Publications

@article{Maqbool_2024b,

title = {Highly Stable Self-Cleaning Paints Based on Waste-Valorized PNC-Doped TiO_{2} Nanoparticles},

author = {Qaisar Maqbool and Orlando Favoni and Thomas Wicht and Niusha Lasemi and Simona Sabbatini and Michael Stöger-Pollach and Maria Letizia Ruello and Francesca Tittarelli and Günther Rupprechter},

url = {https://doi.org/10.1021/acscatal.3c06203},

year  = {2024},

date = {2024-03-15},

journal = {ACS Catalysis},

volume = {14},

issue = {7},

pages = {4820–4834},

abstract = {Adding photocatalytically active TiO_{2} nanoparticles (NPs) to polymeric paints is a feasible route toward self-cleaning coatings. While paint modification by TiO_{2}-NPs may improve photoactivity, it may also cause polymer degradation and release of toxic volatile organic compounds. To counterbalance adverse effects, a synthesis method for nonmetal (P, N, and C)-doped TiO_{2}-NPs is introduced, based purely on waste valorization. PNC-doped TiO_{2}-NP characterization by vibrational and photoelectron spectroscopy, electron microscopy, diffraction, and thermal analysis suggests that TiO_{2}-NPs were modified with phosphate (P═O), imine species (R═N-R), and carbon, which also hindered the anatase/rutile phase transformation, even upon 700 °C calcination. When added to water-based paints, PNC-doped TiO_{2}-NPs achieved 96% removal of surface-adsorbed pollutants under natural sunlight or UV, paralleled by stability of the paint formulation, as confirmed by micro-Fourier transform infrared (FTIR) surface analysis. The origin of the photoinduced self-cleaning properties was rationalized by three-dimensional (3D) and synchronous photoluminescence spectroscopy, indicating that the dopants led to 7.3 times stronger inhibition of photoinduced e^{–}/h^{+} recombination when compared to a benchmark P25 photocatalyst.},

keywords = {P08},

pubstate = {published},

tppubtype = {article}

}

@article{Sidorowicz_2024a,

title = {Microalgae-derived Co_{3}O_{4} nanomaterials for catalytic CO oxidation},

author = {Agnieszka Sidorowicz and Nevzat Yigit and Thomas Wicht and Michael Stöger-Pollach and Alessandro Concas and Roberto Orrù and Giacomo Cao and Günther Rupprechter},

url = {https://doi.org/10.1039/D4RA00343H},

year  = {2024},

date = {2024-02-05},

urldate = {2024-02-05},

journal = {RSC Advances},

volume = {14},

pages = {4575-4586},

abstract = {Efficient carbon monoxide oxidation is important to reduce its impacts on both human health and the environment. Following a sustainable synthesis route toward new catalysts, nanosized Co_{3}O_{4} was synthesized based on extracts of microalgae: Spirulina platensis, Chlorella vulgaris, and Haematococcus pluvialis. Using the metabolites in the extract and applying different calcination temperatures (450, 650, 800 °C) led to Co_{3}O_{4} catalysts with distinctly different properties. The obtained Co_{3}O_{4} nanomaterials exhibited octahedral, nanosheet, and spherical morphologies with structural defects and surface segregation of phosphorous and potassium, originating from the extracts. The presence of P and K in the oxide nanostructures significantly improved their catalytic CO oxidation activity. When normalized by the specific surface area, the microalgae-derived catalysts exceeded a commercial benchmark catalyst. In situ studies revealed differences in oxygen mobility and carbonate formation during the reaction. The obtained insights may facilitate the development of new synthesis strategies for manufacturing highly active Co_{3}O_{4} nanocatalysts.},

keywords = {P08},

pubstate = {published},

tppubtype = {article}

}

@article{Chanka_2024a,

title = {Potassium Permanganate-Impregnated Amorphous Silica–Alumina Derived from Sugar Cane Bagasse Ash as an Ethylene Scavenger for Extending Shelf Life of Mango Fruits},

author = {Napassorn Chanka and Waleeporn Donphai and Metta Chareonpanich and Kajornsak Faungnawakij and Günther Rupprechter and Anusorn Seubsai},

url = {https://doi.org/10.1021/acsomega.3c08119},

year  = {2024},

date = {2024-02-02},

journal = {ACS Omega},

volume = {9},

issue = {6},

pages = {6749–6760},

abstract = {Ethylene, a plant hormone, is a gas that plays a crucial role in fruit ripening and senescence. In this work, a novel ethylene scavenger was prepared from amorphous silica–alumina derived from sugar cane bagasse ash (SC-ASA) and used to prolong the shelf life of mango fruits during storage. KMnO_{4} at 2, 4, or 6 wt %/w was loaded on SC-ASA using an impregnation method. The results showed that 4% w/w KMnO_{4} loaded on SC-ASA (4KM/SC-ASA) was superior for ethylene removal at an initial ethylene concentration of 400 μL L^{–1} for 120 min under ambient conditions (25–27 °C and 70–75% relative humidity), resulting in 100% ethylene removal. The kinetic study of ethylene removal showed that the adsorption data were best fitted with a pseudo-first-order kinetic model. The effects of 4KM/SC-ASA as sachets on the quality changes of the mango fruits were investigated, with the results showing that mango fruits packed in cardboard boxes with 4KM/SC-ASA had significantly delayed ripening, low levels of ethylene production, respiration, and weight loss, high fruit firmness, low total soluble solids, and high acidity compared to those of the control treatment. These findings should contribute to developing an ethylene scavenger to extend the shelf life of fruits, reduce the waste of the sugar and ethanol industries, and make it a valuable material.},

