Publications
2024
Wanzenböck, Ralf; Buchner, Florian; Kovács, Péter; Madsen, Georg K. H.; Carrete, Jesús
Clinamen2: Functional-style evolutionary optimization in Python for atomistic structure searches
Journal ArticleForthcomingOpen AccessIn: Computer Physics Communications, vol. 297, no. 109065, Forthcoming.
Abstract | Links | BibTeX | Tags: P09
@article{wanzenboeck2024,
title = {Clinamen2: Functional-style evolutionary optimization in Python for atomistic structure searches},
author = {Ralf Wanzenböck and Florian Buchner and Péter Kovács and Georg K. H. Madsen and Jesús Carrete},
doi = {10.1016/j.cpc.2023.109065},
year = {2024},
date = {2024-04-01},
urldate = {2024-04-01},
journal = {Computer Physics Communications},
volume = {297},
number = {109065},
abstract = {Clinamen2 is a versatile functional-style Python implementation of the covariance matrix adaptation evolution strategy (CMA-ES) utilizing Cholesky decomposition. On top of a problem-agnostic core algorithm, the software package offers a suite of utilities and library code enabling applications to important atomistic structure searches. Features include massively distributed computation and the BI-Population restart scheme. This article details the general code structure and introduces examples that illustrate some relevant applications for the materials science and chemistry worlds, including interfacing to density-functional-theory codes and machine-learned surrogate models. The functional design renders the code modular and adaptable, and makes the creation of interfaces to other atomistic software straightforward.},
keywords = {P09},
pubstate = {forthcoming},
tppubtype = {article}
}
2023
Backus, Ellen H. G.; Hosseinpour, Saman; Ramanan, Charusheela; Sun, Shumei; Schlegel, Simon J.; Zelenka, Moritz; Jia, Xiaoyu; Gebhard, Maximilian; Devi, Anjana; Wang, Hai I.; Bonn, Mischa
Journal ArticleOpen AccessIn: Angewandte Chemie - International Edition, no. e202312123, 2023, ISSN: 1521-3773.
Abstract | Links | BibTeX | Tags: P11
@article{Backus2024,
title = {Ultrafast Surface‐Specific Spectroscopy of Water at a Photoexcited TiO2 Model Water‐Splitting Photocatalyst},
author = {Ellen H. G. Backus and Saman Hosseinpour and Charusheela Ramanan and Shumei Sun and Simon J. Schlegel and Moritz Zelenka and Xiaoyu Jia and Maximilian Gebhard and Anjana Devi and Hai I. Wang and Mischa Bonn},
doi = {10.1002/anie.202312123},
issn = {1521-3773},
year = {2023},
date = {2023-11-27},
urldate = {2023-11-27},
journal = {Angewandte Chemie - International Edition},
number = {e202312123},
publisher = {Wiley},
abstract = {A critical step in photocatalytic water dissociation is the hole-mediated oxidation reaction. Molecular-level insights into the mechanism of this complex reaction under realistic conditions with high temporal resolution are highly desirable. Here, we use femtosecond time-resolved, surface-specific vibrational sum frequency generation spectroscopy to study the photo-induced reaction directly at the interface of the photocatalyst TiO_{2} in contact with liquid water at room temperature. Thanks to the inherent surface specificity of the spectroscopic method, we can follow the reaction of solely the interfacial water molecules directly at the interface at timescales on which the reaction takes place. Following the generation of holes at the surface immediately after photoexcitation of the catalyst with UV light, water dissociation occurs on a sub-20 ps timescale. The reaction mechanism is similar at pH 3 and 11. In both cases, we observe the conversion of H_{2}O into Ti−OH groups and the deprotonation of pre-existing Ti−OH groups. This study provides unique experimental insights into the early steps of the photo-induced dissociation processes at the photocatalyst-water interface, relevant to the design of improved photocatalysts.},
keywords = {P11},
pubstate = {published},
tppubtype = {article}
}
Raab, Maximilian; Zeininger, Johannes; Suchorski, Yuri; Genest, Alexander; Weigl, Carla; Rupprechter, Günther
Lanthanum modulated reaction pacemakers on a single catalytic nanoparticle
Journal ArticleOpen AccessIn: Nature Communications, vol. 14, no. 7186, 2023.
