Biphase Pd Nanosheets with Atomic‐Hybrid RhO_x/Pd Amorphous Skins Disentangle the Activity‐Stability Trade‐Off in Oxygen Reduction Reaction

Abstract The activity‐stability trade‐off relationship of oxygen reduction reaction (ORR) is a tricky issue that strikes the electrocatalyst population and hinders the widespread application of fuel cells. Here neoteric biphase Pd nanosheets that are structured with ultrathin two‐dimensional crystalline Pd inner cores and ≈1 nm thin atomic‐hybrid RhO_x/Pd amorphous skins, named c/a‐Pd@PdRh NSs, for disentangling this trade‐off dilemma for alkaline ORR are developed. The superthin amorphous skins significantly amplify the quantity of flexibly low‐coordinated atoms for electrocatalysis. An in situ selected oxidation of the top‐surface Rh dopants creates atomically hybrid RhO_x/Pd disorder surfaces. Detailed energy spectra and theoretical simulation confirm that these RhO_x/Pd interfaces can arouse a surface charge redistribution, causing significant electron deficiency and lowered d‐band center for surface Pd. Meanwhile, anticorrosive Rh/RhO_x species can thermodynamically passivate the neighboring Pd atoms from oxidative dissolution. Thanks to these amplified interfacial effects, the biphase c/a‐Pd@PdRh NSs simultaneously exhibit a superhigh ORR activity (5.92 A mg⁻¹, 22.8 times that of Pt/C) and an outstanding long‐lasting stability after 100k cycles of accelerated durability test, showcasing unprecedented electrocatalysts for breaking the activity‐stability trade‐off relationship of ORR. This work paves a bran‐new strategy for designing high‐performance electrocatalysts through creating modulated amorphous skins on low‐dimensional nanomaterials.