Nanoalloys (NAs) have extraordinary catalytic properties, but metals are often immiscible giving compositional limits on catalytic design. It is generally believed that solution‐based chemical synthesis is inadequate for obtaining NAs, and often exotic shock synthesis or severe decomposition or reduction reactions are required. However, such methods only work on the laboratory scale making real‐world applications difficult. Here, a general solvothermal method is reported to obtain phase‐pure bimetallic and high‐entropy nano‐alloys across the entire composition range. Tuning of solvent chemistry and precursors leads to six different bimetallic NAs: PdxRu1‐x, PtxRu1‐x, IrxRu1‐x, RhxRu1‐x, Ir1‐xPtx, and Rh1‐xPtx, without immiscibility regions. All samples have face‐centered‐cubic crystal structures, which have not previously been observed for the ruthenium‐based systems. Additionally, quaternary and quinary systems are produced, demonstrating the ability to obtain medium‐ and high‐entropy NAs. The method described herein provides a simple, general production method of previously unknown solid solutions throughout their entire composition range potentially allowing for detailed tuning of nanocatalyst properties.
High-entropy alloy (HEA) nanoparticles hold great promise as tunable catalysts. Despite the fact that alloy formation is typically difficult in oxygen-rich environments, we found that Pt-Ir-Pd-Rh-Ru nanoparticles can be synthesized under benign low-temperature solvothermal conditions. In situ X-ray scattering and transmission electron microscopy reveal the solvothermal formation mechanism of Pt-Ir-Pd-Rh-Ru nanoparticles. For the individual metal acetylacetonate precursors, formation of single metal nanoparticles takes place at temperatures spanning from ca. 150 8C for Pd to ca. 350 8C for Ir. However, for the mixture, homogenous Pt-Ir-Pd-Rh-Ru HEA nanoparticles can be obtained around 200 8C due to autocatalyzed metal reduction at the (111) facets of the forming crystallites. The autocatalytic formation mechanism suggests that many types of HEA nanocatalysts should accessible with scalable solvothermal reactions, thereby providing broad availability and tunability.
Structural disorder, highly effective in reducing thermal conductivity, is important in technological applications such as thermal barrier coatings and thermoelectrics. In particular, interstitial, disordered, diffusive atoms are common in complex crystal structures with ultralow thermal conductivity, but are rarely found in simple crystalline solids. Combining single-crystal synchrotron X-ray diffraction, the maximum entropy method, diffuse scattering, and theoretical calculations, here we report the direct observation of one-dimensional disordered In1+ chains in a simple chain-like thermoelectric InTe, which contains a significant In1+ vacancy along with interstitial indium sites. Intriguingly, the disordered In1+ chains undergo a static-dynamic transition with increasing temperature to form a one-dimensional diffusion channel, which is attributed to a low In1+-ion migration energy barrier along the c direction, a general feature in many other TlSe-type compounds. Our work provides a basis towards understanding ultralow thermal conductivity with weak temperature dependence in TlSe-type chain-like materials.
High-entropy alloy (HEA) nanoparticles hold great promise as tunable catalysts. Despite the fact that alloy formation is typically difficult in oxygen-rich environments, we found that Pt-Ir-Pd-Rh-Ru nanoparticles can be synthesized under benign low-temperature solvothermal conditions. In situ X-ray scattering and transmission electron microscopy reveal the solvothermal formation mechanism of Pt-Ir-Pd-Rh-Ru nanoparticles. For the individual metal acetylacetonate precursors, formation of single metal nanoparticles takes place at temperatures spanning from ca. 150 8C for Pd to ca. 350 8C for Ir. However, for the mixture, homogenous Pt-Ir-Pd-Rh-Ru HEA nanoparticles can be obtained around 200 8C due to autocatalyzed metal reduction at the (111) facets of the forming crystallites. The autocatalytic formation mechanism suggests that many types of HEA nanocatalysts should accessible with scalable solvothermal reactions, thereby providing broad availability and tunability.
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