Understanding the reversible intercalation of guest molecules into metal-organic frameworks is crucial for advancing their design for practical applications. In this work, we explore the impact of H2O as a guest molecule on the thermal expansion of the zinc-based metal-organic framework GUT-2. Dehydration is achieved by thermal treatment of hydrated GUT-2. Rietveld refinement performed on temperature-dependent X-ray powder diffraction data confirms the reversible structural transformation. Additionally, it allows the determination of anisotropic thermal expansion coefficients for both forms. The hydrated form exhibits an extremely small thermal expansion along the polymer chain direction moderate expansion in the direction of predominantly hydrogen bonds, and the highest expansion in the direction with only van der Waals bonding. Upon activation, the removal of H2O molecules triggers a doubling of the thermal expansion coefficient in the direction, where the hydrogen bonds have been removed. Regarding the dynamics of the process, thermal activation in air occurs within 6 hours at a temperature of 50 °C and takes only 30 minutes when heating to 90 °C. In contrast, full rehydration under standard lab conditions (30% relative humidity) requires two days. During the activation/dehydration processes no change of the widths of the X-ray diffraction peaks is observed, which shows that the underlying crystal structure remains intact during the transition processes. Fitting the transformations by the Avrami equation reveals a quasi one-dimensional evolution of the dehydrated areas for the activation process and a more intricate, predominantly two-dimensional mechanism for the rehydration.

Tetrazole moieties are components of various pharmacologically active molecules. Several synthetic protocols for the synthesis of tetrazoles have been developed. Among those, the reaction of organic nitriles with azides catalyzed by Lewis acids (LAs) provides a convenient access. Nevertheless, generally rather harsh reaction conditions have to be utilized for such syntheses. We have developed a simple, solvent-free procedure which allows a convenient isolation of tetrazoles using a heterogeneous catalyst: we show that polystyrene/AlCl3 composites produce tetrazoles at reasonable yields and allow a simple work-up procedure. We have characterized the AlCl3/polystyrene composite (gas sorption, XRD, IR) and investigated its efficacy in the preparation of aryl-substituted tetrazoles. We also have evaluated MgCl2, CuCl2, and ZnCl2 as Lewis-acid catalysts, but they are clearly outperformed by AlCl3 correlating with the Lewis-acid strength on the Gutmann-Beckett scale.

This work investigates the impact of iron-based oxygen carriers (OCs) on green hydrogen production using a fixed-bed chemical looping (CL) process, aiming for industrial scalability. We conducted a comprehensive material screening of OCs comprising Fe2O3 with support materials (Al2O3, TiO2, ZrO2) at an 80/20 wt.-% ratio. Focus was placed on ZrO2, pure and doped with CaO, MgO, and Y2O3, to examine their effects on redox efficiency and hydrogen production. Notably, ZrO2 doped with MgO and Y2O3 achieved a specific hydrogen production over 12 molH2/kgOC at a small scale, attributed to chemical inertness and porous morphology, enhancing cyclic stability over traditional TiO2 and Al2O3 supports. Large-scale testing of the most promising OC compositions in a 250 g fixed-bed reactor for 100 cycles revealed that doping ZrO2 with Y2O3 not only prevents phase transitions but also ensures higher cyclic stability among tested OCs. Our findings underscore the critical role of microscopic phenomena in the CL process's efficiency and introduce a novel approach for designing environmentally friendly OCs for effective hydrogen production.

