New technique to image degradation of catalysts in their native environment
Fuel cells convert chemical energy into electricity by reacting hydrogen and oxygen at two different electrodes. Functional catalysts such as platinum and other precious metals play an important role in making energy conversion more efficient, but they often undergo irreversible damage. Imaging techniques that are routinely used to analyse structure and morphology of metal specimens in a dry medium cannot be applied in individual particles in a solution because they are not static. The EU-funded project ELWBINSTEM (Development of electrochemical water based in-situ TEM and study of platinum based nanoparticles potential- and time-dependent changes) responded to this challenge by developing a visualisation technique based on in situ transmission electron microscopy (TEM) that directly correlates the structural changes of the catalyst on the atomic scale with its physical and chemical properties. The advanced new imaging method that enhances understanding of the correlation between the electrochemical performance and the fundamental properties of platinum can provide 10 times higher resolution compared to the state of the art. Scientists developed a technique called electrochemical water-based in situ TEM to study metal catalysts in their native liquid environment. This liquid in situ TEM technique utilises special TEM holders that maintain the liquid in a closed container, thereby protecting the metal specimen from the high-vacuum environment of the microscope and the microscope from the liquid. To create this chamber that isolates the metal from the microscope vacuum, the TEM holder users a pair of silicon chips with thin silicon nitride membranes. The chamber is connected to an external potentiostat. By using this highly sophisticated technique, scientists and engineers should benefit from both the high resolution of modern electron microscopes and the analytical capabilities of this electrochemistry system (TEM holder). This will enable scientists to provide further insights into the fundamental physical properties of nanocatalysts and to optimise not only fuel cells but also other electrochemical systems such as batteries.
Keywords
Catalyst, platinum, energy conversion, ELWBINSTEM, electrochemical, in situ TEM