Karlsruhe Institute of Technology: Green hydrogen: an eye on the catalyst surface

Energy from solar modules and wind turbines makes it possible to split water into its components hydrogen and oxygen by means of electrolysis without harmful emissions. Since the availability of the energy from renewable sources for the generation of green – that is, CO₂-neutrally generated – hydrogen fluctuates, it is very important to know the behavior of the catalysts under high load and under dynamic conditions, according to the authors of the study. “With high currents, there is a strong development of oxygen bubbles at the anode, which makes the measurement difficult and has so far made it almost impossible to obtain a reliable measurement signal,” explains the first author of the study, Dr. Steffen Czioska from the Institute for Technical Chemistry and Polymer Chemistry (ITCP) at KIT. The combination of different techniques enabled the scientists to thoroughly research the surface of the iridium oxide catalyst under dynamic working conditions. “For the first time, we have succeeded in investigating the behavior of the catalyst at the atomic level despite strong bubble formation,” says Czioska. The American Chemical Society (ACS) values ​​the importance of the KIT publication for the international scientific community so highly that it has awarded it the ACS Editor’s Choice.

X-ray absorption spectroscopy with synchrotron light used

The Karlsruhe researchers at ITCP, the Institute for Catalysis Research and the Institute for Applied Materials – Electrochemical Technologies have combined X-ray absorption spectroscopy, which is unique for catalysis and which allows changes at the atomic level to be examined with particular precision, and combined other analysis methods. “We were able to see the regular processes on the catalyst surface during the reaction, because everything irregular was filtered out – similar to the long exposure of a nocturnal road – and still recognize the dynamic processes,” says Czioska. “Our investigation shows that particularly at very high voltages and under dynamic conditions, highly unexpected structural changes occur that are related to the stabilization of the catalyst,” says the chemist.

Results should contribute to better, more efficient catalysts

Researching the processes on the catalyst surface paves the way for further investigation of catalysts at high electrical potentials and could help to develop improved and more efficient catalysts for the requirements of the energy transition, emphasizes Czioska. The investigation is part of the priority program “Dynakat” of the German Research Foundation, in which over 30 research groups work together across Germany and is coordinated by the KIT under the leadership of Professor Jan-Dierk Grunwaldt from the ITCP.

Green hydrogen is considered to be an environmentally friendly chemical energy store and thus an essential element in the decarbonization of sectors such as the steel and chemical industries. The National Hydrogen Strategy adopted by the Federal Cabinet in 2020 sees the reliable, affordable and sustainable generation of hydrogen as the basis for its future use.