Tête-à-Tête series- Dr. Ruud Kortlever

Interviewers: Gayathri Hariharan and Sowmya Kumar

Written by Sowmya Kumar

“A chemist who is a bit lost in Mechanical engineering.”
With this opening statement, Ruud introduces himself to us when we start the interview. Having completed a PhD in electrocatalysis in Leiden, he proceeded to CalTech to work in the Joint Center for Artificial Photosynthesis (JCAP) during his post-doc. After joining TU Delft as an Assistant Professor, he started research on the direct conversion of electricity to chemicals. The last 3-4 years, he has been getting this line of research up and running within the Large Scale Energy Storage research group of EFPT.

Can you briefly describe the research activities carried out by your group?

We work on three main electrochemical reactions or routes. The first one is conversion of nitrogen to ammonia. Ammonia is an important fuel and widely used in the industry. The second is the CO2 route involving conversion of carbon dioxide into useful carbon products. The last reaction we work on is water splitting. 

Research in your group seems to be organized into four clusters. Can you tell us the motivation behind the categorization? What are the interactions between the clusters?

The research we carry out relating to these three routes is carried out at different scales. Based on this, we have categorized our research activities into four clusters. At the lowest range, we carry out studies at the molecular scale in electrochemical and electrocatalytic processes using tools such as DFT modelling and spectro-electrochemistry to understand how a molecule behaves on a catalytic surface. Taking what we learnt from the molecular analysis, the second subgroup/cluster develops new electrocatalytic materials that are tailor made to include desirable characteristics. Now, we have an understanding at the molecular level and have developed materials using our learnings, however we need to find the right process conditions at which the materials should be operated to realize maximum efficiency. This analysis is carried out by the third cluster. Recently, in the past year, a high-pressure set-up that could go up to 100 bar was built by a master student to study a process under different pressures. Finally, the last research cluster carries out the prototyping and upscaling of our processes.
The clusters work in parallel with each other with rich interactions between each other. If something does not work in one scale, we give it as an input to the other scale. We do not have the time to wait for things to be perfected on one scale before moving to the other. Such interactions and parallelization of research activities helps speed up the process.

What is the nature of research in your group?

Mostly experimental. However, we do some DFT modelling for understanding the process from a molecular scale, COMSOL modelling of the device and ASPEN modelling of the process. Modelling the process is very important to gauge the success of our research in a real environment. For example, in the lab, you can always plug a cylinder of 100% CO2 to your process to study CO2 conversion to carbon-rich fuels. However, the exhaust gas from an industry is hardly ever pure in CO2. In such cases, we need to know how it affects the process. This helps make further decisions such as the need for a separation system at the exhaust.

The Kortlever Group falls within the Large Scale Energy Storage (LSES) research group of EFPT. Can you tell us about the vision of LSES and elaborate on how your group falls within its goals?

Large-scale energy storage cannot be realized with batteries. We need to convert the energy extracted from wind farms, solar farms and other renewable sources into chemicals that can be stored. These can be industrial chemicals or chemicals that can be used as a fuel to release the energy when needed. This is the motivation behind the research activities of the LSES group. Now, the question is how we can make these chemicals. One way is to produce green H2 in a water splitting electrolyzer powered through renewable energy sources and feed the hydrogen to a thermochemical process to produce useful chemicals. This is referred to as the indirect route in this field. In my group, we adopt the direct route. We build electrolyzers that can work with water and CO2 or nitrogen to directly convert electricity to chemicals for future use. The nice thing about electrochemical processes is that to implement it on a larger scale, we can scale out instead of scaling up. This evades the complications that come up during scaling up.

Catalysts are often made of expensive metals such as Palladium, Platinum and Gold. When we scale out to meet the demands of the industry, would the price of the catalyst make the devices less attractive?

The important aspect to consider while thinking of a catalytic material is stability. Noble metals are very stable, hence, there is no need to replace them often. Non-noble metals or abundant metals, on the other hand, are cheap but are unstable and we perhaps have to replace them every month. 

