Lowering of the oxygen evolution reaction (OER) noble metal catalyst loading on the anode of a polymer electrolyte membrane water electrolysis (PEMWE) is a necessity for enabling the large-scale hydrogen production based on this technology. This study introduces a remarkably active OER catalyst that is based on the dispersion of Ir nanoparticles on a highly conductive oxide support. The catalyst was designed in a way to combine all characteristics that have been reported to enhance the OER activity on an Ir oxide-based catalyst, including high catalyst dispersion and controlling the Ir catalyst particle size, so that this design approach provides both high surface area to Ir mass ratio and at the same time ensures maximum synergetic interaction with the oxide support, termed strong metal−support interaction (SMSI). This was achieved through using a high surface area (50 m 2 /g) and highly conductive antimony-doped tin oxide support (2 S/cm), where combining a high catalyst dispersion and maximum SMSI resulted in a very high OER activity of the Ir/ATO catalyst (≈1100 A/g Ir , at 80 °C and 1.45 V RHE ). This enhanced activity will allow a significant reduction (ca. 75-fold) in the precious metal catalyst loading when this catalyst is implemented in the anode of a PEMWE.

In single-molecule applications, the photostability of fluorescent molecules is a key parameter. We apply fluorescence correlation spectroscopy to compare the photostability of four fluorescein and four borondipyrromethene (BODIPY) dyes of similar structure but different triplet yields. The latter class of dyes are more stable. In the kinetic analysis the, diffusion and photobleaching are treated as competitive processes. Corrections, which account for saturation and for experimental artefacts, are achieved solely by using experimental data. Photobleaching is found to occur mainly through the first excited singlet state S(1), in contrast to previous findings.

The polymer binders used in most lithium-ion batteries (LIBs) serve only a structural role, but there are exciting opportunities to increase performance by using polymers with combined electronic and ionic conductivity. To this end, here we examine dihexyl-substituted poly­(3,4-propylenedioxythiophene) (PProDOT-Hx2) as an electrochemically stable π-conjugated polymer that becomes electrically conductive (up to 0.1 S cm–1) upon electrochemical doping in the potential range of 3.2 to 4.5 V (vs Li/Li+). Because this family of polymers is easy to functionalize, can be effectively fabricated into electrodes, and shows mixed electronic and ionic conductivity, PProDOT-Hx2 shows promise for replacing the insulating polyvinylidene fluoride (PVDF) commonly used in commercial LIBs. A combined experimental and theoretical study is presented here to establish the fundamental mixed ionic and electronic conductivity of PProDOT-Hx2. Electrochemical kinetics and electron spin resonance are first used to verify that the polymer can be readily electrochemically doped and is chemically stable in a potential range of interest for most cathode materials. A novel impedance method is then used to directly follow the evolution of both the electronic and ionic conductivity as a function of potential. Both values increase with electrochemical doping and stay high across the potential range of interest. A combination of optical ellipsometry and grazing incidence wide angle X-ray scattering is used to characterize both solvent swelling and structural changes that occur during electrochemical doping. These experimental results are used to calibrate molecular dynamics simulations, which show improved ionic conductivity upon solvent swelling. Simulations further attribute the improved ionic conductivity of PProDOT-Hx2 to its open morphology and the increased solvation is possible because of the oxygen-containing propylenedioxythiophene backbone. Finally, the performance of PProDOT-Hx2 as a conductive binder for the well-known cathode LiNi0.8Co0.15Al0.05O2 relative to PVDF is presented. PProDOT-Hx2-based cells display a fivefold increase in capacity at high rates of discharge compared to PVDF-based electrodes at high rates and also show improved long-term cycling stability. The increased rate capability and cycling stability demonstrate the benefits of using binders such as PProDOT-Hx2, which show good electronic and ionic conductivity, combined with electrochemical stability over the potential range for standard cathode operation.

We report the synthesis and characterization of the missing reference core compound 4,4-Difluoro-4-bora-(3a,4a)-diaza-s-indacene 1 of the BODIPY fluorescent dye class. The compound exhibits a fluorescence lifetime of 7.2 ns and has a high photostability.

We thank the Deutsche Forschungsgemeinschaft (DFG) for their financial support (EXC81, SFB623). We also acknowledge Stephen Hashmi (Heidelberg University) for fruitful discussions. Volker Huch is gratefully acknowledged for X-ray crystallography. Michael Schwering and Dominik Brox have continuously supported the project with their expertise in microscopy.Supporting information for this article, including details of reagents used, instruments, and analytical data, including spectroscopic characterization, is available on the WWW under http://dx.

Isotactic nonconjugated pendant electroactive polymers (NCPEPs) have recently shown potential to achieve comparable charge carrier mobilities with conjugated polymers. Here we report the broader influence of tacticity in NCPEPs, using poly­((N-carbazolylethylthio)­propyl methacrylate) (PCzETPMA) as a model polymer. We utilized the thiol–ene reaction as an efficient postpolymerization functionalization method to achieve pendant polymers with high isotacticity and syndiotacticity. We found that a stereoregular isotactic polymer showed ∼100 times increased hole mobility (μh) as compared to both atactic and low molecular weight syndiotactic PCzETPMA, achieving μh of 2.19 × 10–4 cm2 V–1 s–1 after annealing at 120 °C. High molecular weight syndiotactic PCzETPMA gave ∼10 times higher μh than its atactic counterpart, comparable to isotactic PCzETPMA after annealing at 150 °C. Importantly, high molecular weight syndiotactic PCzETPMA showed a dramatic increase in μh to 1.82 × 10–3 cm2 V–1 s–1 when measured after annealing at 210 °C, which surpassed the well-known conjugated polymer poly­(3-hexylthiophene) (P3HT) (μh = 4.51 × 10–4 cm2 V–1 s–1). MD simulations indicated short-range π–π stacked ordering in the case of stereoregular isotactic and syndiotactic polymers. This work is the first report of charge carrier mobilities in syndiotactic NCPEPs and demonstrates that the tacticity, annealing conditions, and molecular weight of NCPEPs can strongly affect μh.

The first report on direct arylation polymerization with copper catalysts and aryl-bromide monomers expands the sustainability and practicality of DArP.

We reinvestigated the solvatochromism of 8-hydroxypyrene-1,3,6-trisulfonate (pyranine) in conjunction with that of 8-methoxypyrene-1,3,6-trisulfonate and of 1-hydroxypyrene (pyrenol) by use of 25 different solvents. Conclusions for the prediction of ESPT behaviour of synthetic dyes were drawn by comparison with the solvatochromism of p-hydroxystyryl Bodipy dyes. Solvents were chosen according to their Kamlet-Taft parameters alpha and beta for elucidating the acidicity of the dyes and the basicity of their conjugated bases in the ground and excited state. Comparison of the spectra of pyranine and pyrenol in solvents with varying beta-values revealed that the acidity of both dyes is similar therein. The well-known ESPT behaviour of pyranine in water is assigned to a change of the electronic state at alpha-values approximately 0.7 to 0.8. The high acidity of this excited state also appears in the vanishing solvatochromism of the photoproduct fluorescence. However, prediction of an ESPT tendency of synthetic dyes might fail when only fluorescence emission data are considered. We propose to refer instead to the energetic difference of the 0-0 transition in absorption together with the solvatochromism of the acidic form in aprotic solvents of similar polarity.