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Abstract: γ-Valerolactone (GVL) is a valuable bio-based chemical, solvent and fuel additive derived from levulinic acid, a key platform chemical from lignocellulosic biomass. Catalytic transfer hydrogenation (CTH) of levulinic acid using secondary alcohols as hydrogen donors presents a sustainable alternative to conventional hydrogenation with molecular hydrogen and can be efficiently carried out with inexpensive oxides. Here, we demonstrate how controlled silica incorporation onto zirconia provides a route to tailor acidity and thus direct reactivity in the CTH of levulinic acid and its esters to GVL. Silica-doped zirconia catalysts with varying Si loadings were synthesised via colloidal deposition and comprehensively characterised using ICP-OES, TEM/EDX, XRD, BET, NH3-TPD, pyridine-adsorbed DRIFTS, XPS and NEXAFS. Moderate silica incorporation enhanced surface area, stabilised the tetragonal ZrO2 phase, and increased total acidity, and most importantly, altered the Brønsted-to-Lewis acid balance that dictated the reactivity. Ethyl levulinate conversion was favoured over Lewis acid-rich catalysts, whereas LA conversion required higher Brønsted acidity. The optimal catalyst (6 wt% Si) delivered 80% GVL yield from levulinic acid at 190 °C in 4 hours. Isopropyl levulinate was identified as a side-product that can also convert to GVL via CTH, though less efficiently. The 6 wt% Si/ZrO2 catalyst exhibited excellent stability across three consecutive cycles without calcination, demonstrating resistance to leaching, a major drawback of heterogeneous catalysts in liquid-phase reactions, as well as to carbon deposition. This study demonstrates that silica doping provides an effective means of tuning zirconia acidity, resulting in catalysts that combine good stability with practical applicability in sustainable chemistry.

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Abstract: A combination of experimental methods and computational techniques have been used to investigate the composition of the zinc ferrite (ZnFe2O4) (1 1 1) single crystal surface under different preparation methods. Surface-sensitive XPS and NEXAFS measurements show that upon annealing in ultra-high vacuum (UHV), Zn depletion occurs, leading to the formation of an iron-rich (1 1 1) surface, whereas annealing in the presence of O2 gas maintains a more bulk-like ZnFe2O4 surface composition. Analysis of the Fe 2p photoemission (XPS) and Fe L edge X-ray absorption signals shows a clear difference in iron oxidation state and distribution between the two different preparation conditions. After annealing in UHV, a mixed Fe2+/Fe3+ oxidation state and a cation distribution like that of a magnetite (Fe3O4) structure is observed, whereas after annealing in oxygen gas only Fe3+, mostly in octahedral coordination, is observed, as expected for a ZnFe2O4 structure. Temperature-dependent XPS confirms significant Zn depletion in the near-surface region above 500 °C under UHV, with almost no Zn remaining at 600 °C; under an O2 atmosphere no zinc depletion is observed up to 600 °C. A theoretical model based on DFT simulations illustrates how reduction from ZnFe2O4 to Fe3O4 with formation of O2 and Zn gas is thermodynamically feasible under UHV conditions, whereas the same reaction is not favourable at higher oxygen partial pressures. Our findings demonstrate the strong impact that UHV treatment has on zinc ferrite surfaces, and cautions that UHV environments, routinely employed for surface analysis, can themselves induce substantial modifications to the surface, thereby complicating the interpretation of measurements in the context of catalytically relevant conditions.

