Titel Deelnemers "Korte inhoud" "Understanding surface (un)reactive sites of titania supports towards propyl-phosphonic acid surface modification" "Kaimin Zhang, Jinxin Wang, Vera Meynen" "Organophosphonic acids (PAs) surface modification on metal oxides is important for applications, nevertheless, a detailed study evaluating the influence of metal oxides surface properties on PAs modification is lacking. This work presents a method to qualitatively probe surface (un)reactive sites of titania towards propyl-phosphonic acid (3PA) grafting by methanol. It identifies the more or less reactive sites, i.e., hydroxyl groups and Lewis acid sites, allowing to understand relative differences in maximum modification degrees of 3PA among different titania supports. Therefore, three different types of titania were used, while all other 3PA modification conditions were kept constant. A clear difference in the maximum modification degree on the three titania supports was observed. In-situ diffuse reflectance Fourier transform infrared spectroscopy revealed that not all surface OH groups had reacted with 3PA at the highest modification degree, which were similar to most of the OH groups remaining after methanol chemisorption. Also the adsorption capacities of the strongly bonded chemisorbed methanol elucidated differences in the three titania, which was related to the maximum modification degree of 3PA. Methanol chemisorption can thus aid in the understanding of the kinds of reactive surface sites that play a role in the divergence of 3PA coverage on different types of titania supports." "Sr(II) and Ba(II) alkaline earth metal–organic frameworks (AE-MOFs) for selective gas adsorption, energy storage, and environmental application" "Nikolas Király, Dominika Capková, Róbert Gyepes, Nikola Vargová, Tomáš Kazda, Jozef Bednarčík, Daria Yudina, Tomáš Zelenka, Pavel Čudek, Vladimír Zeleňák, Anshu Sharma, Vera Meynen, Virginie Hornebecq, Andrea Straková Fedorková, Miroslav Almáši" "Two new alkaline earth metal–organic frameworks (AE-MOFs) containing Sr(II) (UPJS-15) or Ba(II) (UPJS-16) cations and extended tetrahedral linker (MTA) were synthesized and characterized in detail (UPJS stands for University of Pavol Jozef Safarik). Single-crystal X-ray analysis (SC-XRD) revealed that the materials are isostructural and, in their frameworks, one-dimensional channels are present with the size of ~11 × 10 Å2. The activation process of the compounds was studied by the combination of in situ heating infrared spectroscopy (IR), thermal analysis (TA) and in situ high-energy powder X-ray diffraction (HE-PXRD), which confirmed the stability of compounds after desolvation. The prepared compounds were investigated as adsorbents of different gases (Ar, N2, CO2, and H2). Nitrogen and argon adsorption measurements showed that UPJS-15 has SBET area of 1321 m2 g−1 (Ar) / 1250 m2 g−1 (N2), and UPJS-16 does not adsorb mentioned gases. From the environmental application, the materials were studied as CO2 adsorbents, and both compounds adsorb CO2 with a maximum capacity of 22.4 wt.% @ 0 °C; 14.7 wt.% @ 20 °C and 101 kPa for UPJS-15 and 11.5 wt.% @ 0°C; 8.4 wt.% @ 20 °C and 101 kPa for UPJS-16. According to IAST calculations, UPJS-16 shows high selectivity (50 for CO2/N2 10:90 mixture and 455 for CO2/N2 50:50 mixture) and can be applied as CO2 adsorbent from the atmosphere even at low pressures. The increased affinity of materials for CO2 was also studied by DFT modelling, which revealed that the primary adsorption sites are coordinatively unsaturated sites on metal ions, azo bonds, and phenyl rings within the MTA linker. Regarding energy storage, the materials were studied as hydrogen adsorbents, but the materials showed low H2 adsorption properties: 0.19 wt.% for UPJS-15 and 0.04 wt.