Enhanced Activity of Small Pt Nanoparticles Decorated with High-Loading Single Fe─N 4 for Methanol Oxidation and Oxygen Reduction via the Assistive Active Sites Strategy.

Decorating platinum (Pt) with a single atom offers a promising approach to tailoring their catalytic activity. In this study, for the first time, an innovative assistive active sites (AAS) strategy is proposed to construct high-loading (3.46wt.%) single Fe─N 4 as AAS, which are further hybridized with small Pt nanoparticles to enhance both oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) activities. For ORR, the target catalyst (Pt/HFe SA -HCS) exhibits a higher mass activity (MA) of 0.98 A mg Pt -1 and specific activity (SA) of 1.39 mA cm Pt -2 at 0.90 V versus RHE. As for MOR, Pt/HFe SA -HCS shows exceptional MA (3.21 A mg Pt -1 ) and SA (4.27 mA cm Pt -2 ) at peak values, surpassing commercial Pt/C by 15.3 and 11.5 times, respectively. The underlying mechanism behind this AAS strategy is to find that in MOR, Fe─N 4 promotes water dissociation, generating more *OH to accelerate the conversion of *CO to CO 2 . Meanwhile, in ORR, Fe─N 4 acts as a competitor to adsorb *OH, weakening Pt─OH bonding and facilitating desorption of *OH on the Pt surface. Constructing AAS that can enhance dual functionality simultaneously can be seen as a successful "kill two birds with one stone" strategy.