LAUSR

Pt nanocatalysts play a critical role in direct methanol fuel cells (DMFCs) due to their appropriate adsorption/desorption energy, yet suffer from an unbalanced relationship between size‐dependent activity and stability. Herein, mixed‐dimensional Pt–Ni alloy polyhedral nanochains (Pt–Ni PNCs) with an ordered assembly of a nanopolyhedra–nanowire–nanopolyhedra architecture are fabricated as bifunctional electrocatalysts for DMFCs, effectively alleviating the size effect. The Pt–Ni PNCs exhibit 7.23 times higher mass activity for the anodic methanol oxidation reaction (MOR) than that of commercial Pt/C. In situ Fourier transform infrared spectroscopy and CO stripping measurements demonstrate the prominent stability of the Pt–Ni PNCs to resist CO poisoning. For the cathodic oxygen reduction reaction (ORR), a positive half‐wave potential exceeding Pt/C is achieved by the Pt–Ni PNCs, and it can be well maintained for 10 000 cycles with negligible activity decay. The designed nanostructure can alleviate the agglomeration and dissolution problems of 0D small‐sized Pt–Ni alloy nanocrystals and enrich surface atom steps and active facets of 1D chain‐like nanostructures. This work provides a proposed strategy to improve the catalytic performance of Pt‐based nanocatalysts by constructing novel interfacial relationships in mixed dimensions to alleviate the imbalance between catalytic activity and catalytic stability caused by size effects.