% for UPJS-16 @ −196 °C and 101 kPa. The enhanced CO2/H2 selectivity could be used to scavenge carbon dioxide from hydrogen in WGS and DSR reactions. The second method of applying samples in the area of energy storage was the use of UPJS-15 as an additive in a lithium-sulfur battery. Cyclic performance at a cycling rate of 0.2 C showed an initial discharge capacity of 337 mAh g−1, which decreased smoothly to 235 mAh g−1 after 100 charge/discharge cycles." "Self‐induced and progressive photo‐oxidation of organophosphonic acid grafted titanium dioxide" "Nick Gys, Bram Pawlak, Kristof Marcoen, Gunter Reekmans, Leticia F. Velasco, Rui An, Kenny Wyns, Kitty Baert, Kaimin Zhang, Léon Luntadila Lufungula, Alessandra Piras, Laurens Siemons, Bart Michielsen, Sabine Van Doorslaer, Frank Blockhuys, Tom Hauffman, Peter Adriaensens, Steven Mullens, Vera Meynen" "While synthesis-properties-performance correlations are being studied for organophosphonic acid grafted TiO2, their stability and the impact of exposure conditions on possible changes in the interfacial surface chemistry remain unexplored. Here, the impact of different ageing conditions on the evolution of the surface properties of propyl- and 3-aminopropylphosphonic acid grafted mesoporous TiO2 over a period of 2 years is reported, using solid-state 31P and 13C NMR, ToF-SIMS and EPR as main techniques. In humid conditions under ambient light exposure, PA grafted TiO2 surfaces initiate and facilitate photo-induced oxidative reactions, resulting in the formation of phosphate species and degradation of the grafted organic group with a loss of carbon content ranging from 40 to 60 wt%. By revealing its mechanism, solutions were provided to prevent degradation. This work provides valuable insights for the broad community in choosing optimal exposure/storage conditions that extend the lifetime and improve the materials' performance, positively impacting sustainability." "Plasma-based dry reforming of methane in a dielectric barrier discharge reactor" "Jinxin Wang, Kaimin Zhang, Myrjam Mertens, Annemie Bogaerts, Vera Meynen" "This study presents new insights on the effect of (sub)micrometer particle sized materials in plasma-based CO2-CH4 reforming by investigating the performance of SiO2 spheres (with/without supported metal) of varying particle sizes. (Sub)micron particles synthesized through the Stöber method were used instead of (sub)millimeter particles employed in previous studies. Increasing particle size (from 120 nm to 2390 nm) was found to first increase and then decrease conversion and energy yield, with optimal performance achieved using 740 nm 5 wt% Ni loaded SiO2, which improved CO2 and CH4 conversion, and energy yield to 44%, 55%, and 0.271 mmol/kJ, respectively, compared to 20%, 27%, and 0.116 mmol/kJ in an empty reactor at the same flow rate. This is the first to achieve significant performance improvement in a fully packed reactor, highlighting the importance of selecting a suitable particle size. The findings can offer guidance towards rational design of catalysts for plasma-based reactions." "3D porous catalysts for plasma-catalytic dry reforming of methane" "Jinxin Wang, Kaimin Zhang, Annemie Bogaerts, Vera Meynen" "The effect of pore size on plasma catalysis is crucial but still unclear. Studies have shown plasma cannot enter micropores and mesopores, so catalysts for traditional thermocatalysis may not fit plasma catalysis. Here, 3D porous Cu and CuO with different pore sizes were prepared using uniform silica particles (10–2000 nm) as templates, and compared in plasma-catalytic dry reforming. In most cases, the smaller the pore size, the higher the conversion of CH4 and CO2. Large pores reachable by more electrons did not improve the reaction efficiency. We attribute this to the small surface area and large crystallite size, as indicated by N2-sorption, mercury intrusion and XRD. While the smaller pores might not be reachable by electrons, due to the sheath formed in front of them, as predicted by modeling, they can still be reached by radicals formed in the plasma, and ions can even be attracted into these pores. An exception are the samples synthesized from 1 μm silica, which show better performance. We believe this is due to the electric field enhancement for pore sizes close to the Debye length. The performances of CuO and Cu with different pore sizes can provide references for future research on oxide supports and metal components of plasma catalysts." "Modifying the Stöber process" "Jinxin Wang, Kaimin Zhang, Safiyye Kavak, Bals, Vera