S- and N-doped graphene-based catalysts for the oxygen evolution reaction

In-situ Raman spectroscopy, rotating ring-disk electrode (RRDE), cyclic voltammetry (CV) and linear sweep voltammetry (LSV) techniques were used to determine the catalytic activity of graphite and heteroatom-doped graphene catalysts toward the oxygen evolution reaction (OER) in alkaline media. Main results indicate that the OER is strongly influenced by the nature and amount of the doping agent in addition to the interaction with the electrolyte media, which also conditioned the Area(D)/Area(G) (A(D)/A(G)) ratio and the position of the D- and G-bands. Additionally, an exhaustive Raman characterization of powder materials and catalyst inks in the presence of air, water and sodium hydroxide is reported. Finally, the percentage of molecular oxygen production is estimated by a novel procedure. This work is not intended to reveal the best catalysts toward the OER, but to show novel techniques to study the OER at graphene-based catalysts. (C) 2020 Elsevier Ltd. All rights reserved.