In a recent study published in the Nature Communications, Chinese scientists have developed a method of obtaining graphene oxide (GO), safe for the environment. The proposed approach is based on electrochemical oxidation and about 100 times faster oxidation by traditional methods.

GO, usually used as a precursor for the synthesis of grapheme, has many unique properties and promising applications. But unlike grapheme, it contains a great number of oxygen-containing functional groups, and it’s strongly hydrophilic.

Usually GO is received by exfoliation of graphite oxide. The most commonly used Hummers method needs 1000 times more water than graphite has to be used, creates a huge amount of waste water containing mixed acids and heavy metal ions and needs a few to hundreds of hours for oxidation. It’s time-consuming and leading to much pollution.

A research team led by Prof. REN Wencai from Institute of Metal Research, Chinese Academy of Sciences (IMR, CAS) recently found a scalable, safe, ultrafast, and green method to synthesize clean GO sheets by water electrolytic oxidation of graphite.

To obtain the GO, the research team proposed the following technique. At first, the flexible graphite paper is subjected to electrochemical intercalation in concentrated sulfuric acid to form stage-I graphite intercalation compound paper. Then, the graphite intercalation compound paper is used as anode for electrochemical reaction in diluted sulfuric acid. After vacuum filtration and cleaning with water, the filter cake is exfoliated in water by sonication to form electrochemically synthesized GO dispersion.

Scientists compared the newly obtained GO with GO obtained by the traditional method, and it turned out that the structures, compositions, optical and conductive properties are almost identical.

In this case, the whole process of obtaining in this way takes no more than half an hour, and the direct oxidation phase takes only a few seconds, which is about 100 times faster than traditional methods of oxidation. Thus the method makes it possible to control the degree of oxidation of graphene, number of layers in formed material, and its transverse sizes by means of change of concentration of sulfuric acid.

The application of this method can be very promising in the field of high-performance transparent conductive films, strong papers and ultra-light elastic aerogels.