Abstract | Links | BibTeX | Tags: P08
@article{Raab2023b,
title = {Lanthanum modulated reaction pacemakers on a single catalytic nanoparticle},
author = {Maximilian Raab and Johannes Zeininger and Yuri Suchorski and Alexander Genest and Carla Weigl and Günther Rupprechter},
doi = {10.1038/s41467-023-43026-3},
year = {2023},
date = {2023-11-08},
urldate = {2023-11-08},
journal = {Nature Communications},
volume = {14},
number = {7186},
abstract = {Promoters are important in catalysis, but the atomistic details of their function and particularly their role in reaction instabilities such as kinetic phase transitions and oscillations are often unknown. Employing hydrogen oxidation as probe reaction, a Rh nanotip for mimicking a single Rh nanoparticle and field electron microscopy for in situ monitoring, we demonstrate a La-mediated local catalytic effect. The oscillatory mode of the reaction provides a tool for studying the interplay between different types of reaction pacemakers, i.e., specific local surface atomic configurations that initiate kinetic transitions. The presence of La shifts the bistable reaction states, changes the oscillation pattern and deactivates one of two pacemaker types for the La-free surface. The observed effects originate from the La-enhanced oxygen activation on the catalyst. The experimental observations are corroborated by micro-kinetic model simulations comprising a system of 25 coupled oscillators.},
keywords = {P08},
pubstate = {published},
tppubtype = {article}
}
Buessler, Martin; Maruyama, Shingo; Zelenka, Moritz; Onishi, Hiroshi; Backus, Ellen H. G.
Journal ArticleOpen AccessIn: Physical Chemistry Chemical Physics, vol. 25, pp. 31471–31480, 2023.
Abstract | Links | BibTeX | Tags: P11
@article{Buessler2023,
title = {Unravelling the interfacial water structure at the photocatalyst strontium titanate by sum frequency generation spectroscopy},
author = {Martin Buessler and Shingo Maruyama and Moritz Zelenka and Hiroshi Onishi and Ellen H. G. Backus},
doi = {https://doi.org/10.1039/D3CP03829G},
year = {2023},
date = {2023-10-31},
urldate = {2023-10-31},
journal = {Physical Chemistry Chemical Physics},
volume = {25},
pages = {31471--31480},
abstract = {The direct conversion of solar energy to hydrogen is considered as a possible method to produce carbon neutral hydrogen fuel. The mechanism of photocatalytic water splitting involves the chemical breakdown of water and re-assembly into hydrogen and oxygen at the interface of a photocatalyst. The selection rules of a suitable material are well established, but the fundamental understanding of the mechanisms, occurring at the interface between the catalyst and the water, remains missing. Using surface specific sum frequency generation spectroscopy, we present here characterisation of the interface between water and the photocatalyst strontium titanate (SrTiO_{3}). We monitor the OH-stretching vibrations present at the interface. Their variations of intensities and frequencies as functions of isotopic dilution, pH and salt concentration provide information about the nature of the hydrogen bonding environment. We observe the presence of water molecules that flip their orientation at pH 5 indicating the point of zero charge of the SrTiO_{3} layer. These water molecules are oriented with their hydrogen away from the surface when the pH of the solutions is below 5 and pointing towards the surface when the pH is higher than 5. Besides, water molecules donating a H-bond to probably surface TiOH groups are observed at all pH.},
keywords = {P11},
pubstate = {published},
tppubtype = {article}
}
Phichairatanaphong, Orrakanya; Yigit, Nevzat; Rupprechter, Günther; Chareonpanich, Metta; Donphai, Waleeporn
Journal ArticleOpen AccessIn: Industrial & Engineering Chemistry Research, vol. 62, iss. 40, pp. 16254–16267, 2023.