The provision of green hydrogen on an industrial scale is one of the challenges for a successful CO2-neutral energy transition. Sintering is still the bottleneck for the use of iron-based oxygen carriers for efficient hydrogen production and storing performance in chemical looping in a large-scale system. In this work, we demonstrate an effective way for hydrogen production by the synthesis of structured oxygen carriers (OC) from cost efficient, green and environment-friendly materials. The novel structured oxygen carriers with a core–shell architecture show an innovative concept to prevent the agglomeration of pellets in the fixed bed reactor system. The environment-friendly iron-based material maintained an oxygen exchange capacity of over 80 % for 100 cycles. The pore network of the catalytic system was preserved by incorporating a structure with separate compartments. A synergistic effect between the sintering, especially of the porous network, and the gas transport was revealed. In addition, an undiscovered leach-out effect of the OC system on the Al2O3 support material, which is associated with a deactivation phenomenon, was also revealed. The work provides fundamental new insights for understanding the phenomena that occur during the sintering process in the OC material and the influence on the lifetime of the chemical looping process. Finally, we present that the structured OC exhibits excellent performance and provides a new approach in material design for successful implementation in high temperature catalytic fixed bed system for long term operation.

Germanium is a promising basis for nanomaterials due to its low toxicity and valuable optical and electronic properties. However, germanium nanomaterials have seen little research compared to other group 14 elements due to unpredictable chemical behavior and high costs. Here, we report the dehydrocoupling of o-tolylgermanium trihydride to amorphous nanoparticles. The reaction is facilitated through reflux at 162 degrees C and can be accelerated with an amine base catalyst. Through cleavage of both H2 and toluene, new Ge-Ge bonds form. This results in nanoparticles consisting of crosslinked germanium with o-tolyl termination. The particles are 2-6 nm in size and have masses above approximately 3500 Da. The organic substituents are promising for further functionalization. Combined with strong absorption up to 600 nm and moderate solubility and air stability, there are numerous possibilities for future applications. o-tolylgermanium trihydride undergoes dehydrogenative coupling to form a germanium nanoparticle with o-tolyl termination. The particles are about 2-6 nm in size and have intense orange to red coloration. image

The scope of this work was to investigate and understand the microscopic effects on the performance of the active catalytic system in the chemical looping process. The inhibiting and accelerating effects of the different materials have been extensively studied. The ZrO2 doped with MgO and Y2O3 showed a chemical inertness and the formation of a porous morphology for an enhanced cyclic stability. Testing in large-scale application indicates that supporting material with higher yttrium content in ZrO2 has an excellent performance for 100 cycles. The HT-XRD and DSC analyzes clearly show microscopic phenomena play a fundamental role in the process and correspond to the phase transition. Stabilization of the cubic/tetragonal crystal structure leads to suppression of the phase transition and exhibits highest activity. The work reveals new fundamental principles for the design of OC in chemical looping hydrogen and understanding the influence of microscopic effects on the stability of oxygen carriers.

In this study, Ag-MnxOy/C composite catalysts deposited on reduced graphene oxide (rGO) and, for the first time on N-doped graphene oxide (NGO), were prepared via a facile synthesis method. The influence of the carbon support material on the activity and stability of the oxygen reduction reaction (ORR) and on the tolerance to ethanol in alkaline medium was focused and investigated. The physicochemical properties of the Ag-MnxOy/C catalysts were analyzed by X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), Brunauer–Emmett–Teller (BET) method, atomic absorption spectroscopy (AAS), inductively coupled plasma-mass spectrometry (ICP-MS), and thermogravimetric gas analysis (TGA). Electrochemical characterization was performed by rotating disk electrode (RDE) experiments. The results show that the active manganese species MnO2 was assembled as nanorods and nanospheres on rGO and NGO, respectively. Ag was assumed to be present as very small or amorphous particles. Similar redox processes for Ag-MnxOy/rGO and Ag-MnxOy/NGO were examined via cyclic voltammetry. The Ag-MnxOy/rGO resulted in a more negative diffusion limiting current density of −3.01 mA cm−2 compared to Ag-MnxOy/NGO. The onset potential of approximately 0.9 V vs. RHE and the favored 4-electron transfer pathway were independent of the support material. Ag-MnxOy/NGO exhibited a higher ORR stability, whereas Ag-MnxOy/rGO showed a better ethanol tolerance.

