Program Day 1

Real time in-situ microscopy imaging of surface structure and atom dynamics of heterogeneous catalysts is an important step for understanding reaction mechanisms [1]. Here, using in-situ environmental transmission electron microscopy (ETEM), we directly visualize surface atom dynamics at manganite perovskite catalysts surfaces for oxygen evolution reaction (OER), which are ≥ 20 times faster in water than in other ambients [2]. Comparing (001) surfaces of La0.6Sr0.4MnO3 and Pr0.67Ca0.33MnO3 with similar initial manganese valence state and OER activity, but very different OER stability, allows us to distinguish between reversible surface adatom dynamics and irreversible surface defect chemical reactions [2,3,4]. We observe enhanced reversible manganese adatom dynamics due to partial solvation in adsorbed water for the highly active and stable La0.6Sr0.4MnO3 system, suggesting that aspects of homogeneous catalysis must be included for understanding the OER mechanism in heterogeneous catalysis. ______________________________________________________________________ [1] S. Raabe, et al, Adv. Funct. Mat., 22 (2012) 3378. [2] G. Lole et al, Communication Materials, accepted for publication [3] D. Mierwaldt et al., Adv. Sustainable Syst. 1 (2017) 1700109. [4] V. Roddatis et al. Catalysts 9, 751 (2019).

A lot of progress has been made in recent years in the development of atomistic potentials employing machine learning (ML) [1]. ML potentials rely on simple but very flexible functional forms and the topology of the potential-energy surface (PES) is “learned” by adjusting a number of parameters with the aim to reproduce a set of reference electronic structure data as accurately as possible. Due to this bias-free construction they are applicable to a wide range of systems without changes in their functional form, and a very high accuracy close to the underlying first-principles data can be obtained in large-scale simulations. One of the most important classes of ML potentials are high-dimensional neural network potentials (HDNNP) [2,3]. In this talk HDNNPs will be used to construct the PES of lithium manganese oxides LixMn2O4 (0<x<2), an important material in lithium ion batteries. This is the first time a ML potential is developed for a system containing a transition metal in different oxidation states. The HDNNP is constructed using reference data from density functional theory (DFT) calculations employing the local PBE0r hybrid exchange correlation functional [4], which provides an accurate description of this material [5]. We demonstrate that the HDNNP is able to provide a wide range of properties in excellent agreement with DFT and experimental data, while simulations of much larger systems are possible providing access to properties beyond the scope of electronic structure methods. ____________________________________________________________________ [1] J. Behler, J. Chem. Phys. 145, 170901 (2016). [2] J. Behler, M. Parrinello, Phys. Rev. Lett. 98, 146401 (2007). [3] J. Behler, Angew. Chem. Int. Ed. 56, 12828 (2017). [4] M. Sotoudeh, S. Rajpurohit, P. Blöchl, D. Mierwaldt, J. Norpoth, V. Roddatis, S. Mildner, B. Kressdorf, B. Ifland, and C. Jooss, Phys. Rev. B 95, 235150 (2017). [5] M. Eckhoff, P. E. Blöchl, J. Behler, Phys. Rev. B. 101, 205113 (2020).