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Abstract: Electrocatalytic water splitting is a sustainable route to high-purity hydrogen, yet its efficiency is hindered by the sluggish kinetics of the oxygen evolution reaction (OER). Replacing OER with the thermodynamically favorable ammonia oxidation reaction (AOR) significantly reduces the energy input required for hydrogen production while simultaneously addressing ammonia utilization. However, progress is limited by the need for expensive noble metal catalysts like PtIr/C and the poor performance of non-noble alternatives. Herein, a series of perovskite oxide catalysts is reported with tunable B-site configurational entropy. Among them, the high-entropy La0.7Sr0.3(Ni0.2Cu0.2Co0.2Mn0.2Fe0.2)O3-δ (LS5B) catalyst demonstrates exceptional activity and stability for the ammonia-water co-oxidation reaction (AWOR), outperforming lower-entropy analogs. The enhanced performance is attributed to its entropy-stabilized structure, which generates abundant surface oxygen vacancies and suppresses atomic diffusion, increasing both active site density and structural durability. Density functional theory (DFT) calculations reveal that the high-entropy configuration lowers the energy barrier for ammonia adsorption and facilitates intermediate formation. In a practical ammonia-water co-electrolyzer, LS5B delivers a current density of 2.6 A·cm−2 at 2.0 V, surpassing PtIr/C and representing the best performance to date. A stable operation over 90 h at ampere-level current demonstrates LS5B's potential for scalable, efficient green hydrogen production via ammonia-water co-electrolysis.

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Abstract: Layered double hydroxides (LDH) based on transition metals are highly flexible in tailoring their dimensionality, lattice, and electronic structures, making them promising candidates as multifunctional 2D materials for the development of clean energy technologies and boosting the use of hydrogen as an energy vector. In this paper, strategic anion substitution in cobalt LDH is an appealing strategy to produce a material with two-fold functionality, electrochemical and magnetocaloric response, offering a sustainable alternative to existing electrocatalysts and cryogenic refrigerants. It is unambiguously demonstrated that (poly)oxomolybdate-based specimens interleave in Co LDH nanosheets up to a Co:Mo = 1:0.4 ratio, leading to an interstratified material. This intercalation greatly benefits the kinetics of the oxygen evolution reaction for H2 production, boosting the catalytic sites due to the expansion of the interlayer space, induced by the bulky molybdates which also partially modify the Co oxidation state of αCo(OH)2 nanolayers, favoring charge transfer. In parallel, the interleaved Mo species strengthen superexchange interactions compared with pristine α-Co(OH)2, effectively adjusting the operating temperature toward the liquid hydrogen range (2030 K). This specific temperature range allows to fill a critical gap in magnetocaloric materials, as few systems can simultaneously achieve both large magnetic entropy changes and structural stability.

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Abstract: P(NDI2OD-T2), commonly referred to as N2200, stands out as a promising electron-transporting (n-type) polymer for low-cost, flexible (photo)electrochemical applications due to its reversible two-electron reduction and high electron mobility. UV–vis spectroelectrochemistry in the tetrabutyl ammonium hexafluorophosphate/acetonitrile electrolyte shows two sets of chemically reversible redox signals in the cyclic voltammetry corresponding to the reduction of the neutral polymer film to polaronic and bipolaronic species. These electrochemical signatures suggest a distinct electronic reorganization upon reduction (polaron/bipolaron formation), highlighting the need for molecular-level insights into how charges are accommodated within the polymer backbone. While it has been previously hypothesized that charge predominantly localizes on the naphthalene diimide (NDI) unit during reductive charging, specific changes in atomic environments that confirm this localization have not been characterized in n-type polymers. Herein, we use near-edge X-ray absorption fine structure (NEXAFS) spectroscopy to probe electronic transitions in an electrochemically charged polymer to deduce charge localization. The O K-edge (1s) spectra exhibit two distinct π* peaks; the intensity of the lower-energy π*a peak that corresponds to an excitation to a largely localized carbonyl state decreases with reductive potentials relative to the higher-energy π*b peak. We corroborate this with Raman spectroscopy at different potentials, which shows a decrease in intensity on the C–C/C═C and C═O stretching bands of NDI as well as a red shift of the carbonyl band due to the formation of a polaron on the NDI. Additionally, new Raman active NDI signals associated with elongated C═O and C═C bonds are observed at lower energy during the formation of charged states. Together with theoretical calculations, these findings show that the injected charge spatially localizes on the NDI units and is dominantly distributed on the carbonyl groups. The combination of NEXAFS, optical and vibrational spectroscopies, and theoretical calculations is generalizable to other pi-conjugated polymers and can identify charge localization for the further development of organic semiconductors.