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Potassium‐ion hybrid capacitors (PIHCs) are regarded as one of the promising candidates for large‐scale energy storage technologies. Nevertheless, the lack of suitable anode materials combined with fast ion diffusion kinetics and favorable cycle stability restricts their application. Herein, a catalyst‐confined graphitization strategy is proposed to synthesize low‐cost coal‐based carbon anodes, which have controllable heteroatom co‐doping and rich defect sites, together with local graphitic domains. Density functional theory calculations and kinetic analysis are performed to uncover the coupling effect for heteroatom dual‐doping and defective structures. Importantly, the introduction of graphitic domains ensures good electric conductivity and charge transfer kinetics while preserving rich defects and active sites. The optimized NC‐950 exhibits superior potassium storage capacity, which delivers a high reversible specific capacity (363.3 mAh g−1), impressive rate capability (93.9 mAh g−1 at 2 A g−1), and stable cycling performance. As a practical device application, the PIHCs (NC‐950//AC) are assembled using the NC‐950 anode and commercial activated carbon (AC) cathode, which exhibits the maximum energy density of 97.0 Wh kg−1 and excellent cycling stability (10 000 cycles). Significantly, this work unveils a new pathway to developing low‐cost and fast reaction kinetics carbon anode for advanced electrochemical supercapacitors. [ABSTRACT FROM AUTHOR]

In this paper, a totally asymmetric simple exclusion process (TASEP) extended model has been used to study the defect sites on symmetric coupling two-channel boundaries. Two classic cases were discussed, defined as Case A, the defect sites on the left boundaries, and Case B, the defect sites on the right boundaries. Through the theory calculation, for symmetric coupling two-lane TASEP with arbitrary hopping rate, the existence conditions of different phases and the property of the system can be obtained. Based on these outcomes, the effects of defect sites on phase evaluation, system density, and currents have been investigated by theoretical and simulative methods. The result indicates that the existing conditions of the maximal current phase depend on the hopping rate of the defect sites. The results from Monte Carlo simulations are in good agreement with that from theoretical calculations. [ABSTRACT FROM AUTHOR]

P-Fe 2 O 3 -CoP nanosheets show high overall freshwater/seawater splitting activity with 1.61/1.65 V at 10 mA/cm2. [Display omitted] • P-Fe 2 O 3 -CoP nanosheets are prepared through a gas-phase phosphorization process. • P doping, defective structure, and interfaces are observed. • High freshwater/seawater oxidation activity occur on P-Fe 2 O 3 -CoP nanosheets. • P-Fe 2 O 3 -CoP nanosheets show high overall freshwater/seawater splitting activity. Tailoring surface composition and coordinative environment of catalysts in a nano-meter region often influence their chemical performance. It is reported that CoP exhibits a low dissociation ability of H–OH, originating from the poor desorption of intermediate species. Herein, we provide a feasible method to construct P-Fe 2 O 3 -CoP nanosheets through a gas-phase phosphorization process. P doping induces the formation of interfacial structure between Fe 2 O 3 and CoP and the generation of defective structures. The resulting P-Fe 2 O 3 -CoP nanosheets afford high freshwater/seawater oxidation activity (250/270 mV@10 mA/cm2) in 1 mol/L (M) KOH, which is even lower than commercial RuO 2. Compared with CoP||CoP, P-Fe 2 O 3 ||P-Fe 2 O 3 , and Co 3 O 4 ||Co 3 O 4 , the assembled P-Fe 2 O 3 -CoP||P-Fe 2 O 3 -CoP exhibits the superior water/seawater electrolysis performance with 1.61/1.65 V@10 mA/cm2. The synergistic effect of P doping, defective structure, and heterojunction leads to high water oxidation efficiency and water splitting efficiency. [ABSTRACT FROM AUTHOR]

Electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for in situ/operando tracking of catalytic reactions that involve paramagnetic species either as a catalyst (e.g. transition metal ions or defects), reaction intermediates (radicals) or poisoning agents such as coke. This article provides a summary of recent experimental examples and developments in resonator design as well as detection schemes that were carried out in our group. Opportunities for applying this technique are illustrated by examples, including studies of transition metal exchanged zeolites and metal-free zeolites as well as metal oxide catalysts. The inherent limitations of EPR applied at high temperatures are discussed, as well as strategies in reducing or lifting these restrictions are evaluated and ideas for future improvements and methodologies are discussed.

Quadrangular-pyramid-octahedral CeO2 with defects was successfully prepared and first used as effective and reusable heterogeneous catalyst for photo- and thermal- synergistic catalytic synthesis of DMC, and it showed better catalytic performance than that of thermocatalysis alone. The corner defects may be the active site based on experimental result and DFT calculation. The CeO2 with specific defects was prepared by PECVD method and first applied for photo-thermal synergistic catalytic synthesis of DMC from CO2 and methanol, which showed superior catalytic performance to that of thermocatalysis alone, and the active site maybe the corner defect. [ABSTRACT FROM AUTHOR]

