Converting CO2 into a valuable energy carrier using a model In2O3 catalyst

Converting CO2 into a valuable energy carrier using a model In2O3 catalyst

New discoveries made possible by In Situ TEM gas and heating

Original article by Athanasia Tsoukalou, Paula M. Abdala, Dragos Stoian, Xing Huang, Marc-Georg Willinger, Alexey Fedorov and Christoph R. Müller. Published in the Journal of the American Chemical Society on 19 July 2019.

Artist impression of methanol synthesis via CO2 hydrogenation using In2O3 catalyst (copyright of the American Chemical Society)

The direct hydrogenation of CO2 to methanol shows promise to be an important technique to reduce the amount of greenhouse gases in the atmosphere and thereby mitigate the negative effects of climate change while producing an important energy carrier. In his contribution to this article, Dr. Xing Huang has used In Situ TEM techniques to assess the limits of In2O3 catalytic performance in CO2 hydrogenation.

In Situ TEM Climate Nano-Reactor study

This catalyst research article by ETH Zürich provides a good demonstration on how in situ TEM experiments can add value to the study of reaction mechanisms. First, the structural changes in the catalyst material were studied with traditional TEM techniques before and after the CO2 reduction. By using the Climate in situ TEM system, the researchers were able to see the dynamics of the reaction, even at much lower pressures (0.8 vs. 20 Bar) than in the original operando experiment.

In Situ TEM video made using the DENSsolutions Climate system, at 300 °C, showing the co-existence of crystalline and amorphous phases as well as the transformation into film structures of the In2O3 catalyst.

Amorphization of the catalyst material inside the Nano-Reactor takes places in a few minutes, compared to hours in the capillary reactor. Re-activation of the catalyst is made easy by the Climate Gas Supply System since the hydrogen plus carbon-dioxide gas flow can be replaced by an oxygen flow at any moment.

“Direct observation using in situ TEM clearly reveals that the structure of In2O3 nanoparticles is highly dynamic under reaction conditions and irradiation of electron beam. The In2O3 is observed to transform into a dynamic structure in which both crystalline and amorphous phases coexist and continuously inter-convert.

This observation is in line with the operando XAS-XRD study revealing formation of the amorphous In0/In2O3 phase with time on stream. To sum up, combination of in situ TEM with other in situ/operando techniques enables to build a direct relationship between the structure and the catalytic performance of the In2O3 catalyst in CO2 hydrogenation to methanol.”

Co-author – Dr. Xing Huang, ETH Zürich

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Interview with Prof. Rafal Dunin-Borkowski, Director of Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons in Jülich

Interview with Prof. Rafal Dunin-Borkowski, Director of Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons in Jülich

Fig. 1. Prof. Rafal Dunin-Borkowski. Photo credit: Forschungszentrum Jülich

We interviewed Rafal Dunin-Borkowski, Director of Ernst Ruska-Centre (ER-C) for Microscopy and Spectroscopy with Electrons in Forschungszentrum Jülich. We talked about his road to ER-C, his research into more energy-efficient electronic devices, the growing importance of software and data analysis and the need for automation to improve the measurement of weak signals. 

“I currently have the greatest personal interest in developing techniques for characterizing the functional properties of working electronic and spintronic devices on the smallest scale and in real time in the presence of stimuli such as applied field, voltage, temperature, light, gases and liquids.”

Where does your passion for Electron Microscopy come from?

My passion for electron microscopy was accidental. It came from being taught by Michael Stobbs as an undergraduate and during my Ph.D. He communicated his enthusiasm for developing and applying characterization techniques as a combination of fundamental physics, materials science and other scientific disciplines. Almost every problem involves exploring a new material or phenomenon at close to the atomic scale that no one has studied before.

Can you tell us about your road to the Ernst Ruska-Centre in Jülich?

It was a long road! First of all, I was in Cambridge University, where I completed my undergraduate degree in physics, my Ph.D. and first postdoctoral appointment with Michael Stobbs. I then went to Arizona State University, where I was sponsored by IBM Almaden and worked with David Smith and Molly McCartney on magnetic recording technology. In Arizona, I also worked with John Cowley, Peter Buseck and Michael Scheinfein. I then went to the Department of Materials in Oxford University for 2 years, where I was responsible for using a new field emission microscope with internal and external users. I then obtained a Royal Society University Research Fellowship, returned to Cambridge University and stayed there for almost 7 years, working primarily on off-axis electron holography and related techniques. After Cambridge, I was employed in the Technical University of Denmark to set up a new department, which was called the Center for Electron Nanoscopy. I stayed there for 5 years.

Fig. 2. Prof. Knut Urban. Photo credit: Forschungszentrum Jülich

In 2011, I took over the Institute for Microstructure Research in Forschungszentrum Jülich in Germany when the previous director, Knut Urban, retired. This institute has a long history in electron microscopy technique development and applications, as well as in the operation of the Ernst Ruska-Centre as a user facility. Together with colleagues in Heidelberg and Darmstadt, Knut Urban contributed to the development of spherical aberration correction for transmission electron microscopy in the 1990s. Forschungszentrum Jülich has been operating the Ernst Ruska-Centre as an international user facility since 2004, together with RWTH Aachen University. 50 % of the access time to the instruments is made available to external users, who work with our experienced scientific and technical staff.

As a director, are you still involved in hands-on research?

