'"Core-shell" electrocatalysts based on mono/plurimetallic carbon nitrides for low-temperature fuel cells (PEMFCs, DMFCs, AFCs and PAFCs) and electrolyzers', brevetto europeo depositato il 22-06-2009.

This invention describes the preparation of electrocatalysts to be mounted at either the anode or the cathode of fuel cells or of H2 electrolysers. The materials described in this invention are particularly suitable for application in polymer electrolyte membrane fuel cells (PEMFCs), direct methanol fuel cells (DMFCs), alkaline fuel cells (AFCs) and phosphoric acid fuel cells (PAFCs). The target of the invention is the preparation of core-shell electrocatalysts where active metal sites supported on carbon nitride nanoclusters (shell) are supported on suitable electron-conducting materials (core) such as active carbons or metal nanopowders. The prepared materials feature a well-controlled metal composition, and also include the desired amount of nitrogen. The preparation protocol consists of three steps. In the first the precursor is obtained through reactions of the type: a) sol-gel; b) gel-plastic; c) coagulation-flocculation-precipitation; d) metal-ligand complexation processes in organic solvent using as a ligand a molecule, a macromolecule or a macromolecular system. The second step consists in a pyrolysis process of the precursor in an inert atmosphere leading to the production of the supported carbon nitride materials. In the last step, the chemical and electrochemical activation of the electrocatalyst is performed. The precursors are obtained through reactions leading to: a) the complexation of a transition metal with another molecule or coordination complex acting as a ligand to obtain clusters; b) the 3-D networking of the resulting clusters through suitable organic molecules and/or macromolecules and/or macromolecular systems on the support.