Morphology and Electrochemical Investigations on Multimetal Carbon Nitride Electrocatalysts Supported on Graphitized Polyketone Nanoballs

One of the most severe bottlenecks in the operation of proton exchange membrane fuel cells (PEMFCs) is the sluggish kinetics of the oxygen reduction reaction (ORR); suitable ORR electrocatalysts are required in order to obtain PEMFCs able to yield a sufficiently high performance. State-of-the-art ORR electrocatalysts for application in PEMFCs are obtained by distributing Pt nanocrystals on active carbon supports characterized by a very large surface area. A new preparation protocol has been proposed recently to obtain electrocatalysts with a well-controlled chemical composition, based on the pyrolysis and activation of hybrid inorganic-organic precursors; the resulting carbon nitride electrocatalysts are able to show an outstanding ORR performance both in “ex-situ” studies and in single-cell configuration. In this work, the morphology and “ex-situ” electrochemical performance of a new family of multimetal carbon nitride electrocatalysts is described. The materials are obtained as described elsewhere by the pyrolysis of a hybrid inorganic-organic precursor including Pt and Ni atoms impregnating an innovative support. The latter is prepared by a three-step process: a) growth of polyketone nanofibers on graphite nanoparticles; b) chemical treatment to make the nanofibers infusible; and c) pyrolysis process under an inert atmosphere. An aliquot of each of the final electrocatalysts is treated with H2O2. The resulting samples undergo an extensive characterization by HR-TEM. Finally, the “ex-situ” electrochemical performance in the ORR is determined by the CV-TF-RRDE method. These studies allow to obtain the correlations between the morphology and “ex-situ” electrochemical performance of these high-performing multimetal carbon nitride ORR electrocatalysts.