Carbon nanospikes (CNSs) are a new nanomaterial that has enhanced surface roughness and surface oxide concentration, increasing the sensitivity for dopamine detection. However, CNS-modified electrodes (CNSMEs) have not been characterized for other neurochemicals, particularly those with higher oxidation potentials. The purpose of this study was to evaluate CNSMEs for the detection of adenosine, hydrogen peroxide (H2O2), and histamine. The sensitivity increased with CNSs, and signals at CNSMEs were about 3.3 times higher than CFMEs. Normalizing for surface area differences using background currents, CNSMEs show an increased signal of 4.8 times for adenosine, 1.5 times for H2O2, and 2 times for histamine. CNSMEs promoted the formation of secondary products for adenosine and histamine, which enables differentiation from other analytes with similar oxidation potentials. CNSs also selectively enhance the sensitivity for adenosine and histamine compared to H2O2. A scan rate test reveals that adenosine is more adsorption-controlled at CNS electrodes than CFMEs. CNSMEs are antifouling for histamine, with less fouling because the polymers formed after histamine electrooxidation do not adsorb due to an elevated number of edge planes. CNSMEs were useful for detecting each analyte applied in brain slices. Because of the hydrophilic surface compared to CFMEs, CNSMEs also have reduced biofouling when used in tissue. Therefore, CNSMEs are useful for tissue measurements of adenosine, hydrogen peroxide, and histamine with high selectivity and low fouling. [ABSTRACT FROM AUTHOR]

Lignin hydrogenolysis is a key step in the sustainable production of renewable bio‐based chemicals and fuels. Heterogeneous metal catalysts have led to high yields but they rapidly deactivate, notably due to nanoparticle sintering and carbonaceous deposit formation. While these deposits can be removed by regeneration, sintering is irreversible and a significant barrier to commercialization. Here, simple liquid phase atomic layer deposition is used to deposit an alumina layer to protect nickel particles from sintering. In the gas phase, it is proved that alumina can prevent sintering during reduction up to 600 °C. This catalyst for hydrogenolysis of extracted lignin in batch and continuous operation is used. In batch, the overcoated catalyst maintains high monomer yields with little sintering over four cycles of reuse while the yield obtained with the catalyst without an overcoat reduces to half and severe sintering occurs. In a continuous flow reactor, deactivation rates are three times lower for the catalyst with the alumina overcoat. Microscopy images confirm that the alumina overcoat largely preserves nickel particle sizes after ten days of operation. The results demonstrate that catalyst overcoating with metal oxides substantially slows irreversible deactivation during lignin hydrogenolysis, which could facilitate the development of continuous lignin upgrading. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H 2 O 2 ) is a crucial chemical used in numerous industrial applications, yet its manufacturing relies on the energy-demanding anthraquinone process. Solar-driven synthesis of H 2 O 2 is gaining traction as a promising research area, providing a sustainable method for its production. Herein, a controllable activation of n → π* electronic transition is presented to boost the photocatalytic H 2 O 2 evolution in ionic carbon nitrides. This enhancement is achieved through the simultaneous introduction of structural distortions and defect sites (─C ≡ N groups and N vacancies) into the KPHI framework. The optimal catalyst (2%Ox-KPHI) reached an apparent quantum yield of 41% at 410 nm without the need for any cocatalysts, outperforming most previously reported carbon nitride-based photocatalysts. Extensive experimental characterizations and theoretical calculations confirm that a corrugated configuration and the presence of defects significantly broaden the light absorption profile, improve carrier separation and migration, promote O 2 adsorption, and lower the energy barriers for H 2 O 2 desorption. Transient absorption spectroscopy indicates that the enhanced photocatalytic performance of 2%Ox-KPHI is largely attributed to the preferential migration of electrons at defect sites over extended timescales, following the diffusion of geminate carriers across the PHI sheets., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

[Display omitted] • Zn 0.5 Cd 0.5 S are synthesized by hydrothermal, solvothermal and ion-exchange methods. • Photocatalytic activity is varied with the microstructural change. • Zn and S vacancies can respectively capture the photogenerated holes and electrons. • Lactic acid can be oxidized to pyruvic acid, with H+ releasing. As an excellent photocatalytic material, Zn x Cd 1-x S is widely used in photocatalytic H 2 production due to its good visible light response and suitable band position. Based on our previous studies, this paper systematically studies the relationship of Zn 0.5 Cd 0.5 S (ZCS) material between microstructure and photocatalytic activity. By controlling the synthesized temperature, S sources and solvents, a series of ZCS nanomaterials with different morphology and crystalline phase have been prepared by hydrothermal, solvothermal and ion-exchange methods. When several sacrificial agents are added in photocatalytic H 2 production, ZCS performs the highest activity synthesized by solvothermal method, about 12.15 mmol g−1 under 4 h's visible light illumination. To explore the difference of ZCS samples in photocatalytic performance, many factors are considered, such as crystal size, crystallinity, separation of photogenerated charge carriers (PCCs), specific surface area and defect sites, which play important roles in the improving photocatalytic activity. This work provides a new direction for the design of photocatalyst from the microstructural regulation to achieve highly efficient activity. [ABSTRACT FROM AUTHOR]

