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Thermal treatments can have detrimental effects on the photocatalytic hydrogen (H2) evolution performance and impact the formation mechanism of the active state of surface‐supported co‐catalysts. In this work, a range of Ni‐based co‐catalysts is investigated immobilized on TiO2, evaluated their H2 evolution rates in situ over 21 h, and analyzed the samples at various stages with a comprehensive set of spectroscopic and microscopy techniques. It is found that achieving the optimal hydrogen evolution (HER) performance requires the right Ni0:Ni2+ ratio, rather than only Ni0, and that Ni needs to be weakly adsorbed on the TiO2 surface to create a dynamic state. Under these conditions, Ni can undergo an efficient redox shuttle, involving the transformation of Ni2+ to Ni0 and back after releasing the accumulated electrons for H+ reduction (i.e., Ni2+ ↔ Ni0). Yet, when the calcination temperature of the Ni/TiO2 photocatalysts increases, resulting in stronger coordination/adsorption of Ni on TiO2, this process is gradually inhibited, which ultimately leads to decreased HER performances. This work emphasizes the significance and influence of thermal treatments on the Ni active state formation – a process that can be relevant to other HER co‐catalysts. [ABSTRACT FROM AUTHOR]

Photocatalytic production of CO from CO 2 has the potential for safe and atom-economic production of feedstock chemicals via in situ carbonylation chemistry. We developed novel ionic liquid-based polymeric materials through radical copolymerisation of 1-butyl-3-vinylimidazolium chloride and photocatalytically active Re- and Ru-complexes that serve as the CO 2 reduction catalyst and photosensitiser, respectively. The crosslinked polymeric framework allows for the facile immobilisation of molecular organometallic complexes for use as heterogenised catalysts; moreover, the involved imidazolium core units co-catalyze the reduction of CO 2 via covalent interaction. The ratio of sensitiser and catalyst was analysed by laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS) and set in relation to results from photocatalytic experiments. Ultimately, the heterogenous polymeric framework showed high selectivity for CO formation on photocatalytic CO 2 reduction with improved stability to the corresponding homogenous system., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The ongoing transition to renewable energy sources and the implementation of artificial photosynthetic setups call for an efficient and stable water oxidation catalyst (WOC). Here, we heterogenize a molecular all-inorganic [Co III Co II (H 2 O)W 11 O 39 ] 7- ({Co III Co II W 11 }) Keggin-type polyoxometalate (POM) onto a model TiO 2 surface, employing a 3-aminopropyltriethoxysilane (APTES) linker to form a novel heterogeneous photosystem for light-driven water oxidation. The {Co III Co II W 11 }-APTES-TiO 2 hybrid is characterized using a set of spectroscopic and microscopic techniques to reveal the POM integrity and dispersion to elucidate the POM/APTES and APTES/TiO 2 binding modes as well as to visualize the attachment of individual clusters. We conduct photocatalytic studies under heterogeneous and homogeneous conditions and show that {Co III Co II W 11 }-APTES-TiO 2 performs as an active light-driven WOC, wherein {Co III Co II W 11 } acts as a stable co-catalyst for water oxidation. In contrast to the homogeneous WOC performance of this POM, the heterogenized photosystem yields a constant WOC rate for at least 10 h without any apparent deactivation, demonstrating that TiO 2 not only stabilizes the POM but also acts as a photosensitizer. Complementary studies using photoluminescence (PL) emission spectroscopy elucidate the charge transfer mechanism and enhanced WOC activity. The {Co III Co II W 11 }-APTES-TiO 2 photocatalyst serves as a prime example of a hybrid homogeneous-heterogeneous photosystem that combines the advantages of solid-state absorbers and well-defined molecular co-catalysts, which will be of interest to both scientific communities and applications in photoelectrocatalysis and CO 2 reduction., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Molybdenum disulphide (MoS 2 ) thin films have received increasing interest as device-active layers in low-dimensional electronics and also as novel catalysts in electrochemical processes such as the hydrogen evolution reaction (HER) in electrochemical water splitting. For both types of applications, industrially scalable fabrication methods with good control over the MoS 2 film properties are crucial. Here, we investigate scalable physical vapour deposition (PVD) of MoS 2 films by magnetron sputtering. MoS 2 films with thicknesses from ≈10 to ≈1000 nm were deposited on SiO 2 /Si and reticulated vitreous carbon (RVC) substrates. Samples deposited at room temperature (RT) and at 400 °C were compared. The deposited MoS 2 was characterized by macro- and microscopic X-ray, electron beam and light scattering, scanning and spectroscopic methods as well as electrical device characterization. We find that room-temperature-deposited MoS 2 films are amorphous, of smooth surface morphology and easily degraded upon moderate laser-induced annealing in ambient conditions. In contrast, films deposited at 400 °C are nano-crystalline, show a nano-grained surface morphology and are comparatively stable against laser-induced degradation. Interestingly, results from electrical transport measurements indicate an unexpected metallic-like conduction character of the studied PVD MoS 2 films, independent of deposition temperature. Possible reasons for these unusual electrical properties of our PVD MoS 2 thin films are discussed. A potential application for such conductive nanostructured MoS 2 films could be as catalytically active electrodes in (photo-)electrocatalysis and initial electrochemical measurements suggest directions for future work on our PVD MoS 2 films.