Distance Effect of Ni-Pt Dual Sites for Active Hydrogen Transfer in Tandem Reaction

Tailoring the Brønsted acidity of Ti-OH species by regulating Pt-TiO2 interaction

Bifunctional catalysts comprising metal and acid sites are commonly used for many reactions. Interfacial acid sites impact intermediate reactions more than other sites. However, controlling the type and amounts of interfacial acid sites by regulating metal-support interaction (MSI) via traditional methods is difficult. Thus, the influence of MSI on interfacial acid sites remains unclear. We prepared Pt-mTiO2/α-Al2O3 (m represents the cycle number of TiO2) catalysts via atomic layer deposition (ALD). New Brønsted acid sites were generated via Pt-TiO2 interaction, and the acidity was precisely regulated by regulating Pt-TiO2 interaction by changing the TiO2 nanolayer thickness. We chose levulinic acid (LA) hydrogenation as a model reaction. The catalytic activity varied with the TiO2 nanolayer thickness and was linearly correlated with the Ti-OH species (Brønsted acid) content. Pt-40TiO2/α-Al2O3, with the highest acid site content of 0.486 mmol/g, exhibited the best catalytic activity. Hydrogen spillover and water dissociation at the Pt-TiO2 interface promoted Ti-OH species generation.

Intermediate Transfer Rates and Solid-State Ion Exchange are Key Factors Determining the Bifunctionality of In2O3/HZSM-5 Tandem CO2 Hydrogenation Catalyst

Identifying the descriptors for the synergistic catalytic activity of bifunctional oxide-zeolite catalysts constitutes a formidable challenge in realizing the potential of tandem hydrogenation of CO2 to hydrocarbons (HC) for sustainable fuel production. Herein, we combined CH3OH synthesis from CO2 and H2 on In2O3 and methanol-to-hydrocarbons (MTH) conversion on HZSM-5 and discerned the descriptors by leveraging the distance-dependent reactivity of bifunctional In2O3 and HZSM-5 admixtures. We modulated the distance between redox sites of In2O3 and acid sites of HZSM-5 from milliscale (∼10 mm) to microscale (∼300 μm) and observed a 3-fold increase in space-time yield of HC and CH3OH (7.5 × 10-5 molC gcat-1 min-1 and 2.5 × 10-5 molC gcat-1 min-1, respectively), due to a 10-fold increased rate of CH3OH advection (1.43 and 0.143 s-1 at microscale and milliscale, respectively) from redox to acid sites. Intriguingly, despite the potential of a three-order-of-magnitude enhanced CH3OH transfer at a nanoscale distance (∼300 nm), the sole product formed was CH4. Our reactivity data combined with Raman, Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) revealed the occurrence of solid-state-ion-exchange (SSIE) between acid sites and Inδ+ ions, likely forming In2O moieties, inhibiting C-C coupling and promoting CH4 formation through CH3OH hydrodeoxygenation (HDO). Density functional theory (DFT) calculations further revealed that CH3OH adsorption on the In2O moiety with preadsorbed and dissociated H2 forming an H-In-OH-In moiety is the likely reaction mechanism, with the kinetically relevant step appearing to be the hydrogenation of the methyl species. Overall, our study revealed that efficient CH3OH transfer and prevention of ion exchange are the key descriptors in achieving catalytic synergy in bifunctional In2O3/HZSM-5 systems.

Selective Oxidation of Methane to Oxygenates using Oxygen via Tandem Catalysis

Selective oxidation of methane to oxygenates using low-cost and environment-friendly molecular oxygen (O₂ ) under mild reaction conditions is a promising strategy but still remains grand challenge. It is of great importance to accelerate the activation of O₂ to generate highly active oxygen species, such as hydroxyl peroxide and hydroxyl species to improve catalytic performance for selective oxidation of methane. Selective oxidation of methane using O₂ by coupling with in situ generation of hydrogen peroxide via tandem catalysis ensures the easy formation of active oxygen species for methane activation, leading to high oxygenates productivity under mild conditions. In this concept, we summarized the recent progresses for selective oxidation of methane to oxygenates using O₂ based on tandem catalysis by coupling with in situ generation of hydrogen peroxide. The remaining challenges and future perspectives for selective oxidation of methane to oxygenates via tandem catalysis were also proposed.

