Modulating Oxygen Species Proportion in Graphene Oxide—Towards Influencing the N-Doping Process

Graphene oxide (GO) has emerged as a key precursor for nitrogen-doped graphene due to its unique structure, which includes a variety of oxygen-containing functional groups such as epoxides, hydroxyls, carboxyls and carbonyls among others. These oxygen could be impacting the doping process in a different manner. Understanding the transformation and reorganization of these functional groups should be essential for optimizing the nitrogen doping of graphene.<br/>The oxygen functionalities in graphene oxide are reactive and can undergo significant reorganization under controlled conditions, such as mild thermal treatments or by pH-dependent chemical procedures. This reconfiguration could promote the desired surface chemistry that facilitate the incorporation of nitrogen atoms into the carbon network of graphene. By carefully selecting and tuning these treatments, it should be possible to convert certain oxygen species into configurations that favor the nitrogen doping. Therefore, this approach of modifying the oxygen functional groups in the graphene oxide to be used as the precursor should represent a promising strategy for improving the efficiency of nitrogen doping and optimizing the performance of nitrogen-doped graphene in electrocatalytic applications.<br/>In this study, we explore the redistribution of oxygen species proportion by different post-synthesis treatment of graphene oxide. Techniques such as X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), Raman spectroscopy, X-ray diffraction (XRD), were used to monitor the changes in the chemical and structural properties of the Graphene oxide. This was analyzed together with feasible organic chemistry reactions and DFT calculations to understand in deep the different processes. The ability to control the oxygen species on the graphene oxide surface is crucial, as it could influence the subsequent nitrogen doping efficiency and the nature of the nitrogen incorporation (e.g., pyridinic, graphitic, or pyrrolic nitrogen).<br/><br/>Acknowledgements:<br/>We thank financial support from the DGAPA-UNAM through PAPIIT project IN111223 and IN105722. Calculations were performed in the DGTIC-UNAM Supercomputing Center projects LANCAD-UNAM-DGTIC-051 and LANCAD-UNAM-DGTIC-382. We thank Francisco Ruíz, Eduardo Murillo, David Dominguez, Lazaro Huerta, Eloísa Aparicio, Israel Gradilla, Jesús Díaz and Jaime Mendoza for technical support. Similarly, we are very thankful to all the AG&P groupmates for fruitful discussions.