Stabilizing the Unstable: Enhancing OER Durability with 3d-Orbital Transition Metal Multielemental Alloy...

Earth-abundant 3d-orbital late transition metals are the most used and highly desired catalysts for the oxygen evolution reaction (OER) but are prone to quick oxidative dissolution, leading to poor durability. We first report that FeCoNiCu multielemental alloy nanoparticles (MEA NPs) can be stabilized with only 0.3 at. % Pd, a 4d-orbital element. Although pure Pd is known for extremely poor OER activity and durability, Pd-FeCoNiCu sustains 1000 h at 10 mA cm^-2. In an accelerating durability test (ADT) at 100 mA cm^-2, it exhibits a mere 8.9 mV increase over 25 h with a degradation rate of 0.356 mV h^-1, which is 1/350th that of FeCoNiCu (125 mV h^-1) and among the most stable OER catalysts reported so far. Aberration-corrected HAADF-STEM and X-ray absorption fine structure (XAFS) reveal that atomically dispersed Pd atoms, surrounded by Fe, Co, Ni, and Cu atoms, contributed to a more delocalized electronic structure and stronger bonding via strong d-d/sp hybridization and the vibronic coupling induced by atomic displacement. The altered local density of states (LDOS) of Fe, Co, Ni, and Cu mitigates the oxidation of FeCoNiCu in OER by over 50%, quantified by hard X-ray photoelectron spectroscopy (HAXPES), making the combination of these five dissoluble elements a durable catalyst.