Twin PdPtIr porous nanotubes as a dual-functional catalyst for oxygen reduction and evolution reactions

Twin defects, high index facets (HIF5), and high surface/volume ratios play an important role in improving the electrocatalytic performance of 1D nanocatalysts in oxygen reduction (ORR) and oxygen evolution reactions (OER). The design and synthesis of materials with such features is highly desirable, but challenging. Here, we successfully synthesized PdPtIr porous nanotubes (PdPtIr PNTs-400, PdPtIr PNTs annealed at 400 degrees C) combining the advantages of abundant twin defects, HIF5, and an ultrahigh surface/volume ratio. The mass activity of PdPtIr PNTs-400 is 1.26 A mg(pd+pt+lr)(-1) and the specific activity is 1.3 A cm(-2) in acidic media. PdPtIr PNTs-400 are also stable in acidic electrolyte, and show little change after 30 000 cycles. Specifically, the overpotential gap between the ORR overpotential at -3 mA cm(-2) and OER overpotential at 10 mA cm(-2) (ORR-OER) is 642 mV, which is the lowest when compared with catalysts reported in the literature. Such an ultra-low overpotential gap reveals their superior oxygen reduction and evolution reaction activity. The DFT calculation results show that the adsorption energy E-0 of oxygen upon introducing Ir atoms into a Pt and Pd composite is optimal on the (211) facet. This study provides a new strategy for the effective design of multiple "active sites" in 1D nanomaterials, which is helpful when preparing oxygen electrocatalysts with superior performance.