Composition- and shape-controlled synthesis of the PtNi alloy nanotubes with enhanced activity and durability toward oxygen reduction reaction.

The development of the fuel cell catalysts with high durability and high activity for oxygen reaction reduction remains a great challenge. Various material designs such as alloys, core@shell structure and shape control provide the promising ways to improve the electrocatalytic performance. Herein, on the basis of both the alloy effect and the nanotube structure effect, we demonstrate a high-performance PtNi alloy catalyst with one-dimensional nanotube structure via a galvanic replacement reaction combined with Kirkendall effect. Meanwhile, the PtNi alloy phase and the tube structure are selectively controlled by tuning the PtNi atomic ratio and the wall thickness of the nanotube, respectively. Subsequently, the understanding of the composition effect and the shape effect on the activity and the durability is systematically investigated. The optimized PtNi nanotube catalyst shows significant improvements on the activity (6.2-fold increase in specific activity compared to the commercial Pt/C) and the durability (only 8.6% loss in mass activity after 10000 cycles), attributing to the alloy effect by introducing Ni to the Pt lattice, the Pt-rich surface and the shape effect of the unique one-dimensional hollow tube structure. Image 1 • PtNi alloy NTs are synthesized with tunable compositions and wall thicknesses. • Composition, size and nanotube effects on the performance are systematically studied. • PtNi-NTs show 1.1 times higher in MA and 6.2 times higher in SA at 0.9 V than Pt/C. • PtNi-NTs achieve an enhanced durability of 8.6% loss in MA after 10 k cycles. [ABSTRACT FROM AUTHOR]