Publications

@article{Pollitt_2025a,

title = {Engineering Catalytic Efficiency by Thiolate-Protected Trimetallic (Cu, Pd, Au) Nanoclusters: Single-Atom Alloy Catalysts for Water–Gas Shift},

author = {Stephan Pollitt and Thomas Haunold and Sakiat Hossain and Gereon Behrendt and Michael Stöger-Pollach and Tokuhisa Kawawaki and Noelia Barrabés and Malte Behrens and Yuichi Negishi and Günther Rupprechter},

doi = {10.1021/acscatal.5c04165},

year  = {2025},

date = {2025-08-22},

journal = {ACS Catalysis},

volume = {15},

pages = {15459–15474},

abstract = {The “crude oil exodus” and energy transition will finally hinge on the availability of hydrogen. Catalytic processes like the water–gas shift (WGS) reaction may significantly contribute to its production and become crucial for utilizing alternative feedstocks. This work demonstrates how thiolate-protected gold nanoclusters can be employed as precursors for single-atom alloy (SAA) catalysts. The clusters serve as carriers of heteroatom dopants (Cu, Pd) while precisely maintaining 25 metal atoms per cluster (<1 nm). Using the 2PET ligand during synthesis led to high yield and cluster stability, but ligand exchange was required to link clusters to a ZnO support efficiently. Introducing pMBA as a ligand enabled a homogeneous cluster distribution on the ZnO surface, creating a well-defined catalyst with dual functionality. This SAA catalyst, outperforming a Cu/ZnO/Al_{2}O_{3} benchmark in WGS, may get industrial relevance when upscaled while still serving as a well-defined model system in catalysis. Thereby, it bridges the gap between practical applications and fundamental research. Pre- and postreaction analysis by XPS proved the presence of the dopants in the catalysts in the expected stoichiometry, showed changes in the electronic structures, but also revealed sulfur migration from the clusters/ligands to the support, forming ZnS. Furthermore, XPS unveiled a pretreatment-induced SMSI decoration effect, stabilizing the small particles during catalysis. (S)TEM indicated a homogeneous cluster distribution on ZnO after synthesis and proved small particle sizes throughout the experiments. In situ DRIFTS confirmed the accessibility of the dopant atoms by the reactant CO and also detected adsorbed byproducts. The precise size and doping control of thiolate-protected SAA nanoclusters, together with their catalytic performance, demonstrate the potential for targeted future investigations in a wide range of industrial applications.},

keywords = {P08},

pubstate = {published},

tppubtype = {article}

}

@article{Sidorowicz_2025a,

title = {Influence of MXene and TiO_{2} on the Performance of Microalgae-Derived Ru-Based Catalysts for CO_{2} Hydrogenation to Methane},

author = {Agnieszka Sidorowicz and Thomas Wicht and Michael Stöger-Pollach and Roberta Licheri and Giacomo Cao and Alessandro Concas and Günther Rupprechter},

doi = {10.1021/acscatal.5c04285},

year  = {2025},

date = {2025-08-19},

journal = {ACS Catalysis},

volume = {15},

pages = {15261–15278},

abstract = {Controlling the selectivity of CO_{2} hydrogenation to produce value-added fuels and chemicals is an actual challenge in catalysis research. The exact mechanisms underlying selectivity control often remain poorly understood, slowing the design of more efficient catalysts. In this study, we investigated RuO_{2} nanoparticles supported on MXene or TiO_{2} for CO_{2} hydrogenation at atmospheric pressure. Microalgal extracts were incorporated in the synthesis to explore their influence on catalyst properties, such as surface area, morphology, and elemental distribution. Although lower surface area and less uniform RuO_{2} dispersion were observed on MXenes than on TiO_{2}, after reductive pretreatment Ru/MXene exhibited superior catalytic activity, demonstrating that its unique textural properties and active site availability compensated for the lower surface area. A reducibility study revealed that MXene-supported catalysts undergo a more complex reduction process than those with TiO_{2} as the support. Additionally, bridge adsorption sites on MXene likely contributed to the enhanced CO_{2} hydrogenation activity, whereas TiO_{2} seemed to present a twin CO binding environment. Higher Ru loading on MXene increased the methane selectivity and conversion, whereas lower loading favored CO formation, highlighting the importance of optimizing catalyst loading. Operando diffuse reflectance infrared Fourier transform spectroscopy analysis revealed the critical role of methoxy intermediates in affecting the catalytic pathway, suggesting the potential for tuning synthesis conditions to improve yields. A partial encapsulation of Ru on MXene enhances the catalytic performance, while the stronger SMSI effect on TiO_{2} leads to complete encapsulation, reducing the catalytic efficiency. The findings underscore the promise of MXene as a support material for metal catalysts in CO_{2} hydrogenation toward environmentally friendly fuel production.},

