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  2. Chemical Physics division / XSoLaS group
  3. Research
  4. Research
  5. Chemical Energy Transformations and Catalysis

Chemical Energy Transformations and Catalysis

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1) CO2 reduction

The conversion of CO22 into fuels or other useful chemicals is a quickly growing field of interest in the scientific community as it would help mitigate the effects of CO2 emission on climate change. The best catalyst material for electroreduction of CO2 to higher order hydrocarbons, such as ethylene and ethanol, is copper, with nanostructured surfaces presenting interesting changes in activity and selectivity. Using an online electrochemical mass spectrometer (OLEMS), our group can track the evolution of CO2 reduction products as a function of potential in real time, and have discovered a unique copper surface covered with nanocubes to be highly selective towards ethylene production. We are also designing experiments to detect CO2 reduction reaction intermediates and determine catalyst active sites by using in situ X-ray spectroscopy techniques. There is a particular emphasis on ambient pressure X-ray photoelectron spectroscopy (APXPS) in order to be at humidity levels suitable for electrochemical reaction conditions while simultaneously detecting reaction intermediates and surface-specific oxidation states.

Here are some publications:

High Selectivity for Ethylene from Carbon Dioxide Reduction over Copper Nanocube Electrocatalysts. Roberts, F. S.; Kuhl, K. P.; Nilsson, A. Angew. Chem. Int. Ed. 2015, 54 (17), 5179.

Structure, Redox Chemistry, and Interfacial Alloy Formation in Monolayer and Multilayer Cu/Au(111) Model Catalysts for CO2 Electroreduction. Friebel, D.; Mbuga, F.; Rajasekaran, S.; Miller, D. J.; Ogasawara, H.; Alonso-Mori, R.; Sokaras, D.; Nordlund, D.; Weng, T.-C.; Nilsson, A., J. Phys. Chem. C 2014, 118 (15), 7954.


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2) Electrocatalysis

To avoid catastrophic effects of CO2 emissions, we need to switch all of our energy use to renewable sources such as wind and solar energy. Replacing 1 billion conventional road vehicles with electric vehicles could take several decades, therefore a source of “renewable gasoline” generated from renewable electricity is urgently needed, as well fuel cells that use alternative fuels such as hydrogen much more efficiently than combustion engines. Our research aims at the discovery of fundamental design principles for four classes of new electrocatalyst materials that catalyze 1. The oxygen reduction reaction (ORR) in proton exchange membrane fuel cells 2. The oxygen evolution reaction (OER), which is needed in all electrochemical fuel-generating devices 3. The hydrogen evolution reaction (HER) 4. The CO2 reduction reaction (CO2RR) for the conversion of CO2 to hydrocarbon or alcohol fuels.

We use a complementary set of operando x-ray spectroscopies to determine the relationships between chemical bonding at the catalyst/electrolyte interface, structure of the operating catalyst, and catalytic activity and selectivity.

Structure of operating catalyst Operando hard x-ray absorption spectroscopy (XAS) in the high resolution fluorescence detection (HERFD) mode probes the chemical bonding in the catalyst material, and also the bonding of adsorbates when ultrathin catalyst layers or small nanoparticles are studied. Extended x-ray absorption fine structure (EXAFS) provides complementary structure information.

Nature of adsorbates We use ambient pressure x-ray photoemission spectroscopy (AP-XPS) to detect adsorbed intermediates and electronic structure/composition changes of the catalyst at triple-phase boundaries typical for gas diffusion electrodes, or at solid/liquid interfaces.

Online electrochemical mass spectroscopy We have built an online electrochemical mass spectroscopy (OLEMS) setup to study new catalyst materials for the CO2RR. OLEMS measurements allow us to detect volatile CO2RR products simultaneously with cyclic voltammetry.


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3) Heterogenous catalysis

Molecules of gas and liquids have a tendency to adsorb on surfaces, resulting in a distortion of the molecular orbitals and thus the energy levels of the electrons of the molecule. In catalysis, one takes advantage of this distortion to ease the rearrangement of bonds within adsorbed molecules. For more than 30 years the energy levels of the surface and the absorbed species have been examined using X-ray Photoelectron Spectroscopy (XPS). The technique uses high energy photons to ionize core level electrons of the sample and measures the kinetic energy of the emitted electrons, yielding information about the electronic states of both the surface and the adsorbent. Due to the short mean free path of electrons, XPS is almost exclusively used in high vacuum regimes below 10-6 mbar. Significant effort has been taken to increase the pressure and closing the so called ”pressure gap” to where most catalytic reactions take place. Latest achievement have been done in our research group reaching 100 Torr(Kaya et al., Catalysis Today 205 (2013) 101–105).


(We would like to thank our sponsors:)

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