In Situ / Operando Reaction Imaging & Analysis
Most electron microscopy captures a frozen snapshot of a material. In situ and operando techniques move beyond that limit, allowing us to follow reactions as atoms, phases, and interfaces reorganize under electrical, thermal, or chemical stimuli. Our real-time studies of alloying anodes connect ion diffusion, reaction-front migration, and volume expansion with the mechanisms that govern material behavior. Building on this experience, we are extending dynamic microscopy to gas-cell experiments and correlative 4D-STEM / EELS analysis of hydrogen and catalyst materials.
Watch reactions unfold
A before-and-after image tells us what changed. In situ microscopy reveals how it changed. By applying electrochemical bias, heat, or a controlled gas atmosphere inside the microscope, we follow reaction fronts, phase transformations, and mechanical deformation as they develop.
Time-resolved observations connect the onset of a reaction with its subsequent pathway. By comparing the same region as conditions change, we can identify transient structures and local bottlenecks that a final-state image cannot capture. The experiment is designed around the timescale and length scale of the process we want to understand.
Revealing ion transport as reactions unfold
Where does a reaction begin, and what controls its advance? Tracking reaction fronts and volume changes in real time connects visible motion with the ion-transport mechanisms inside a material. Our published Sn sodiation studies demonstrate this approach: in situ SEM revealed how crystal orientation, particle size, and deformation shape the reaction. These studies provide a foundation for our expanding work on dynamic reactions in energy materials.
Crystal orientation and reaction behavior
Sn sodiation along three crystal orientations: capturing reaction fronts and expansion in real time.
By comparing crystals with different orientations, we revealed isotropic sodiation behavior and the role of the amorphous reaction layer. ACS Applied Materials & Interfaces (2018).
Size, deformation, and ion transport
Comparing reaction behavior across pillar sizes helped reveal how deformation and dislocations affect sodium transport. The study showed that diffusion along dislocations can mitigate self-limiting Na diffusion—connecting a visible reaction to its underlying transport mechanism. Small (2020).
Li–Si/C: revealing the pathway of lithium
Silicon offers high lithium-storage capacity, but its expansion must be understood within the surrounding carbon network. In our Si–C composite anode study, in situ electrochemical measurements and SEM observations revealed a sequential reaction pathway: carbon lithiation → nanopore filling → silicon lithiation and expansion.
Following lithium through a Si–C composite. Lee, Moon, Byeon et al., ACS Energy Letters (2022), Fig. 4.
The nanopores act as local lithium reservoirs before substantial silicon expansion begins. Connecting voltage, morphology, and pore filling revealed how the internal architecture controls the reaction—providing a basis for designing high-capacity composite anodes. Read the paper.
Gas-cell TEM: reactions under a controlled atmosphere
Gas, heat, and an electron beam: tracking catalyst evolution. AI concept illustration.
We build on this experience with open-cell electrochemical experiments, in situ heating, and gas-cell TEM. Our developing hydrogen and catalyst studies combine dynamic imaging, 4D-STEM, and EELS to track morphology, strain, and chemical changes in the same reacting region.
Gas composition and temperature provide experimental handles for testing how a catalyst responds to its environment. By linking structural movies with selected diffraction and spectroscopic measurements, we aim to distinguish reversible transformations from accumulated damage and connect local changes with the conditions that trigger them.
The aim is to explain where a reaction starts, how it propagates, and which structural changes control the outcome—providing a direct basis for designing more durable and reactive materials.
Read about the Gas TEM timing & dose planner: an introduction to comparing gas-switching delays, acquisition intervals and beam blanking, with a link to the interactive tool.