The DFT+U method provides an effective approach to correctly reproduce the material bulk properties of strongly correlated transition metal oxides (TMO) such as magnetic ground states, electronic ...structure, and redox reaction energies. Therefore, the catalysis processes over these strongly correlated TMO surfaces are frequently simulated utilizing the DFT+U method with the U value fit by these reported bulk properties. However, it is generally acknowledged that the calculated results utilizing the DFT+U method depend on the applied effective U value. Due to the significantly different coordination environments, the fit U value based on the bulk properties might not be proper for the simulation of the catalysis process. Moreover, the possibly caused calculation errors still remain elusive. To clarify it, we systematically investigate the influence of the Hubbard U value on the molecule adsorption at different sites, CO oxidation, and first C–H activation of methane over Co3O4(110). It is found that with the change of U value, the activities of surface Co cations and surface O anions exhibit reverse variation tendencies. This results in the fact that the transition state (TS) occupying both Co and O sites energetically exhibits lower dependences on the U value, especially for those TSs such as the first C–H bond activation of CH4 and CO oxidation by lattice oxygen. However, the strong dependency of the energies of intermediates occupying only either Co or O sites on the U value makes it still essential to identify the reliable U value to achieve the correct energy profile of the reaction pathway. To uniformly reproduce surface chemical properties of both Co and O sites, we put forward a surface–bulk bi-U strategy, utilizing the RPA results of adsorption energy as the benchmark for the surface U fitting combined with the bulk U fitting from formation enthalpy of oxides. The combination of surface U = 1.35 eV and bulk U = 3.4 eV is found to simultaneously describe the accurate reaction performance at both surface Co sites and O sites of Co3O4(110). These understandings may provide a benchmark to identify the influence of U value on the understanding of catalytic reactions and a possible strategy to accurately reproduce surface properties of catalyst.
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Metal/metal oxide clusters possess a higher count of unsaturated coordination sites than nanoparticles, providing multiatomic sites that single atoms do not. Encapsulating metal/metal oxide clusters ...within zeolites is a promising approach for synthesizing and stabilizing these clusters. The unique feature endows the metal clusters with an exceptional catalytic performance in a broad range of catalytic reactions. However, the encapsulation of stable FeOx clusters in zeolite is still challenging, which limits the application of zeolite-encapsulated FeOx clusters in catalysis. Herein, we design a modified solvent-free method to encapsulate FeOx clusters in pure siliceous MFI zeolites (Fe@MFI). It is revealed that the 0.3-0.4 nm subnanometric FeOx clusters are stably encapsulated in the 5/6-membered rings intersectional voids of the pure siliceous MFI zeolites. The encapsulated Fe@MFI catalyst with a Fe loading of 1.4 wt % demonstrates remarkable catalytic activity and recycle stability in the direct oxidation of methane, while also promoting the direct oxidation of cyclohexane, surpassing the performance of conventional zeolite-supported Fe catalysts.
