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Exploration of efficient molecular water oxidation catalysts for long-term application remains a key challenge for the conversion of renewable energy sources into fuels. Cuboidal {Co4O4} complexes keep attracting interest as molecular water oxidation catalysts as they combine features of both heterogeneous and homogeneous catalysis with bio-inspired motifs. However, the application of many cluster-based catalysts for the oxygen evolution reaction still requires new stabilization strategies. Drawing inspiration from the stabilizing effects of natural polymers, we introduce a conductive polymer-hybrid approach to covalently immobilize {Co4O4} cubane oxo clusters as oxygen evolution catalysts. Polypyrrole is applied as an efficient p-type conducting polymer that promotes hole transfer during the oxygen evolution reaction, resulting in higher turnover frequency compared to the pristine {Co4O4} oxo cluster and heterogeneous Co-oxide benchmarks. The asymmetric coordination of {Co4O4} not only mitigates catalyst decomposition pathways, but also increases the catalytic efficiency by exposing a directed cofacial dihydroxide motif during catalysis. Cuboidal {Co4O4} complexes are attractive molecular water oxidation catalysts as they combine features of both heterogeneous and homogeneous catalysis with bio-inspired motifs, but their application requires stabilization strategies. Here, the authors introduce a conductive polymer-hybrid approach to covalently immobilize {Co4O4} clusters. [ABSTRACT FROM AUTHOR]

Atomically defined assemblies of dye molecules (such as H and J aggregates) have been of interest for more than 80 years because of the emergence of collective phenomena in their optical spectra.sup.1-3, their coherent long-range energy transport, their conceptual similarity to natural light-harvesting complexes.sup.4,5, and their potential use as light sources and in photovoltaics. Another way of creating versatile and controlled aggregates that exhibit collective phenomena involves the organization of colloidal semiconductor nanocrystals into long-range-ordered superlattices.sup.6. Caesium lead halide perovskite nanocrystals.sup.7-9 are promising building blocks for such superlattices, owing to the high oscillator strength of bright triplet excitons.sup.10, slow dephasing (coherence times of up to 80 picoseconds) and minimal inhomogeneous broadening of emission lines.sup.11,12. So far, only single-component superlattices with simple cubic packing have been devised from these nanocrystals.sup.13. Here we present perovskite-type (ABO.sub.3) binary and ternary nanocrystal superlattices, created via the shape-directed co-assembly of steric-stabilized, highly luminescent cubic CsPbBr.sub.3 nanocrystals (which occupy the B and/or O lattice sites), spherical Fe.sub.3O.sub.4 or NaGdF.sub.4 nanocrystals (A sites) and truncated-cuboid PbS nanocrystals (B sites). These ABO.sub.3 superlattices, as well as the binary NaCl and AlB.sub.2 superlattice structures that we demonstrate, exhibit a high degree of orientational ordering of the CsPbBr.sub.3 nanocubes. They also exhibit superfluorescence--a collective emission that results in a burst of photons with ultrafast radiative decay (22 picoseconds) that could be tailored for use in ultrabright (quantum) light sources. Our work paves the way for further exploration of complex, ordered and functionally useful perovskite mesostructures. Through precise structural engineering, perovskite nanocrystals are co-assembled with other nanocrystal materials to form a range of binary and ternary perovskite-type superlattices that exhibit superfluorescence., Author(s): Ihor Cherniukh [sup.1] [sup.2] , Gabriele Rainò [sup.1] [sup.2] , Thilo Stöferle [sup.3] , Max Burian [sup.4] , Alex Travesset [sup.5] , Denys Naumenko [sup.6] , Heinz Amenitsch [sup.6] [...]

Metal‐based chalcogenides exhibit great promise for overall water splitting, yet their intrinsic catalytic reaction mechanisms remain to be fully understood. In this work, we employed operando X‐ray absorption (XAS) and in situ Raman spectroscopy to elucidate the structure–activity relationships of low‐crystalline cobalt sulfide (L−CoS) catalysts toward overall water splitting. The operando results for L−CoS catalyzing the alkaline hydrogen evolution reaction (HER) demonstrate that the cobalt centers in the bulk are predominantly coordinated by sulfur atoms, which undergo a kinetic structural rearrangement to generate metallic cobalt in S−Co−Co−S moieties as the true catalytically active species. In comparison, during the acidic HER, L−CoS undergoes local structural optimization of Co centers, and H2 production proceeds with adsorption/desorption of key intermediates atop the Co−S−Co configurations. Further operando characterizations highlight the crucial formation of high‐valent Co4+ species in L−CoS for the alkaline oxygen evolution reaction (OER), and the formation of such active species was found to be far more facile than in crystalline Co3O4 and Co‐LDH references. These insights offer a clear picture of the complexity of active species and site formation in different media, and demonstrate how their restructuring influences the catalytic activity. [ABSTRACT FROM AUTHOR]

Catalytic hydrogenolysis has the potential to convert high‐density polyethylene (HDPE), which comprises about 30 % of plastic waste, into valuable alkanes. Most investigations have focused on increasing activity for lab grade HDPEs displaying low molecular weight, with limited mechanistic understanding of the product distribution. No efficient catalyst is available for consumer grades due to their lower reactivity. This study targets HDPE used in bottle caps, a waste form generated globally at a rate of approximately one million units per hour. Ultrafine ruthenium particles (1 nm) supported on titania (anatase) achieved up to 80 % conversion into light alkanes (C1−C45) under mild conditions (498 K, 20 bar H2, 4 h) and were reused for three cycles. Small ruthenium nanoparticles were critical to achieving relevant conversions, as activity sharply decreased with particle size. Selectivity commonalities and peculiarities across HDPE grades were disclosed by a reaction modelling approach applied to products. Isomerization cedes to backbone scission as the reaction progresses. Within this trend, low molecular weight favor isomerization whilst high molecular weight favor cleavage. Commercial caps obeyed this trend with decreased activity, anticipating the influence of additives in realistic processing. This study demonstrates effective hydrogenolysis of consumer grade polyethylene and provides selectivity patterns for product control. [ABSTRACT FROM AUTHOR]

Using a highly coherent focused electron probe in a 5th order aberration-corrected transmission electron microscope, we report on resolving a crystal spacing less than 50 pm. Based on the geometrical source size and residual coherent and incoherent axial lens aberrations, an electron probe is calculated, which is theoretically capable of resolving an ideal 47 pm spacing with 29percent contrast. Our experimental data show the 47 pm spacing of a Ge 114 crystal imaged with 11-18percent contrast at a 60-95percent confidence level, providing the first direct evidence for sub 50-pm resolution in ADF STEM imaging.