Mixed double: What is it like to work as a visiting scientist?

Dr. Jasna Jankovic, Associate Professor at the Department of Materials Science and Engineering at the University of Connecticut, worked as a visiting scientist at Fraunhofer ISE from December 2024 to May 2025 as part of the Fraunhofer Bessel Research Award she received. The joint research focused on the development of advanced ex-situ characterization methods for cutting-edge, innovative fuel cell and electrolyzer materials. At the same time, Dr. Hannes Höffler, fuel cell expert at Fraunhofer ISE, worked at the University of Connecticut. In this double interview, they talk about their experience of the exchange across the Atlantic.

How did the mutual exchange come about?

Jasna: I had been planning my research stay at Fraunhofer ISE as part of my Fraunhofer Bessel Research Award for some time, and when I spoke to Ulf Groos, head of the Fuel Cell Department at Fraunhofer ISE, about the stay, the topic of housing shortages in Freiburg came up. Ulf suggested that we could ask if anyone at Fraunhofer ISE would be interested in a house swap. At that time, the idea seemed like a long shot. However, when Ulf asked his team if anyone would be interested, Hannes raised his hand. We had never met before, so we met over a video call once, and then Hannes came to visit the University of Connecticut and my home in the summer of 2024, and he liked what he saw. He showed me his apartment over a video, and I liked it as well. So, we decided to swap homes, offices and teams. Hannes stayed with his family in my home in Willington near Storrs, Connecticut, and used my office at UConn at the Center for Clean Energy Engineering and Department of Materials Science and Engineering, while I stayed in his apartment at Freiburg and used his office at Fraunhofer ISE. He worked with my team, while I was hosted by his team and participated in their research and meetings. I believe we both had a great experience!

What topics did you work on during your stay abroad at?

Hannes: The research group of Jasna at UConn is internationally known for their expertise in understanding the microstructure of fuel cell catalyst coated membranes (CCMs). During my stay at UConn, I had the opportunity to work with highly advanced equipment like transmission electron microscopes (TEMs), focused ion beam microscopes (FIBs) and X-Ray Diffraction (XRD). I was allowed to use the equipment to investigate samples that were produced in our laboratories at Fraunhofer ISE. But more importantly, apart from just using the equipment, I had the chance to use it together with the experts of Jasna’s research group, which largely contributed to my understanding on the interpretation of results. One specific topic of interest that we worked on was the visualization of pure hydrocarbon (HC) ionomer within the catalyst layers of HC-CCMs. Such HC-CCMs provide an alternative to the environmentally damaging PFSA components used in conventional fuel cell CCMs.

Jasna: At ISE, I worked with the team on a very novel way of doing analysis by XPS (X-ray photoelectron spectroscopy): Dr. Sebastian Praß, working in the field of Fuel Cell Characterization at Fraunhofer ISE, and I prepared fuel cell samples in a very special way, so that we can do cross-sectional analysis of XPS (something that has not been successfully done before). My colleague from Fraunhofer ISE, Dr. Michael Günthel, and I collected a huge amount of XPS data using ISE’s innovative near-ambient XPS instrument. We also established good protocols for using this system for fuel cell (and electrolyzer) samples and set up all needed conditions.

Jasna: We also worked on some novel PFSA-free catalyst layers, supplied by the ISE team, and tried to understand how these new catalyst layers differ from typical, PFSA-based ones. At the same time, Hannes was analyzing the same samples at UConn with my team using TEM, SEM and XRF. We will combine our results into one study. We expect at least 3-4 publications from all this work together. Ulf Groos and I also organized a great network workshop “Research and Education Accelerated by Connections in Clean Hydrogen REACH2”, attended by 120 people from 16 countries. This was a great success.  I would like to thank Fraunhofer ISE and, above all, my colleagues for welcoming me to the Fuel Cell department. A huge thank you to Ulf Groos and Dr. Nada Zamel for nominating me for the Fraunhofer Bessel Research Award and for organizing everything, and the Alexander von Humboldt Foundation for funding this stay. I am so grateful to everyone for this amazing opportunity!

The academic world is basically very internationally oriented. Are there nevertheless differences in research work between the USA and Germany?

Jasna: I have not noticed any major differences in conducting research between USA and Germany. Both teams are very passionate about their research, both institutions have great complementary capabilities, and we work seamlessly together. I felt right at home here at ISE 😊  

Hannes: It was different working at a university compared to working at Fraunhofer. At Fraunhofer the link to industry is very strong, while at UConn there was a stronger focus on writing publications from their high-quality research. Nevertheless, being at UConn – and this is probably different to German universities – I experienced a rather strong collaboration with partners from industry. Overall, I would say that differences between the individual research groups are probably larger than general differences between Germany and USA.

What differences have you noticed in everyday life? Is there anything you would like to adopt for your everyday life back home?

Jasna: I really enjoyed the great work-life balance in Germany! To me, this is the major difference. I enjoyed the beautiful streets of Freiburg, the vibrant cafés, hikes and walks, and quick trips to surrounding cities (by train). In the US, people (at least me) work too much and enjoy life too little. We should have a better balance, more free time and … more trains for easy travel. I also liked how sustainable Freiburg is – everyone is on bikes or people walk everywhere. I try to do that at home as well, but the roads are more set up for cars. I also liked our daily lunches with the team. Hearing someone call “”Mahlzeit” at 11:30 am every day, and then eating lunch with the team every day was amazing. I am so thankful to my ISE team for accepting me like one of their own.          

Hannes: It was surely an interesting experience for us as a family to live in a house in the forest, while in Freiburg we are used to living in the city. I really enjoyed sitting on the terrace and just listening to the sounds of wildlife. All the people I met were very friendly and it was easy to get into conversation. I did miss though just going into a street café with my bicycle or even by foot. That was not possible. If I had to choose one thing though which I would like to take home, it would be the middle school, which my 13-year-old son attended during our stay. The motivation and the positive attitude of the school and teachers was overwhelming.

Will there be further joint projects between ISE and UConn? On which topics?

Hannes: There will certainly be an ongoing collaboration between our research groups. This could either be based on collaborative publications and would ideally be backed up by funding. Especially when it comes to visualization of microstructures in hydrocarbon CCMs and their understanding, scientifically interesting questions could be identified during the exchange. But more importantly I think that the exchange strengthened the trust between the people of each research group, which is the very foundation of productive collaboration.

Thank you very much, Jasna and Hannes, for your answers, and all the best for the future transatlantic cooperation!

In the research topic Fuel Cell, Fraunhofer ISE supports the development of membrane fuel cells for mobile applications.  Our core competencies are ex-situ materials analysis, in-situ characterization, modeling and production research of membrane electrode assemblies. Our in-situ characterization is carried out using single cells and cell stacks.