Meynen" "The Stöber method is one of the most important and fundamental processes for the synthesis of inorganic (nano)materials, but has the drawback of using a large amount of organic solvent. Herein, we used ethanol as an example to explore if the organic solvent in a typical Stöber method can be omitted. We found that ethanol increases the particle size of the obtained silica spheres and aids the formation of uniform silica particles rather than forming a gel. Nevertheless, the results indicated that an organic solvent in the initial synthesis mixture is not indispensable. We discovered, an initially immiscible synthesis method, which can replace the organic solvent based Stöber method to successfully synthesize silica particles with the same size ranges as the original Stöber process without addition of organic solvents. Moreover, this process can be of further value to be extended to synthesis processes of other materials based on the Stöber process." "Dry reforming in a dielectric barrier discharge reactor with non-uniform discharge gap" "Jinxin Wang, Kaimin Zhang, Vera Meynen, Annemie Bogaerts" "The application of dielectric barrier discharge (DBD) plasma reactors is promising in various environmental and energy processes, but is limited by their low energy yield. In this study, we put a number of stainless steel rings over the inner electrode rod of the DBD reactor to change the local discharge gap and electric field, and we studied the dry reforming performance. At 50 W supplied power, the metal rings mostly have a negative impact on the performance, which we attribute to the non-uniform spatial distribution of the discharges caused by the rings. However, at 30 W supplied power, the energy yield is higher than at 50 W and the placement of the rings improves the performance of the reactor. More rings and with a larger cross-sectional diameter can further improve the performance. The reactor with 20 rings with a 3.2 mm cross-sectional diameter exhibits the best performance in this study. Compared to the reactor without rings, it increases the CO2 conversion from 7% to 16 %, the CH4 conversion from 12% to 23%, and the energy yield from 0.05 mmol/kJ supplied power to 0.1 mmol/kJ (0.19 mmol/kJ if calculated from the plasma power), respectively. The presence of the rings increases the local electric field, the displaced charge and the discharge fraction, and also makes the discharge more stable and with more uniform intensity. It also slightly improves the selectivity to syngas. The performance improvement observed by placing stainless steel rings in this study may also be applicable to other plasma-based processes." "Post-synthesis modified metal-porphyrin framework GaTCPP for carbon dioxide adsorption and energy storage in Li-S batteries" "Nikolas Kiraly, Dominika Capkova, Miroslav Almasi, Tomas Kazda, Ondej Cech, Pavel Cudek, Andrea Strakova Fedorkova, Maxim Lisnichuk, Vera Meynen, Vladimir Zelenak" "Lithium−sulphur batteries attract increasing interest due to their high theoretical specific capacity, advantageous economy, and “eco-friendliness”. In this study, a metal-organic framework (MOF) GaTCPP containing a porphyrinic base ligand was used as a conductive additive for sulphur. GaTCPP was synthesized, characterized, and post-synthetically modified by the transition metal ions (Co2+/Ni2+). The doping of GaTCPP ensured an increase in the carbon dioxide adsorption capacities, which were measured under different conditions. Post-synthetic modification of GaTCPP with Co2+/Ni2+ ions has been shown to increase carbon dioxide storage capacity from 22.8 wt.% for unmodified material to 23.1 wt.% and 26.5 wt.