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IJS, KILJ, NUK, PNG, UL, UM
ABSTRACT
The spontaneous formation of self-assembly monolayer (SAM) on various substrates represents an effective strategy for interfacial engineering of optoelectronic devices. Hole-selective SAM is ...becoming popular among high-performance inverted perovskite solar cells (PSCs), but the presence of strong acidic anchors (such as –PO3H2) in state-of-the-art SAM is detrimental to device stability. Herein, we report for the first time that acidity-weakened boric acid can function as an alternative anchor to construct efficient SAM-based hole-selective contact (HSC) for PSCs. Theoretical calculations reveal that boric acid spontaneously chemisorbs onto indium tin oxide (ITO) surface with oxygen vacancies facilitating the adsorption progress. Spectroscopy and electrical measurements indicate that boric acid anchor significantly mitigates ITO corrosion. The excess boric acid containing molecules improves perovskite deposition and results in a coherent and well-passivated bottom interface, which boosts the fill factor (FF) performance for a variety of perovskite compositions. The optimal boric acid-anchoring HSC (MTPA-BA) can achieve power conversion efficiency close to 23% with a high FF of 85.2%. More importantly, the devices show improved stability: 90% of their initial efficiency is retained after 2400 h of storage (ISOS-D-1) or 400 h of operation (ISOS-L-1), which are 5-fold higher than those of phosphonic acid SAM-based devices. Acidity-weakened boric acid SAMs, which are friendly to ITO, exhibits well the great potential to improve the stability of the interface as well as the device.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The activation of oxygen molecules is an important issue in the gold-catalyzed partial oxidation of alcohols in aqueous solution. The complexity of the solution arising from a large number of solvent ...molecules makes it difficult to study the reaction in the system. In this work, O2 activation on an Au catalyst is investigated using an effective approach to estimate the reaction barriers in the presence of solvent. Our calculations show that O2 can be activated, undergoing OOH* in the presence of water molecules. The OOH* can readily be formed on Au(211) via four possible pathways with almost equivalent free energy barriers at the aqueous-solid interface: the direct or indirect activation of O2 by surface hydrogen or the hydrolysis of O2 following a Langmuir-Hinshelwood mechanism or an Eley-Rideal mechanism. Among them, the Eley-Rideal mechanism may be slightly more favorable due to the restriction of the low coverage of surface H on Au(211) in the other mechanisms. The results shed light on the importance of water molecules on the activation of oxygen in gold-catalyzed systems. Solvent is found to facilitate the oxygen activation process mainly by offering extra electrons and stabilizing the transition states. A correlation between the energy barrier and the negative charge of the reaction center is found. The activation barrier is substantially reduced by the aqueous environment, in which the first solvation shell plays the most important role in the barrier reduction. Our approach may be useful for estimating the reaction barriers in aqueous systems.
Designing artificial molecular machines to execute complex mechanical tasks, like coupling rotation and translation to accomplish transmission of motion, continues to provide important challenges. ...Herein, we demonstrated a novel molecular machine comprising a second-generation light-driven molecular motor and a bistable 1rotaxane unit. The molecular motor can rotate successfully even in an interlocked 1rotaxane system through a photoinduced cis-to-trans isomerization and a thermal helix inversion, resulting in concomitant transitional motion of the 1rotaxane. The transmission process was elucidated via 1H NMR, 1H–1H COSY, HMQC, HMBC, and 2D ROESY NMR spectroscopies, UV–visible absorption spectrum, and density functional theory calculations. This is the first demonstration of a molecular motor to rotate against the appreciably noncovalent interactions between dibenzo-24-crown-8 and N-methyltriazolium moieties comprising the rotaxane unit, showing operational capabilities of molecular motors to perform more complex tasks.
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It has been noted that anterior cruciate ligament (ACL) injury-induced cartilage degeneration is the key risk factor for post-traumatic osteoarthritis (PTOA). However, whether the cartilage ...degeneration after ACL injury is caused by inflammation, abnormal biomechanics or both remains largely unknown, as there has been no animal model for separating the two factors so far.
Eighteen-month-old female mini-pigs were divided into an “idealized” anterior cruciate ligament reconstruction (IACLR) group and a control group (n = 16 limbs per group). Real-time PCR, safranine O staining and indian ink staining were performed to verify whether animal models were successfully established or not. Multiple linear regression analysis was used to evaluate the correlation between levels of the inflammatory factors (including interferon IFN-γ, interleukin IL-1β, IL-4, IL-6, IL-8, IL-10, IL-12 and tumor necrosis factor TNF-α measured by the Luminex method) and changes in cartilage histology (quantified by morphological scoring) after surgery.
