Development and optimization of nanostructured carbon-based materials for energy application

Bioelectrochemical Systems (BES) represent a renewable technology that in the past 15 years become an important renewable energy source due to its promising potential of wastewater treatment, energy recovery and storage. However, the slow kinetics of the oxygen reduction is one of the major factors that leads to the use of expensive catalysts, such as platinum, limiting the overall performance output and applicability of BES technology. Recently, a new class of catalysts based on nanostructured carbon was developed as an efficient, low-cost, alternative to platinum for oxygen reduction in fuel cells. Since then, great progress has been made, and car bon-based Pt-free catalysts have been demonstrated to be effective for enhancing electrocata lytic processes. Transition metal, as manganese, iron, and cobalt, supported on nanostructured carbon (i.e., carbon black, carbon nanotubes, graphene and activated carbon) allowed achieving oxygen reduction reaction (ORR) rate comparable to Pt. In fact, efficiency and durability of ORR active sites are strongly affected by catalyst structure and morphology, and heteroatom doping (nitrogen, phosphorus or sulphur). In this context, the present study involves methods of synthesis, optimization and characterization of nanostructured electrocatalysts based on tran sition metal and carbon materials, with special emphasis on graphene oxide, nitrogen-doped graphene oxide, Fe and Mn-functionalized carbon and metal-free catalysts. To improve the cat alytic activity of the nanostructured materials, we developed strategies to optimize the state-of the-art cathode through a combination of materials and facile methods of synthesis. The cata lysts and cathodes prototypes were characterized by combining the use of electrochemical and spectroscopic techniques to correlate the different morphologies and surface chemistry to elec trocatalytic activity towards ORR. The Microbial Fuel Cell (MFC) performance was also eval uated, and the results show that nanostructured electrocatalyst are good candidates to replace platinum at the cathode side of MFCs.