Structure engineered Pt₂CoNi donut plates with chemical ordering for enhanced oxygen reduction reaction performance

Ordered donut-plate (O-DP) Pt₂CoNi/C ternary alloy nanocatalysts were synthesized through a surfactant-free molten-salt-assisted strategy and were systematically investigated as advanced oxygen reduction reaction (ORR) electrocatalysts for proton exchange membrane fuel cells (PEMFCs). X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the formation of an ordered face-centered tetragonal (fct) intermetallic structure with a characteristic donut-plate morphology and a mean particle size of 12 nm. The O-DP Pt 2 CoNi/C catalyst showed almost 14-fold higher ORR activity than the commercial Pt/C and exhibited excellent electrochemical durability over 60,000 cycles of the accelerated stress test. In a single-cell PEMFC test with H₂/O₂ condition, the catalyst exhibited a peak power density of 1.749 W cm −2 at 4.07 A cm −2 and kept about 91% of its initial performance after 30,000 durability cycles. The XRD, TEM, X-ray photoelectron spectroscopy (XPS) and electrochemical analyses showed that the enhanced activity was derived from the compressive strain, Pt electronic modulation and special donut-plate architecture, while the post-accelerated stability test (AST) characterization confirmed the excellent structural and electronic stability up to 60,000 cycles. The density functional theory (DFT) calculations revealed that Co and Ni incorporation optimized the Pt electronic structure via ligand and strain effects leading to a favorable downshift of the d-band center, weakened adsorption of oxygenated intermediates, and enhanced thermodynamic stability. Additionally, a MATLAB-based degradation model that incorporated the experimentally measured evolution of the electrochemically active surface area (ECSA) successfully predicted stable PEMFC operation up to ∼60,000 cycles, followed by gradual long-term degradation. This provided valuable insights into the influence of catalyst aging on stack voltage, power output, thermal behavior, and overall fuel cell efficiency.