3-D porous imprinted UiO-66-D@loofah membrane with more active imprinted sites for targeted separation of Artemisinin by smart situ deposition method. [Display omitted] • A novel UiO-66 structure was suggested for efficient adsorption of Art using effective sites from a 'template molecule'. • The transfer of UiO-66-D to the pore surface by delayed phase transition makes it more convenient for adsorption cycle experiments. • PAN-coated loofah membrane evenly disperses the Art solution, greatly enhancing defective UiO-66 utilization. Artemisinin (Art) is the primary therapies for plasmodium falciparum malaria. However, it is very cumbersome to extract artemisinin from the plant Artemisia annua L. Herein, a novel defect-type UiO-66 structure was proposed, which can adsorb artemisinin through effective sites provided by 'template molecules'. At the same time, the delayed phase inversion technology was used to prepare the loofah membrane to make the defect-type UiO-66 uniformly dispersed in the pores. In addition, the inside of the biomass loofah membrane had good mechanical properties and loofah membrane wrapped with polyacrylonitrile (PAN) can make Art solution evenly dispersed in each channel, greatly improving the utilization rate of defect-type UiO-66. The defect-type UiO-66 and the UiO-66-D@loofah membrane were characterized using various methods, including SEM, EDS, FT-IR, XRD, contact angle, and mechanical performance analyses. Compared with the static adsorption behavior of powder and loofah membrane, it was found that the adsorption performance presented an optimal adsorption capacity (56.548 mg g−1) at the flow rate of 5 mL min−1, which was better than that of powder (27.096 mg g−1) as well as the static loofah membrane (33.127 mg g−1). The structural design of the membrane has provided a new solution for the extraction of Art from Artemisia annua L. [ABSTRACT FROM AUTHOR]

This paper deals with the synthesis conditions–defect formation relationship in zeolites. Silicalite‐1 (MFI‐type) is used as a model material. Samples synthesized from a system with high basicity (at 100 °C), a system with moderate basicity (at 150 °C), and a fluoride‐containing system in neutral medium (at 170 °C) are compared. Well‐crystallized materials with sizes ≈0.1, 1–10, and 30–40 µm are obtained. The samples are analyzed by complementary methods providing information on the short‐ and long‐range order in the zeolite framework. A strong correlation between the number of point defects in the zeolite framework and preparation conditions is established. Silicalite‐1 synthesized under mild synthesis conditions from a highly basic system exhibits a larger number of framework defects and thus low hydrophobicity. Further, the calcined samples are subjected to aluminum and silicon incorporation by postsynthesis treatment. The Al/Si incorporation in the zeolite framework and its impact on the physicochemical properties is studied by XRD, TEM/SEM, solid‐state NMR, FTIR, and thermogravimetric analyses. The defects healing as a function of the number of point defects in the initial material and zeolite crystal size is evaluated. The results of this study will serve for fine‐tuning zeolite properties by in situ and postsynthesis methods. [ABSTRACT FROM AUTHOR]

The incorporation of Mg in aragonite was experimentally investigated as a function of mineral growth rate at 5, 15 and 25 °C using the constant addition technique. Aragonite growth rate was found to be the major parameter affecting the Mg partitioning coefficient (i.e. D Mg = (Mg Ca) solid (Mg Ca) fluid ) between aragonite and fluid, whereas the effect of temperature is smaller but measurable. At similar surface normalized growth rates, D Mg values decrease as temperature increases from 5 to 25 °C. The magnitude of decrease as a function of temperature is similar for all the experiments of this study where growth rate varied in the range 10-8.6 ≤ r p ≤ 10-7.1 (mol/m2/s). The combined effect of aragonite growth rate and temperature on D Mg can be described by the linear equation: Log D Mg = 0.583(±0.020) Log r p − 0.026(±0.001) T + 0.863(±0.153); R2 = 0.97. where T is the temperature in degrees Celsius. The increase of D Mg values at decreasing temperatures in experiments conducted at similar growth rates is consistent with the increase of fluid supersaturation with respect to aragonite. Thus, it can be inferred that increased Mg incorporation at higher supersaturation is associated with the greater presence of defect sites on the growing mineral surface, similar to the incorporation of other incompatible ions in carbonate minerals. Overall, the relationship between Mg content of aragonite with the degree of saturation of the fluid with respect to this mineral phase suggests that D Mg values or Mg/Ca ratio in natural aragonites can be used as a proxy for saturation degree of the formation fluid with respect to CaCO 3 minerals. [ABSTRACT FROM AUTHOR]

Abstract This paper deals with the synthesis conditions–defect formation relationship in zeolites. Silicalite‐1 (MFI‐type) is used as a model material. Samples synthesized from a system with high basicity (at 100 °C), a system with moderate basicity (at 150 °C), and a fluoride‐containing system in neutral medium (at 170 °C) are compared. Well‐crystallized materials with sizes ≈0.1, 1–10, and 30–40 µm are obtained. The samples are analyzed by complementary methods providing information on the short‐ and long‐range order in the zeolite framework. A strong correlation between the number of point defects in the zeolite framework and preparation conditions is established. Silicalite‐1 synthesized under mild synthesis conditions from a highly basic system exhibits a larger number of framework defects and thus low hydrophobicity. Further, the calcined samples are subjected to aluminum and silicon incorporation by postsynthesis treatment. The Al/Si incorporation in the zeolite framework and its impact on the physicochemical properties is studied by XRD, TEM/SEM, solid‐state NMR, FTIR, and thermogravimetric analyses. The defects healing as a function of the number of point defects in the initial material and zeolite crystal size is evaluated. The results of this study will serve for fine‐tuning zeolite properties by in situ and postsynthesis methods.

