Ultrathin PtCo nanorod assemblies with self-optimized surface for oxygen reduction reaction

Controllable synthesis of Pt-based materials at the nanoscale can efficiently tailor their electrocatalytic performance, enabling enhancement in both activity and durability. Herein, we report the synthesis of ultrathin PtCo nanorod assemblies (NRAs) terminated with high index facets through a grain-boundary corrosion approach. Atomic insight reveals that grain boundaries and other defects are formed in PtCo nanowire assemblies (NWAs) during the hydrothermal reaction. With a further increase in reaction time, selective dissolution at these sites generated PtCo NRAs composed of shorter nanorod assemblies with larger surface areas and high index facets termination. The carbon-supported catalyst of PtCo NRAs exhibits high mass activity of 0.914 A/mgPt at 0.9 V vs RHE for ORR, 2.4 times higher than those of the smooth PtCo NWAs (0.377 A/mgPt), 5.7 times higher than those of the commercial Pt/C (0.161 A/mgPt). Most significantly, the PtCo NRAs show high stability with about 25.6% loss of mass activity after 10,000 cycles, while only 22.3% loss of mass activity from 10,000 cycles to 50,000 cycles of accelerated durability test. The high durability is mainly attributed to the jagged surface resulted from the surface reconstruction of PtCo NRAs during the electrochemical process. This self-optimization phenomenon may lead to a new effective long-life electrocatalyst.