Abstract | Links | BibTeX | Tags:
@article{Phichairatanaphong2023,
title = {Highly Efficient Conversion of Greenhouse Gases Using a Quadruple Mixed Oxide-Supported Nickel Catalyst in Reforming Process},
author = {Orrakanya Phichairatanaphong and Nevzat Yigit and Günther Rupprechter and Metta Chareonpanich and Waleeporn Donphai},
doi = {10.1021/acs.iecr.3c02030},
year = {2023},
date = {2023-10-02},
urldate = {2023-10-02},
journal = {Industrial & Engineering Chemistry Research},
volume = {62},
issue = {40},
pages = {16254--16267},
abstract = {The greenhouse gas reduction as well as the utilization of more renewable and clean energy via a dry reforming reaction is of interest. The impact of a CeMgZnAl oxide quad-blend-supported Ni catalyst on performance and anticoking during dry reforming reactions at 700 °C was studied. A high Ce–Mg/Zn ratio, as seen in the CeMg_{0.5}ZnAl-supported nickel catalyst, enhances lattice oxygen, and the presence of strong basic sites, along with the creation of the carbonate intermediate species, is accompanied by the production of gaseous CO through a gasification reaction between the carbon species and Ni-CO_{ads-lin} site. The phenomena caused the outstanding performance of the Ni/CeMg_{0.5}ZnAl catalyst─CH_{4} (84%), CO_{2} (83%) conversions, and the H_{2}/CO (0.80) ratio; moreover, its activity was also stable throughout 30 h.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Redondo, Jesús; Michalička, Jan; Kraushofer, Florian; Franceschi, Giada; Šmid, Břetislav; Kumar, Nishant; Man, Ondřej; Blatnik, Matthias; Wrana, Dominik; Mallada, Benjamin; Švec, Martin; Parkinson, Gareth S.; Setvin, Martin; Riva, Michele; Diebold, Ulrike; Čechal, Jan
Journal ArticleOpen AccessIn: Advanced Materials Interfaces, no. 2300602, 2023.
Abstract | Links | BibTeX | Tags: P02, P04
@article{Redondo2023,
title = {Hematite α-Fe_{2}O_{3}(0001) in Top and Side View: Resolving Long-Standing Controversies about Its Surface Structure},
author = {Jesús Redondo and Jan Michalička and Florian Kraushofer and Giada Franceschi and Břetislav Šmid and Nishant Kumar and Ondřej Man and Matthias Blatnik and Dominik Wrana and Benjamin Mallada and Martin Švec and Gareth S. Parkinson and Martin Setvin and Michele Riva and Ulrike Diebold and Jan Čechal},
doi = {10.1002/admi.202300602},
year = {2023},
date = {2023-08-18},
urldate = {2023-08-18},
journal = {Advanced Materials Interfaces},
number = {2300602},
publisher = {Wiley},
abstract = {Hematite is a common iron oxide found in nature, and the α-Fe_{2}O_{3}(0001) plane is prevalent on the nanomaterial utilized in photo- and electrocatalytic applications. The atomic-scale structure of the surface remains controversial despite decades of study, partly because it depends on sample history as well as the preparation conditions. Here, a comprehensive study is performed using an arsenal of surface techniques (non-contact atomic force microscopy, scanning tunneling microscopy, low-energy electron diffraction, and X-ray photoemission spectroscopy) complemented by analyses of the near surface region by high-resolution transmission electron microscopy and electron energy loss spectroscopy. The results show that the so-called “bi-phase” termination forms even under highly oxidizing conditions; a (1 × 1) surface is only observed in the presence of impurities. Furthermore, it is shown that the biphase is actually a continuous layer distorted due to a mismatch with the subsurface layers, and thus not the proposed mixture of FeO(111) and α-Fe_{2}O_{3}(0001) phases. Overall, the results show how combining surface and cross-sectional imaging provides a full view that can be essential for understanding the role of the near-surface region on oxide surface properties.},
keywords = {P02, P04},
pubstate = {published},
tppubtype = {article}
}
Tangpakonsab, Parinya; Genest, Alexander; Yang, Jingxia; Meral, Ali; Zou, Bingjie; Yigit, Nevzat; Schwarz, Sabine; Rupprechter, Günther
Kinetic and Computational Studies of CO Oxidation and PROX on Cu/CeO2 Nanospheres
Journal ArticleOpen AccessIn: Topics in Catalysis, vol. 66, pp. 1129–1142, 2023.