In the institute that I direct in Jülich, we currently have about 100 active scientists and students, many of whom are paid from 3rd party funding. This means that we respond to external funding decisions, which determine the scientific directions that we work on. It also means that I spend a lot of time raising funding or managing research projects. I therefore have little time to do hands-on research myself. However, I try to stand behind people when they use the electron microscopes and help them with writing software and data analysis. In addition, if any research paper has my name on it I try to make sure that I comment on it line by line. In this way, I try to take as active a role in scientific research as I can.

Which were defining moments that accelerated your career?

Scientifically, there were certain people I worked with who were very helpful in my development
as a scientist. In particular, working with Michael Stobbs, David Smith, John Cowley and others gave
me key experiences and insight. Now, I try to facilitate an environment for people to do the kind of
work that I would like to be doing myself. I look forward to not being a director and going back to
doing hands-on research in the future, because I regard this as my strength.

Fig. 3. Members of the ER-C team (from the left): Dr. Karsten Tillmann, Dr. Juri Barthel, Marita Schmidt and Dr. Andreas Thust.
Photo credit: Forschungszentrum Jülich

What makes the ER-C a unique institute?

The Ernst Ruska-Centre is unique in many ways. It is managed both from the Jülich Research Center and from RWTH Aachen University. This means that there is frequent interaction between people who work in both places, as well as with external users of the facility. We encourage external users to come for as long as possible, so that they are genuine collaborators with our research staff, who each have their own research topic to work on. We also try to encourage our staff to work on technique and instrumentation development to tackle new problems that are brought to us.

The Ernst Ruska-Centre is now moving from research only in the physical sciences to also include soft materials and life science. This change in the breadth of our research allows us to apply techniques, instrumentation and software that have been developed to tackle problems in the physical sciences to soft and biological materials, and vice versa. We are also establishing closer links with other characterization techniques, especially neutron science and synchrotron X-rays, as well as with data scientists.

Fig. 4. Forschungszentrum Jülich – Staff. Photocredit: Forschungszentrum Jülich

What is the role of the ER-C on a global scale?

On a global scale, at first sight the Ernst Ruska-Centre resembles how user facilities work elsewhere, for example in the US National Laboratories. In practice, the working principle is different, in particular with regard to the fact that all of our staff work on as long-term a collaborative basis as possible with incoming scientists and students, in order to optimize experiments and data analysis together with them, rather than concentrating on serving many users.

Do you collaborate with industry to develop new techniques?

In the ER-C, we try to go beyond the techniques and capabilities that are available elsewhere, for example by undertaking ambitious development projects with manufacturers, where we commit our staff time in return for access to technology that is not yet available commercially. Software and instrumentation that is developed in the ER-C is then often licensed back to the manufacturers for the benefit of their future customers and the community as a whole.

In which research topics are you personally interested?

We currently have more than 10 working groups in the ER-C, many of which focus strongly on technique development, as well as on specific materials problems. I have an interest in almost every activity in the institute.

Fig. 5. Artist impression of Spintronics.

However, I currently have the greatest personal interest in developing techniques for characterizing the functional properties of working electronic and spintronic devices on the smallest scale and in real time in the presence of stimuli such as applied field, voltage, temperature, light, gases and liquids. Many of these capabilities have only recently become available. The experiments are carried out at the highest spatial resolution using phase contrast and spectroscopic techniques in both TEM and STEM imaging modes. They also require the development of new approaches for handling the increased amount and rate of data coming from the microscopes.

To what extent do societal challenges determine your choice in your research topics?

Societal priorities have a decisive factor on which scientific topics are funded. In turn, they drive our research. In the Helmholtz Association, we work on the basis of program oriented funding. Every 5 years, our scientific priorities are redefined, in part by societal needs. At the same time, by its very nature much of our research is exploratory and operates over longer timescales, especially with regard to technique and instrumentation development.

Will in situ techniques play a role in the research of ER-C and why are these in situ techniques becoming relevant?

A variety of different problems come under the heading of in situ electron microscopy. Some of our experiments involve “in situ” chemical reactions in gas or liquid environments, while others involve passing electrical currents through or applying magnetic fields to nanoscale materials, or studying the effect of temperature, light or mechanical stress.

One of the scientific priorities of the Hemlholtz Association, which funds much our research, is to understand and develop more energy-efficient devices for future computing applications. In our institute, we use electron microscopy to map the local crystallography, microstructure and functional properties of novel nanoscale devices in real time. We would like to make these measurements on ever faster timescales and are currently developing new hardware and software that we hope will give us access to the sub-nanosecond regime.

What do you expect from DENSsolutions in the future?

We have a partnership agreement and many specimen holders from DENSsolutions, which we are very pleased with. We would like to have an even closer partnership in the future and have many ideas for more ambitious technical developments, as well as for the automation of complicated workflows. In particular, the current practice of performing experiments manually limits our ability to measure very weak signals, which would require repeating the same sequence of steps many thousands of times. For this reason, we need the kind of automation of experiments that is now available in the life sciences. We understand that there is a greater variety of samples and experiments in the physical sciences and that such workflows would then have to be more flexible.

Is your goal with automation to get a higher throughput for your experiments?

This is not the priority. I would primarily like to use automation to improve the measurement of weak signals and to obtaining better statistics in certain measurements, rather than simply to achieve high throughput. We therefore also need more stable specimen stages and a cleaner environment in the microscope column so that the sample does not change over time. There is one other aspect of automation that does not exist at the moment, which is the ability to store samples, for example in inert environments in individual cartridges, until they are no longer needed, perhaps over many years, so that the same region of the same sample can be reassessed quickly, easily and reproducibly as many times as required.

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