Gas-Pressure-Driven Phase Engineering of PdZn Ordered Intermetallics for Enhanced Oxygen Reduction Electrocatalysis

Precise phase engineering at the atomic scale is central to advanced catalyst design, yet controlling high-temperature phase transitions remains challenging because of large kinetic barriers. Here, we report a gas-pressure-induced strategy that establishes gas pressure as an independent dimension for nanoscale phase engineering. Mechanistic studies reveal that modulating the gas-phase diffusion coefficient via the gas pressure can control the structural evolution of crystal phases. As a demonstration of this methodology, an optimal pressure effectively overcomes high-temperature constraints and retards the escape of volatile species, enabling the precise construction of phase-pure ordered PdZn intermetallics. This strategy extends to ternary PdZnCu ordered alloys, inducing significant compressive strain while preserving the long-range ordered lattice. The resulting catalyst delivers a high oxygen reduction mass activity of 1.09 A mgPd-1 and long-term durability over 30 000 cycles. This gas-pressure-induced approach circumvents conventional thermodynamic and kinetic constraints, providing a pathway for the design of advanced intermetallic catalysts.