A Pt-Fe Carbon Nitride Nano-electrocatalyst for Polymer Electrolyte Membrane Fuel Cells and Direct-Methanol Fuel Cells: Synthesis, Characterization, and Electrochemical Studies

This report describes the preparation of a new nano-electrocatalyst for applications in polymer electrolyte fuel cells operating with H2 and methanol. The nano-electrocatalyst, having the composition K0.12[Pt1Fe1.6C55N0.12], consists of a distribution of Pt and Fe bimetallic clusters supported on carbon nitride nanoparticles. This material was synthesized by thermal treatment of a zeolitic inorganic–organic polymer electrolyte-like (Z-IOPE) precursor, prepared by reacting H2PtCl6 and K3Fe(CN)6 in the presence of sucrose, as organic binder, in a water solution. This reaction allows the desired material to be prepared by means of a sol→gel process followed by a gel→plastic transition. The morphology and surface properties of K0.12[Pt1Fe1.6C55N0.12] were studied via scanning and high-resolution transmission electron microscopies and X-ray photoelectron spectroscopy. Far-infrared, mid-infrared, and micro-Raman-laser spectroscopies, as well as X-ray diffraction studies, together with detailed compositional data reveal the structural information and describe the interactions characterizing the mass activity of the K0.12[Pt1Fe1.6C55N0.12] system. This material has structural and morphological features that are very different to those usually found in commercially available electrocatalysts for application in H2 polymer electrolyte membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs). K0.12[Pt1Fe1.6C55N0.12] consists of active bimetallic catalytic sites supported on a mixture of a and graphitic carbon nitride-like nanoparticles. The studies performed by cyclic Voltammetry with the thin-film rotating-disk electrode indicate that the performance of K0.12[Pt1Fe1.6C55N0.12] and of the EC-20 reference material is a) equal to –255 and –216 A/g Pt, respectively, in the oxygen-reduction reaction at 0.75 V; and b) equal to 967 and 533 A/g Pt, respectively, in the hydrogen-oxidation reaction at potentials lower than 0.2 V. The activation potential of K0.12[Pt1Fe1.6C55N0.12] is about 15 mV higher than that of the EC-20 reference. In conclusion, the proposed synthesis route is general and promising for the development of new, improved nano-electrocatalysts for low-temperature fuel cells such as PEMFCs and DMFCs.