Highly Durable PtNiCo Beads-On-Nanowires with Pt-Skin Surface for Oxygen Reduction Reaction in Acidic Media

The oxygen reduction reaction (ORR) is catalyzed at the cathode in polymer electrolyte fuel cells (PEFCs). PEFCs can be utilized for heavy-duty fuel cell vehicles, including trucks and buses. The ORR activity of electrocatalysts is known to limit the overall PEFC performance. PEFCs particularly for heavy-duty fuel cells provide harsh electrochemical conditions at high temperatures (≥ 353 K) and low pH values (≤ 1). However, highly active and durable ORR electrocatalysts under such harsh electrochemical conditions remain a great challenge. In this work, we report the ORR activity and durability of PtNiCo nanowires (NWs) that were prepared at different heating temperatures of 493, 533, and 573 K in oleylamine under Ar. The heating temperature affects the presence of coexisting nanoparticles and the metal composition: higher heating temperatures tend to produce fewer nanoparticles and lower 3d transition metal content. Carbon-supported PtNiCo NWs that were prepared at 493 K (PtNiCo NW493 K/C) exhibited the highest durability, and their mass-based activities increased from 0.66 to 0.69 A (mgPt)−1 after accelerated durability tests (ADTs) at 353 K in acidic media. This MA after ADT is higher than that of the corresponding bimetallic PtNi NW493 K/C after ADT, indicating that the trimetallic PtNiCo alloy is more beneficial to improve the ORR activity. PtNiCo NW493 K/C showed a structural transformation from NWs to beads-on-nanowires with the Pt-rich skin surface, which is associated with the downshift of the d-band center of the surface Pt, as confirmed by CO stripping voltammetry. Our study demonstrates that doping Co into PtNi NWs is effective to improve the ORR durability, and PtNiCo beads-on-nanowires with the Pt skin produced during potential cycles will be utilized for practical PEFC applications such as heavy-duty fuel cell vehicles.