Trace Tungsten Microalloying PtCuCo Medium Entropy Alloys: Substructure Reconstruction-Triggered High-Performance for PEMFC.

Refractory metals (W, Nb, or Mo) microalloying Pt-based alloys with unprecedented performance may serve as advanced electrocatalysts for proton exchange membrane fuel cells (PEMFCs). These alloys are endowed with unique stabilizing substructures or lattice defects through the microalloying effect. Herein, trace W microalloying PtCuCo medium entropy alloys (W-PtCuCo) are reported via a stepwise synthesis strategy, starting with home-made Cu nanowires as sacrificial templates by anhydrous solid-phase milling route, and then followed by galvanic replacement-assisted solvothermal in ethylene glycol (EG). In PEMFC tests, the obtained W-PtCuCo exhibits an ultrahigh peak power density and mass power density (relative to cathode) reaching 2.09 W cm and 20.9 W mg , respectively. During the accelerated degradation test (ADT), the mass activity just lost only 3% after 30 k cycles, much better than the above benchmark catalyst. The microalloying-dependent performances shall be attributed to the presence of abundant stepped surfaces, twisted edges, and other lattice defects terminated by W via substructure reconstruction that indeed alters the electronic structure and strain level of the alloys. This work first provides an atomic-level insight into the microalloying-dependent electrocatalytic performance of Pt-based alloys, which is of great significance for developing next-generation efficient catalysts for PEMFC.