Precise synthesis of targeted noble metal-based high-entropy alloy nanomaterials.

Noble metal-based high-entropy alloys (NM-HEAs) are promising catalysts because of their diverse compositions and complex surface structures, although understanding their formation and achieving precise atomic control remain challenging. Our team introduces a cost-effective synthesis method combining spray drying and thermal decomposition-reduction to produce HEA three-dimensional nanoframeworks (HEA-3DNFs) from quinary to octonary compositions, including Pt-, Ir-, Ru-, and PtRu-based HEAs. Mild heating in H2 facilitates simultaneous reduction of multiple elements, forming single-phase solid solution alloys. The PtNiCoCuRuIr HEA-3DNF exhibits superior methanol oxidation reaction performance (2637 milliamperes per milligram Pt), 15 times higher than commercial Pt black. Noble metals (Pt, Ru, and Ir) lower activation energy for reducing transition metals (Ni, Co, Cu, and Fe). In situ scanning transmission electron microscopy and density function theory calculations reveal phase transformation from a Pt-based face-centered cubic to Ru-based hexagonal close-packed structure, with control over phase composition by adjusting reduction temperatures and Pt-to-Ru ratios. These findings offer insights for developing high-performance and tunable NM-HEA catalysts.