The dual heteroatom doped mesoporous carbon (MC) is an excellent substitute for platinum‐based catalyst in cathodic oxygen reduction reaction (ORR) of fuel cells. In this work, nitrogen (N) as the primary heteroatom doping, phosphorus (P), boron (B), and sulfur (S) as the secondary heteroatom doping are introduced in the MC framework. Santa barbara amorphous (SBA‐15) employed as the supporting material to investigate the secondary heteroatom doping effect on MC towards ORR performance. Compared with B and S doping, the P doping modifies the charge delocalization in the MC structure. In addition, it enhances the surface area (971 m2/g), defect sites (1.18), high pyridinic (28.72 %) and high graphitic content (44.42 %) thereby facilitated the remarkable ORR activity. Moreover, electrochemical studies proved that N and P dual doped mesoporous carbon (NPMC) has a better carrier concentration (5.58×1015 cm−3) and higher flat band potential (0.548 V vs RHE) which is confirmed by the Mott‐Schottky analysis. Further, ORR studies demonstrated that NPMC material exhibited more positive onset potential (0.86 V), two‐electron pathway, lower Tafel slope (63 mV/dec) as well as Rct (11 Ω/cm2). In addition, the resultant material is found to be highly active towards ORR with excellent methanol tolerance and stability. [ABSTRACT FROM AUTHOR]

Exploring effective bi-functional catalysts is of great significance to enhance the electrochemical activity for overall water splitting. To date, Fe 7 S 8 has been rarely reported to realize electrochemical overall water splitting because of its intrinsic poor conductivity. In this paper, Fe 7 S 8 /FeS 2 heterostructured nanosheets with interface structures and defect sites are prepared via a facile hydrothermal method. Fe 7 S 8 /FeS 2 /C electrocatalysts are constructed through the addition of carbon powder to weaken the electron transfer barrier. As expected, Fe 7 S 8 /FeS 2 /C requires the overpotential of 262 mV and 198 mV to reach 10 mA/cm2 toward oxygen evolution reaction and hydrogen evolution reaction, respectively. Moreover, Fe 7 S 8 /FeS 2 /C attains a voltage of 1.67 V at 10 mA/cm2 and maintains long-term stability for 24 h toward overall water splitting in a two-electrode system. The excellent activity can be related to interface structures and surface defect sites, which boost the charge transfer rate owing to the rich active sites. Fe 7 S 8 /FeS 2 /C exhibits the good performance toward overall water splitting due to the heterojunction structures and defect sites. [Display omitted] • Fe 7 S 8 /FeS 2 heterostructured nanosheets are hydrothermally prepared. • Fe 7 S 8 /FeS 2 nanosheets expose interface structures and defect sites. • Fe 7 S 8 /FeS 2 /C exhibits the good performance toward overall water splitting. • The good activity is associated with interface structures and defect sites. [ABSTRACT FROM AUTHOR]

How to directionally design the hollow zeolite via a green route is of great significance. Here, we successfully synthesized the hollow Fe-silicate-1 encapsulated ultra-small Fe2O3 nanoparticles (2.5 nm) with higher yield (85.2%) by mother liquid than traditional dissolution-recrystallization for the first time, which was achieved by precisely regulating the number and distribution of defects in zeolite and cleverly utilizing the TPAOH and nuclei in mother liquor. The effects of synthetic temperature, synthetic period and addition amount of parent zeolite on the formation of hollow zeolite have been investigated and the effect of synthetic conditions on the defects in parent zeolite has been also firstly quantified. The corresponding formation mechanism has been proposed. The abundant inner defects provided by the zeolite synthesized at 130 °C for 1 day and large amount of TPAOH remaining in mother liquid are conducive to the formation of hollow zeolite. Meanwhile, both parent zeolite and nuclei (4-, 5-member rings and structure units) in mother liquid obtained at 130 °C play the crucial roles in enhancing the zeolite yield. Notably, Fe2O3 nanoparticles could decompose into small fragments by the interaction with nuclei in mother liquid. Partial ultra-small Fe2O3 nanoparticles would be encapsulated in cavity and the rest could be inserted in the zeolite framework, which is significantly different from the conventional dissolution-recrystallization mechanism. The obtained encapsulated catalyst shows the superior catalytic performance and stability in phenol and tetracycline degradation reactions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Acid treatment can partially remove organic linkers in the structure of MOF-808(Zr). • Rich defect sites can be created in tha structure of MOF-808(Zr) by acid treatment. • The acid-treated MOF-808(Zr) exhibits superior catalytic ODS performance. • The acid-treated MOF-808(Zr) is a heterogeneous catalyst and can be reused. The development of active oxidative desulfurization (ODS) catalysts is of practical importance. Recently, MOF-808(Zr) has been attempted to use as ODS catalyst due to its various advantages. However, generally MOF-808(Zr) prepared by conventional method was less active in the oxidation reactions due to the lack of defect sites in the structure. In this contribution, we report that the catalytic oxidative performance of MOF-808(Zr) can be enhanced by acid treatment due to the formation of defect sites resulting from the partial removal of organic linkers in the structure. During the experiment, the effect of acid concentration, treatment time, the addition amount of oxidant and reaction parameters on the performance of MOF-808(Zr) was studied. The catalytic results show that MOF-808(Zr) treated with 0.4 M HCl for 1h can catalyze the oxidation of dibenzothiophene completely at 60°C in 15 min. The activity (mole number of converted DBT per hour per unit mass) is 70 mmol h−1 g−1, which is much higher than that (45 mmol h−1 g−1) of parent MOF-808(Zr). In addition, the catalyst can be reused several times without obvious loss of catalytic performance. [ABSTRACT FROM AUTHOR]

Electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for in situ/operando tracking of catalytic reactions that involve paramagnetic species either as a catalyst (e.g. transition metal ions or defects), reaction intermediates (radicals) or poisoning agents such as coke. This article provides a summary of recent experimental examples and developments in resonator design as well as detection schemes that were carried out in our group. Opportunities for applying this technique are illustrated by examples, including studies of transition metal exchanged zeolites and metal-free zeolites as well as metal oxide catalysts. The inherent limitations of EPR applied at high temperatures are discussed, as well as strategies in reducing or lifting these restrictions are evaluated and ideas for future improvements and methodologies are discussed., (Copyright 2024 Jörg Fischer, Mikhail Agrachev, Jörg Forrer, Rene Tschaggelar, Oliver Oberhänsli, Gunnar Jeschke. License: This work is licensed under a Creative Commons Attribution 4.0 International License.)

