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A 3-D rendering of a gas diffusion electrode, used in fuel cells and CO2 electrolyzers, where a thin, uniform, and crack-free catalyst layer is crucial to efficient operation. Image Credit: University of Illinois
A pioneering new technique has been used by researchers at the University of Illinois to shine new light on the relationship between the performance of electrodes and the structure of catalysts.
The research team included Molly Jhong (a graduate student at the Department of Chemical and Biomolecular Engineering), ChemE professor Paul Kenis, MIT assistant professor Fikile Brushett, and Dr. Leilei Yin (research scientist from the Beckman Institute at Illinois), and a paper reporting their findings was recently published in the journal Advanced Energy Materials.
‘Electrodes play a vital role’
Electrodes are ubiquitous in many electrical circuits, and are used to make contact with a part of the circuit that is not highly electrically conductive (such as a non-metallic semiconductor). They are used in many applications, including fuel cells, electroplating and medical apparatus.
As Molly Jhong explains:
"Electrodes play a vital role in all devices based on heterogeneous electrochemical reactions for energy conversion, energy storage, and chemical synthesis,"
One of the most important considerations when developing electrodes for industrial use is the processes that occur at the interface between the electrode and the accompanying
catalyst, with the performance of the catalyst often governing how well the electrode performs.
For instance, one of the reasons that commercialization of polymer-electrolyte membrane fuel cells has been stilted is because in order to meet performance requirement these fuel cells need a relatively large amount of expensive platinum for catalysis.
Fuel cells convert chemical energy (commonly from hydrogen or hydrocarbons) into electrical energy through oxidation reactions, and could be important in future generations of electric vehicles.
Moreover, electrochemical reactors which convert carbon dioxide into more useful chemicals will only be an economically viable option when catalysts with high enough performance become readily available.
Combination of 3D structural analysis and electrochemical characterization
In this research, the team combined the analytical techniques of X-ray tomography and electrochemical analysis to see if the relationship between electrode and catalyst could be better understood.
Tomography is a non-destructive technique that allows the user to build up a 3D image of an object (in this case the catalyst) by superimposing image sections obtained by penetrating radiation.
X-ray tomography is commonly used, but there are a wide variety of tomographical techniques that are also used in both material science and the medical profession. For example, MRI machines utilise radio-wave tomography. Tomography is a great technique to use in this situation because of its high spatial and temporal resolution.
Below is a wonderful short video showing X-Ray Tomography being used to analyse a lily.
Whilst the tomography gauges the change in 3D structure of the catalyst, the electrochemical analysis helps to measure the relative performance of the electrode.
Because of this combination of 3D structural analysis and electrochemical characterization, the changes in catalyst morphology can be directly related to the performance of the electrode, giving a greater understanding of how the catalysts are degrading electrode performance.
This research will hopefully be useful in the progression of research into electrolysers, fuel cells and energy storage, as well as potentially improving catalyst deposition mechanisms.
Original Source: University of Illinois College of Engineering
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