Drinking water plumbing systems appear to be a unique environment for microorganisms as they contain few nutrients but a high mineral concentration. Interactions between mineral content and bacteria, such as microbial calcium carbonate precipitation (MCP) however, has not yet attracted too much attention in drinking water sector. This study aims to carefully examine MCP behavior of two drinking water bacteria species, which may potentially link scaling and biofouling processes in drinking water distribution systems. Evidence from cell density evolution, chemical parameters, and microscopy suggest that drinking water isolates can mediate CaCO3 precipitation through previously overlooked MCP mechanisms like ammonification or biosorption. The results also illustrate the active control of bacteria on the MCP process, as the calcium starts to concentrate onto cell surfaces only after reaching a certain cell density, even though the cell surfaces are shown to be the ideal location for the CaCO3 nucleation.

Direct ethanol fuel cells (DEFC) still lack active and efficient electrocatalysts for the alkaline ethanol oxidation reaction (EOR). In this work, a new instant reduction synthesis method was developed to prepare carbon supported ternary PdNiBi nanocatalysts with improved EOR activity. Synthesized catalysts were characterized with a variety of structural and compositional analysis techniques in order to correlate their morphology and surface chemistry with electrochemical performance. The modified instant reduction synthesis results in well-dispersed, spherical Pd85Ni10Bi5 nanoparticles on Vulcan XC72R support (Pd85Ni10Bi5/C(II-III)), with sizes ranging from 3.7 ± 0.8 to 4.7 ± 0.7 nm. On the other hand, the common instant reduction synthesis method leads to significantly agglomerated nanoparticles (Pd85Ni10Bi5/C(I)). EOR activity and stability of these three different carbon supported PdNiBi anode catalysts with a nominal atomic ratio of 85:10:5 were probed via cyclic voltammetry and chronoamperometry using the rotating disk electrode method. Pd85Ni10Bi5/C(II) showed the highest electrocatalytic activity (150 mA⋅cm−2; 2678 mA⋅mg−1) with low onset potential (0.207 V) for EOR in alkaline medium, as compared to a commercial Pd/C and to the other synthesized ternary nanocatalysts Pd85Ni10Bi5/C(I) and Pd85Ni10Bi5/C(III). This new synthesis approach provides a new avenue to developing efficient, carbon supported ternary nanocatalysts for future energy conversion devices.

Please change equations on page 204.

The study focuses on the influence of Ni and Bi on alkaline ethanol oxidation reaction (EOR) activities, stabilities and structure characteristics of carbon supported Pd-based nanocatalysts (Pd/C, Pd60Ni40/C, Pd60Bi40/C, Pd60Ni20Bi20/C) by cyclic voltammetry/chronoamperometry using rotating disk electrode and various physico-chemical methods such as X-ray powder diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy coupled with energy dispersive X-ray spectroscopy and inductively coupled plasma optical emission spectrometry. Nickel generates more adsorbed OH on the Pd catalyst surface than Bi and promotes the oxidation of adsorbed ethanol species. This results in a low onset potential toward ethanol oxidation with high current density. The presence of Bi facilitates high tolerance toward various reaction intermediates resulting from the incomplete ethanol oxidation, but might also initiate the agglomeration of Pd nanoparticles. The novel Pd60Ni20Bi20/C nanocatalyst displays exceptional byproduct tolerance, but only satisfying catalytic activity toward ethanol oxidation in an alkaline medium. Therefore, the EOR performance of the novel carbon supported ternary PdxNiyBiz anode catalyst with various atomic variations (Pd70Ni25Bi5/C, Pd70Ni20Bi10/C, Pd80Ni10Bi10/C and Pd40Ni20Bi40/C) using the common instant reduction synthesis method was further optimized for the alkaline direct ethanol fuel cell. The carbon supported Pd: Ni: Bi nanocatalyst with atomic ratio of 70:20:10 displays outstanding catalytic activity for the alkaline EOR compared to the other PdxNiyBiz/C nanocatalysts as well as to the benchmarks Pd/C, Pd60Ni40/C and Pd60Bi40/C. The synergy and the optimal content in consideration of the oxide species of Pd, Ni and Bi are crucial for the EOR kinetic enhancement in alkaline medium.