Recent Progress of Diatomic Catalysts: General Design Fundamentals and Diversified Catalytic Applications

In recent years, some experiments and theoretical work have pointed out that diatomic catalysts not only retain the advantages of monoatomic catalysts, but also introduce a variety of interactions, which exceed the theoretical limit of catalytic performance and can be applied to many catalytic fields. Here, the interaction between adjacent metal atoms in diatomic catalysts is elaborated: synergistic effect, spacing enhancement effect (geometric effect), and electronic effect. With regard to the classification and characterization of various new diatomic catalysts, diatomic catalysts are classified into four categories: heteronuclear/homonuclear, with/without carbon carriers, and their characterization measures are introduced and explained in detail. In the aspect of preparation of diatomic catalysts, the widely used atomic layer deposition method, metal-organic framework derivative method, and simple ball milling method are introduced, with emphasis on the formation mechanism of diatomic catalysts. Finally, the effective control strategies of four diatomic catalysts and the key applications of diatomic catalysts in electrocatalysis, photocatalysis, thermal catalysis, and other catalytic fields are given.

Enhanced Stability and Catalytic Performance of Active Rh Sites on Al2O3 Via Atomic Layer Deposited ZrO2

Modulating the Rh active sites on surfaces of Al₂O₃ is crucial to developing effective three-way catalysts. Herein, an ultralow amount of ZrO₂ (0.0179%) was deposited onto Al₂O₃ nanorods via atomic layer deposition (ALD) to form a catalyst with both thermal stability and low-temperature activity. The results demonstrate that the ALD-ZrO₂ is conducive to improve the catalytic activity of the Rh site and inhibit the formation of irreducible Rh species at high temperature. The obtained catalysts show satisfactory performance for a model NO-CO reaction even after thermal aging at 1050 °C. This strategy shows that a molecularly precise synthesis can lead to the robust promotion of Rh activity under low temperature and provide a promising path toward reducing the deactivation of catalysts at high temperature.

Enhanced diffraction efficiency with angular selectivity by inserting an optical interlayer into a diffractive waveguide for augmented reality displays

The overall efficiency and image uniformity are important criteria for augmented reality display. The conventional in-coupling grating design intending to improve only the first-order diffraction efficiency without considering the multiple interactions with diffracted light in the waveguide is insufficient. In this work, the back-coupling loss (BCL) on the in-coupling surface relief grating, and the power of light arriving at the out-coupling grating over that of incident light (denoted as optical efficiency in waveguide, OEW) are introduced for the design of in-coupling grating. A simple and effective method to increase diffraction efficiency with unique angular selectivity is demonstrated by inserting an interlayer between the waveguide and grating. The optimized average OEW and its uniformity under a field of view of 40° are increased from 8.02% and 24.83% to 8.34% and 35.02% by introducing a region-selective MgF₂ interlayer.

Radiolabeling of Nanomaterials: Advantages and Challenges

Quantifying the distribution of nanomaterials in complex samples is of great significance to the toxicological research of nanomaterials as well as their clinical applications. Radiotracer technology is a powerful tool for biological and environmental tracing of nanomaterials because it has the advantages of high sensitivity and high reliability, and can be matched with some spatially resolved technologies for non-invasive, real-time detection. However, the radiolabeling operation of nanomaterials is relatively complicated, and fundamental studies on how to optimize the experimental procedures for the best radiolabeling of nanomaterials are still needed. This minireview looks back into the methods of radiolabeling of nanomaterials in previous work, and highlights the superiority of the “last-step” labeling strategy. At the same time, the problems existing in the stability test of radiolabeling and the suggestions for further improvement are also addressed.

