"Visualising reactions in real time with such high resolution will allow us to explore many unanswered questions in the chemical and physical sciences," said associate professor Jen Dionne.
The team’s experiments focused on hydrogen moving into palladium. The reaction is claimed to be analogous to how ions flow through a battery or fuel cell during charging and discharging. Observing this process in real time provides insight into why nanoparticles make better electrodes than bulk materials.
For these experiments, the Dionne lab created palladium nanocubes and then placed them in a hydrogen gas environment within an electron microscope. The researchers knew that hydrogen would change both the dimensions of the lattice and the electronic properties of the nanoparticle.
The researchers then examined the nanocubes during intermediate stages of hydrogenation using dark-field imaging, which relies on scattered electrons. These dark-field images served as a way to check that the application of the electron beam hadn't influenced the previous observations and allowed the researchers to see detailed structural changes during the reaction.
The researchers saw the hydrogen atoms move in through the corners of the nanocube and observed the formation of various imperfections within the particle.
"The nanoparticle has the ability to self-heal," said Dionne. "When you first introduce hydrogen, the particle deforms and loses its perfect crystallinity. But once the particle has absorbed as much hydrogen as it can, it transforms itself back to a perfect crystal again."
This ability of the nanocube to self-heal makes it more durable, which is said to be a key property needed for energy storage materials to sustain many charge and discharge cycles.
In the future, the team will look at a variety of material compositions and compare how the sizes and shapes of nanoparticles affect the way they work. At present, the researchers have moved on to experimenting with nanorods, which promise potentially faster kinetics.
