A multitechnique study of C₂H₄ adsorption on Fe₃O₄(001)

L. Puntscher, P. Sombut, C. Wang, M. Ulreich, J. Pavelec, A. Rafsanjani-Abbasi, M. Meier, A. Lagin, M. Setvin, U. Diebold, C. Franchini, M. Schmid, G. S. Parkinson

Institut für Angewandte Physik, TU Wien, 1040 Wien, Austria
Faculty of Physics, Center for Computational Materials Science, University of Vienna, 1090 Wien, Austria
Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, Prague 18000, Czech Republic
Dipartimento di Fisica e Astronomia, Università di Bologna, 40126 Bologna, Italy

J. Phys. Chem. C 127 (2023) 18378-18388

The adsorption/desorption of ethene (C₂H₄), also commonly known as ethylene, on Fe₃O₄(001) was studied under ultrahigh vacuum conditions using temperature-programmed desorption (TPD), scanning tunneling microscopy, X-ray photoelectron spectroscopy, and density functional theory (DFT)-based computations. To interpret the TPD data, we have employed a new analysis method based on equilibrium thermodynamics. C₂H4 adsorbs intact at all coverages and interacts most strongly with surface defects such as antiphase domain boundaries and Fe adatoms. On the regular surface, C₂H₄ binds atop surface Fe sites up to a coverage of 2 molecules per (√2×√2)R45° unit cell, with every second Fe occupied. A desorption energy of 0.36 eV is determined by analysis of the TPD spectra at this coverage, which is approximately 0.1-0.2 eV lower than the value calculated by DFT + U with van der Waals corrections. Additional molecules are accommodated in between the Fe rows. These are stabilized by attractive interactions with the molecules adsorbed at Fe sites. The total capacity of the surface for C₂H₄ adsorption is found to be close to 4 molecules per (√2×√2)R45° unit cell.

Corresponding author: Gareth S. Parkinson (parkinson).

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