Multienzyme Cascades Based on Highly Efficient Metal-Nitrogen-Carbon Nanozymes for Construction of Versatile Bioassays

Distinguished by the coupled catalysis-facilitated high turnover and admirable specificity, enzyme cascades have sparked tremendous attention in bioanalysis. However, three-enzyme cascade-based versatile platforms have rarely been explored without resorting to tedious immobilization procedures. Herein, we have demonstrated that formamide-converted transition metal-nitrogen-carbon (f-MNC, M = Fe, Cu, Mn, Co, Zn) with a high loading of atomically dispersed active sites possesses intrinsic peroxidase-mimetic activity following the activity order of f-FeNC > f-CuNC > f-MnNC > f-CoNC > f-ZnNC. Ulteriorly, benefitting from the greatest catalytic performance and explicit catalytic mechanism of f-FeNC, versatile enzyme cascade-based colorimetric bioassays for ultrasensitive detection of diabetes-related glucose and α-glucosidase (α-Glu) have been unprecedentedly devised using f-FeNC-triggered chromogenic reaction of 3,3',5,5'-tetramethylbenzidine as an amplifier. Notably, several types of α-Glu substrates can be effectively utilized in this three-enzyme cascade-based α-Glu assay, and it can be further employed for screening α-Glu inhibitors that are used as antidiabetic and antiviral drugs. These versatile assays can also be extended to detect other H₂O₂-generating or -consuming biomolecules and other bioenzymes that are capable of catalyzing glucose generation procedures. These nanozyme-involved multienzyme cascades without intricate enzyme-engineering techniques may provide a concept to facilitate the deployment of nanozymes in celestial versatile bioassay fabrication, disease diagnosis, and biomedicine.

Tuning Phase Structure of Nickel-Ruthenium Alloys via MOFs In Situ Hydrolysis toward Enhanced Hydrogen Evolution Performance in Alkaline

Metal organic frameworks (MOFs) and corresponding derivatives have attracted wide attention. As electrocatalysts, these derivatives (metal, metal compound, and associated composites) have a wide range of application in water-splitting devices, fuel cells, and other hydrogen-related technologies. However, with the exception of pyrolysis, limited studies have documented generated metal nanoparticles from MOFs hydrolysis reactions. Herein, NiRu dual-phase alloy nanoparticles are synthesized via in situ MOFs hydrolysis mediating solvothermal reduction reaction. The hcp-phase NiRu alloys can be rationally tuned by modulating experimental parameters of feeding metal ratio and reaction time. The volcanic link between hydrogen evolution reaction activity and the descriptor of d band center is investigated using experimentally determined valence bands. Furthermore, compared with fcc-phase NiRu alloys, it is theoretically revealed that hcp-phase NiRu alloys optimize d band structure and have a lower energy barrier. This finding broadens the range of application for MOFs hydrolysis reactions and highlights advantages of metal alloys manufactured from MOFs hydrolysis reactions.

Encapsulation of atomically dispersed Pt clusters in porous TiO2 for semi-hydrogenation of phenylacetylene

The synthesis of atomically dispersed metal clusters with strong interaction with the support is attractive for the design of high-efficiency catalysts. Here, we report a multilayered catalyst (1.91%Pt@TiO₂), in which atomically dispersed Pt clusters are encapsulated in the porous TiO₂. As a result, 1.91%Pt@TiO₂ exhibited high activity, selectivity (92.9%), and excellent stability in the semi-hydrogenation of phenylacetylene.

Perceptions on the Treatment of Apparent Isotope Effects during the Analyses of Reaction Rate and Mechanism

Isotope substitution, a compelling tool of physical chemistry, has been broadly applied in the research field of heterogeneous catalysis. In general, upon the differences in mass-related atomic vibrational frequencies and...

The Dehydrogenation of H-S Bond into Sulfur Species on Supported Pd Single Atoms Allows Highly Selective and Sensitive Hydrogen Sulfide Detection

The supported metal catalysts on scaffolds usually reveal multiple active sites, resulting in the occurrence of side reaction and being detrimental to the achievement of highly consistent catalysis. Single atom catalysts (SACs), possessed with highly consistent single active sites, have great potentials for overcoming such issues. Herein, the authors used SACs to modulate kinetic process of gas sensitive reaction. The supported Pd SACs, established by a metal organic frameworks-templated approach, promoted greatly the detection capacity to hydrogen sulfide (H₂ S) gas with a very high sensitivity and selectivity. Density functional theory calculations show that the supported Pd SACs not only increased the number of electrons transferring from H₂ S molecules to Pd SACs, but strengthened surface affinity to H₂ S. Moreover, the HS bonds of H₂ S molecules absorbed on Pd atomic sites are more likely to be dehydrogenated directly into sulfur species. Significantly, quasi in situ XPS analysis confirmed the presence of sulfur species during H₂ S detection process, which may be a major cause for such detection signal. Based on these results, a suitable sensing principle for H₂ S gas driven by Pd SACs was put forward. This work will enrich catalytic electronics in chemiresistive gas sensing.