keywords = {P08},

pubstate = {published},

tppubtype = {article}

}

@article{Wang2024,

title = {CO‐Induced Dimer Decay Responsible for Gem‐Dicarbonyl Formation on a Model Single‐Atom Catalyst},

author = {Chunlei Wang and Panukorn Sombut and Lena Puntscher and Zdenek Jakub and Matthias Meier and Jiri Pavelec and Roland Bliem and Michael Schmid and Ulrike Diebold and Cesare Franchini and Gareth S. Parkinson},

doi = {10.1002/anie.202317347},

issn = {1521-3773},

year  = {2024},

date = {2024-01-31},

journal = {Angewandte Chemie - International Edition},

number = {e202317347},

publisher = {Wiley},

abstract = {The ability to coordinate multiple reactants at the same active site is important for the wide-spread applicability of single-atom catalysis. Model catalysts are ideal to investigate the link between active site geometry and reactant binding, because the structure of single-crystal surfaces can be precisely determined, the adsorbates imaged by scanning tunneling microscopy (STM), and direct comparisons made to density functional theory. In this study, we follow the evolution of Rh_{1} adatoms and minority Rh_{2} dimers on Fe_{3}O_{4}(001) during exposure to CO using time-lapse STM at room temperature. CO adsorption at Rh_{1} sites results exclusively in stable Rh_{1}CO monocarbonyls, because the Rh atom adapts its coordination to create a stable pseudo-square planar environment. Rh_{1}(CO)_{2} gem-dicarbonyl species are also observed, but these form exclusively through the breakup of Rh_{2} dimers via an unstable Rh_{2}(CO)_{3} intermediate. Overall, our results illustrate how minority species invisible to area-averaging spectra can play an important role in catalytic systems, and show that the decomposition of dimers or small clusters can be an avenue to produce reactive, metastable configurations in single-atom catalysis.},

keywords = {P02, P04, P07},

pubstate = {published},

tppubtype = {article}

}

@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}

}

@article{Gamba2023,

title = {Formation and stability of Fe-rich terminations of the Fe_{3}O_{4}(001) surface},

author = {Oscar Gamba and Moritz Eder and Matthias Poglitsch and Jiri Pavelec and Panukorn Sombut and Matthias Meier and Ulrike Diebold and Michael Schmid and Gareth S. Parkinson},

doi = {10.1088/2053-1591/ad0ac5},

year  = {2023},

date = {2023-11-22},

urldate = {2023-11-22},

journal = {Materials Research Express},

volume = {10},

number = {116517},

issue = {44},

publisher = {IOP Publishing},

abstract = {Understanding how the structure of iron oxide surfaces varies with their environment is essential for rationalizing their role in (geo-)chemistry and optimizing their application in modern technologies. In this paper, we create Fe-rich terminations of Fe_{3}O_{4}(001) by depositing iron directly onto the 'subsurface cation vacancy'-reconstructed surface, which is the most stable surface under ultrahigh vacuum conditions. Scanning tunneling microscopy and x-ray photoelectron spectroscopy data reveal that the excess iron is initially accommodated as two-fold coordinated adatoms and later incorporates into the subsurface cation vacancies. As the coverage increases, small patches of the octahedral pair termination (also known as the 'Fe dimer' termination) nucleate, eventually covering the entire surface after the deposition of 2 iron atoms per (√2×√2)R45° unit cell. This conclusion effectively rules out some existing models for the termination and provides support for the model proposed by Rustad \textit{et al.} (Surface Science 432, L583-L588, 1999), highlighting the need for further theoretical work to complete the Fe_{3}O_{4}(001) surface phase diagram. The octahedral pair termination is found to be unstable above 523 K and upon exposure to molecular O2 because the excess iron atoms agglomerate to form small FeO_{x} clusters.},

keywords = {P02, P04},

pubstate = {published},

tppubtype = {article}

}

@article{10.1063/5.0169384,

title = {Molecular Hessian matrices from a machine learning random forest regression algorithm},

author = {Giorgio Domenichini and Christoph Dellago},

doi = {https://doi.org/10.1063/5.0169384},

year  = {2023},

date = {2023-11-20},

urldate = {2023-11-20},

journal = {The Journal of Chemical Physics},

volume = {159},

number = {194111},

issue = {19},

abstract = {In this article, we present a machine learning model to obtain fast and accurate estimates of the molecular Hessian matrix. In this model, based on a random forest, the second derivatives of the energy with respect to redundant internal coordinates are learned individually. The internal coordinates together with their specific representation guarantee rotational and translational invariance. The model is trained on a subset of the QM7 dataset but is shown to be applicable to larger molecules picked from the QM9 dataset. From the predicted Hessian, it is also possible to obtain reasonable estimates of the vibrational frequencies, normal modes, and zero point energies of the molecules.},

keywords = {P12},

pubstate = {published},

tppubtype = {article}

}

@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}

}

@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}

}

@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 = {P08},

pubstate = {published},

tppubtype = {article}

}