Desorption of chemical species during thermal reduction of graphene oxide films

Abstract

Graphene oxide (GO) reduced by thermal or chemical processes has been used in conductive transparent layers, solar cells, chemical sensors among dozens of other applications. Although some researchers have focused on identifying the reduction mechanisms, there is a lack of detailed investigation of species effusion processes. Here we report a systematic investigation on the effusion of chemical species from thermally reduced multilayered GO using the thermal desorption mass spectroscopy technique. The identification of chemical species with the use of the mass spectrometer associated with the formation energy was used to identify the reactions that occur in GO during the thermal reduction. This allows to give support or rule out numerous proposals for effusion processes in GO presented in the literature. It was observed that the main desorption regime centered at ∼230 °C encompassed a collective desorption of H2O, CO2, CO, and H with formation energies ranging from 1.20 to 1.40 eV. For temperatures higher than 400 °C, uncoupled CO2 and CO desorptions were the only species detected, with formation energies of 1.87 and 3.09 eV, respectively. An insulating-conductive transition occurred in the annealing temperature range (ambient to 1000 °C) with a variation of 7 orders of magnitude in conductivity. The results support new routes for reducing GO in order to obtain films closer to pristine graphene multilayers.