Fluorinated Graphite (FG)-Modified Li-S Batteries with Superhigh Primary Specific Capacity and Improved Cycle Stability

Lithium-sulfur (Li-S) batteries have received extensive attention because of their high theoretical energy density and low cost. However, the low sulfur utilization and the shuttle effect of polysulfide cause low initial capacity and serious capacity decay. Herein, fluorinated graphite (FG) is introduced to the cathode to alleviate these issues. The results indicated that the FG could provide additional capacity during the first discharge process and increase the porosity and polarity of the cathode via in situ formation of lithium fluoride (LiF) nanocrystals, which can enhance the infiltration of electrolyte and polysulfide adsorption. As a result, the as-prepared cathode containing FG shows a high initial specific capacity of 1602 mA h g-1 and the reversible specific capacity is 650 mA h g-1 at 0.5C after 300 cycles. Moreover, its specific capacity remains at 860 mA h g-1 at 5C, which is 367% higher than that of the sample without FG. This paper provides a new strategy to improve the energy density and the cycle stability of Li-S batteries.

Nanoparticles Determination by Laser Ablation Inductively Coupled Plasma Mass Spectrometry

Quantitatively studying the biodistribution and transformation of nanomaterials is of great importance for nanotoxicological evaluation. Recently, laser ablation inductively coupled plasma mass spectrometry has been employed to distinguish nanoparticles (NPs) with their dissolved ions in biological samples. The principle of the proposal is based on a hypothesis that the intact NPs sampled by laser ablation will generate discrete sharp pulses of signals in ICP-MS measurement, being totally different from the continuous, relatively lower signals generated by ions. However, it is still a controversy whether NPs could maintain their intactness during the laser ablation. This work found a way to exactly determine the number of NPs sampled for each LA-ICP-MS measurement. It made possible to reveal the signal profile of a single NP in LA-ICP-MS analysis. The results suggest that AuNR, AgNP and TIO₂ NP were broken into much smaller secondary NPs during the laser ablation, therefore generating continuous signals in the analyzer. There was a certain probability that the fragmentation of large-sized NP or multiple NPs by laser ablation was not sufficient, leaving some NPs unbroken or some secondary NPs with relatively large sizes to generate discrete pulses of signals in the analyzer. When the intactness of NPs during laser ablation cannot be assured, it is impossible to determine the attribution of mass spectrum signals. These findings compromise the reliability of distinguishing NPs from their dissolved ions by LA-ICP-MS.

Atomic layer deposition of silica to improve the high-temperature hydrothermal stability of Cu-SSZ-13 for NH3 SCR of NOx

The improvement of stability is a crucial and challenging issue for industrial catalyst, which affects not only the service time but also the cost of catalyst. This is especially prominent for that applied in harsh environment atmospheres, such as the exhaust of diesel vehicles. Herein, we reported a new strategy to improve the high-temperature hydrothermal stability of Cu-SSZ-13, which is a promising catalyst for the treatment of exhaust emitted from diesel vehicles through the NH₃-SCR NO_x route. Different from that reported in literature, we managed to improve the high-temperature hydrothermal stability of Cu-SSZ-13 by coating the surface with a nanolayer of stable SiO₂ material using the atomic layer deposition (ALD) method. The coating of SiO₂ layers effectively suppressed the leaching of alumina from the SSZ-13 molecular sieve even after the hydrothermal aging at 800 °C for 16 h with 12.5% water in air. Meanwhile, the ultra-thin SiO₂ nanolayer does not block the pores of zeolites and affect the catalytic activity of Cu-SSZ-13 contribute to the superiority of the ALD technology.

