, the oxidation degree and oxygen-containing functional groups of GO could be finely tuned. Based on the experiment, to achieve a continuous production line with an annual yield of 60 tons, a total volume of only 6.5L of microreactors is required.

Moreover, the reaction in transparent microreactors permitted in-situ monitoring of the oxidation processes with Raman spectroscopy. From the in-situ characterizations of Raman G peaks’ evolution in the oxidation process, the researchers found that reaction kinetics was closely connected with flow velocity, raw graphite species, and flakes. They also demonstrated the capabilities of reduction and assembly of GO in microchannels, and its thermally and electrically conductive abilities.

Photo of graphene (Image from Pixabay)

This study lays a foundation for the preparation and application of GO via microfluidic technology.

Paper link: https://onlinelibrary.wiley.com/doi/10.1002/adma.202107083

(Written by YANG Min, edited by JIANG Pengcen, USTC News Center)