Transition metal nitrides and oxynitrides exhibit catalytic properties that make them promising candidates as alternatives to noble metals. A series of high-surface-area chromium oxynitrides, CrOxN1-x (0.10 < x < 0.25), was synthesized from a cheap hydroxide precursor and investigated as unconventional heterogeneous catalysts for the Water-Gas Shift (WGS) reaction. Currently, this reaction is predominantly catalyzed by platinum. Replacing platinum with chromium oxynitrides could provide a more cost-effective and environmentally friendly solution.

(Text in French) Semiconductors for photovoltaic and photoelectrochemical cells. The development of stable and efficient photoelectrochemical and photovoltaic cells benefits from the creation of new photoactive layers based on semiconductor materials and a detailed understanding of their physicochemical properties. This article aims to highlight the research conducted at ISCR in this field and related collaborative efforts. Topics covered will include photovoltaic solar cells based on halogenated perovskites as well as antimony triselenide, the design of photoelectrodes (photoanodes and photocathodes) through the assembly of inorganic molecular nanoclusters, and photoelectrodes based on silicon or III-V semiconductors epitaxially grown on silicon for water photoelectrolysis.

Identifying systems composed of earth-abundant elements capable of photoinduced electron-transfer represents a major breakthrough for the development of sustainable photocatalytic processes. Herein, we demonstrate that octahedral tungsten-halide clusters constitute a promising new class of robust photosensitizers, owing to their exceptional chemical stability, intense luminescence, and long-lived triplet excited states. Upon irradiation in aqueous solution, these species transfer an electron to polyoxometalates (POMs), well-known molecular catalysts capable of multielectron redox chemistry. More specifically, we investigate the photophysical properties of supramolecular systems combining the cluster-based motif [{W6Ii8}Cla6]2- and a series of archetypal POMs ([PW12O40]3-, [SiW12O40]4-, [BW12O40]5-, [P2W18O62]6-) as electron-acceptor units, in the presence of γ-cyclodextrin (γ-CD), which acts as both a supramolecular assembly scaffold and a stabilizing agent. The photoinduced electron-transfer process was investigated using steady-state and time-resolved optical spectroscopy, complemented by spectro-electrochemical measurements, which unambiguously confirm electron transfer from the excited cluster to the POMs. Furthermore, we demonstrate that both the ionic charge of the POMs and the presence of γ-CD significantly influence the efficiency of the process. This work highlights the dual role of γ-CD, which facilitates the association of two negatively charged inorganic units and stabilizes the charge-separated state by maintaining an appropriate spatial arrangement within the supramolecular assembly.

Lead halide perovskite solar cells, despite their outstanding optoelectronic properties, suffer from poor long-term stability under environmental stressors, limiting their industrial scalability. To address this, we explored photoelectrodes composed of...

An original synthesis route for tailoring the hydrogen evolution reaction (HER) activity of alpha-Mo2C-based catalysts is reported using soluble and air-stable halide precursors built from nanosized [Mo6Cl14]2- cluster units, namely (H3O)2[Mo6Cl14]7H2O and ((n-C4H9)4N)2[Mo6Cl14], combined with sucrose as a biosourced carbon source. The resulting catalysts consist of nanosized alpha-Mo2C crystallites embedded in residual carbon, with molybdenum preserved in the +2 oxidation state from the halide precursor to the final material. The chemical nature of the precursor strongly influences the phase composition, homogeneity, specific surface area, and morphology of the resulting alpha-Mo2C powders. Among the synthesized materials, the catalyst derived from ((n-C4H9)4N)2[Mo6Cl14] exhibits the highest HER performance in alkaline media, characterized by the lowest overpotential at 10 mA cm-2, the largest electrochemical surface area, and the smallest Tafel slope. Long-term electrochemical testing also reveals surface activation during operation, enhancing both activity and stability. These findings indicate that the catalytic behavior of alpha-Mo2C cannot be attributed solely to nanostructuring effects but arises from a subtle interplay between crystallite size, porosity, and surface chemistry. The use of Mo6 cluster-based precursors thus provides an effective and versatile approach to control the composition and molybdenum oxidation state of molybdenum carbides, enabling the design of advanced powder materials with optimized surface and electrocatalytic properties.