• The morphology and phase changes in γ-Al 2 O 3 during wet impregnation. • The morphology and phase changes are related with defect (AlV) sites on alumina. • Controlling the catalyst preparation is important to understand catalyst properties. The surface properties of support have a large influence on the catalyst properties and the catalyst properties are usually interpreted based on the characterization results of the support surface. However, in many cases, especially when γ-Al 2 O 3 is used as the support, the alumina surface can be changed during catalyst preparation. Here, the significant changes in the physical and chemical properties of γ-Al 2 O 3 were observed during catalyst preparation by using incipient wetness impregnation, which follows the general protocols of catalyst production. These changes were confirmed with transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses. To investigate the origin of such changes from hydrolysis, low-crystalline γ-Al 2 O 3 (A600) was prepared, which has abundant defect sites (AlV) on its surface and bulk. Through 27Al magic angle spinning nuclear magnetic resonance (MAS-NMR) and XRD studies, it could be demonstrated that defect sites (AlV) play a crucial role in the hydrolysis of alumina. Further, the hydrolysis of the alumina surface could be controlled by altering the solvent properties like changing the volume ratio of ethanol. These results suggest that the change in the support's surface during the catalyst preparation should be considered carefully when correlating the characteristics of the alumina surface with the characteristics of an alumina-based catalyst. [ABSTRACT FROM AUTHOR]

With the growth in power and size of energy conversion devices, the consideration of current distribution inside cells and stacks becomes increasingly important. In light of understanding the effect of the material properties of graphitic compound materials on current distribution, we developed a novel measurement cell based on a segmented current feed and a segmented measurement board. Using this cell, we determined the cross‐conduction of current in three commercial graphitic compound materials used for the manufacturing of bipolar plates. The conduction behaviors, with respect to compacting pressure as well as total current density, were explained by differences in resistance of conduction pathways. Large observed differences between the materials were discussed in terms of the ratio of through‐plane and in‐plane resistivities. Additionally, we compared several methods to emulate defect sites, in order to evaluate their effect using the novel measurement cell and showed the effect of their size on the current distribution. Finally, we discuss improvements on the measurement setup. [ABSTRACT FROM AUTHOR]

We show that it is possible to tune the magnetic properties in MoS2 without any intentional magnetic dopants but by simply controlling the magnetically active defect sites. The layer thickness and defect-density-controlled MoS2 (2H-phase) nanosheets are obtained by annealing a wet-chemical precursor from 500 to 900 °C. High-resolution transmission electron microscopy images show the presence of planar and edge defects arising from abruptly terminating edges, bends, tears, and folding of nanosheets. In addition, Mo5+ and sulfur vacancy point defects are predominant, as evidenced from the electron paramagnetic resonance and X-ray photoelectron spectra. Nanosheets gradually become more crystalline and devoid of defects upon annealing, with MoS2 (900 °C) becoming >70% defect-free. The interlayer spacing decreases monotonically from ∼6.351 to 6.231 Å with annealing; however, the lattice parameter a increases from 3.107 to 3.172 Å. These structural changes induce a large local strain (∼9%) in MoS2 (500 °C) nanosheets compared to the small strain (∼3%) present in MoS2 (900 °C). Raman spectroscopy further manifests control on the defect density, with the intensity ratio of the defect-induced LA-(M) mode (∼227 cm–1) relative to the E2g1 and A1g modes decreasing monotonically with the annealing temperature. We demonstrate that magnetically active defect sites can be tuned to enhance the ferromagnetism. Magnetization (at 5 K) systematically varies with 1 order higher MS (=0.10 emu/g) found in MoS2 (500 °C) nanosheets compared to MoS2 (900 °C). Interestingly, temperature-dependent magnetization shows a ferromagnetic-like transition around 120 K, which becomes more pronounced in defect-rich MoS2. The ferromagnetic interaction is more likely due to a bound magnetic polaron made up of a spin 1/2 Mo5+ ion with trapped carriers present at the sulfur vacancies. These findings open a new way of exploring spintronic devices such as spin-field-effect switches, spin valves, magnetic sensors, and ultrathin high-density data storage devices using MoS2 2D nanosheets by controlling magnetically active defect sites. [ABSTRACT FROM AUTHOR]

