Nitrogen-Doped Reduced Graphene Oxide Supported Pd(4.7)Ru Nanoparticles Electrocatalyst for Oxygen Reduction Reaction

It is imperative to design an inexpensive, active, and durable electrocatalyst in oxygen reduction reaction (ORR) to replace carbon black supported Pt (Pt/CB). In this work, we synthesized Pd(4.7)Ru nanoparticles on nitrogen-doped reduced graphene oxide (Pd(4.7)Ru NPs/NrGO) by a facile microwave-assisted method. Nitrogen atoms were introduced into the graphene by thermal reduction with NH(3) gas and several nitrogen atoms, such as pyrrolic, graphitic, and pyridinic N, found by X-ray photoelectron spectroscopy. Pyridinic nitrogen atoms acted as efficient particle anchoring sites, making strong bonding with Pd(4.7)Ru NPs. Additionally, carbon atoms bonding with pyridinic N facilitated the adsorption of O(2) as Lewis bases. The uniformly distributed ~2.4 nm of Pd(4.7)Ru NPs on the NrGO was confirmed by transmission electron microscopy. The optimal composition between Pd and Ru is 4.7:1, reaching −6.33 mA/cm(2) at 0.3 V(RHE) for the best ORR activity among all measured catalysts. Furthermore, accelerated degradation test by electrochemical measurements proved its high durability, maintaining its initial current density up to 98.3% at 0.3 V(RHE) and 93.7% at 0.75 V(RHE), whereas other catalysts remained below 90% at all potentials. These outcomes are considered that the doped nitrogen atoms bond with the NPs stably, and their electron-rich states facilitate the interaction with the reactants on the surface. In conclusion, the catalyst can be applied to the fuel cell system, overcoming the high cost, activity, and durability issues.