Fuel cells in the light of the new synchrotron

An example in the field of research on fuel cells, a sector which also benefits from the support of the Hydrogen plan presented by the government on Tuesday, September 8.

Imagine a source of very energetic X-rays, 10,000 billion times more intense than the X-rays used in hospitals. This is what the new Grenoble synchrotron offers, recently inaugurated after two years of refurbishment, ushering in a new era in the exploration of the complexity of materials and living matter. Thanks to its electron beam 2 micrometers high and 20 micrometers wide (thirty times thinner than before) circulating at a speed close to that of light, the ESRF-EBS (Extremely Brilliant Source) produces rays X, themselves brighter, allowing matter to be dissected at the smallest scales with exceptional precision down to the nanometric level. And for researchers, that changes everything. Raphaël Chattot, who is doing his post-doctorate between LEPMI (member of Carnot Énergies du futur) (CNRS, Grenoble INP, UGA, Université Savoie Mont-Blanc) and ESRF, uses X-rays from the ID31 beamline to develop more efficient fuel cell (FC) electrodes.

Optimizing Fuel Cell

The development of hydrogen technologies and heat pumps are part of the objective of decarbonizing energy. Used as an energy carrier, the hydrogen produced by the electrolysis of water reacts in the CAP to produce electricity to power an electric motor, with water as the only emission.

In batteries, hydrogen reacts with oxygen. The oxidation and reduction reactions of these two elements are catalyzed by platinum, a very expensive material which, moreover, degrades over time.

The work of Raphaël Chattot and his colleagues at LEPMI and ESRF precisely aims to use platinum in a form that is both more efficient and durable over time. "To reduce the amount of platinum needed in the electrode, it is used in the form of nanoparticles," explains the researcher. However, platinum in this form does not retain its initial surface properties throughout the life of the battery. Crystal defects appear, which have a non-trivial impact on the performance of the system. Counter-intuitively, the decrease in overall catalyst activity over time is accompanied by an increase in activity on a very local scale, around certain faults. "

To produce materials that are both efficient and durable over time, the ideal compromise must be found by introducing the "good" structural defects from the design of nanoparticles. And for this, researchers need to associate the occurrence of a given type of fault with performance. This is where the ESRF-EBS comes in. The nanoparticles are focused there with X-rays, the diffraction patterns of which can be traced back to their crystalline structures. By producing much more intense X-rays, the new synchrotron will make it possible to observe matter directly in the electrode in operation, and to make the link between structure and performance in real time. "The new source, among other things, producing a much greater number of photons per unit of time than before, it also increases the speed of image acquisition," explains Raphaël Chattot. It is also thinner than before, which allows the separated electrocatalytic layers to be probed with better precision than just a few microns in the heart of the PAC. This type of operando study is essential for the development of this technology beyond the laboratory scale. "

In the end, the new beam makes it possible to study rapid phenomena in operating systems much more closely. It will provide valuable information in many areas.

Source Grenoble INP