For the development of safe and long-lasting lithium-ion batteries we need electrolytes with excellent ionic transport properties. Argyrodite-type Li6PS5X (X: Cl, Br, I) belongs to a family of such a class of materials offering ionic conductivities, at least if Li6PS5Br and Li6PS5Cl are considered, in the mS cm-1 range at room temperature. Although already tested as ceramic electrolytes in battery cells, a comprehensive picture about the ion dynamics is still missing. While Li6PS5Br and Li6PS5Cl show an exceptionally high Li ion conductivity, that of Li6PS5I with its polarizable I anions is by some orders of magnitude lower. This astonishing effect has not been satisfactorily understood so far. Studying the ion dynamics over a broad time and length scale is expected to help shed light on this aspect. Here, we used broadband impedance spectroscopy and 7Li NMR relaxation measurements and show that very fast local Li ion exchange processes are taking place in all three compounds. Most importantly, the diffusion-induced NMR spin-lattice relaxation in Li6PS5I is almost identical to that of its relatives. Considering the substitutional disorder effects in Li6PS5X (X = Br, Cl), we conclude that in structurally ordered Li6PS5I the important inter-cage jump processes are switched off, hindering the ions from taking part in long-range ion transport.

Fig. S1 Crystallographic data of Li6PS5Br, Li6PS5Cl, Li6PS5I, and Li6PS5Cl0.50Br0.50 obtained from X-ray powder diffraction. GoF means goodness of fit (GoF), the weighted R-profile (Rwp) and the R-Bragg (RBragg) values are also included. The differential plot as well as the hkl indices are shown, too. The hump at approximately 25° is due to the mercatpo foil, which was used for the measurement Li6PS5Cl

On-board desulfurization is essential to operate fuel-cell-based auxiliary power units (APU) with commercial fuels. In this work, both (i) on-board desulfurization and (ii) on-board regeneration performance of Ag-Al2O3 adsorbent is investigated in a comprehensive manner. The herein investigated regeneration strategy uses hot APU off-gas as the regeneration medium and requires no additional reagents, tanks, nor heat exchangers and thus has remarkable advantages in comparison to state-of-the-art regeneration strategies. The results for (i) show high desulfurization performance of Ag-Al2O3 under all relevant operating conditions and specify the influence of individual operation parameters and the combination of them, which have not yet been quantified. The system integrated regeneration strategy (ii) shows excellent regeneration performance recovering 100% of the initial adsorption capacity for all investigated types of fuels and sulfur heterocycles. Even the adsorption capacity of the most challenging dibenzothiophene in terms of regeneration is restored to 100% over 14 cycles of operation. Subsequent material analyses proved the thermal and chemical stability of all relevant adsorption sites under APU off-gas conditions. To the best of our knowledge, this is the first time 100% regeneration after adsorption of dibenzothiophene is reported over 14 cycles of operation for thermal regeneration in oxidizing atmospheres.

