Abstract
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 Pd4.7Ru nanoparticles on nitrogen-doped reduced graphene oxide (Pd4.7Ru NPs/NrGO) by a facile microwave-assisted method. Nitrogen atoms were introduced into the graphene by thermal reduction with NH3 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 Pd4.7Ru NPs. Additionally, carbon atoms bonding with pyridinic N facilitated the adsorption of O2 as Lewis bases. The uniformly distributed ~2.4 nm of Pd4.7Ru 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/cm2 at 0.3 VRHE 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 VRHE and 93.7% at 0.75 VRHE, 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.
Highlights
nitrogen-doped reduced graphene oxide (NrGO) was synthesized by doping nitrogen atoms to graphene oxide
We fabricated Pd4.7 Ru NPs decorated catalysts supported by NrGO and characterized them with a series of analytical methods
The NrGO was fabricated by thermal annealing of the GO in Ar/NH3 atmospheres, followed by anchoring 4.1 wt % of Pd4.7 Ru NPs on the carbon supports with the microwave-assisted method
Summary
The fuel cell is one of the promising energy systems due to H2 fuel, which has high energy density. It emits only water as a by-product, without any pollutants such as carbon dioxide. ORR, the complex four electrons and multi-stepped reaction, works as the rate-determining step in fuel cells. Carbon black supported Pt (Pt/CB) catalyst has been used the most widely due to its remarkable ORR performance It has fatal disadvantages, including its high price, the scarcity of platinum, and the deterioration of carbon black under long operation periods. Innovative alternatives of Pt/CB with lower prices, abundance, and durability are essential for the development of renewable energy devices
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