Tuning the morphology of Ag3PO4 photocatalysts with an elevated concentration of KH2PO4 have been successfully conducted. This photocatalyst was prepared by starting material of AgNO3 and KH2PO4. The KH2PO4 aqueous solution with five concentrations of 0.10 M, 0.15 M, 0.30 M, 0.45 M, and 0.60 M was reacted with AgNO3 aqueous solution. The products were characterized using X-ray Diffraction (XRD), UV-Vis Diffuse Reflectance Spectroscopy (DRS), and Scanning Electron Microscopy (SEM). The concentration of KH2PO4 significantly affected the morphology, size, and crystallinity of catalyst. The morphology of Ag3PO4 may be tuned with the synthesis using an elevated concentration of KH2PO4. The sample with the synthesis using 0.15 M of KH2PO4 exhibited the excellent photocatalytic activity. The high photocatalytic activity was caused by the small size of mixed morphology of sphere and tetrahedron, high crystallinity and defect sites. Copyright © 2019 BCREC Group. All rights reserved. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Defect sites can have a greater influence on low-pressure CO 2 adsorption in MOFs than the co-adsorption of water. • CO 2 and H 2 O adsorption on UiO-66 MOF occurs non-ideally. • Molecular simulations accurately capture trends observed in experimentally measured CO 2 /H 2 O binary adsorption isotherms. Abstract Metal organic frameworks are frequently examined as potential solutions to complex gas phase separations problems. In many cases, the gas phase adsorption properties of these materials are quantified using single component gas adsorption isotherms and breakthrough experiments. In adsorption separations, however, it is common that the adsorbent participates in a multicomponent adsorption event. In the literature there is a general absence of multicomponent adsorption data with most data predicted via the Ideal Adsorbed Solution Theory or molecular simulations. Therefore, in this work, binary adsorption data of CO 2 and water on UiO-66 were measured experimentally using a volumetric method at three different water loadings. Molecular simulations of isotherms were compared to the experimental measurements and the impact of two different MOF defect sites on the multicomponent CO 2 /H 2 O adsorption behavior was determined. The experimental data show a slight enhancement of CO 2 loading when CO 2 is co-adsorbed with water, which is a result that was confirmed via molecular simulations. Also, the simulation results show that defect sites can have a greater influence on low-pressure CO 2 adsorption in MOFs than the co-adsorption of water. Furthermore, the simulations provide a molecular-level understanding of the role of these defects on the single and binary adsorption behavior. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Hydrodeoxygenation of phenol at gas phase over Pd/Ce x Zr 1-x O 2 catalysts. • There is no correlation between oxygen vacancies amount and deoxygenation activity. • Deoxygenation is promoted by oxophilicity of the Zr4+/Zr3+ cations in the support. • The stronger interaction O - Zr4+/Zr3+ accumulate byproducts on catalyst surface. Abstract This work studies the effect of support defect sites on the performance of Pd/Ce x Zr 1-x O 2 (x = 0.00; 0.25; 0.50; 0.75; 0.90) catalysts for the hydrodeoxygenation of phenol in the gas phase at 573 K. The activity and selectivity for hydrodeoxygenation of phenol depends significantly on the support used. Increasing the Zr content from x = 0.0 to 0.5, the reaction rate for hydrodeoxygenation and the selectivity to benzene remains very low. However, upon increasing the Zr content above x = 0.5 a sudden jump in reaction rate and selectivity to benzene is observed. Interestingly, this activity and selectivity boost has no direct correlation with the density of acid sites or the concentration of defects on the support. Rather, the selectivity to deoxygenated products is found to depend on the oxophilicity of the support. Increasing the Zr content enhances the strength of the interaction between the O of the carbonyl group and the oxophilic site. It is proposed that the oxophilicity of these catalysts is related to the structure of the Ce x Zr 1-x O 2 solid solution formed. In addition, it is observed that the degree of deactivation during the reaction also depends on the Ce/Zr molar ratio of the support. Pd/ZrO 2 , Pd/Ce 0.10 Zr 0.90 O 2 and Pd/Ce 0.25 Zr 0.75 O 2 catalysts readily deactivate during reaction, whereas the phenol conversion only slightly decreases for Pd/CeO 2 , Pd/Ce 0.75 Zr 0.25 O 2 and Pd/Ce 0.50 Zr 0.50 O 2 catalysts. The results reveal that the density of Zr species on the surface is responsible for catalyst deactivation. The stronger adsorption between the oxygen from the phenol with Zr cations resulted in an accumulation of O-containing byproducts and catalyst deactivation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Ceria based ozonation catalysts. • Ceria nanorods, nanocubes and nanooctahedra with different exposed facets. • OH, surface peroxide and atomic oxygen contributed to efficient catalytic activity. • Surface basicity and defects densities/oxygen vacancies. Abstract Ceria based catalysts have been widely applied in ozonation of organic pollutants in wastewater treatment. Ceria with different exposed facets have not been used in catalytic ozonation. In this study, ceria nanorods (R-CeO 2), nanocubes (C-CeO 2) and nanooctahedra (O-CeO 2) with different exposed facets (110) + (100), (100) and (111)) respectively were used in catalytic ozonation of p-nitrophenol. Two calcination temperatures 300 and 500 °C were selected for comparative catalytic activity. Ceria nanoparticles (NP-CeO 2) were also prepared for comparative catalytic activity. Approximately 86%, 71%, 68%, 64%, 60% and 40% TOC was removed by ozonation catalyzed by R300-CeO 2 , C300-CeO 2 , CeO 2 -NP, O300-CeO 2 , R500-CeO 2 and ozonation alone respectively. Nanorod calcined at 500 °C (R500-CeO 2) showed lower catalytic activity as compared to R300-CeO 2. O 3 was also rapidly decomposed by R300-CeO 2 as compared to other catalysts and single ozonation. Inorganic hydroxyl radical scavengers and several characterization techniques were applied for investigating the underlying mechanism of catalytic ozonation. Hydroxyl radicals, surface peroxide and surface atomic oxygen as reactive oxygen species were generated for enhancing the catalytic activity. Furthermore, irrespective of surface area, the difference in catalytic activity of ceria nanoshapes were assigned to the differences in the abundance of surface basic sites, defects densities/oxygen vacancies (OVs) and coordination number of surface atoms. This study provides an insight to use other metals with variety of exposed facets for catalytic ozonation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The Mn-Ag 3 PO 4 was successfully synthesized using the co-precipitation and calcination. • Mn incorporation decreases the broad absorption and increases the atomic ratio of O/Ag. • Mn doping reduces the large defect on the surface of Ag 3 PO 4. • The enhanced activity of Mn-Ag 3 PO 4 was due to suppressing the defect sites in the surface. Abstract The highly active Mn-doped Ag 3 PO 4 photocatalyst was successfully synthesized under coprecipitation method using AgNO 3 , Na 2 HPO 4 ·12H 2 O, and MnSO 4 ·H 2 O, followed by annealing. The products were characterized using the SEM, XRD, DRS, XPS, and BET. The results showed that the Mn doping decreased the broad absorption in the visible region and increased the atomic ratio of O/Ag. The hydroxyl defects and oxygen vacancies can be suppressed by Mn doping and the photocatalytic activity under visible light irradiation could be improved. This excellent photocatalytic activity was caused by decreasing the recombination of electron and holes due to suppressing the defect sites in the surface of Ag 3 PO 4. [ABSTRACT FROM AUTHOR]