Abstract | Links | BibTeX | Tags: P08
@article{Tangpakonsab2023,
title = {Kinetic and Computational Studies of CO Oxidation and PROX on Cu/CeO_{2} Nanospheres},
author = {Parinya Tangpakonsab and Alexander Genest and Jingxia Yang and Ali Meral and Bingjie Zou and Nevzat Yigit and Sabine Schwarz and Günther Rupprechter},
doi = {10.1007/s11244-023-01848-x},
year = {2023},
date = {2023-07-31},
journal = {Topics in Catalysis},
volume = {66},
pages = {1129--1142},
publisher = {Springer Science and Business Media LLC},
abstract = {As supported CuO is well-known for low temperature activity, CuO/CeO_{2} nanosphere catalysts were synthesized and tested for CO oxidation and preferential oxidation of CO (PROX) in excess H_{2}. For the first reaction, ignition was observed at 95 °C, whereas selective PROX occurred in a temperature window from 50 to 100 °C. The catalytic performance was independent of the initial oxidation state of the catalyst (CuO vs. Cu^{0}), suggesting that the same active phase is formed under reaction conditions. Density functional modeling was applied to elucidate the intermediate steps of CO oxidation, as well as those of the comparably less feasible H_{2} transformation. In the simulations, various Cu and vacancy sites were probed as reactive centers enabling specific pathways.},
keywords = {P08},
pubstate = {published},
tppubtype = {article}
}
Asencios, Yvan J. O.; Yigit, Nevzat; Wicht, Thomas; Stöger-Pollach, Michael; Lucrédio, Alessandra F.; Marcos, Francielle C. F.; Assaf, Elisabete M.; Rupprechter, Günther
Partial Oxidation of Bio-methane over Nickel Supported on MgO–ZrO2 Solid Solutions
Journal ArticleOpen AccessIn: Topics in Catalysis, vol. 66, pp. 1539–1552, 2023.
Abstract | Links | BibTeX | Tags: P08
@article{Asencios2023,
title = {Partial Oxidation of Bio-methane over Nickel Supported on MgO–ZrO_{2} Solid Solutions},
author = {Yvan J. O. Asencios and Nevzat Yigit and Thomas Wicht and Michael Stöger-Pollach and Alessandra F. Lucrédio and Francielle C. F. Marcos and Elisabete M. Assaf and Günther Rupprechter},
doi = {10.1007/s11244-023-01822-7},
year = {2023},
date = {2023-05-24},
urldate = {2023-05-24},
journal = {Topics in Catalysis},
volume = {66},
pages = {1539--1552},
publisher = {Springer Science and Business Media LLC},
abstract = {Syngas can be produced from biomethane via Partial Oxidation of Methane (POM), being an attractive route since it is ecofriendly and sustainable. In this work, catalysts of Ni supported on MgO–ZrO_{2} solid solutions, prepared by a one-step polymerization method, were characterized by HRTEM/EDX, XRD, XPS, H_{2}-TPR, and in situ XRD. All catalysts, including Ni/ZrO_{2} and Ni/MgO as reference, were tested for POM (CH_{4}:O_{2} molar ratio 2, 750 ºC, 1 atm). NiO/MgO/ZrO_{2} contained two solid-solutions, MgO–ZrO2 and NiO-MgO, as revealed by XRD and XPS. Ni (30 wt%) supported on MgO–ZrO_{2} solid solution exhibited high methane conversion and hydrogen selectivity. However, depending on the MgO amount (0, 4, 20, 40, 100 molar percent) major differences in NiO reducibility, growth of Ni^{0} crystallite size during H_{2} reduction and POM, and in carbon deposition rates were observed. Interestingly, catalysts with lower MgO content achieved the highest CH_{4} conversion (~ 95%), high selectivity to H_{2} (1.7) and CO (0.8), and low carbon deposition rates (0.024 g_{carbon} g_{cat}^{−1} h^{−1}) with Ni_{4}MgZr (4 mol% MgO) turning out to be the best catalyst. In situ XRD during POM indicated metallic Ni nanoparticles (average crystallite size of 31 nm), supported by MgO–ZrO_{2} solid solution, with small amounts of NiO–MgO being present as well. The presence of MgO also influenced the morphology of the carbon deposits, leading to filaments instead of amorphous carbon. A combustion-reforming mechanism is suggested and using a MgO–ZrO_{2} solid solution support strongly improves catalytic performance, which is attributed to effective O_{2}, CO_{2} and H_{2}O activation at the Ni/MgO–ZrO_{2} interface.},
keywords = {P08},
pubstate = {published},
tppubtype = {article}
}
Hijes, Pablo Montero; Romano, Salvatore; Gorfer, Alexander; Dellago, Christoph
The kinetics of the ice–water interface from ab initio machine learning simulations
Journal ArticleOpen AccessIn: The Journal of Chemical Physics, vol. 158, no. 20, pp. 204706, 2023.
