Electronic Structure at the Liquid/Solid Interface

In our research, we plan to establish computational strategies, and improve available methodologies to enable the investigations of structural and electronic rearrangements of reactive molecules in solutions and molecular assemblies at liquid/solid interface. To this purpose, we will design models of the systems under study, simulate the structural evolution under specific conditions (thermodinamic and electrochemical), and characterise the relevant electronic properties.
We investigate transient electronic structure changes and hydrogen bond dynamics along oxidoreduction mechanisms in aqueous solutions[1]. We combine advanced sampling methods to explore free energy surfaces and determine reaction mechanisms, with the characterisation of the intermediates by means of X-ray absorption spectroscopy. The latter is used as local probe of both, the charge-density changes at the proton donating group and the coupled hydrogen-bond dynamics, before, during and after the proton transfer event.
We also study processes occurring at hetero junctions composed of molecular catalysts or photosensitisers adsorbed at metal or metal-oxide surfaces[2][3]. In this field there are many aspects that need to be considered, like the structural features of the surfaces, e.g., defects or reconstructions, the assembly of molecular layers, the positioning of band edges, the formation of dipole layers (electric double layers), the functionalisation by activation of reaction processes, the dynamics of the solvent at the interface.
In order to shed light on the fundamental aspects of the electronic and structural phenomena related to redox processes in homogeneous solution or at functionalised electrochemical interfaces, we employ advanced computational methodologies based on density functional theory (DFT) and ab initio molecular dynamics (AIMD). Often we model systems taking inspiration from the work of our experimental partners who, among other techniques, employ near edge X-ray absorption spectroscopy (NEXAS) and X-ray photoelectron spectroscopy (XPS) to determine ex-situ, as well as under operating conditions the composition, structure, chemical environment, and function of the systems of interest. Therefore we develop computational work flows to better combine our DFT and AIMD investigation tools with the methods for the simulation of core level spectroscopy. This complement other approaches that we usually apply for the study of complex materials, thus contributing to the interpretation of experimental results: optimisation of structures, transition pathways, and sampling of configurations of adsorbates and co-adsorbates (superstructures)[4], simulation of STM and AFM images[5], calculation of vibrational spectra[6], characterisation of electronic properties at the interface, e.g., by imaging of molecular orbitals or estimating surface dipoles and charge transfer.

1. G. Smolentsev, M. A. Soldatov, B. Probst, C. Bachmann, N. Azzaroli, R. Alberto, M. Nachtegaal, and J. A. van Bokhoven; ChemSusChem 11, 3087 (2018).
2. D. Leuenberger, W. D. Zabka, O. F. R. Shah, S. Schnidrig, B. Probst, R. Alberto, and J. Osterwalder; Nano Lett 17, 6620 (2017).
3. Wick-Joliat, R.; Musso, T.; Prabhakar, R. R.; Loeckinger, J.; Siol, S.; Cui, W.; Svery, L.; Moehl, T.; Suh, J.; Hutter, J.; Iannuzzi, M.; Tilley, S. D.; Energy and Environmental Science, (2019).
4. G. Mette, D. Sutter, Y. Gurdal, S. Schnidrig, B. Probst, M. Iannuzzi, J. Hutter, R. Alberto, and J. Osterwalder; Nanoscale (2016).
5. M. Iannuzzi, F. Tran, R.Widmer, T. Dienel, K. Radican, Y. Ding, J. Hutter, and O. Gröning;Phys Chem Chem Phys 16, 12374 (2014).
6. J. Lan, J. Hutter, and M. Iannuzzi; J. Phys. Chem. C 122, 24068 (2018).