Development of Free-Metal Electrocatalyst from Inexpensive Sources of Carbon: A Novel Electrode Material for Cathode Reaction in PEM Fuel Cells

The development of alternative energy sources is of great interest in the scientific community in last decades. Fuel cells are a clean and sustainable alternative for power generation. However, the development of the polymer exchange membrane fuel cells (PEMFC) has been limited due that this systems use platinum as catalyst. Platinum is expensive and scarce, which limited the production of the PEMFC at industrial scale. Moreover, oxygen reduction reaction (ORR) is the reaction in the cathode of the PEMFC. This reaction has the slower kinetic, so limiting the kinetics of the entire cell.

Recently, free noble metal electrocatalysts have been obtained, which are capable of carrying out the ORR with comparable performance to Pt. These novel electrocatalysts are doped nanostructured carbon (ej. nitrogen doped carbon nanotubes N-NTC and nitrogen doped reduced graphene, N-rG). Nowadays, the synthesis of these nanostructured materials has several technological challenges, because it production is still expensive and has a significant environmental impact. In this work, we have obtained novel metal-free electrocatalysts from two different inexpensive carbon source: i) an organic waste and ii) mineral coal from Sabinas region in Coahuila Mexico. These electrocatalysts have a significantly lower cost than conventional platinum based electrocatalysts and the recently synthetized nanostructure free-metal catalyst.

The organic waste were pyrolyzed in a nitrogen atmosphere, and then an activation process with chemical agents was carried out. Moreover, in order to increase their surface area and modify the C-N chemical bond, a thermochemical process was carried out for mineral coal.

 The features and electrochemical performance of both electrocatalyst were compared. The electrocatalysts obtained have surface areas until of 2000 m²/g. The morphology and structural features were observed by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and Raman Spectroscopy. The electrocatalytic activity for these novel electrocatalysts was evaluated for the oxygen reduction reaction (ORR) by rotary disk electrode technique. The results show that these electrocatalysts are an inexpensive and promising alternative for use as cathodes in PEMFC.