In the European Union, there is a list of materials that are declared ‘critical’ due to their low availability. The preference is to avoid using these materials. In our group, for CO2 conversion, copper, which is abundantly available, is used as the catalyst and it works well. Tin, on the other hand, is used in the process to produce formate and is less stable. The challenge in the next decade is the stability of abundant materials that can be used as catalysts. 

Developing new electrocatalytic materials is also a research interest of your group. What are the techniques you use to develop new catalytic materials?

We can use some tricks to design a material towards a certain application. Carbon catalysts are cheap and abundant. We make carbon-based catalysts from biomass derived carbon to make use of the inherent structure of biomass. The porosity of biomass, for example, enhances the mass transport in and out of the material. We collaborate with Prof. Wiebren De Jong for this work. For the carbon route, since most of the processes are hydrothermal, we dope the carbon with active materials such as nitrogen and boron. Since carbon itself is not very active, doping helps to create active materials. For metal catalysts, the standard material is a mono-metallic foil. However, we can make our own foil materials by depositing layers of a metal on a substrate using physical vapor deposition. Nanoparticle catalysts are made by impregnating a substrate with a metal salt and reducing the metal salt to the corresponding metal. We also collaborate with the chemical engineering department of TU Delft to develop materials through atomic layer deposition (ALD) through which we get molecular control over how the material must look like.

With so many techniques available to combine different materials and develop new materials with desirable features, the possibilities seem limitless. Do you think Machine Learning (ML) can help us with making intelligent choices?

There are two ways through which we can develop new materials. The first one is through iterative design which is a conceptual path. The other is high-throughput – we make thousands of materials and employ rapid testing methods to see which one works. Machine learning is a shortcut to this- given enough data points, it optimizes.
The challenge with electrochemistry is that there are a lot of parameters. So, the question is, which parameter should I optimize for? Do we optimize the structure and properties of the catalyst, or its interaction with the electrolyte? Even if we do find a property, there are not enough experimental data points we could use. I am not certain about other fields, but in my field, it seems unclear if ML can make a mark. I have been giving this idea a lot of thought and discussing it with experts in ML within 3mE.

Computers can speed up research, but cannot replace human intuition and creativity.

Electrification of the entire industry seems like a dream. Are we being too optimistic?

I think it is a question of economics. Can we do it in research? Yes, we can. There are questions we still need to answer and improvements to make. However, we can do it. The challenge is that fossil fuels are cheap today and it is hard to compete with it. It is sad to me to say but everything in the world today is about money. Perhaps, that’s why I ended up in academia.

Will the industry have to redesign their plant to run on the alternate fuels you are proposing? How challenging is this transition?

We don’t have to change everything, only parts of it. For example, an important process in making plastics is ethylene polymerization. Currently, ethylene is obtained from oil. However, we can selectively produce ethylene from CO2 through electrochemistry. The first step is changed from oil to an alternate CO2 feedstock, but the rest of the process remains the same. That being said, even changing a part of the process can be challenging. Polymerization, for example, is basically gluing many monomers together and any impurity in the raw materials can stop the process.

In your opinion, what is the ‘catalyst’ that can drive this dream of electrifying the industry?

The involvement of R&D, the government and the industry is important as well as good communication between those three. All of us need to be pushed out of our comfort zone. Sometimes in academia, we continue to do what we know well. We carry out research, write papers and we are done with it. However, we should aim towards having an application up and running. For this, we have to keep thinking about the boundary conditions within which we should work. These are inputs that come from the industry. If a process needs a certain conversion rate, we have to develop electrochemical cells that can handle that.

What is the role of institutes such as the e-refinery in this?

The e-refinery is unique- it facilitates interaction between different engineering disciplines. From electrochemistry, reactor design, flow and transport studies, electrical engineering, electronics to economic analysis, we have experts from all fields working on this research goal. As a result, we are well suited to deal with the scalability of our ideas.
The e-refinery institute connects people. Industries are involved, sometimes directly, and oftentimes through research projects. We have an industrial advisory board to which we share our plans and receive feedback. The 100 KW electrolyzer is one of the current goals that was discussed with the board and set as a realistic goal that if achieved in the lab can be scaled up in the industry.