Amazing stuff! This seems to be a very promising approach!
"A counterintuitive technique developed by researchers ... allows pentametallic nanoparticles of relatively uniform size and composition to form spontaneously from a precursor solution containing the five metals. The nanoparticles are a promising catalyst for the decomposition of ammonia into hydrogen and the technique could also potentially be extended to produce other multimetallic nanoparticles. ...
Multimetallic nanocrystals can sometimes offer catalytic properties that nanocrystals of a single metal cannot such as higher atom economy for a precious metal or synergistic interactions between the metals.
However, they can be difficult to synthesise because different reactivities or natural crystal structures of the constituent metals may not lead to compositionally uniform products. ...
approach, depositing the metals from solution onto ruthenium nanoparticle seeds by mixing them with metal acetylacetonate precursor solutions and heating the mixture. When they studied bimetallic compositions, they found differing results. Iron formed variably sized, self-nucleated nanoparticles separate from ruthenium, copper formed core–shell nanoparticles, and cobalt and nickel both formed mixtures of the two. ..."
From the editor's summary and abstract:
"Editor’s summary
Multimetallic nanocrystals offer valuable properties but are challenging to synthesize. Yoon et al. systematically explored how the interplay of ruthenium seeds with iron, cobalt, nickel, and copper precursors can be exploited to produce uniform pentametallic nanocrystals.
They showed that progressive addition of multiple metals suppresses unwanted nucleation and directs growth toward a uniform product. The resulting nanocrystals exhibited high thermal stability and enhanced catalytic activity for ammonia decomposition, highlighting a general strategy for designing complex functional nanomaterials. ...
Structured Abstract
INTRODUCTION
Multimetallic nanocrystals exhibit physical and chemical properties unattainable in monometallic systems, arising from the synergistic interplay of their constituent elements.
Synthesizing these materials with precise control over their size and composition represents an important goal. Differences in reduction potentials, interfacial energies, and nucleation and growth kinetics among metal precursors create both thermodynamic and kinetic challenges that often lead to asynchronous reduction and incorporation processes. Rather than forming a single, uniform product, these disparities frequently generate multiple particle populations with distinct sizes and compositions. Therefore, rational design principles that govern competitive reduction and growth processes are critical to directing multimetallic synthesis toward uniform products.
RATIONALE
We hypothesized that the inherent chemical complexity of reduction for multiple metal precursors could be exploited rather than avoided. Specifically, we investigated whether introducing a high number of different competing metals simultaneously during a seed-mediated synthesis might suppress the formation of unwanted heterogeneous products. Under such competitive conditions, mutual affinities and altered energy barriers control the reaction pathways, guiding synthesis toward a single, compositionally uniform product.
RESULTS
We discovered a counterintuitive, composition-focusing effect in which increasing the number of reacting metals dramatically improved product uniformity.
Whereas introducing one or two base metals to ruthenium seeds yielded inhomogeneous products, simultaneously adding four metal precursors suppressed side reactions, resulting in a single pentametallic nanocrystal product. Time-lapse analysis during the heating process demonstrated that the metals deposited sequentially.
The initial elements that deposited acted as mediators that lowered the energy barrier for the addition of subsequent metals, building a multidomain architecture. This focusing phenomenon also proved highly versatile, successfully yielding uniform products regardless of seed size, precursor ratios, or the constituent metals. When used as ammonia decomposition reaction catalysts, the pentametallic nanocrystal-based catalysts achieved a catalytic rate more than four times higher than that of ruthenium catalysts and maintained their structural integrity and performance even after high-temperature treatments up to 900°C.
CONCLUSION
Our study demonstrates that competitive reactivity, typically viewed as a hurdle in chemical synthesis, can actively drive the formation of highly uniform multimetallic nanocrystals.
By increasing the number of competing elements, side reactions could be suppressed to focus the growth into a single structure.
The design rules established in this study provide a generalizable strategy for synthesizing complex multimetallic nanocrystals, offering a versatile platform for advancing catalysis and sustainable energy technologies."
Pentametallic nanoparticles self-assemble for ammonia decomposition catalyst | Chemistry World
Composition-focusing in multimetallic nanocrystal synthesis.
