Lattice-Vacancy-Mediated Structural Ordering of Pt-Based Alloy Nanocatalysts for Durable PEM Fuel Cell Cathodes

Atomically ordered Pt-based intermetallic alloys have gained interest as promising cathode materials catalyzing the oxygen reduction reaction (ORR) in hydrogen-fueled proton exchange membrane fuel cells (PEMFCs) with special durability requirements. This is the case because ordered Pt intermetallic alloys are believed to display superior chemical durability over their disordered counterparts. However, achieving the atomic-disorder-to-order phase transition typically necessitates prolonged high-temperature annealing, which often induces nanoparticle sintering and reduces Pt utilization. These challenges are particularly pronounced in acid-stable early transition metal Pt–M alloy systems (e.g., Pt–V), where alloy formation is hindered by the large disparity in reduction potentials. Here we present a lattice-vacancy-mediated synthesis strategy using evaporating Zn atoms as a cataloreactant to trigger the formation of the L12 intermetallic phase in the Pt–V system. This approach enabled the synthesis of highly ordered Pt–V alloy nanocatalysts with significantly suppressed non-noble transition metal leaching, thereby delivering enhanced PEMFC performance and durability. Online spectrometric and in situ spectroscopic analyses suggest distinct degradation mechanisms, characterized by isotropic V leaching in the ordered structure versus anisotropic segregation in the disordered structure. These findings underscore the efficacy of vacancy-mediated ordering as a synthetic paradigm for designing durable, high-performance intermetallic catalysts for PEMFC applications.