Following the reactions: in-situ and in-operando study of processes.

The ability to see processes as they happen at the nanoscale is essential to deepen our understanding of the chemical reactions/materials transformation and to design sustainable technological solutions for the future. In our group we are particularly interested in understanding processes that are relevant to materials for energy harvesting and storage, such as sodium-ion storage mechanisms and electrode-electrolyte interactions in batteries, early stages of molecular precursor condensation in sustainable sorbents, etc.

The video shows early stages of in-situ condensation of uric acid inside a scanning transmission electron microscope. The development of the porosity of the surface of the particles during the early stages of condensation governs the subsequent release of volatiles and the formation of a hierarchical pore structure of the material.

Specific attention is given to understand and control electron-beam-induced interactions during observations, since they can considerably modify studied processes. In this respect we often combine in-situ studies with ex-situ time-dependent measurements. This approach has been applied to study the mechanism of CeO₂ mesocrystal formation in water solution without additives. We showed that in the absence of additives, CeO₂ mesocrystal growth is guided by amorphous hydrated Ce(IV)-hydroxides, formed at the very early stages of the reaction, and serve as an intermediate in the liquid-to-solid phase transformation (Figure 2). In addition, our in-operando experiments in TEM/STEM showed that varying the dose rate of the radiation changes the growth mechanism and enables to control the morphology and structure of the obtained CeO₂ nanoparticles.