A significant OA cartilage damage with increased MMP-1, MMP-13 mRNA levels and reduced aggrecan mRNA/protein levels was observed in IACLR groups. As a result, the IACLR gross morphology score was dramatically increased than control. Moreover, IACLR significantly increased the levels of IL-1β, IL-4, IL-6 and TNF-α in the synovial fluid of the knee. Most importantly, a close relationship was found between IL-1β, IL-6 and TNF-α concentrations and morphological score of PTOA, respectively.
These results demonstrated that inflammatory factors are independently responsible for the onset of PTOA.
•An “idealized” anterior cruciate ligament reconstruction (IACLR) model using mini-pigs innovatively was developed.•This study, for the first time, proves that inflammatory factors are independently responsible for the onset of PTOA.•Luminex liquid chip is used to detect inflammatory factors in synovial fluid.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Constructing superstructured crystalline materials by crystal engineering is an attractive objective for miscellaneous fields of researchers spanning biomimetics to catalytic materials. Zeolite is a ...kind of important crystalline catalyst, and superstructured zeolite has great potential for widespread applications. However, the ambiguous crystallization mechanisms hamper the effective and scientific fabrication of superstructured zeolite with exceptional properties. Herein, a fractal superstructured MTW zeolite with mesocrystal side branches is prepared via a nanoparticle-based nonclassical pathway with twinning-plane induced crystallization, which is distinct from the formation of general mesocrystal via crystal–crystal oriented attachment. Deformed atomic connection at a specific crystallographic plane contributes to the production of side branches. Moreover, this intriguing morphology could be regulated merely via adjusting the crystallization kinetics based on the unequivocal nonclassical crystallization mechanism. It will open a new avenue for design and synthesis of targeted crystals with superstructure and extraordinary properties.
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The microkinetics based on density function theory (DFT) calculations is utilized to investigate the reaction mechanism of crotonaldehyde hydrogenation on Pt(111) in the free energy landscape. The ...dominant reaction channel of each hydrogenation product is identified. Each of them begins with the first surface hydrogenation of the carbonyl oxygen of crotonaldehyde on the surface. A new mechanism, 1,4-addition mechanism generating enols (butenol), which readily tautomerize to saturated aldehydes (butanal), is identified as a primary mechanism to yield saturated aldehydes instead of the 3,4-addition via direct hydrogenation of the ethylenic bond. The calculation results also show that the full hydrogenation product, butylalcohol, mainly stems from the deep hydrogenation of surface open-shell dihydrogenation intermediates. It is found that the apparent barriers of the dominant pathways to yield three final products are similar on Pt(111), which makes it difficult to achieve a high selectivity to the desired crotyl alcohol (COL).
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A simple cadmium sulfide nanomaterial is found to be an efficient and stable electrocatalyst for CO2 reduction in aqueous medium for more than 40 h with a steady CO faradaic efficiency of ...approximately 95 %. Moreover, it can realize a current density of −10 mA cm−2 at an overpotential of −0.55 V on a porous substrate with similar selectivity. Theoretical and experimental results confirm that the high selectivity for CO2 reduction is due to its (0 0 0 2) face with sulfur vacancies that prefers CO2 molecule reduction in aqueous medium.
Come on you rods! Simple nanorod‐like CdS is found to be an efficient and stable electrocatalyst for reduction of carbon dioxide in aqueous medium for more than 40 h with a steady CO faradaic efficiency of approximately 95 %, indicating the capacity of CdS for aqueous electrocatalytic carbon dioxide reduction.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Reactivity of supported gold catalysts is a hot topic in catalysis for many years. This communication reports an investigation on the dissociation of molecular hydrogen at the perimeter sites of ...Au/TiO(2) and the spillover of hydrogen atoms from the gold to the support using density functional theory calculations. It is found that the heterolytic dissociation is favoured in comparison with homolytic dissociation of molecular hydrogen at the perimeter sites. However, the surface oxygen of the rutile TiO(2)(110) surface at these sites can be readily passivated by the formed OH, suggesting that further dissociation of molecular hydrogen may occur at pure gold sites.
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