ABSTRACT A phosphorescent molybdenum octahedral cluster compound is homogeneously associated with organic liquid crystals by means of weak supramolecular interactions up to a doping concentration of 45.8 wt.%. Polarized Optical Microscopy, Differential Scanning Calorimetry, and X‐ray Scattering experiments demonstrate that such class of new compounds shows a calamitic liquid crystal‐like behavior at low temperature, even below 0°C. Photophysical studies reveal a strong emission in the red‐NIR with a high oxygen sensitivity. This first of its kind material offers promising perspectives in the field of optoelectronics, sensing, and photonics.

(Text in French)Dihydrogen: production by water electrolysis, molecular storage and conversion in a fuel cell. The production of dihydrogen (H2) by water electrolysis, its molecular storage and its use in fuel cells are strong research topics at ISCR, requiring complementary expertises in electrochemistry, molecular chemistry and materials chemistry. This know-how has been applied to elaborate and optimise structured catalytic electrode materials based on transition metals, primarily Ni, Mo and their derivatives, for the alkaline electrolysis of water at room temperature or near-room temperature. Innovative electrode materials are also being developed to convert this molecule into electricity in solid oxide fuel cells (SOFC), which have the advantage of operating at lower temperatures and for longer periods compared to conventional fuel cells. In addition to this work, the ISCR is also investigating the storage of H2 in small organic molecules that are liquid at room temperature, such as formic acid. Using ad-hoc organometallic catalysts, these small molecules can be efficiently dehydrogenated.

Correction for ‘From cluster halides to catalysts: nanostructured molybdenum carbides for efficient hydrogen evolution reaction’ by Guillaume Dubois et al. , J. Mater. Chem. A , 2026, 14 , 11332–11343, https://doi.org/10.1039/D5TA09668E.

Photoelectrodes based on transition metal clusters (MCs) are critical for advancing solar energy conversion, where precise control over film morphology and electronic properties is essential. While electrophoretic deposition (EPD) has been widely used for the design of MCs-based photoelectrodes, its intrinsic limitations-such as poor film homogeneity, crack formation, and limited microstructural control-compromise device performance. In this study, we demonstrate that electrodeposition (ED) of [{Mo6Ii 8}Ia 6]2- clusters produces homogeneous, crack-free films with the composition [{Mo6Ii 8}Ia 4(H2O)a 2}]& centerdot;xH2O. The ED process, driven by a two-step oxidation mechanism (1.1 and 1.6 V vs. Ag/AgCl), enables unprecedented control over film thickness (60-600 nm) and microstructure, resulting in increased photoconductivity (photocurrent 2-3 times higher and lower charge transfer resistance, R tc similar to 500 Omega). The films exhibit ambipolar conductivity and a quasi-pinned mid-gap Fermi level, confirming their potential for high-performance solar energy applications. Compared to EPD-derived films, ED films show enhanced charge extraction efficiency and minimized recombination losses, which are attributed to their defect-free microstructure and stable electronic properties. This work establishes ED as a superior method for fabricating high-quality MC-based photoelectrodes, addressing key limitations of traditional deposition techniques.

The optical properties, photo-decomposition and photo-reactivity of [Mo6I14]2- clusters and their associated photo-products are examined in the gas phase. The UV-visible optical spectrum of the electron-rich [Mo6I14]2- cluster is measured and the wavelength dependence of the principal fragments is interpreted on the basis of the quantum chemistry (QC) simulated spectrum and detailed transitions. A special focus of attention is the photo-generated [Mo6I14]- and photo-specific radical [Mo6I13]2-˙ as well as halogen-depleted clusters [Mo6In]- with n < 14. The fragmentation and reaction energetics of all species are examined with a combination of mass spectrometry experiments, ion-molecule reactions with O2 and CO2 under irradiation and QC simulations. Reactions with O2 are shown to be very exergonic with up to 5 eV release when O2 is dissociated on the cluster. Experimental evidence for the photo-decomposition of CO2 into CO and O on [Mo6In]- ions is provided together with detailed QC energetics.

Transition metal carbides and nitrides demonstrate very interesting electrocatalytic properties, close to those of noble metals. Indeed,platinum being a scarce and expensive element, carbides and nitrides could be an interesting alternative to make this technology economically viable. Recently, different authors reported promising (electro)catalytic properties of molybdenum carbides and nitrides. Herein we report the synthesis of Mo nitrides and carbides from original routes using transition metal cluster-based precursors or laser pyrolysis. The resulting nitrides and carbides were characterized by several complementary techniques (XRD, BET, SEM, etc.). These innovative modes of synthesis afford nanostructured compounds and the evaluation of Mo5N6 for the WGS reaction is reported.

The use of photonic crystals (PCs) is gaining interest regarding the interaction between light and organized structures. However, there are limitations to their use, such as production cost, rate, and substrate size. This study demonstrates an efficient and cost-effective fabrication of an opal structure based on the electrophoretic deposition (EPD) of self-made silica particles. The process allows one to reduce the fabrication time compared to classical evaporation or sedimentation methods, which can take days (evaporation) or weeks to months (sedimentation), while this method takes only 2 min. Silica particles with a diameter of less than 300 nm exhibit a markedly low sedimentation rate. Nevertheless, when they form a close-packed structure, they display a partial band gap in the visible region. The resulting opals are iridescent, from blue to red, and display additional angle-dependent colors. Furthermore, the synthesis of silica particles was completed within a 2 h time frame. Their washing, including a centrifugation step, did not result in the formation of aggregates. Such particles tend to break the long-range order in the PCs.

In this study, we investigate structural disorder and its implications in metal cluster (MC)-based compounds, specifically focusing on Cs2[{Mo6Xi8}Xa6] (X = Cl and Br). Utilizing synchrotron radiation X-ray diffraction, Fourier transform infrared spectroscopy, and luminescence measurements, we examined the incorporation of water molecules into these compounds and their effects on the crystal structure and optical properties. Our findings reveal that the presence of water molecules induces the lattice disorder, particularly the displacement of Cs atoms. Density functional theory calculations, including dispersion corrections (DFT-D), were employed to model superlattices incorporating varying positions and amounts of water molecules. The DFT-D results corroborated experimental data, indicating that water molecules notably impact the lattice structure by causing the Cs disorder without altering the fundamental trigonal arrangement of MC units. Our results reveal that the composition of the compounds, specifically the Cs/[{Mo6Xi8}Xa6] ratio, remains stoichiometric, regardless of the amount of water in their lattice. Luminescence spectroscopies confirmed that the water incorporation and the lattice disorder had little effect on the luminescence wavelength, but purification enhanced the luminescence efficiency. This study highlights the importance of understanding structural disorders in MC-based compounds for optoelectronic applications and demonstrates the utility of DFT calculations in exploring complex crystallographic phenomena.

We present detailed findings on the imaging, structure, and vibrational properties of novel hybrids of the red-emitting octahedral cluster-based compound Cs2Mo6Br14 encapsulated within single-walled carbon nanotubes (SWCNTs) of varying diameter. We explore the subtle relationship between the SWCNT internal diameter and Cs2Mo6Br14 cluster packing and find a hierarchical relationship between the nature of the cluster packing and a progressive tendency toward formation of one-dimensional (1D) structures as the SWCNT diameter narrows from 24 to 11 Å. As the internal SWCNT van der Waals radius approaches the outside diameter (OD) of the [{Mo6IIBr8i}Br6a]2- (more simplistically, [Mo6IIIBr14]2-) molecular anion species, SWCNT steric confinement causes a compositional elimination and polymerization resulting in the formation of reduced extended [Mo2IIIBr6]x nanoribbons which approximate 1D Ising model structures. Our experimental results, obtained through high-resolution transmission electron microscopy and Raman spectroscopy, are supplemented by density functional theory (DFT) calculations.