Abstract | Links | BibTeX | Tags: P12
@article{Hijes2023a,
title = {The kinetics of the ice–water interface from \textit{ab initio} machine learning simulations},
author = {Pablo Montero Hijes and Salvatore Romano and Alexander Gorfer and Christoph Dellago},
doi = {10.1063/5.0151011},
year = {2023},
date = {2023-05-24},
urldate = {2023-05-24},
journal = {The Journal of Chemical Physics},
volume = {158},
number = {20},
pages = {204706},
publisher = {AIP Publishing},
abstract = {Molecular simulations employing empirical force fields have provided valuable knowledge about the ice growth process in the past decade. The development of novel computational techniques allows us to study this process, which requires long simulations of relatively large systems, with ab initio accuracy. In this work, we use a neural-network potential for water trained on the revised Perdew–Burke–Ernzerhof functional to describe the kinetics of the ice–water interface. We study both ice melting and growth processes. Our results for the ice growth rate are in reasonable agreement with previous experiments and simulations. We find that the kinetics of ice melting presents a different behavior (monotonic) than that of ice growth (non-monotonic). In particular, a maximum ice growth rate of 6.5 Å/ns is found at 14 K of supercooling. The effect of the surface structure is explored by investigating the basal and primary and secondary prismatic facets. We use the Wilson–Frenkel relation to explain these results in terms of the mobility of molecules and the thermodynamic driving force. Moreover, we study the effect of pressure by complementing the standard isobar with simulations at a negative pressure (−1000 bar) and at a high pressure (2000 bar). We find that prismatic facets grow faster than the basal one and that pressure does not play an important role when the speed of the interface is considered as a function of the difference between the melting temperature and the actual one, i.e., to the degree of either supercooling or overheating.},
keywords = {P12},
pubstate = {published},
tppubtype = {article}
}
Winkler, Philipp; Raab, Maximilian; Zeininger, Johannes; Rois, Lea M.; Suchorski, Yuri; Stöger-Pollach, Michael; Amati, Matteo; Parmar, Rahul; Gregoratti, Luca; Rupprechter, Günther
Journal ArticleOpen AccessIn: ACS Catalysis, vol. 13, no. 11, pp. 7650–7660, 2023.
Abstract | Links | BibTeX | Tags: P08
@article{doi:10.1021/acscatal.3c00060,
title = {Imaging Interface and Particle Size Effects by In Situ Correlative Microscopy of a Catalytic Reaction},
author = {Philipp Winkler and Maximilian Raab and Johannes Zeininger and Lea M. Rois and Yuri Suchorski and Michael Stöger-Pollach and Matteo Amati and Rahul Parmar and Luca Gregoratti and Günther Rupprechter},
doi = {10.1021/acscatal.3c00060},
year = {2023},
date = {2023-05-23},
urldate = {2023-01-01},
journal = {ACS Catalysis},
volume = {13},
number = {11},
pages = {7650--7660},
abstract = {The catalytic behavior of Rh particles supported by three different materials (Rh, Au, and ZrO_{2_{) in H_{2_{ oxidation has been studied in situ by correlative photoemission electron microscopy (PEEM) and scanning photoemission electron microscopy (SPEM). Kinetic transitions between the inactive and active steady states were monitored, and self-sustaining oscillations on supported Rh particles were observed. Catalytic performance differed depending on the support and Rh particle size. Oscillations varied from particle size-independent (Rh/Rh) via size-dependent (Rh/ZrO_{2_{) to fully inhibited (Rh/Au). For Rh/Au, the formation of a surface alloy induced such effects, whereas for Rh/ZrO_{2_{, the formation of substoichiometric Zr oxides on the Rh surface, enhanced oxygen bonding, Rh-oxidation, and hydrogen spillover onto the ZrO_{2_{ support were held responsible. The experimental observations were complemented by micro-kinetic simulations, based on variations of hydrogen adsorption and oxygen binding. The results demonstrate how correlative in situ surface microscopy enables linking of the local structure, composition, and catalytic performance.},
keywords = {P08},
pubstate = {published},
tppubtype = {article}
}