CATALIGHT addresses fundamental challenges in the design of photocatalytically active materials for solar energy conversion. Inspired by the design principles of natural photosynthesis, CATALIGHT will provide fundamental insights into the performance of molecular photocatalysts[1,2] embedded in functional and hierarchically structured soft matter materials.[3,4] To this end, general synthetic strategies are developed to tune the reactivity of molecular light-absorbers and catalysts.[5,6] Complementary synthetic routes will be established to access functional polymeric matrices for the site-specific binding of the molecular building blocks.[3,4] In addition, synergistic reactivity and stability control by tuning the molecule-matrix interactions will become possible. Experimental and theoretical analyses across multiple length- and timescales will be used to rationalize photochemical reactivity[1,2,5,6] and to understand new effects arising from embedding such components within a suitable matrix. Such effects will lead to novel material properties, e.g. materials capable of self-regulating their photocatalytic activity or materials where photocatalytic activity can be repaired both on a molecular and material level. CATALIGHT will lead to new paradigms, which break down the current boundaries between the realms of molecule-based reactivity and bottom-up material design. This will result in fundamentally new, knowledge-guided concepts for light-driven productive chemistry in hybrid materials – opening new research opportunities for chemistry, biology and materials science. ______________________________________________________________________ [1] L. Zedler, A.K. Mengele, K.M. Ziems, Y. Zhang, M. Wächtler, S. Gräfe, T. Pascher, S. Rau, S. Kupfer, B. Dietzek, Angew. Chem. Int. Ed. 58, 13140–13148 (2019). [2] I. Krivtsov, D. Mitoraj, C. Adler, M. Ilkaeva, M. Sardo, L. Mafra, C. Neumann, A. Turchanin, C. Li, B. Dietzek, R. Leiter, J. Biskupek, U. Kaiser, C. Im, B. Kirchhoff, T. Jacob, R. Beranek, Angew. Chem. Int. Ed. 59, 487–495 (2020). [3] I. Romanenko, M. Lechner, F. Wendler, C Hörenz, C. Streb, F.H. Schacher, J. Mat. Chem. A 5 , 15789–15796 (2017). [4] N. Hannewald, P. Winterwerber, S. Zechel, D. Y. W. Ng, M. D. Hager, T. Weil, U. S. Schubert, Angew. Chem. Int. Ed. (2020), accepted manuscript https://doi.org/10.1002/anie.202005907. [5] Y. Luo, S. Maloul, M. Wächtler, U.S. Schubert, A. Winter, C. Streb, B. Dietzek, Chem. Commun. (2020), accepted manuscript DOI 10.1039/D0CC04509H. [6] D. Gao, I. Trentin, L. Schwiedrzik, L. González, C. Streb, Molecules 25, 157 (2020).

The CataLight Project Area A develops the molecular components used in CataLight for light-absorption, charge-separation and catalytic turnover, and develops concepts to enable their soft matter integration. Within this presentation, we will present design concepts for molecular photosensitizers based on metal complexes and organic chromophores[1] and molecular catalysts based on metal complexes and metal chalcogenide clusters.[2] In addition, we will describe linkage strategies to develop robust photosensitizer-catalyst dyads. In the first part of the presentation, we will provide an overview of the synthetic concepts and resulting materials classes used within CataLight, while the second part of the presentation provides more detailed discussions of recent studies where the photochemistry and photophysics of model systems have been studied in detail,[3,4,5] e.g. using time resolved in situ methods. We will illustrate how insights gained from these studies allows us to rationalize reactivity, understand stability limitations and enables us to suggest design routes to advanced molecular components for light-driven catalysis. ______________________________________________________________________ [1] R. Staehle, C. Reichardt, J. Popp, D. Sorsche, L. Petermann, K. Kastner, C. Streb, B. Dietzek, S. Rau, Eur. J. Inorg. Chem. 2015, 3932–3939 (2015). [2] S. Schönweiz, M. Heiland, M. Anjass, T. Jacob, S. Rau, C. Streb, Chem. Eur. J. 23, 15370–15376 (2017). [3] Y. Luo, S. Maloul, S. Schönweiz, M. Wächtler, C. Streb, B. Dietzek, Chem. – A Eur. J. 26, 8045–8052 (2020). [4] Y. Luo, S. Maloul, M. Wächtler, U.S. Schubert, A. Winter, C. Streb, B. Dietzek, Chem. Commun. (2020), accepted manuscript DOI 10.1039/D0CC04509H. [5] L. Zedler, A.K. Mengele, K.M. Ziems, Y. Zhang, M. Wächtler, S. Gräfe, T. Pascher, S. Rau, S. Kupfer, B. Dietzek, Angew. Chem. Int. Ed. 58, 13140–13148 (2019).

All speakers of the session can be asked more specific questions in individual group chats. Please join the speaker of your choice at the "Meet-the-speaker table".