Post-annealing Effect on Optical and Electronic Properties of Thermally Evaporated MoOX Thin Films as Hole-Selective Contacts for p-Si Solar Cells

Owing to its large work function, MoOX has been widely used for hole-selective contact in both thin film and crystalline silicon solar cells. In this work, thermally evaporated MoOX films are employed on the rear sides of p-type crystalline silicon (p-Si) solar cells, where the optical and electronic properties of the MoOX films as well as the corresponding device performances are investigated as a function of post-annealing treatment. The MoOX film annealed at 100 °C shows the highest work function and proves the best hole selectivity based on the results of energy band simulation and contact resistivity measurements. The full rear p-Si/MoOX/Ag-contacted solar cells demonstrate the best performance with an efficiency of 19.19%, which is the result of the combined influence of MoOX's hole selectivity and passivation ability.

Artificial Structural Colors and Applications

Structural colors are colors generated by the interaction between incident light and nanostructures. Structural colors have been studied for decades due to their promising advantages of long-term stability and environmentally friendly properties compared with conventional pigments and dyes. Previous studies have demonstrated many artificial structural colors inspired by naturally generated colors from plants and animals. Moreover, many strategies consisting of different principles have been reported to achieve dynamically tunable structural colors. Furthermore, the artificial structural colors can have multiple functions besides decoration, such as absorbing solar energy, anti-counterfeiting, and information encryption. In the present work, we reviewed the typical artificial structural colors generated by multilayer films, photonic crystals, and metasurfaces according to the type of structures, and discussed the approaches to achieve dynamically tunable structural colors.

Selective Hydrogenolysis of Erythritol over Ir-ReOx /Rutile-TiO2 Catalyst

Partial hydrogenolysis of erythritol, which can be produced at large scale by fermentation, to 1,4-butanediol (1,4-BuD) is investigated with Ir-ReO_x /SiO₂ and Ir-ReO_x /rutile-TiO₂ catalysts. In addition to the higher conversion rate over Ir-ReO_x /TiO₂ than over Ir-ReO_x /SiO₂ , which has been also reported for glycerol hydrogenolysis, Ir-ReO_x /TiO₂ showed higher selectivity to 1,4-BuD than Ir-ReO_x /SiO₂ , especially at low conversion levels, leading to high 1,4-BuD productivity of 20 mmol_1,4-BuD  g_Ir ^-1  h^-1 at 373 K (36 % conversion, 33 % selectivity). The productivity based on the noble metal amount is higher than those reported previously, although the maximum yield of 1,4-BuD (23 %) is not higher than the highest reported values. The reactions of various triols, diols and mono-ols are tested and the selectivity and the reaction rates are compared between catalysts and between substrates. The Ir-ReO_x /TiO₂ catalyst showed about twofold higher activity than Ir-ReO_x /SiO₂ in hydrogenolysis of the C-OH bond at the 2- or 3-positions in 1,2- and 1,3-diols, respectively, whereas the hydrogenolysis of C-OH at the 1-position is less promoted by the TiO₂ support. Lowering the loading amount of Ir on TiO₂ (from 4 wt % to 2 or 1 wt %) decreases the Ir-based activity and 1,4-BuD selectivity. Similarly, increasing the loading amount on SiO₂ from 4 wt % to 20 wt % increases the Ir-based activity and 1,4-BuD selectivity, although they remain lower than those for TiO₂ -supported catalyst with 4 wt % Ir. High metal loadings on the support seem to be important.

Realization of strong coupling between 2D excitons and cavity photons at room temperature

Two-dimensional (2D) semiconductors of graphene, as well as transition-metal dichalcogenides, have performed strong interaction with light. Here the strong light-matter interaction between monolayer tungsten disulphide (WS₂) excitons and microcavity photons at room temperature is well studied by the introduction of a gain material embedded dielectric optical microcavity structure. A Rabi splitting of about 36 meV is observed in angle-resolved reflectance spectra at room temperature, which agrees well with the theoretical results simulated by using the transfer matrix method. Since the cavity structures and 2D semiconductors can be prepared, the cavity and the gain materials, respectively, can be optimized separately in this platform. An all-dielectric Fabry-Pérot microcavity provides a simple but effective way to study the room temperature strong coupling between cavity photons and 2D excitons.