% at 0 °C and 1 bar for Co2+ and Ni2+-doped analogues, respectively. As a conductive part of cathode material, MOFs displayed successful sulphur capture and encapsulation proven by stable charge/discharge cycle performances, high-capacity retention, and Coulombic efficiency. The electrodes with pristine GaTCPP showed a discharge capacity of 699 mAh g-1 at 0.2 C in the fiftieth cycle. However, the doping of GaTCPP by Ni2+ has a positive impact on the electrochemical properties, the capacity increased to 778 mAh g-1 in the fiftieth cycle at 0.2 C." "Amino-alkylphosphonate-grafted TiO₂" "Nick Gys, Rui An, Bram Pawlak, David Vogelsang, Kenny Wyns, Kitty Baert, Alexander Vansant, Frank Blockhuys, Peter Adriaensens, Tom Hauffman, Bart Michielsen, Steven Mullens, Vera Meynen" "Amino-alkylphosphonic acid grafted TiO2 materials are of increasing interest in a variety of applications such as metal sorption, heterogeneous catalysis, CO2 capture and enzyme immobilization. To date, systematic insights into the synthesis-properties-performance correlation are missing for such materials, albeit giving important know-how towards their applicability and limitations. In this work, the impact of the chain length and modification conditions (concentration and temperature) of amino-alkylphosphonic acid grafted TiO2 on the surface properties and adsorption performance of palladium is studied. Via grafting with aminomethyl-, 3-aminopropyl- and 6-aminohexylphosphonic acid, combined with the spectroscopic techniques (DRIFT, 31P NMR, XPS) and zeta potential measurements, differences in surface properties between the C1, C3 and C6 chain are revealed. The modification degree decreases with increasing chain length under the same synthesis conditions, indicative of folded grafted groups that sterically shield an increasing area of binding sites with increasing chain length. Next, all techniques confirm the different surface interactions of a C1 chain compared to a C3 or C6 chain. This is in line with palladium adsorption experiments, where only for a C1 chain, the adsorption efficiency is affected by the precursor concentration used for modification. The absence of a straightforward correlation between the number of free NH2 groups and the adsorption capacity for the different chain lengths, indicates that other chain-length specific surface interactions are controlling the adsorption performance. The increasing pH stability in the order of C1 < C3 < C6 can possibly be associated to a higher fraction of inaccessible hydrophilic sites due to the presence of folded structures. Lastly, the comparison of adsorption performance and pH stability with 3-aminopropyl(triethoxysilane) grafted TiO2 reveals the applicability of both grafting methods depending on the envisaged pH during sorption." CHEMampere "Elias Klemm, Carlos M.S. Lobo, Armin Löwe, Verena Schallhart, Stephan Renninger, Lara Waltersmann, Remi Costa, Andreas Schulz, Ralph-Uwe Dietrich, Lukas Moeltner, Vera Meynen, Alexander Sauer, K. Andreas Friedrich" "The chemical industry must become carbon neutral by 2050, meaning that process-, energy-, and product-related CO2 emissions from fossil sources are completely suppressed. This goal can only be reached by using renewable energy, secondary raw materials, or CO2 as a carbon source. The latter can be done indirectly through the bioeconomy or directly by utilizing CO2 from air or biogenic sources (integrated biorefinery). Until 2030, CO2 waste from fossil-based processes can be utilized to curb fossil CO2 emissions and reach the turning point of global fossil CO2 emissions. A technology mix consisting of recycling technologies, white biotechnology, and carbon capture and utilization (CCU) technologies is needed to achieve the goal of carbon neutrality. In this context, CHEMampere contributes to the goal of carbon neutrality with electricity-based CCU technologies producing green chemicals from CO2, N-2, O-2, and H2O in a decentralized manner. This is an alternative to the e-Refinery concept, which needs huge capacities of water electrolysis for a centralized CO2 conversion with green hydrogen, whose demand is expected to rise dramatically due to the decarbonization of the energy sector, which would cause a conflict of use between chemistry and energy. Here, CHEMampere's core reactor technologies, that is, electrolyzers, plasma reactors, and ohmic resistance heating of catalysts, are described, and their technical maturity is evaluated for the CHEMampere platform chemicals NH3, NOx, O-3, H2O2, H-2, CO, and CxHyOz products such as formic acid or methanol. Downstream processing of these chemicals is also addressed by CHEMampere, but it is not discussed here."