Platinum-free Carbon Nitride Electrocatalysts for PEMFCs Based on Pd, Co and Ni: Effect of Nitrogen on the Structure and Electrochemical Performance

摘要

This report describes two new synthesis protocols for the preparation of "core-shell" platinum-free electrocatalysts consisting of graphite cores covered by carbon nitride shells embedding the active sites. The resulting systems are characterized by a well-controlled chemical composition with different wt% of nitrogen in their supports. The protocols rely on the thermal decomposition of precursors obtained by networking suitable metal coordination complexes with an organic binder over active carbon nanoparticles. The resulting electrocatalysts showed a higher thermal stability in oxidizing conditions with respect to a reference system. The materials provided a remarkable performance in the oxygen reduction reaction (ORR), even if a lower selectivity towards the desired 4-electron pathway is observed. Membrane electrode assemblies (MEAs) tested in operative conditions with the proposed materials applied at the cathode required a lower mass of noble metal (up to 0.46 g/kW) to achieve the same electrical power as the platinum-based reference (1.1 g/kW).