Proton-Conducting Membranes from Polyphenylenes Containing Armstrong's Acid.

This study demonstrates the use of 1,5-naphthalenedisulfonic acid as a suitable building block for the efficient and economic preparation of alternating sulfonated polyphenylenes with high ion-exchange capacity (IEC) via Suzuki polycondensation. Key to large molar masses is the use of an all-meta-terphenyl comonomer instead of m-phenyl, the latter giving low molar masses and brittle materials. A protection/deprotection strategy for base-stable neopentyl sulfonates is successfully implemented to improve the solubility and molar mass of the polymers. Solution-based deprotection of polyphenylene neopentyl sulfonates at 150 °C in dimethylacetamide eliminates isopentylene quantitatively, resulting in membranes with high IEC (2.93 mequiv/g) and high proton conductivity (σ = 138 mS/cm). Water solubility of these copolymers with high IEC requires thermal cross-linking to prevent their dissolution under operating conditions. By balancing the temperature and time of the cross-linking process, water uptake can be restricted to 50 wt %, retaining an IEC of 2.33 mequiv/g and a conductivity of 85 mS/cm. Chemical stability is addressed by treatment of the membranes under Fenton's conditions and by considering barrier heights for desulfonation using density functional theory (DFT) calculations. The DFT results suggest that 1,5-disulfonated naphthalenes are at least as stable as sulfonated polyphenylenes against desulfonation.

The crystal structure of quaternary (Sn,Pb,Bi)Pt.

Quaternary (Sn,Pb,Bi)Pt was synthesized by melting of the elements in an evacuated silica glass ampoule. The crystal structure was established by single-crystal X-ray diffraction and adopts an atomic arrangement of the NiAs type with additional occupation of the voids. Decisive for the refinement was the composition of the crystals as determined by energy dispersive X-ray spectroscopy (EDXS), resulting in a formula of (Sn0.15Pb0.54Bi0.31)Pt.

Synthesis of Isostructural Intermetallic Sn-Pb-Bi-Pt Platform Materials for Catalytic Investigations.

The isostructural region (Sn,Pb,Bi)Pt has been established over a wide range of the quasi-ternary section of the quaternary phase diagram. A synthesis protocol was developed, and single-phase compounds were thoroughly characterized, revealing linear relationships between the volume of the unit cell and the substitution degree for the NiAs type of crystal structure. Together with the already established (Pb,Bi)Pt series, the isostructural cut at 50 atom % Pt forms an ideal platform to independently investigate the influence of electronic and structural properties for physical and chemical applications, such as electrocatalysis. The three binary endmembers SnPt, PbPt, and BiPt are active materials in a variety of electrocatalytic oxidation and reduction reactions such as methanol oxidation and oxygen reduction, respectively. By gradual substitution, a fully independent tuning of interatomic distances and electronic densities can be achieved without altering the crystal structure. This unique adaptability is gated behind the requirement of extended homogeneity ranges of at least quaternary intermetallic compounds. Here, we present this new platform for systematic investigations in (electro) catalysis.

Disentangling Electronic and Geometric Effects in Electrocatalysis through Substitution in Isostructural Intermetallic Compounds.

Efficient development of catalytic materials requires knowledge of the decisive parameters defining the catalytic properties. In multicomponent metallic catalysts, these are categorized as electronic and geometric effects, yet they are strongly interrelated. A systematic disentanglement can be achieved by fixing one parameter while altering the other, which becomes possible through the substitution in isostructural intermetallic compounds. This approach enables the evaluation of electronic or geometric contributions both individually and combined. Herein, this is achieved by substitution of indium (three valence electrons) with tin (four valence electrons) in the series In1-xSnxPd2, which allows for a systematic variation of the total number of electrons per unit cell with only a minor variation of the unit cell parameters and thus the evaluation of the electronic effect. Geometric effects were evaluated by substitution of indium with gallium in the Ga1-xInxPd2 series, which allows for a systematic variation of the interatomic distances while maintaining the same number of valence electrons per unit cell and close atomic coordinates. By substituting gallium with tin in the Ga1-xSnxPd2 series, both effects are combined and addressed simultaneously. The activity enhancement of the methanol oxidation reaction on the Ga1-xSnxPd2 series is attributed to the synergy of the combined effects.

Challenging the Durability of Intermetallic Mo-Ni Compounds in the Hydrogen Evolution Reaction.

Molybdenum-nickel materials are catalysts of industrial interest for the hydrogen evolution reaction (HER). Well-characterized surfaces of the single-phase intermetallic compounds Ni7Mo7, Ni3Mo, and Ni4Mo were subjected to accelerated durability tests (ADTs) and thorough characterization to unravel whether crystallographic ordering affects the activity. Their intrinsic instability leads to molybdenum leaching, resulting in higher specific surface areas and nickel-enriched surfaces. These are more prone to form Ni(OH)2 layers, which leads to deactivation of the Mo-Ni materials. The crystal structure of the intermetallic compounds has, due to the intrinsic instability of the materials in alkaline media, no effect on the activity. Ni7Mo7, identified earlier as durable, proves to be highly unstable in the applied ADTs. The results show that the enhanced activity of unsupported bulk Mo-Ni electrodes can solely be ascribed to increased specific surface areas.

Thin Coatings of α- and ß-Bi2O3 by Ultrasonic Spray Coating of a Molecular Bismuth Oxido Cluster and their Application for Photocatalytic Water Purification Under Visible Light.

Invited this month's cover picture are the groups of Professor Michael Mehring and Professor Marc Armbrüster at Chemnitz University of Technology. The cover pictures shows a graffiti displaying a distinctive part of the city center of the town. The artwork is oversprayed with the letters "TUC" (Technische Universität Chemnitz) using an bismuth oxido cluster from solution to obtain a yellow semiconductor coating of bismuth oxide, used to degrade the medicinal drug ethinyl estradiol under visible light irradiation. Read the full text of their Full Paper at https://doi.org/10.1002/open.201900323.

Thin Coatings of α- and ß-Bi2O3 by Ultrasonic Spray Coating of a Molecular Bismuth Oxido Cluster and their Application for Photocatalytic Water Purification Under Visible Light.

Thin coatings of Bi2O3 were deposited on glass substrates by ultrasonic spray coating of THF solutions of the molecular precursor [Bi38O45(OMc)24(DMSO)9] ⋅ 2DMSO ⋅ 7H2O (OMc=O2CC3H5) followed by hydrolysis and subsequent annealing. Depending on the synthetic protocol, the bismuth oxido cluster was transformed into either α- or ß-Bi2O3. The as-synthesized Bi2O3 coatings were characterized by powder X-ray diffraction (PXRD), thickness measurements, diffuse reflectance UV-Vis spectroscopy (DRS), photoluminescence (PL) spectroscopy, Raman spectroscopy and scanning electron microscopy (SEM). The thin coatings (thickness: 5-16 µm) were compared with regard to their performance in photocatalytic rhodamine B (RhB) decomposition under visible light irradiation. The ß-Bi2O3 coatings, that showed the highest photocatalytic activity, were used for the photocatalytic decomposition of other pollutants such as triclosan and ethinyl estradiol. In addition, the interplay between the photooxidation that is induced by the excitation of the catalyst using visible light and the photosensitized decomposition pathway was studied by degradation experiments of aqueous rhodamine B solutions using ß-Bi2O3 coatings.