Renewable energy sources, such as solar and wind, are intermittent, and the energy generated must be stored to be available when needed. A very efficient way of storing energy is in the form of chemical bonds. The conversion of carbon dioxide back into fuels via electrochemistry is a very attractive alternative. In addition to storing energy, we also reduce the amount of carbon dioxide emitted into the atmosphere.

Sergey Koroidov, Researcher, The Department of Physics

- I started my career as a researcher in 2010 with my Ph.D. project work at Umeå University, which was mainly dedicated to studying catalytic water oxidation reactions. Also, as a part of my Ph.D. work, I began to gain practical experience in optical and X-ray spectroscopy at Lawrence Berkeley National Laboratory (LBNL). I was fascinated by spectroscopic capabilities to study catalytic reactions, which led me to pursue my research in the same direction, says Sergey.

After graduation, he became a postdoctoral fellow at Stanford University and SLAC national accelerator laboratory, the home of the world’s first hard x-ray free-electron laser (LSLC). The opportunity of doing work at this facility was very appealing to him.

- In 2017 I returned to Sweden (Stockholm University; Fysikum) as a Research Associate and worked with Anders Nilsson. Since 2020 I have started to develop my independent research directions.
These research activities aim to deliver knowledge that leads to a sustainable CO2 reduction reaction (CO2RR) to obtain higher hydrocarbons (HCs) and alcohols as an unrivaled energy resource in energy density, storage, and distribution.

How to convert carbon dioxide into renewable fuels
Still, for an efficient process we need to develop materials that can catalytically convert carbon dioxide efficiently into the desired products.
- In my studies, I am developing the necessary understanding of these reactions by following time-resolved transformation at the atomic and molecular level. We do this with X-rays from synchrotron light sources and ultra-short pulses from new X-ray lasers. The goal is to understand processes how to convert carbon dioxide into renewable fuels as efficiently as possible, says Sergey Koroidov. He is a member of the XSoLaS group, X-ray Science of Liquids and Surfaces (XSoLaS), at the Department of Physics.

Improved technology for energy conversion based on renewable sources
Today, 80% of all energy comes from fossil fuels, and the societal need for energy is expected to increase. We face major challenges both from the limited supply of fossil fuels and climate change due to the increasing carbon dioxide content in the atmosphere and oceans. To create an economically, socially, and environmentally sustainable society, we must improve technology for energy conversion based on renewable sources. Suppose we can store solar and wind energy in the form of liquid fuels. In that case, we can take advantage of their high energy density,currently existing in energy transport systems, and bridge periods when solar and wind make small contributions.

In other words, one of the most significant scientific challenges today is: to develop renewable sources of liquid hydrocarbons and alcohols from carbon dioxide on a cost-effective industrial scale.

We need to understand and control the catalyst
Almost all chemical processes involved in energy conversion are based on catalysis. The scientific challenge in converting CO2 to fuels is the lack of efficient catalysts for large-scale transformation of these gases when captured from carbon-intensive sources or the atmosphere when that technology becomes available. Copper is currently the only known metal that can convert CO2 to hydrocarbons, but how the process works is not fully known. There is a need to understand and control the catalyst in detail, from how the electrons are redistributed to how the atoms move during the reaction and how different catalysts can affect them.

Utilizing X-rays to understand catalysis
New developments in synchrotron and X-ray free-electron facilities have created new opportunities. The ultra-short pulses function as a high-speed camera at electron and atomic levels that make it possible to follow their movements on the time scale they move on and thereby "see" how chemical bonds are formed and broken. By using different energies of the X-rays, we can choose which atoms we follow. The experiments are carried out using instruments that are designed and built here at Fysikum.

The reaction takes different paths on different materials
We use these chambers and end stations to investigate transient processes and intermediates formed on the surface and how they develop further during catalytic reactions in real-time. At any given moment in the continuous process, the amount of intermediates is vanishingly small, but by starting the reaction synchronously, we can increase the proportion and characterize these crucial intermediates. They are essential when we talk about which path the reaction takes on different materials, which in turn allows designing materials for the desired end products.

Different formulations of copper as an electrode
In other words, the goal of our study is to develop a fundamental understanding of all reaction steps, which intermediates are involved and how they bind to the catalyst, determine reaction barriers and energy transfer between the electrode and adsorbed molecules by analysing relevant model systems. In the first place, we are focusing on different formulations of copper as an electrode. Some of these may give a high selectivity for the desired product ethylene over the unwanted greenhouse gas methane for currently unknown reasons. What determines this and how it can be optimized is a significant challenge for the attack. With the methods we now have available, this is within reach.

Electrochemical reduction of CO2

Mitigating the impact on climate change
This project thus has the potential to mitigate our impact on climate change and secure our access to energy in the fossil-free future. Our well-being has strongly been linked to access to energy and the environment. Recycling CO2 into valuable industrial chemicals and fuels (Fig. 1) instead of adding carbon to the carbon cycle by utilizing fossil sources will directly attack the source of anthropogenic climate change. The breakthrough will alleviate Swedish dependence on non-Swedish sources of fuels and chemicals and lead towards domestic production. These research activities thus have the potential to mitigate our impact on climate change and secure our access to fossil-free energy in the future.

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