Researchers from Skoltech have uncovered physical principles governing the remote “tuning” of nanocatalysts, where the ultra-thin platinum layer’s properties can be controlled exclusively by modifying its metallic core’s composition and structure. This paves the way for creating catalytic materials for hydrogen energy and exhaust gas purification that will maintain high efficiency but contain several times less of the precious and scarce platinum than current counterparts. The results of this fundamental research are published in the Materials Today Energy journal.
At the heart of the study are core-shell nanoparticles, where a core made of one or several metals is coated with an ultra-thin platinum shell. Platinum is an excellent catalyst for many chemical reactions; however, it is a limited and expensive resource. Scientists have long been seeking ways to use it with maximum efficiency. The new research demonstrates that the properties of such nanoparticles can be tuned through two key levers: the composition of the core and its internal structure.
Using computer modeling methods based on density functional theory, the scientists analyzed how different metals in the core (silver, gold, copper, iridium, palladium, rhodium, ruthenium), as well as a special core form — a high-entropy alloy consisting of all these seven metals simultaneously — affect the catalytic properties of the platinum shell. For the first time, the role of an amorphous, that is, disordered, core structure was studied in detail compared to the traditional crystalline one.
“Our research demonstrates that the nanoparticle core serves as an active modulator of the platinum shell’s properties. By varying the chemical composition and crystalline state of the core, we gain direct control over the electronic structure and reactivity of the platinum surface,” explained the study’s lead author, Ilya Chepkasov, a senior research scientist at the Skoltech Materials Center.
Catalyst nanoparticles do not operate on their own but under the guidance of their core. The scientists managed to decipher this mechanism: A core made of different metals influences the platinum shell in three ways simultaneously. It can change its electronic properties, slightly “compress” or “stretch” its atomic lattice, and thereby tune the chemical activity of the platinum. For instance, if the core is made of copper, the platinum surface becomes richer in electrons and will better attract oxygen molecules —this is a key process for fuel cells.
“The obtained results establish principles for the rational design of catalysts. The combination of core composition — be it a transition metal or a high-entropy alloy — and its structural state represents two independent and powerful parameters for precise optimization of catalytic activity, stability, and selectivity. This lays the groundwork for developing the next generation of high-performance systems with minimal platinum content,” shared the co-author and scientific supervisor of the study, Alexander Kvashnin, a professor at the Skoltech Materials Center and the head of the Laboratory for Industry-Oriented Computational Discovery at Skoltech.
The practical takeaway of the work is that the platinum shell should be made as thin as possible. When it consists of a single atomic layer, the influence of the core is amplified, and each platinum atom is used with maximum efficiency. This opens the path to creating catalysts where the precious metal content is several times lower, but without losing its activity.