keywords = {P08},

pubstate = {published},

tppubtype = {article}

}

@article{Tampieri_2025a,

title = {Phase-Dependent Catalytic Oxidation of Secondary Alcohols Using Spinel Cobaltite Catalysts Under Liquid- and Gas-Phase Flow Conditions},

author = {Alberto Tampieri and Federica Romanelli and Michael Pittenauer and Thomas Lederer and Karin Föttinger},

doi = {10.1002/cctc.202500778},

year  = {2025},

date = {2025-08-15},

urldate = {2025-08-15},

journal = {ChemCatChem},

pages = {e00778},

abstract = {Selective partial oxidation of alcohols is a straightforward synthetic pathway to access aldehydes and ketones, important building blocks for the chemical industry. The catalytic oxidation of higher secondary alcohols is challenging, which entails the need for low temperatures to preserve the selectivity or, in practice, the use of a liquid phase. In this work, we explored the applicability of Co-based spinel oxides as alternatives to noble metal-based supported catalysts for the oxidation of alcohols such as 2-butanol and 2-propanol. We developed a small-scale tri-phasic process in flow operable for consecutive weeks and using technical grade porous catalysts, en route to more industrially-relevant systems, focusing on the practical aspects of the process. Co_{3}O_{4}, MnCo_{2}O_{4}, NiCo_{2}O_{4}, ZnCo_{2}O_{4}, and CoFe_{2}O_{4} were synthesized by combustion and characterized by XRD, SEM, EDX, XPS, N_{2}-physisorption, and FT-IR spectroscopy. The same catalysts were tested in batch in the liquid phase to explore the impact of the reaction conditions on the reaction outcome and to rule out flow-specific effects. Gas phase reactions unveiled the different behavior of the same catalysts in different environments, highlighting phase-specific effects such as the beneficial (liquid phase) versus inhibiting (gas phase) impact of Mn doping.},

keywords = {P10},

pubstate = {published},

tppubtype = {article}

}

@article{Amin_2025a,

title = {Switchable Behavior of Ru–TiO_{2} Catalysts in HMF Conversion},

author = {Babar Amin and Jaroslav Aubrecht and Oleg Kikhtyanin and Evgeniya Grechman and Gustavo Andrade Silva Alves and Alberto Tampieri and Karin Föttinger and Marcin Jędrzejczyk and Agnieszka M. Ruppert and Francisco Ruiz-Zepeda and David Kubička},

doi = {10.1021/acssuschemeng.5c04908},

year  = {2025},

date = {2025-07-17},

urldate = {2025-07-17},

journal = {ACS Sustainable Chemistry & Engineering},

volume = {13},

issue = {29},

pages = {11652-11667},

abstract = {5-Hydroxymethylfurfural (HMF) is a platform chemical that can be catalytically valorized into high-value-added chemicals. Despite the extensive use of titania-supported metal catalysts in HMF conversion, the specific influence of the TiO_{2} support on the formation of metal active sites, their dispersion, and their role in HMF conversion is not addressed sufficiently. In this work, we investigated five TiO_{2} supports, four anatase- and one rutile-dominant, varying in surface area and acidity, which were loaded with 1 wt % Ru using RuCl_{3}. Characterization results revealed that the Ru environment, charge distribution, and surface features (transition from Ru–Cl to Ru–O species) varied depending on the TiO_{2} support used. Their catalytic performance was assessed in HMF hydrogenation. Despite identical Ru loadings, the Ru/TiO_{2} catalysts exhibited remarkably different catalytic activities and selectivity. High-surface-area anatase TiO_{2} led to the formation of smaller Ru particles and supported the conversion of HMF to 5-methylfurfural. In contrast, lower surface area anatase and rutile supports favored the formation of larger Ru particles and redirected the reaction course from 5-MF toward the hydrogenation route, yielding primarily 2,5-bis(hydroxymethyl)furan. This study revealed the switchable behavior of Ru/TiO_{2} catalysts and exposed the critical role of TiO_{2} structural and morphological features for reaction pathways in HMF valorization over Ru/TiO_{2}. These insights provide a refined framework for the rational design of oxide-supported catalysts tailored for the selective conversion of biomass.},

keywords = {P10},

pubstate = {published},

tppubtype = {article}

}

@article{Kender_2025a,

title = {Automatic Determination of Quasicrystalline Patterns from Microscopy Images},

