A sequential hydrogen-adsorption-assisted bond-weakening strategy for preparing sub-2-nm ordered Pt alloy nanocrystals

Synthesis of highly active sub-2 nm Pt-based alloy nanocrystals for oxygen reduction reaction (ORR), especially by a confinement-free route, remains a challenge. Herein, we report a sequential hydrogen-adsorption-assisted bond-weakening strategy. To Pt-3 clusters deposited on Fe-N-5-C surface, due to stronger Pt-H than N-H interaction, H would firstly adsorb on Pt and then on N, which then weakens Pt-Pt and Fe-N bonds, improves atomic mobility, and thus significantly decreases the kinetic barriers for alloying Pt clusters with single Fe species, As a result, Pt alloys can be prepared at a lower temperature, which largely inhibits the size growth and successfully leads to 1.55 nm Pt3Fe and 1.25 nm Pt3Ni intermetallic nanocrystals. Under an ultralow cathodic loading of 0.03 mg(Pt) cm(-2), the H-2-O-2 fuel cell assembled with Pt3Ni cathode delivers extraordinary activity (1.60 A cm(-2)@0.67 V; 13.7 W mg(Pt)(-1) for the whole cell).

Automated summary

By using a sequential hydrogen-adsorption-assisted bond-weakening strategy, highly active sub-2 nm Pt-based alloy nanocrystals for oxygen reduction reaction (ORR) can be synthesized, leading to a significant improvement in the efficiency of the reaction.