Nitrogen-Doped Rhombohedral Ordered Intermetallic Nanocatalyst Boosts the Oxygen Reduction Reaction

Abstract

Low platinum-group-metal (PGM) ordered intermetallic catalysts have been considered one of the most promising candidates for catalyzing the oxygen reduction reaction (ORR) in fuel cells, but achieving the desired performances in terms of activity, durability and cost is still a grand challenge for the fuel cell research field. We found that nitrogen (N)-doping through a thermal treatment in an NH3 gas to intermetallic-structured PtNi catalysts can boost their ORR performance.1 Herein, we report the synthesis of a rhombohedral L11-ordered PtCu catalyst for the ORR. We demonstrate that, by applying N-doping, the activity and stability of the N-doped, rhombohedral ordered PtCu (Int-PtCuN/KB) catalyst can be further enhanced.2 The mass activity and specific activity of the Int-PtCuN/KB catalyst is 1.15 A mgPt -1 and 1.81 mA cm-2 at 0.9 V, which are nearly 5-fold and 4-fold enhancement, respectively, relative to those of commercial Pt/C. In situ synchrotron X-ray absorption and pair-distribution-function measurements reveal that both the formation of the ordered intermetallic structure and N-doping synergistically improve the corrosion resistance of the PtCu catalyst by lowering the Cu diffusivity, and introduce a compressive strain effect regulating the adsorption of oxygenated species on the Pt surface, thus accounting for the improved ORR kinetics. This work provides valuable insights and possibilities to design binary even ternary Pt-based electrocatalysts with high performance and long-term durability for the ORR.