Influence of the reducing agent on the physicochemical and electrocatalytic properties of graphene-based aerogels

In-depth research was carried out with different characterization techniques (Scanning Electron Microscope (SEM), Fourier-Transform InfraRed spectroscopy (FTIR), X-ray Diffraction (XRD), picnometry, N2 adsorption/desorption) on the influence various nitrogenous and non-nitrogenous reducing agents have on the properties of graphene-based aerogels. The reducing agent used were ethylene glycol, hydrazine monohydrate, 2-chloroethylamine hydrochloride and ethylenediamine. These aerogels were synthesized by hydrothermal reduction of graphene oxide (GO) and later underwent freeze-drying. Thus, the relationship between the underlying reduction conditions with each reducing agent and certain properties such as textural and crystallographic ones and these, in turn, with electrochemical performance were elucidated. Electrocatalytic performance of the resulting graphene-based aerogels was strongly influenced by porosity, density, crystallinity and the presence of nitrogenous and oxygenated functional groups. To maximize electrocatalytic performance in the hydrogen evolution reaction (HER), a nitrogen-doped graphene aerogel with a low level of remaining oxygen functional groups, high surface mesopore area and porosity and exceptionally low density was needed. The presence of N species was found to have a positive effect on HER performance. Furthermore, adding N through hydrazine assisted hydrothermal synthesis seemed to be preferable for HER.