Controlling Metal Nanoparticle Exsolution with Ion Irradiation

Saturday - January 6 2024, 09:31 UTC - 10 months ago

MIT researchers recently developed a method of controlling the parameters related to metal nanoparticle exsolution through ion irradiation. This method provides better control over exsolution to realize its full potential and enables the production of nanostructured oxides from a single-step reductive or oxidative treatment. It can also be used to reduce the size of nanoparticles down to 2 nm, and tailor nanoparticle composition from unitary metal to metal alloy. The nanocatalysts produced have shown superior catalytic activity towards water-splitting reactions than those produced using conventional exsolution methods.

Developing advanced methods to synthesize stable, active, and cost-efficient nanomaterials is critical to modern technologies. A recent advance in this regard is to prepare nanostructured oxides in a phase precipitation process termed "exsolution". In exsolution, the to-be-exsolved metal cations are first dissolved in the host oxide as dopants, forming a metal oxide solid solution. Then, upon a single-step reductive or oxidative treatment, metal cations phase precipitate out of the host oxides as well-dispersed metal nanoparticles. Due to the simple processing and broad applications, exsolution has powered advances in the performance of electrochemical and electronic devices. For example, by exsolving nanoparticles on the oxide surface, researchers have prepared nanocatalysts with exceptional (electro)chemical stability and self-regeneration capabilities for clean energy and fuel conversion. By exsolving nanoparticles in the bulk of oxides, self-assembled oxide nanocomposites with unique transport, redox, and magnetic properties were achieved for next-generation electrochemical and electronic devices.

With the promising applications described above, there is substantial motivation in the field to gain better control over exsolution to realize its full potential. Today’s nanoparticle exsolution often results in unitary mechnframework with controllable synthesis conditions. MIT researchers present ion irradiation as a general platform to allow control over these parameters during metal nanoparticle exsolution, by simultaneous sputtering, implantation, and defect generation mechanisms. Using thin-film perovskite and binary oxides as model systems, they showed ion beams can controllably reduce the size of exsolved nanoparticles down to 2 nm through ion sputtering. They tailored the exsolved nanoparticle composition from unitary metal to metal alloy via ion implantation. Furthermore, irradiation creates point defects and defect clusters, which serve as nucleation sites for metal exsolution. By leveraging this process, they were able to tune the density and spatial distribution of exsolved nanoparticles. Furthermore, they demonstrated that nanocatalysts prepared by irradiation-assisted exsolution exhibit superior catalytic activity towards water-splitting reactions than those produced using conventional exsolution methods.

These findings highlight the potential of ion irradiation for engineering nanoparticle exsolution in diverse materials systems, with broad implications for electrochemical and electronic applications. The nanoparticle production control achieved through ion irradiation includes controlling the size of exsolved nanoparticles down to 2 nm, tailoring the composition of nanoparticles exsolved both at the surface and in the bulk, and controlling the density and location of exsolved nanoparticles at specific sample locations using ion irradiation. These groundbreaking results present ion irradiation as a general platform to control the parameters in metal nanoparticle exsolution and open a promising future ahead.