author = {Tano Kim Kender and Marco Corrias and Cesare Franchini},

doi = {10.1002/aidi.202500043},

year  = {2025},

date = {2025-07-09},

journal = {Advanced Intelligent Discovery},

pages = {202500043},

abstract = {Quasicrystals are aperiodically ordered solids that exhibit long-range order without translational periodicity, bridging the gap between crystalline and amorphous materials. Due to their lack of translational periodicity, information on atomic arrangements in quasicrystals cannot be extracted by current crystalline lattice recognition softwares. This work introduces a method to automatically detect quasicrystalline atomic arrangements and tiling using image feature recognition coupled with machine learning, tailored toward quasiperiodic tilings with 8-, 10-, and 12-fold rotational symmetry. Atom positions are identified using clustering of feature descriptors. Subsequent nearest-neighbor analysis and border following on the interatomic connections deliver the tiling. Support vector machines further increase the quality of the results, reaching an accuracy consistent with those reported in the literature. A statistical analysis of the results is performed. The code is now part of the open-source package AiSurf.},

keywords = {P07},

pubstate = {published},

tppubtype = {article}

}

@article{Sringam_2025a,

title = {Direct conversion of methane to value-added hydrocarbons using alkali metal-promoted cobalt catalysts},

author = {Sarannuch Sringam and Punyanut Thansiriphat and Thongthai Witoon and Waleeporn Donphai and Metta Chareonpanich and Chularat Wattanakit and Hiesang Sohn and Nevzat Yigit and Günther Rupprechter and Anusorn Seubsai},

doi = {10.1039/D5RA02408K},

year  = {2025},

date = {2025-07-07},

journal = {RSC Advances},

volume = {15},

issue = {28},

pages = {23103-23114},

abstract = {The oxidative coupling of methane (OCM) is a promising pathway for directly converting methane into higher hydrocarbons (C_{2+}). This research investigated the influence of alkali metal promoters (Li, Na, K, or Rb) on Co/Al_{2}O_{3} catalysts prepared based on incipient wetness impregnation for the OCM reaction. The catalyst investigations demonstrated that the catalysts promoted with K and Rb had superior performance, with the 4.6K–Co/Al_{2}O_{3} catalyst achieving a maximum C_{2+} yield of 8.1%, C_{2+} selectivity of 24.0%, and CH_{4} conversion of 32.1% at 640 °C. Catalyst characterization, based on XRD, HR-TEM, BET, XPS, CO_{2}-TPD, and H_{2}-TPR analyses, revealed the structural and physicochemical properties responsible for the enhanced catalytic activity. Specifically, K and Rb promoters increased surface basicity and enhanced the electron density of active sites, thereby promoting selective methane activation. In-situ DRIFTS and mechanistic studies highlighted the role of reactive oxygen species in promoting C_{2+} hydrocarbon formation. These results should position K–Co/Al_{2}O_{3} as a promising catalyst for OCM and provide valuable guidance for designing more efficient catalytic systems for methane utilization.},

keywords = {P08},

pubstate = {published},

tppubtype = {article}

}

@article{Phichairatanaphong_2025a,

title = {Calcium-Functionalized MgCeAl-Supported Nickel Catalysts for Enhancing Syngas Production via Dry Reforming},

author = {Orrakanya Phichairatanaphong and Nevzat Yigit and Thomas Wicht and Sanchai Kuboon and Thongthai Witoon and Günther Rupprechter and Metta Chareonpanich and Waleeporn Donphai},

doi = {10.1021/acs.iecr.5c00941},

year  = {2025},

date = {2025-06-18},

urldate = {2025-06-18},

journal = {Industrial & Engineering Chemistry Research},

volume = {64},

issue = {24},

pages = {11782–11793},

abstract = {The dry reforming reaction offers a promising pathway to transform CO_{2} and CH_{4} gases into H_{2} and CO, which serve as vital reactants and fuel gases in various industrial chemical processes. This research focused on the modification of Ni-based catalysts with alkaline earth metal for a dry reforming reaction. Nickel impregnated into mixed MgCeAl (MCA) oxide supports, tailored with calcium (Ca), was fabricated through a soft template-assisted coprecipitation technique, employing cetyltrimethylammonium chloride (CTAC) as the template. The calcium modification of MCA oxides supporting the nickel catalyst augmented the reducibility of nickel and intensified the interaction between nickel and the oxide support. In evaluating performance, Ni/0.3Ca-MCA catalyst demonstrated superior CH_{4} and CO_{2} conversions, an optimal H_{2}/CO ratio, and enhanced stability compared to other catalysts. This improvement can be attributed to the Ca addition, which likely enhances the basic sites on the catalyst, promoting CO_{2} adsorption and its simultaneous dissociation and thereby reducing coke formation.},