Abstract The effect of hydroxyapatite on structure, particle size, and band gap energy of silver orthophosphate (Ag 3 PO 4) have been investigated. The hydroxyapatite as a source of phosphate ion was prepared using the coprecipitation of CaCl 2 and KH 2 PO 4. To produce the product of Ag 3 PO 4 , the as-synthesized hydroxyapatite was suspended in water and quickly added to a silver nitrate solution. The obtained photocatalysts were characterized using XRD, SEM, DRS, and XPS. The high crystallinity of single phase Ag 3 PO 4 was easily produced using the hydroxyapatite. Photocatalytic activities of the product were evaluated using RhB decomposition under blue light irradiation. The hydroxyapatite as a source of phosphate ion dramatically decreases the particle size and increases the absorption in the visible region. This obtained photocatalyst significantly improves the photocatalytic activity. The mechanism of reaction works in the following order: holes > superoxide radical > hydroxyl radical. Graphical abstract Image Highlights • The Ag 3 PO 4 was successfully synthesized using hydroxyapatite. • Hydroxyapatite could be used as a source of phosphate ion. • Hydroxyapatite dramatically decreases the particle size of Ag 3 PO 4. • The highly enhanced Ag 3 PO 4 could be easily produced. [ABSTRACT FROM AUTHOR]

Photocatalytic converting CO 2 into C 2 products is highly desirable but is extremely sensitive to catalyst structure. In this work, Ti-H species and oxygen vacancies are simultaneously integrated on hydrogenated SrTiO 3 surface by thermally treating with NaBH 4 , which promotes the activation of CO 2 into HCOO- and CO* intermediates. The proximity of oxygen vacancies and Ti-H species contributes to the C-C coupling of intermediates into acetylene (C 2 H 2) products. To the best of our knowledge, this is the first example for the photocatalytic CO 2 reduction into C 2 H 2 main products. The optimal hydrogenated SrTiO 3 has the C 2 H 2 yield of 39.0 μmol·g−1 with a 76.0 % selectivity among C 2 products. Therefore, this work provides an approach of designing the adjacent active sites for photocatalytic CO 2 conversion into C 2+ products. [Display omitted] • Hydrogenation induces Ti-H species and oxygen vacancies coexisting on SrTiO 3 surface. • Hydrogenated SrTiO 3 has a photocatalytic activity for the selective reduction of CO 2 into C 2 H 2. • The selectivity of C 2 H 2 is as high as 76 % in C 2 products. • The proximity of oxygen vacancies and Ti-H species plays a vital important role in C–C coupling. [ABSTRACT FROM AUTHOR]

The catalytic preparation of renewable fuels from biomass using palmitic acid as a model compound of bio-oil has been a research focus in the field of renewable energy in recent years. However, the development of highly active, low-priced, and hydrothermal stable catalysts remains a challenging task. Here, a trace potassium-assisted activation method is proposed to improve the hydrothermal hydrogenation/deoxygenation activity of palmitic acid in this work. The conversion was successfully increased from 71.7% to 96.2%, and the total yield of alkanes was increased from 38.0% to 82.5% at 260 °C for 180 min. The research results indicate that additional defect sites and a small amount of P doping in coconut shell carbon are generated with K 3 PO 4 -assisted activation, enhancing the stronger metal-support interaction, and improving the hydrothermal stability and catalytic activity of the catalyst. XPS and H 2 -TPR jointly illustrate that K 3 PO 4 -assisted activation makes nickel species on the surface of the catalyst more easily reduced, resulting in a significant increase in the Ni0/Ni2+ ratio and oxygen vacancies during the carbothermal reduction process. This work provides a new strategy to further improve catalytic activity of bio-oil deoxygenation. [Display omitted] • A K-assisted activation strategy for manufacturing carbon defects has been developed. • K 3 PO 4 -assisted activation enhances the stronger metal-support interaction and promotes the hydrothermal hydrogenation/deoxygenation activity of fatty acids. • The defect anchoring Ni improves the hydrothermal stability of the catalyst. [ABSTRACT FROM AUTHOR]