This work deals with the introduction and investigation of a novel system-integrated thermal regeneration strategy based on hot off-gas for on-board desulfurization units. A highly thermally stable Ag-Al2O3 material was used as the adsorbent because it has the advantage of being active in the oxidized form so that it requires no activation after regeneration in an oxidative atmosphere. Dibenzothiophene (DBT) was used as the representative polycyclic aromatic sulfur heterocycle (PASH) in Jet A-1 fuel with a total sulfur concentration of 900 ppmw. This PASH has a stronger adsorption energy and is significantly more stable than benzothiophene or thiophene. This is why oxidative thermal regeneration strategies had formerly been failing to fully regenerate any type of adsorbent after the adsorption of DBT. This work reports excellent regeneration results upon the use of the hot off-gas from a solid-oxide-fuel-cell-(SOFC-) driven auxiliary power unit (APU) as the regeneration medium. The highly thermally stable Ag-Al2O3 showed a high breakthrough adsorption capacity of 2.2 mg-S/g-adsorbent in the first desulfurization cycle that was fully recovered by regeneration with hot APU off-gas. This is the first time that 100% regeneration has been reported for thermal regeneration after the adsorption of DBT. Additional investigations were performed to gain deeper insight into the overall desorption mechanism. The H2O content has an especially significant influence on the overall desorption mechanism of DBT. With a H2O content of 12.4 mol %, full regeneration was also obtained by reducing the final regeneration temperature from 525 to 450 degrees C. The results reported herein show that this novel regeneration strategy requires no additional regeneration medium, no additional tanks, and no additional bulky equipment and is thus fully integrated into the concept of an S OF C-op erated APU.

Bifunctional air electrodes with tuned composition consisting of two precious metal-free oxide catalysts are manufactured for application in rechargeable zinc-air flow batteries and electrochemically tested via long-term pulse charge and discharge cycling experiments at 50 mA cm(-2) (mean). NiCo2O4 spinel, synthesized via direct impregnation on carbon nanofibers or nickel powder and characterized by energy dispersive X-ray spectroscopy and X-ray diffraction experiments, shows high activity toward oxygen evolution reaction with low charge potentials of < 2.0 V vs. Zn/Zn2+. La0.6Sr0.4Co0.2Fe0.8O3 perovskite exhibits bifunctional activity and outperforms the NiCo2O4 spinel in long-term stability tenfold. By combining the catalysts in one bi-catalyzed bifunctional air electrode, stable performances of more than 1000 h and 450 cycles are achieved when supplied with oxygen and over 650 h and 300 cycles when supplied with synthetic air. In addition, the pulse charging method, which is beneficial for compact zinc deposition, is successfully tested on air electrodes during long-term operation. The oxygen evolution potentials during pulse, i.e. at tripled charge current density of 150 mA cm(-2), are only 0.06-0.08 V higher compared to constant charging current densities. Scanning electron microscopy confirms that mechanical degradation caused by bubble formation during oxygen evolution results in slowly decreasing discharge potentials. (C) 2017 Elsevier Ltd. All rights reserved.

Chemical hydrogen storage via conversion with carbon dioxide into methane is a promising technology in an energy system that relies on renewable energy resources. Robust heterogeneous catalysts are needed for this reaction to proceed at relevant levels. Ni/MgO is a promising catalyst in terms of activity and stability. Although several microscale catalyst studies exist, there is a lack of knowledge on catalyst performance and reactor control at larger scale for carbon dioxide methanation at ambient pressure and a technically relevant stoichiometric H2:CO2 (4:1) feed. Two catalysts with a loading of 11 and 17wt.% nickel were prepared by wet impregnation, producing a Ni/MgO solid solution with a cubic lattice. Controlled increase (‘scanning experiment’) of the catalyst temperature to 500°C for the highly exothermic CO2 methanation was compared to steady-state experiments. Scanning and steady-state experiments yield comparable results in terms of carbon dioxide conversion and methane selectivity, whereas scanning experiments lead to considerable time saving. At a moderate temperature of 325°C and a feed flow consisting of H2:CO2:N2=4:1:5 at a flow rate of 250cm3STPmin−1, CO2 conversion and CH4 selectivity near thermodynamic equilibrium are achievable. The long-term stability of Ni/MgO (17wt.% Ni) at 330°C was proven during reactor operation for several days.

•Selective ORR catalysts are presented for alkaline direct ethanol fuel cells.•Perovskite based cathode catalysts show high tolerance toward ethanol.•A membrane-free alkaline direct ethanol fuel cell is presented.