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.
The search for suitable synthesis methods and parameters capable of controlling the length, diameter, and yield of silver nanowires (AgNWs) is still an emerging strategy today. Therefore, a method for high-yield synthesis of long AgNWs via chromic chloride and a stable reaction environment was proposed. The results show that Cr3+ could restore the adsorbed atomic oxygen quickly and provide a high efficiency in the prevention of the oxidative etching, for the ion of Cr2+ oxidized to Cr3+ has a lower standard electrode potential, and a more stable reaction environment provided by the coupling method could avoid disturbing the growth of the {111} reactive sites of the wires; then, the yield and length of the AgNWs were improved. The length of the AgNWs was over 75 μm and even 160 μm; the yield of the AgNWs was over 90%, which provides the referable basis for the synthesis of ultralong AgNWs.
19 December 2024 in Journal of Colloid and Interface Science