In situ Formation of Intermetallic PtZn Alloy Nanoparticles Embedded in Mesoporous Carbon Boosting the Oxygen Reduction Reaction

Coupling the structure advantages of platinum (Pt)-based active composites, transition-metal single sites, and porous carbon is highly desirable to reduce the Pt usage in proton-exchange membrane fuel cells (PEMFCs) but remains a great challenge. Herein, we report the in situ construction of synergistic oxygen reduction reaction (ORR) catalysts with intermetallic PtZn alloy nanoparticles confined in mesoporous carbon doped with atomic Co–N₄ and Zn–N₄ moieties. Mesoporous carbon doped with Co–N₄ and Zn–N₄ moieties could be fabricated by carbonization of CoSO₄-doped ZIF-8 precursors and SO₄^2– has been verified to be responsible for the formation of mesopores and defects with narrow pore size distribution. More importantly, systematical characterizations revealed that Pt could in situ alloy with Zn–N₄ sites, which could effectively prevent the agglomeration of Pt during high-temperature treatment, leading to the formation of uniform and well-dispersed PtZn nanoparticles with a mean diameter of ∼3.06 nm. The as-synthesized PtZn@Meso/Zn₁Co₁/NC shows an excellent mass activity of 490 mA mg_Pt^–1 @ 0.9 V as well as excellent durability with an activity retention of 79% after 20,000 potential cycles in 0.1 M HClO₄, showing that the nanoarchitecture of the mesopore-encased PtZn alloy has a high resistance to migration due to the pore confinement effect and anchoring effect of the support. In addition to developing robust Pt-based catalysts, this study also lays out a straightforward strategy for designing synergistic catalysts, which might have far-reaching implications for fuel cells and beyond.