Engineering Active Sites into Iron Hydroxide/Pt-Based Nanocatalysts to Enrich the Oxygen Reduction Reaction

Surface engineering of nanocatalysts─including defect engineering and metal–metal (hydr-)oxide interfacial site generation─can improve catalytic activity. Here, we report that the incorporation of iron hydroxide into Pd_18.3Pt₁₁W₁ (PPW-14) ternary alloy nanocatalysts boosts the electrocatalytic activity of the oxygen reduction reaction (ORR). Iron hydroxide incorporation into PPW-14 alloy catalysts modifies the catalyst surface by exposing more active metal-hydroxide interface sites. The small quantities of W and Fe in the core–shell contributed to surface reconstruction, modifying the electronic structure of the surface active sites. Consequently, numerous defects were created on the surfaces, enhancing both the electrochemical activity and durability. In addition, the chemical states of iron incorporated into core–shell structures under ORR conditions were evaluated through the construction of Pourbaix diagrams, applying first-principles calculations to various iron hydroxide nanostructures on PdPt(111). The iron hydroxide interfacial sites served as active sites for ORR intermediate adsorption, effectively modulating the OH and OOH binding free energies. The iron hydroxide decoration contributed to the observed synergistic effects in nanocatalysts, which also improved the catalyst stability. By combining experimental and theoretical insights, this strategy enables precise structural tailoring to develop highly active ORR electrocatalysts.