Conclusions and outlook
Carbon materials can be produced with a wide range of textures, structures, morphologies and surface chemistries, playing a decisive role towards the development of efficient and cost-effective electrochemical devices for energy conversion and storage. The textural and surface chemical properties of carbon materials can be modified in a controlled way, addressing the needs of the specific applications envisaged. Micro-mesoporous hierarchical carbons can be synthesized by sol-gel, soft-templating and hydrothermal routes. The hazardous compounds traditionally used in these syntheses can be advantageously replaced by carbohydrates and other biomass-derived precursors, with the assistance of nanocarbons such as GO and CNTs. These hierarchical carbons offer more favourable kinetic properties for application in electrochemical devices, when compared with the currently available activated carbons. Composites consisting of nanostructured carbons self-assembled with metal oxides or carbides have been developed as electrocatalysts for the HER. On the other hand, nitrogen-doped and sulphur-doped carbons have demonstrated excellent activities as electrocatalysts for the ORR. This is an extremely active field of research, driven by the need to replace platinum and other noble metals which are hindering the wide-scale implementation of the new energy paradigm based on hydrogen and renewable sources.
