Electrochemical Properties of Model Catalyst Systems

We have developed a versatile eletrochemical cell that allows us to measure most relevant electrochemical properties and stability of surface science model systems. We investigate both single crystals surfaces (such as Cu and Ni), and supported systems such as oxide nanoparticles on these supports. The cell enables STM and XPS characterization before and after electrochemical measurements, and is currently used to investigate electrocatalysts for the oxygen evolution reaction (OER), oxygen reduction (ORR) and CO₂ reduction (CO2RR).

The construction was funded by Carlsbergfondet (2018-2021)

Sun, Z.; Lauritsen, J. V., A versatile electrochemical cell for hanging meniscus or flow cell measurement of planar model electrodes characterized with scanning tunneling microscopy and x-ray photoelectron spectroscopy. Review of Scientific Instruments 2021, 92 (9), 094101

Sun, Z.;  Curto, A.;  Rodríguez-Fernández, J.;  Wang, Z.;  Parikh, A.;  Fester, J.;  Dong, M.;  Vojvodic, A.; Lauritsen, J. V., The Effect of Fe Dopant Location in Co(Fe)OOHx Nanoparticles for the Oxygen Evolution Reaction. ACS Nano 2021, 15 (11), 18226-18236.

Ambient Pressure Surface Science

We invesitgate surface science model catalysts in operando conditions using ambient pressure scanning tunneling microscopy (AP-STM) and x-ray photoemission spectroscopy (AP-PES). The SPECS Aarhus STM allows us to image surfaces in controlled atmospheres at at elevated temperature, i.e. under conditions that are approaching the real catalytic conditions. AP-XPS is carried out at synchtrons, such as MAX-IV, Lund, Sweden.

The project is funded by a Villumfonden Research Project (#13264)

Grønborg, S. S.;  Salazar, N.;  Bruix, A.;  Rodríguez-Fernández, J.;  Thomsen, S. D.;  Hammer, B.; Lauritsen, J. V., Visualizing hydrogen-induced reshaping and edge activation in MoS₂ and Co-promoted MoS₂ catalyst clusters. Nature Communications 2018, 9 (1), 2211.

Bruix, A.;  Füchtbauer, H. G.;  Tuxen, A. K.;  Walton, A. S.;  Andersen, M.;  Porsgaard, S.;  Besenbacher, F.;  Hammer, B.; Lauritsen, J. V., In situ detection of active edge sites in single-layer MoS₂ catalysts. ACS nano 2015, 9 (9), 9322-9330.
 

Hydrotreating Catalysis with Metalsulfide Catalysts

In the project we study the fundamental properties of metal-sulfide nanocatalyst using the Scanning Tunneling Microscope (STM). The hydrotreating catalyst based on MoS₂ is among the most important heterogeneous catalysts used today, since it is used for upgrading crude oil. More importantly, the same catalyst are also important for the transition to renewable energy, since the same catalyst types can be used for upgrading of various types of bio-oils Using the STM, we can successfully use the STM to provide a genuine atomic-scale view of the active MoS₂ nanoclusters and follow in atomic detail the key intermediate steps in the desulfurization process, and based on this insight we collaborate with an industry partner to develop new hydrotreating catalyst. We participate in the HyProFuel project (Innovation Fund Denmark, 2022-2026), that specifically aims to develop catalysts for production of fuels from bio-waste.

Grønborg, S. S.;  Salazar, N.;  Bruix, A.;  Rodríguez-Fernández, J.;  Thomsen, S. D.;  Hammer, B.; Lauritsen, J. V., Visualizing hydrogen-induced reshaping and edge activation in MoS₂ and Co-promoted MoS₂ catalyst clusters. Nat. Commun. 2018, 9 (1), 2211.

Earth Abundant Materials for Water Splitting Catalysis

Mixed oxides based on CoFe or NiFe are among the best performers as future alternative electrocatalysts for the water splitting reaction with attractive properties in terms of stability, efficiency, abundance and low-cost. However, fundamental understanding of the catalytic properties of these oxides is still limited.To elucidate the fundamental structure, composition and surface chemistry of Fe-CoO_x based catalysts, we characterize the surface of CoO_x nanoislands under ultra-high vacuum conditions by high-resolution Scanning Tunneling Microscopy (STM) and X-Ray Photoelectron and Absorption Spectroscopies (XPS and XAS) and combine these measurements with theory insight and direct measurement of the elecrochemical performance.

Fester, J.;  Makoveev, A.;  Grumelli, D.;  Gutzler, R.;  Sun, Z.;  Rodríguez-Fernández, J.;  Kern, K.; Lauritsen, J. V., The Structure of the Cobalt Oxide/Au Catalyst Interface in Electrochemical Water Splitting. Angewandte Chemie International Edition 2018, 57, 11893-11897.

Sun, Z.;  Curto, A.;  Rodríguez-Fernández, J.;  Wang, Z.;  Parikh, A.;  Fester, J.;  Dong, M.;  Vojvodic, A.; Lauritsen, J. V., The Effect of Fe Dopant Location in Co(Fe)OOHx Nanoparticles for the Oxygen Evolution Reaction. ACS Nano 2021, 15 (11), 18226-18236.

The project is funded by Independent Research Fund Denmark (1127-00130B)

Epitaxially grown 2D Materials

MoS₂ is, like graphite, a layered structure which can exist in single layer form. Unlike graphene, single-layer MoS₂ has a nonzero bandgap qualifying it for use in 2-dimensional transistors and optoelectronic devices. In these studies we investigate the synthesis and properties of epitaxially grown "perfect" layers of MoS₂. The samples allow for example detailed Angle-resolved Photoemission Spectroscopy studies (collaboration with Ph. Hofmann, Dept of Physics and Astronomy, AU)

Haastrup, M. J.;  Mammen, M. H. R.;  Rodríguez-Fernández, J.; Lauritsen, J. V., Lateral Interfaces between Monolayer MoS2 Edges and Armchair Graphene Nanoribbons on Au(111). ACS Nano 2021, 15 (4), 6699-6708.

Grønborg, S. S.;  Thorarinsdottir, K.;  Kyhl, L.;  Rodriguez-Fernández, J.;  Sanders, C. E.;  Bianchi, M.;  Hofmann, P.;  Miwa, J. A.;  Ulstrup, S.; Lauritsen, J. V., Basal plane oxygen exchange of epitaxial MoS 2 without edge oxidation. 2D Materials 2019, 6 (4), 045013.