The first example of light driven, homogeneous hydrogen evolution reactivity of a molecular molybdenum sulfide is presented together with experimental and theoretical insights into the reasons for the unusually high activity.

Low-valent iron centers are critical intermediates in chemical and bio-chemical processes. Herein, we show the first example of a low-valent Fe center stabilized in a high-valent polyoxometalate framework. Electrochemical studies show that the Fe -functionalized molecular vanadium(V) oxide (DMA)[Fe ClV O Cl] (DMA=dimethylammonium) features two well-defined, reversible, iron-based electrochemical reductions which cleanly yield the Fe species (DMA)[Fe ClV O Cl] . Experimental and theoretical studies including electron paramagnetic resonance spectroscopy and density functional theory computations verify the formation of the Fe species. The study presents the first example for the seemingly paradoxical embedding of low-valent metal species in high-valent metal oxide anions and opens new avenues for reductive electron transfer catalysis by polyoxometalates.

High-performance batteries and supercapacitors require the molecular-level linkage of charge transport components and charge storage components. This study shows how redox-tunable Lindqvist-type molecular metal oxide anions [V n M 6-n O 19 ] (2+n)− (M = W(VI) or Mo(VI); n = 0, 1, 2) can be incorporated in cationic polypyrrole (PPy) conductive polymer films by means of electrochemical polymerization. Electron microscopy and (spectro-)electrochemistry show that the electroactivity and morphology of the composites can be tuned by Lindqvist anion incorporation. Reductive electrochemical "activation" of the Lindqvist-PPy composites leads to significantly increased electrical capacitance (range: ≈25-38 F g −1 , increase up to ≈25×), highlighting that this general synthetic route gives access to promising capacitive materials with suitable long-term stability. Electrochemical, electron microscopic, and Raman spectroscopic analyses together with density functional theory (DFT) calculations provide molecular-level insight into the effects of Lindqvist anion incorporation in PPy films and their role during reductive activation. The study therefore provides fundamental understanding of the principles governing the bottom-up integration of molecular components into nanostructured composites for electrochemical energy storage.The ORCID identification number(s) for the author(s) of this article can be found under http://dx.The combination of in situ (spectro-)electrochemistry and theoretical calculations allows us to provide initial molecular level understanding of the underlying activation mechanism. The study therefore provides new molecular design principles for capacitive charge storage devices.

The enhanced catalytic and photocatalytic activities of a RuO 2 layer deposited on the TiO 2 (110) surface were examined by constructing model RuO 2 /TiO 2 (110) heterostructures with and without oxygen vacancies and performing density functional calculations. The formation of the heterojunction only weakly affects the atomic structure of the interface due to a pseudomorphic deposition but causes a strong electron density accumulation in the interface as well as a bending of the valence and conduction bands of TiO 2 . The electron accumulation in the interface creates a strong internal electric field, which helps to effectively separate photogenerated electron−hole pairs during a photocatalytic process. Finally, we report on the catalytic role of oxygen vacancies at the surface.

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