New Aspects of Platinum Group Metal‐Based Solid‐Solution Alloy Nanoparticles: Binary to High‐Entropy Alloys

Abstract

with any combination and composition is not an easy task owing to the metallurgicala spects. In this minireview,t he focus is on recent advances in PGM-based solid-solution alloy NPs, andi np articular those with immiscible alloy systems. Concepts, synthesis, and properties of the alloy NPs are introduced, and the existing challenges and future perspectives are discussed.[a] Dr. Figure 2. The number of papers including the keywords "PGM-M" or "M-PGM", which means PGM-based binaryalloy systems (where PGMorMis the atomic symbol of aP GM element or acounterpart of the alloy system) such as "Ru-Sc" or "Sc-Ru",and "nano" through the Web of Science,and the periodic table of the elementsi ndicating the type of alloy system classified into six groups, as follows: class 1( yellow)c onsists of only intermetallic phases;class 2( green) covers bothintermetallic and solid-solutionp hases (at least morethan 10 at %o fs olid-solution phases at 1000 8C);class 3( purple) is mostly solid-solution phases (more than 70 at %a t1 000 8C);class 4( blue) is all-proportional solid solutions;class 5( pink) is partly solid-solution phases( less than 70 at %a t 1000 8C);and class 6( red) is completely immiscible, and unknown (gray). a) Ru, b) Os, c) Rh,d)Ir, e) Pd, f) Pt.

Slow Synthesis Methodology‐Directed Immiscible Octahedral PdxRh1−x Dual‐Atom‐Site Catalysts for Superior Three‐Way Catalytic Activities over Rh

“…However, there are significant challenges in synthesizing solid solutions, especially for immiscible alloys, whose constituent elements cannot be mixed in the bulk‐scale phase diagram [9] . We have proposed a coreduction methodology in immiscible alloy systems by measuring the reaction times of different precursors [13] .…”

Highly Stable and Active Solid‐Solution‐Alloy Three‐Way Catalyst by Utilizing Configurational‐Entropy Effect

“…[3][4][5][6] These alloys consisting of immiscible constituents are synthesized by a chemical synthetic method using a nonequilibrium condition in which the ions of constituents are concurrently reduced. [7,8] However, these solid-solution alloys often exhibit phase segregation at high temperatures because they are obtained at room temperature as thermodynamically nonequilibrium phases. One of the most attractive advantages of the solidsolution alloy is the ability to continuously control its electronic structure, affecting most of the physical and chemical properties by tuning the composition of the constituents.…”

Continuous-flow syntheses of alloy nanoparticles

“…Alloys are one of the hot topics in nanomaterials science because alloy NPs often show unique physical and chemical properties that cannot be observed in or are superior to monometallic NPs. 4,5 To improve their properties, various types of alloy NPs have been developed. For example, core shell-type alloy NPs, which are unique nanostructured alloys, are heterostructures that have an inner core metal structure and an outer thin shell of a different metal.…”