An Electrifying View on Catalysis

The future of chemistry is ‘electrifying’: With increasing availability of cheap electrical energy from renewables, it will soon become possible to drive many chemical processes by electrical power. In this way, chemical products and fuels can be produced via sustainable routes, replacing current processes which are based on fossil fuels.
In most cases, such electrically driven reactions make use of so-called electrocatalysts, complex materials which are assembled from a large number of chemical components. The electrocatalyst plays an essential role: It helps to run the chemical reaction while keeping the loss of energy minimal, thereby saving as much renewable energy as possible. In most cases, electrocatalysts are developed empirically and the chemical reactions at their interfaces are poorly understood. A better understanding of these processes is essential, however, for fast development of new electrocatalysts and for a directed improvement of their lifetime, one of the most important factors that currently limit their applicability.

Figure 1.  Introducing well-defined model electrocatalysts into the field of electrochemistry.
 

At present, electrocatalysis faces a ‘materials gap’ that is very similar to the one in conventional heterogeneous catalysis bridged successfully by the model catalysis approach. As simple preparation methods do not allow building up complex electrode surfaces, new strategies are required to close this gap. A team of researchers from the Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), the Helmholtz-Institute for Renewable Energies Erlangen-Nürnberg (HI-ERN), the Charles University in Prague, the Max-Planck-Institut für Eisenforschung, Düsseldorf, and the Materials Science beamline at Elettra proposed to ‘electrify’ complex yet well-defined oxide-based model catalysts made by surface science methods to explore electrocatalytic reactions in liquid electrolytes. Details of this new strategy were reported in the journal Nature Materials. The work involved a wide range of techniques including electrochemical infrared reflection absorption spectroscopy(EC-IRRAS), cyclic voltammetry (CV), electrochemical scanning flow cell (SFC) inductively coupled with plasma mass spectrometry (ICP-MS), LEED, Scanning Tunnelling Microscopy (STM), synchrotron radiation X-ray photoelectron spectroscopy (SR-XPS), and X-ray photoelectron spectroscopy (XPS) coupled with an electrochemical cell. As a model electrocatalyst, the researchers employed highly dispersed Pt nanoparticles supported on well-ordered Co₃O₄(111) films grown on Ir(100). The model electrocatalyst were transferred between the UHV and the electrochemical cell under well-defined condition preserving the atomic structure of the films.
 

Figure 2.  Electrifying the Pt/Co₃O₄(111) model catalyst prepared in UHV by in situ transfer into the electrochemical environment.

First experiments performed under electrochemical conditions established a stability region (pH 10, 0.30 to 1.30 VRHE, K/H₃PO₄buffer) in which there is no dissolution as detected by SFC ICP-MS and no change in thickness or chemical state of the Co₃O₄(111) (apart from surface hydroxylation) as detected by XPS (Figure 2). In this region, LEED experiments showed that the characteristic diffraction pattern of the Co₃O₄(111) was preserved after immersion into the electrolyte, potential cycling and subsequent back-transfer into UHV.
Thus, the researchers demonstrated that it is possible to assemble a complex electrocatalyst with ‘atomic level control’ and to use such a system to study the individual steps of electrically driven reactions. Following this strategy, it will now be possible to build a wide range of new electrocatalysts with unprecedented control over their structure and composition, thus helping to develop a fundamental understanding of the ‘electrifying’ chemistry of the future.

This research was conducted by the following research team:

Firas Faisal,¹ Corinna Stumm,¹ Manon Bertram,¹ Fabian Waidhas,¹ Yaroslava Lykhach,¹ Serhiy Cherevko,^2,3 Feifei Xiang,⁴ Maximilian Ammon,⁴ Mykhailo Vorokhta,⁵ Břetislav Šmíd,⁵ Tomáš Skála,⁵ Nataliya Tsud,⁵ Armin Neitzel,¹ Klára Beranová,⁶ Kevin C. Prince,⁶ Simon Geiger,² Olga Kasian,² Tobias Wähler,¹ Ralf Schuster,¹ M. Alexander Schneider,⁴ Vladimír Matolín,⁵ Karl J.J. Mayrhofer,^2,3 Olaf Brummel,¹ Jörg Libuda^1,7

¹ Lehrstuhl für Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
² Department of Interface Chemistry and Surface Engineering, Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany
³ Helmholtz-Institute Erlangen-Nürnberg for Renewable Energy (IEK-11), Forschungszentrum Jülich GmbH, Erlangen, Germany
⁴ Lehrstuhl für Festkörperphysik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
⁵ Department of Surface and Plasma Science, Charles University, Prague, Czech Republic
⁶ Elettra-Sincrotrone Trieste SCpA, Basovizza-Trieste, Italy
⁷ Erlangen Catalysis Resource Center, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany

Contact persons:

Yaroslava Lykhach, email:
Olaf Brummel, email:
Jörg Libuda, email: