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The redox interactions between transition metal oxides and sulfur-containing compounds play a key role in catalytic processes and gas sensing technologies. In this study, we investigated the redox dynamics of Co₃O₄(111)/Ir(100) model catalysts in response to the adsorption and decomposition of hydrogen sulfide (H₂S) using synchrotron radiation photoelectron spectroscopy. Upon adsorption at 300 K, H₂S partially dissociates to form a mixture of SO₃²⁻, S²⁻, OH⁻, SH⁻, and chemisorbed H₂S. Subsequent annealing in ultrahigh vacuum induces H₂ desorption below 400 K followed by desorption of H₂S and H₂O above 400 K. At temperatures exceeding 500 K, S²⁻ is progressively oxidized to SO₃²⁻ and subsequently to SO₄²⁻. These transformations are accompanied by temperature-dependent redox processes involving the Co₃O₄(111) surface: initial reduction upon formation of SO₃²⁻ species at 300 K, partial re-oxidation upon H₂ desorption, and further reduction with H₂O release. Above 550 K, annealing induces charge redistribution and lattice oxygen migration, leading to a more homogeneous stoichiometry of the Co₃O₄(111) film. This phenomenon reduces the redox response to chemical transformations at the surface. The obtained insights into H₂S–Co₃O₄ redox interactions provide a foundation for the rational design of cobalt oxide-based catalytic gas sensors.

The catalytic conversion of biomass-derived sugars to 5-hydroxymethylfurfural (5-HMF) over zeolites is challenging due to internal mass transfer limitations arising from their microporous framework. To overcome this chronic issue, we prepared a set of micro-mesoporous zeolites (22 samples), whose properties were fully characterized in our previous study using XRD, XRF, N₂ Physisorption, IR with pyridine and tri-tert-butylpydirine, and ²⁷Al NMR. In this study, we aim to investigate how highly correlated zeolite properties, such as textural and acidic characteristics, influence fructose dehydration to 5-HMF, and to identify the key properties that govern the catalyst efficiency for sugar conversion. Since simple correlations of catalytic activity with individual descriptors of texture and acidity could not be found, we employed a chemometric approach, by using a combination of principal component analysis (PCA) and multiple linear regression (MLR). PCA was used to visualize the relationship between properties and catalyst performance, and to reduce redundant features for the subsequent MLR model, which was developed to correlate selected catalyst properties with 5-HMF yield. The model shows strong predictive performance, with randomly scattered residuals around zero. The property activity relationships reveal that preservation of the crystalline framework and enhancement of active sites accessibility are the key factors for improving catalytic performance for sugar conversion. However, this remains valid under the condition that excessive amorphization and related Lewis acidity are minimized. This study demonstrates that chemometrics is effective for analyzing property-activity relationships in a set of zeolites when these relationships are complex and highly correlated.

Biomass-derived levulinic acid and furfural are promising alternatives to traditional fossil-fuel-based raw materials for applications such as biofuels, biosolvents, resins, and bioplastics. In this work, we present the synthesis and characterization of highly reactive compounds that have been reported previously but remain unexplored in biomass valorization: diphosphine cobalt (I) complexes of the type [(diphosphine)CoPPh₃Cl]. These complexes are closely related to reported copper (I) and palladium (II) complexes, which have been successfully used in levulinic acid hydrogenation under impressive reaction conditions. These complexes were synthesized using commercially available, low-cost precursors and feature bidentate ligands with different bite angles and electronic and steric parameters. We applied these cobalt complexes in the direct hydrogenation of levulinic acid and furfural to produce selectively gamma-valerolactone (total conversion at 120°C and H₂ 300 psi, 99% yield) and tetrahydrofurfuryl alcohol (total conversion at 100°C and H₂ 300 psi, 98% yield), respectively, using relatively mild reaction conditions, among the mildest for nonnoble metals systems and through the in situ formation of cobalt nanoparticles which allows a high dispersion and TOFs of 41.7 for both system at its respective optimal conditions.

The influence of vanadium surface density and support nature (MoO₃, Nb₂O₅, and SiO₂) on V₂O₅-supported catalysts was systematically investigated for the CO₂-assisted oxidative dehydrogenation of propane (CO₂-ODHP). Two catalyst series were prepared: one with a fixed V₂O₅ loading (5 wt.%), leading to high vanadium surface densities, and another targeted to a theoretical density of 2 V.nm⁻², corresponding to highly dispersed species. The materials were characterized by XRD, N₂ physisorption, ED-XRF, H₂-TPR, UV-vis, and in situ Raman spectroscopy. Structural analyses revealed that high vanadium densities favored the aggregation into polymeric domains and clusters, whereas lower densities stabilized isolated and oligomeric VO₄ species. Catalytic tests showed that these isolated/oligomeric species were the most active for CO₂-ODHP, with those supported on MoO₃ and Nb₂O₅ exhibiting the highest propylene-specific activities due to strong VO_X-support interactions. Notably, the highly dispersed VO_x species on MoO₃ exhibited the best overall performance, owing not only to the presence of monomeric and polymeric vanadium domains but also to the intrinsic activity of MoO_x sites. Indeed, in this catalyst, CO₂ can effectively reoxidize V─O_v─V and V─O_v─Mo interfaces, as well as V═O terminal oxygen sites, through the rWGS reaction, thereby improving catalytic stability and preventing coke formation.

Cu/ZnO/ZrO₂ (CZZ) catalysts outperform conventional Cu/ZnO/Al₂O₃ (CZA) materials in methanol synthesis. Building on recent findings that CZA catalysts enable hydrogen release from the oxygen-containing LOHC compound dicyclohexylmethanol (H14-BP) below 200°C, this study investigates structure-activity correlations with CZZ catalysts in the partial dehydrogenation of H14-BP as a model reaction. CZZ materials were produced by continuous co-precipitation with subsequent batch suspension ageing. A ZrO₂ content between 4 and 8 mol% increased the specific surface area and catalytic activity. Zn-rich materials with elevated aurichalcite [(Cu,Zn)₅(OH)₆(CO₃)₂] content in the catalyst precursor achieved higher activity despite a reduced specific surface area. Ageing at 70°C promoted aurichalcite formation and improved performance, whereas higher temperatures reduced the specific surface area. An initial pH value of 6.7 enhanced Zn uptake during ageing and increased dehydrogenation productivity by 45% compared to pH 7.1. High catalyst productivity correlated with aurichalcite contents up to 98% and small crystallite sizes. Overall, CZZ outperformed CZA catalysts in the partial dehydrogenation of H14-BP, with the aurichalcite phase playing a crucial role. Our results demonstrate the potential of this material class for selective dehydrogenation reactions and enable targeted further development based on the correlation between material-specific properties and catalytic activity.

Herein, we present a concept for CO₂-assisted direct aqueous-phase hydrogenation of sodium acetate to ethanol, offering a salt-tolerant approach that circumvents energy-intensive acidification and simplifies biomass valorization. The reaction was performed over highly dispersed Pt on the CoAlPt (CAP) catalyst, which improves H₂ activation and drives hydrogen spillover, thereby increasing the reactive surface hydrogen species while mitigating excessively strong H adsorption that suppresses activity under alkaline conditions. The CAP catalyst achieved 90.88% ethanol selectivity with a productivity of 3.63 mmol·g⁻¹·h⁻¹ at 180°C without CO₂ addition. Introducing CO₂ (0.1 MPa) increased ethanol productivity to 4.92 mmol·g⁻¹·h⁻¹ by converting OH⁻ to HCO₃⁻ and shifting acetate speciation toward molecular acetic acid, which is more readily hydrogenated. The results obtained in this concept study highlight the potential of using CO₂ as a promoter for direct acetate hydrogenation towards a sustainable strategy for converting acetate-rich aqueous streams to ethanol and other value-added products.

Sustainable hydrogen production via low-temperature water electrolysis is key to advancing the hydrogen economy, with polymer electrolyte membrane water electrolysis (PEM-WE) as a central technology. However, sluggish oxygen evolution reaction (OER) kinetics at the anode limit PEM-WE efficiency. Iridium-based catalysts remain the benchmark due to their balance of activity and stability under harsh conditions, though iridium scarcity necessitates designs with reduced Ir content. Here, we report a highly active and stable OER catalyst based on TaO_x–IrO₂ nanoparticles synthesized via a reverse microemulsion method and calcined at 800°C. Encapsulation in silica nanoreactors enabled precise control over particle size and crystallinity during thermal treatment. The TaO_x–IrO₂ catalyst achieves a mass activity of 619 ± 93 mA mg_Ir⁻¹ at 1.55 V_RHE, outperforming commercial IrO₂ by a factor of 2.5 and bare IrO₂ synthesized under identical conditions. While TaO_x is electrochemically inactive, it shows exceptional dissolution resistance. The intrinsic stability of TaO_x–IrO₂, expressed via the S-number, exceeds that of commercial IrO₂ and matches bare IrO₂ calcined at 600°C. These results highlight TaO_x–IrO₂ as a promising OER catalyst, combining enhanced activity with notable stability, and support the development of durable, efficient catalysts for PEM-WE.