Fast Gas–Solid Reaction Kinetics of Nanoparticles Unveiled by Millisecond In Situ Electron Diffraction at Ambient Pressure

Abstract

Acquiring the kinetics of gas-nanoparticle fast reactions under ambient pressure is ac hallenge owingt ot he lacko fa ppropriate in situ techniques.N ow an approach has been developed that integrates time-resolved in situ electron diffraction and an atmospheric gas cell system in transmission electron microscopy, allowing quantitative structural information to be obtained under ambient pressure with millisecond time resolution. The ultrafast oxidation kinetics of Ni nanoparticles in oxygen was vividly obtained. In contrast to the wellaccepted Wagner and Mott-Cabrera models (diffusion-dominated), the oxidation of Ni nanoparticles is linear at the initial stage (< 0.5 s), and follows the Avrami-Erofeev model (n = 1.12) at the following stage,which indicates the oxidation of Ni nanoparticles is an ucleation and growth dominated process. This study gives new insights into Ni oxidation and paves the way to study the fast reaction kinetics of nanoparticles using ultrafast in situ techniques.

Insights into Chemical Dynamics and Their Impact on the Reactivity of Pt Nanoparticles during CO Oxidation by Operando TEM

“…In addition, due to the very small wavelength of the electrons (λ = 1.96 pm at 300 kV acceleration voltage), the radius of the Ewald sphere is large with respect to a lattice constant and can be considered flat (Figure S15). Hence, in electron diffraction experiments, the information of low and high index planes can be recorded simultaneously and with sufficient signal-to-noise ratio even at millisecond time scales . This combination of high temporal and spatial resolution is a crucial strength of in situ and operando TEM investigations since it allows monitoring of local changes over time that are associated with the catalytic reaction.…”

“…Hence, in electron diffraction experiments, the information of low and high index planes can be recorded simultaneously and with sufficient signal-to-noise ratio even at millisecond time scales. 56 This combination of high temporal and spatial resolution is a crucial strength of in situ and operando TEM investigations since it allows monitoring of local changes over time that are associated with the catalytic reaction.…”

Analytics at the nanometer and nanosecond scales by short electron pulses in an electron microscope

“…These high heating rates combined with low heat capacities of the nanoparticles tends to generate reaction temperatures exceeding those in bulk materials. Taking these arguments together, it is obvious that chemical transformations of nanoparticles may be very fast, particularly at high temperatures, therefore the mechanism and the kinetics might be different from the corresponding reactions in bulk materials [4]. Accordingly, the lifetime of possible transient states may be short and the states are challenging to observe.…”

Nanosecond electron pulses in the analytical electron microscopy of a fast irreversible chemical reaction

“…Furthermore, the large magnetization of some transition metal nanoparticles is lost immediately upon oxidation, and the rapid reduction can be an indispensable reconditioning process for such applications. Understanding these transformations needs detailed knowledge about the reaction kinetics 4–6 and the appearance of transition states during the reaction.…”