Thanks to the unique properties of graphite oxides and graphene oxide (GO), this material has become one of the most promising materials that are widely studied. Graphene oxide is not only a precursor for the synthesis of thermally or chemically reduced graphene: researchers revealed a huge amount of unique optical, electronic, and chemical properties of graphene oxide for many different applications. In this review, we focus on the structure and characterization of GO, graphene derivatives prepared from GO and GO applications. We describe GO utilization in environmental applications, medical and biological applications, freestanding membranes, and various composite systems.

The oxygen evolution and reduction reactions are two extremely important reactions in terms of energy applications. Currently, the Oxygen Evolution Reaction (OER) hinders the efficient running of electrolyzer devices which convert water into molecular H₂. This H₂ can subsequently be used in a H₂/O₂ fuel cell for the renewable generation of electricity with only H₂O as a by-product. However, this fuel cell process is not economy feasible due to the sluggish kinetics of the Oxygen Reduction Reaction (ORR) at the device cathode, even with expensive state-of-the-art electrocatalytic materials. As of late, the amount of interest in the OER and ORR, from research laboratories from all over the globe, has risen rapidly in order to find cheap and efficient catalysts to replace the expensive platinum based catalysts currently used in the two aforementioned energy conversion/generation technologies. Layered transition metal oxides, based on the cheap transition metal oxides Mn, Co, Ni and Fe have been reported as viable catalysts for the OER and ORR. Layered structures have an added advantage over non-layered materials as the surface area can be increase by means of exfoliation, with potential for tailoring electrocatalytic activity. It has been shown that the fabrication process and post-synthetic treatments, e.g. anion exchange or exfoliation, of these materials can alter the catalytic activity of these materials. Here we summarise various fabrication methods and modifications utilised in literature to tailor the performance of layered transition metal and hydroxide based catalysts for the ORR and OER toward that of the state-of-the-art materials for these technologies.

Herein, we compare the bulk, 2H and 3R phases of two most prevalent TMD materials: MoS₂ and WS₂.