keywords = {P08},

pubstate = {published},

tppubtype = {article}

}

@article{Birschitzky_2024b,

title = {Machine Learning Small Polaron Dynamics},

author = {Viktor C. Birschitzky and Luca Leoni and Michele Reticcioli and Cesare Franchini},

url = {https://doi.org/10.1103/PhysRevLett.134.216301},

year  = {2025},

date = {2025-05-27},

urldate = {2024-09-24},

journal = {Physical Review Letters},

volume = {134},

issue = {21},

pages = {216301},

abstract = {Polarons are crucial for charge transport in semiconductors, significantly impacting material properties and device performance. The dynamics of small polarons can be investigated using first-principles molecular dynamics. However, the limited timescale of these simulations presents a challenge for adequately sampling infrequent polaron hopping events. Here, we introduce a message-passing neural network combined with first-principles molecular dynamics within the Born-Oppenheimer approximation that learns the polaronic potential energy surface by encoding the polaronic state, allowing for simulations of polaron hopping dynamics at the nanosecond scale. By leveraging the statistical significance of the long timescale, our framework can accurately estimate polaron (anisotropic) mobilities and activation barriers in prototypical polaronic oxides across different scenarios (hole polarons in rocksalt MgO and electron polarons in pristine and F-doped rutile TiO_{2}) within experimentally measured ranges.},

keywords = {P07},

pubstate = {published},

tppubtype = {article}

}

@article{Sokolovic_2025a,

title = {Duality and degeneracy lifting in two-dimensional electron liquids on SrTiO_{3}(001)},

author = {Igor Sokolović and Eduardo B. Guedes and Thomas P. van Waas and Fei Guo and Samuel Poncé and Craig Polley and Michael Schmid and Ulrike Diebold and Milan Radović and Martin Setvín and J. Hugo Dil},

url = {https://doi.org/10.1038/s41467-025-59258-4},

year  = {2025},

date = {2025-05-17},

journal = {Nature Communications},

volume = {16},

issue = {1},

pages = {4594},

abstract = {Two-dimensional electron liquids (2DELs) have increasing technological relevance for ultrafast electronics and spintronics, yet significant gaps in their fundamental understanding are exemplified on the prototypical SrTiO_{3}. We correlate the exact SrTiO_{3}(001) surface structure with distinct 2DELs through combined microscopic angle-resolved photoemission spectroscopy and non-contact atomic force microscopy on truly bulk-terminated surfaces that alleviate structural uncertainties inherent to this long-studied system. The SrO termination is shown to develop a 2DEL following the creation of oxygen vacancies, unlike the intrinsically metallic TiO_{2} termination. Differences in degeneracy of the 2DELs, with nearly the same band filling and identical band bending, are assigned to polar distortions of the Ti atoms in combination with spin order, supported with the extraction of fundamental electron-phonon coupling strength. These results not only resolve the ambiguities regarding 2DELs on SrTiO_{3} thus far, but also pave the way to manipulating band filling and spin order in oxide 2DELs in general.},

keywords = {P02},

pubstate = {published},

tppubtype = {article}

}

@article{Sringam_2024a,

title = {Effect of calcination temperature on the performance of K-Co/Al_{2}O_{3} catalyst for oxidative coupling of methane},

author = {Sarannuch Sringam and Thongthai Witoon and Chularat Wattanakit and Waleeporn Donphai and Metta Chareonpanich and Günther Rupprechter and Anusorn Seubsai},

url = {https://doi.org/10.1016/j.crcon.2024.100261},

doi = {10.1016/j.crcon.2024.100261},

issn = {2588-9133},

year  = {2025},

date = {2025-05-17},

urldate = {2024-05-28},

journal = {Carbon Resources Conversion},

volume = {8},

issue = {2},

pages = {100261},

abstract = {The oxidative coupling of methane (OCM) involves directly converting methane to C_{2+} hydrocarbons (such as ethylene and ethane) via a reaction with oxygen. This study elucidated the effect of the calcination temperature on the structure and catalytic performance of potassium-doped-cobalt oxide supported on an alumina (K-Co/Al_{2}O_{3}) catalyst for the OCM reaction. The catalyst was highly active at relatively low reactor temperatures (500–640 °C). Four calcination temperatures (400, 500, 600, and 700 °C) were investigated, with the results showing that the calcination temperature strongly affected catalytic properties, such as the crystalline phases, elemental distribution, physical properties, and catalytic basicity, leading to a wide range in catalytic performances. The catalyst calcined at 400 °C was superior among the catalysts, with 8.3 % C_{2+} yield, 24.8 % C_{2+} selectivity, and 33.6 % CH_{4} conversion at 640 °C. Furthermore, the catalyst was robust over 24 h of testing.},

keywords = {P08},

pubstate = {published},

tppubtype = {article}

}