Coating Porous TiO 2 Films on Carbon Nanotubes to Enhance the Durability of Ultrafine PtCo/CNT Nanocatalysts for the Oxygen Reduction Reaction.

The development of excellent activity and durability catalysts for the oxygen reduction reaction (ORR) is essential for the commercialization of proton exchange membrane fuel cells (PEMFCs). Reducing the size of catalyst particles can provide more reaction sites to mitigate the performance degradation caused by reduced platinum loading. However, at the same time, it makes the particles more prone to agglomeration and exfoliation, leading to a rapid reduction in catalyst activity. Here, we present the design of a composite support (TiO 2 /CNT) with a porous TiO 2 film that immobilizes PtCo nanoparticles (NPs) loaded on the support while protecting the carbon nanotubes inside. The particle size of PtCo NPs was only 1.99 nm (determined by transmission electron microscopy), but the nanocatalyst (PtCo/TiO 2 /CNT) maintained high catalytic performance and stability on account of the strong metal support interaction (SMSI). PtCo/TiO 2 /CNT exhibited a high mass activity (MA, 0.476 A mg Pt -1 ) and was found to have MA retention rates of 91.7 and 88.8% in durability tests performed at 0.6-1.0 V and 1.0-1.5 V, respectively.