Analysis of surface oxygen groups of thermally reduced graphene oxide via temperature programmed desorption method

In this paper the influence of thermal reduction on oxygen functional groups of graphene oxide, synthesized by modified Hummer's method, has been investigated. The graphene oxide was characterized by X-ray diffraction analysis, ultraviolet-visible spectroscopy, scanning and transmission electron microscopy. Atomic force microscopy was used for thickness analysis of graphene oxide layers before and after of thermal reduction. Changes in surface functional groups of thermally reduced graphene oxide were monitored by temperature programmed desorption method (TPD). TPD analysis of the samples showed removal of surface groups whose stability range is below temperature of the thermal reduction. It was shown that thermal reduction at 300 °C induces desorption of epoxy, alkoxy and carboxyl groups as well as carbonyl groups prone to transformation to α-substituted ketones and aldehydes. Similarly, thermal reduction at 600 °C is capable of desorbing carboxylic anhydrides. TPD analysis of samples recorded certain period of time after thermal reduction showed partial restoring of surface oxygen groups with time