Synthesis and Thermal Stability of Immiscible Metal (Au–Rh, Au–Ir, Au–Ir–Rh and Pd-Rh) Nanoalloys
The report highlights synthetic approach to the preparation of nanoalloys of immiscible metals based on thermolysis of single-source precursors. We successfully prepared nanoalloys in the systems of Au–Ir, Au–Rh, Au–Ir–Rh and Pd-Rh with large bulk miscibility gaps, in one-run reactions under thermal decomposition of specially synthesised double-complex salts [AuEn2][Ir(NO2)6], [AuEn2][Ir(NO2)6]х[Rh(NO2)6]1–х, [AuEn2][Rh(NO2)6], [Rh(NH3)5Cl][Pd(NO2)4], [PdEn2]3[Rh(NO2)6]2·2.67H2O and [RhEn3]2[Pd(NO2)4]3. The TEM microscopy observations show that the nanoalloy structures are composed of well-dispersed aggregates of crystalline domains with a mean size of 5±3 nm. EDX analysis and XRD measurements confirm the formation of AuIr, AuRh, AuIrxRh1-x, PdxRh1-x metastable solid solutions. In situ high-temperature synchrotron XRD was used to study the formation mechanism of nanoalloys. The obtained metastable nanoalloys exhibit essential thermal stability. Exposure to 180 ºC for 30 h does not cause any dealloying process.
The work has been supported by grant of Russian Science Foundation (project №16-13-10192).