Surface and Interface Engineering of Noble Metal Heterostructures for Superior ORR Performance: Unlocking Ultralow Loading and Maximum Catalyst Utilization.

The quest for sustainable and high-efficiency energy conversion technologies has driven intense research into oxygen reduction reaction (ORR) catalysts, particularly those based on noble metals, due to the harsh redox environment of these devices. Despite their unparalleled activity, the scarcity and high cost of noble metals like platinum remain significant bottlenecks for large-scale application. Recent advances in surface and interface engineering of noble metal heterostructures offer a promising pathway to address these challenges. By precisely tailoring surface atomic arrangements, modulating interfacial electronic structures, and constructing synergistic heterojunctions, researchers have unlocked unprecedented catalytic efficiencies with dramatically reduced metal loading. This review systematically explores the latest strategies in designing surface- and interface-optimized noble metal heterostructures for ORR, highlighting how these innovations enable maximum utilization of active sites while enhancing activity and durability. We delve into various synthesis techniques, structural modulation approaches, and mechanistic insights gained from advanced characterization and theoretical modeling. Special emphasis is placed on understanding the critical role of heterointerfaces in tuning adsorption energies, charge transfer dynamics, and reaction pathways. Finally, we outline current challenges and propose future directions for the rational design of next-generation ORR catalysts that combine minimal noble metal usage with exceptional performance.