Against the background of dwindling resources for fossil fuels and the threats of climate change, sustainable and environmentally friendly production processes for fuels and chemical feedstocks become all the more important . Catalysts are complex material systems that accelerate desired chemical reactions and are the key to the realization of such production processes, both at solid/gas and the solid/liquid interface. To improve catalyst performance, an atomic-scale understanding of the catalyst structure and its surface chemistry in correlation with the catalytic activity under realistic reaction conditions is inevitable.
In recent years, we have pioneered in the development of synchrotron-based operando methods that allow for investigating model catalysts under realistic reaction conditions. Thus, the technique of High Energy Surface X-ray Diffraction (HESXRD) provides a fast data acquisition of diffraction signals and allows for tracking surface structural changes of catalysts at work with sub-second temporal resolution [2-4]. Using HESXRD, we could track the composition-dependent sintering of nanoparticles during CO oxidation  and monitor transient surface oxides and hydroxide phases at the solid/gas and solid/liquid interface, respectively . Combining HESXRD with gas phase laser diagnostics, we could moreover directly correlate the gas composition above the sample surface to its structural changes during self-sustained reaction oscillations, during which a catalyst shuts it activity periodically off. High Pressure X-ray Photoelectron Spectroscopy yields complementary information on the catalyst surface chemistry, where in a recent landmark experiment we studied a model catalyst under unprecedented pressures of 1 bar .
In addition to reporting the aforementioned experimental findings, the presentation will give an outlook on the future use of these operando methods to study chemical reactions important for a sustainable future. The focus will be on reactions that transform greenhouse gases such as CO2 and CH4 into value-added products such as the high energy density fuel methanol, as well as the production of green H2 via the water-splitting reaction.
 Hejral et al., J. Catal. 405, 183 (2022).  Gustafson et al., Science 343, 758 (2014).  Hejral et al., J. Phys.: Condens. Matter 33, 073001 (2021).  Hejral et al., Phys. Rev. B 96, 195433 (2017).  Hejral et al., Nat. Commun. 7, 1 (2016).  Shipilin,.., Hejral et al., J. Phys. Chem. C 119, 15469 (2015).  Blomberg, Hejral et al., ACS Catal. 11, 9128 (2021).
Contact: Maria Abrahamsson, Director, Materials Science Area of Advance.
Leif Asp, Co-Director, Materials Science Area of Advance.