Metal atom clusters are well-defined nanoscale objects containing a precise number of metal atoms and ligands. Face-capped cluster units of the type [{M6L8i}L '(a)(6)] (M = Mo, Re, L = S, Se or I, L ' = Cl, Br, I, CN or H2O) exhibit unique optical and electronic properties that make them relevant building blocks for the rational design of nanomaterials using nanoarchitectonic concepts. Photoelectrodes based on Mo-6 and Re-6 clusters with various compositions obtained by deposition of uniform layers of those building blocks onto semiconducting surfaces were recently reported. Remarkably, high quality interfaces were formed not only between building blocks but also between the building blocks and the semiconducting surfaces. On the one hand, layers based on active {Mo6I8i} cluster cores exhibit an ambipolar behavior like carbon nanotube, graphene and transition metal chalcogenides. On the other hand, mixing the two types of {Re6S8i} and {Re6Se8i}-based building blocks enables the creation of micro-(p-n) junctions with enhanced photogenerated current intensity. Herein, we report new advances in the design of photoelectrodes using heterometallic Re4Mo2 cluster-based building blocks. The association of Mo and Re in {Re(4)Mo(2)Q(8)(i)} cluster cores (Q = S and Se) leads to electronic properties and absorption properties significantly different from those of homometallic {Mo6I8i} and {Re(6)Q(8)(i)}. Indeed, beyond different molecular orbital diagrams, the {Re(4)Mo(2)Q(8)(i)} cluster-based units exhibit 22 valence electrons per cluster (VEC) whereas the VEC value for {Mo6I8i} and {Re(6)Q(8)(i)} cluster units is 24. The mixing of rhenium and molybdenum within the same heterometallic cluster enables not only the optical and transport properties of the active layers to be optimized but it also enables the position of the energy levels to be tuned. This appears very appealing for band alignment engineering in order to design optimized photoelectrodes for solar energy conversion. We show herein that the energy levels of the photoelectrodes built on {Re(4)Mo(2)Q(8)} cluster-based layers immobilized on FTO surfaces are compatible with the photoelectrochemical water splitting.

A supramolecular hybrid organic–inorganic framework is generated by combining a blue fluorescent tetraphenylethylene-based dication and a red-NIR phosphorescent octahedral rhenium cluster tetra-anion.

The influence of the metal ratio on the geometric characteristics and crystal structures of heterometallic clusters with {Re6−xMoxQ8} cores was studied. Complexes with the same apical ligands form isostructural packings and form the solid solutions.

The enhanced photoluminescence of the Mo6 cluster was first reported by its incorporation into the anodic aluminum oxide (AAO), a photonic structure to delocalize the emission light. Two AAO structures with different pore sizes, densities, and shapes were controlled by pore widening treatment. The deposition of the negatively charged clusters at the bottom of the ordered AAO resulted in narrowing the PL peak at 680 nm with an enhanced intensity of 230 %. In addition, the disordered AAO supported the deposition of clusters on the surface that efficiently adjusted the shift of the PL peak position, obtaining a high intensity by more than 300 % in comparison with that of clusters deposited on the ITO-coated glass. The cluster-integrated photonic crystal could be an interesting material for applications that require efficient luminescence.

The mixing of rhenium and molybdenum within the same heterometallic cluster enables to modulate optoelectronic properties of the photo-active layers. Such {Re 4 Mo 2 Q 8 }-based photoelectrodes appear promising for the photoelectrochemical water splitting.

The mixing of rhenium and molybdenum within the same heterometallic cluster enables to modulate optoelectronic properties of the photo-active layers. Such {Re4Mo2Q8}-based photoelectrodes appear promising for the photoelectrochemical water splitting.