High surface area micro-mesoporous graphene for electrochemical applications.

The manuscript presents results on the influence of external pressure on graphene exfoliation and subsequent 3D structuring by means of liquid-phase exfoliation. In contrast to known and applied exfoliation methods, the current study exploits the enhancement of splitting forces caused by the application of high pressure. The manufacturing pathway allowed to increase the surface area from 750 m/g (nanoplatelets) to ca. 1100 m/g (after 3D structuring). Electrochemical studies revealed that the 3D graphene materials were active in the oxygen reduction reaction (ORR). The outstanding ORR activity of 3D structured graphene materials should not be ascribed to heteroatom catalytic centers since such heteroatoms were successively removed upon increasing the carbonization temperature. XPS data showed that the presence of transition metals and nitrogen (usually regarded as catalytic centers) in G-materials was marginal. The results highlight the importance of structural factors of electrodes in the case of graphene-based materials for Zn-air batteries and ORR.