The role of defects introduced into photocatalysts has been controversial, as some claim they serve as electron-trapping sites for improving the photogenerated charge separation, while others argue they act as exciton recombination centers to shorten the lifetime and mean free path of photocarriers. In the current study, we show the defect sites introduced into Zinc indium sulfide (ZIS) function as a double-bladed sword: on one hand, they act as recombination centers to impede photogenerated electron-hole separation in bulk ZIS; on the other hand, they drive electroless deposition and activation of the Pt co-catalyst through strong electronic coupling and thereby drastically enhance photocatalytic hydrogen production. As such, the defect-rich ZIS with a moderate Pt loading manifests the best hydrogen evolution rate of 15.56 mmol h−1 g−1 with a superb Pt-based TOF of 2334 h−1, apart from a high TON of 99610 in 92 h, which are among the best reported in literature for chalcogenide-based photocatalysts. Comprehensive microscopic, spectroscopic and photoelectrochemical characterizations unveil that the intimate coupling between the ZIS vacancy sites and deposited Pt atoms/clusters not only promotes photoexcited electron-hole separation, but also modulates local charge polarization to leverage the intrinsic activity of the co-catalyst. [Display omitted] • Different synthetic protocols result in different defect states of ZIS nanosheets. • Defects on ZIS nanosheets promote deposition and activation of the Pt co-catalyst. • A remarkable TOF of 2334 h−1 and TON of 99610 were achieved for photocatalystic hydrogen evolution. • Electronic coupling between ZIS and Pt at the defect sites promotes both the electro-kinetics and redox activity. • The double-edged role of defects in ZIS was explicitly clarified. [ABSTRACT FROM AUTHOR]

High-silica MFI zeolite can hardly be prepared by the conventional hydrothermal synthesis route in the absence of amines, which is ascribed to the competitive growth of quartz, magadiite, or kenyaite phase. In this work, these impurity phases were excluded from the synthetic gel through a low-temperature crystallization method, while the growth of zeolite phase was promoted by seed-directed and C 2 H 5 OH filling. Consequently, well-crystallized ZSM-5 samples with controllable Si/Al ratios (46–205) and uniform particle sizes were successfully prepared, and the crystallization process was tracked by multiple characterization techniques, pointing toward a nonclassical particle attachment crystallization process. Interestingly, we found that the optimal C 2 H 5 OH/SiO 2 ratio can be proportionally reduced by decreasing the H 2 O/SiO 2 ratio in the synthetic gel. More importantly, the obtained high-silica MFI zeolite exhibited a much higher catalytic stability than the conventional sample synthesized using tetrapropylammonium as the template during the methanol-to-propylene and n-butene cracking reactions, which may be attributed to its fewer defect sites determined by 1H magic angle spinning nuclear magnetic resonance techniques. Overall, this work provides an efficient route for the large-scale production of high-silica ZSM-5 samples. [Display omitted] [ABSTRACT FROM AUTHOR]

Collapsed titania nanotubes (cTiNT) were synthesized by the calcination of titania nanotubes (TiNT) at 650 °C, which leads to a collapse of their tubular morphology, a substantial reduction in surface area, and a partial transformation of anatase to the rutile phase. There are no significant changes in the position of the XPS responses for Ti and O on oxidation or reduction of the cTiNTs, but the responses are more symmetric than those observed for TiNTs, indicating fewer surface defects and no change in the oxidation state of titanium on oxidative and/or reductive pretreatment. The interaction of H2O and CO2 with the cTiNT surface was studied. The region corresponding to OH stretching absorptions extends below 3000 cm−1, and thus is broader than is typically observed for absorptions of the OH stretches of water. The exchange of protons for deuterons on exposure to D2O leads to a depletion of this extended absorption and the appearance of new absorptions, which are compatible with deuterium exchange. We discuss the source of this extended low frequency OH stretching region and conclude that it is likely due to the hydrogen-bonded OH stretches. Interaction of the reduced cTiNTs with CO2 leads to a similar but smaller set of adsorbed carbonates and bicarbonates as reported for reduced TiNTs before collapse. Implications of these observations and the presence of proton sources leading to hydrogen bonding are discussed relative to potential chemical and photochemical activity of the TiNTs. These results point to the critical influence of defect structure on CO2 photoconversion.

Stable platforms of host-guest catalysts are indispensable in the field of heterogeneous catalysis, however, clarifying the specific effect of host remains challenging. Herein, polyoxometalate (POM) is encapsulated in three types of UiO-66(Zr) with different controlled densities of defects by the aperture opening and closing strategy at ambient-temperature. It is found that catalytic activity of POM for oxidative desulfurization (ODS) at room temperature is turned on when encapsulated in the defective UiO-66(Zr), and the sulfur oxidation efficiency shows an obvious increasing trend (from 0.34 to 10.43 mmol g -1 h -1 ) with the increased concentration of defects in UiO-66(Zr) host. The as-prepared catalyst with the most defective host displays ultrahigh performance which removed 1000 ppm sulfur with exceptionally diluted oxidant at room-temperature within 25 min. The turnover frequency can reach 620.0 h -1 at 30 °C, which surpassed all the reported MOFs based ODS catalysts. A substantial guest/host synergistic effect mediated by the defective sites in UiO-66(Zr) is responsible for the enhancement. Density functional theory calculations reveal that OH/OH 2 capped on the open Zr sites of host UiO-66(Zr) can decompose H 2 O 2 to OOH group and enables the formation of W VI -peroxo intermediates that determine the ODS activity., (© 2023 Wiley-VCH GmbH.)

Defects in amorphous oxide thin-film transistor (TFT) influence major transistor parameters such as the threshold voltage, mobility, and subthreshold slope. Thus, understanding these defects is crucial in securing high-reliability and high-performance devices. However, only very limited electrical analysis methods such as multifrequency ${C}$ – ${V}$ and temperature-dependent ${I}$ – ${V}$ methods have been applied to accumulation mode devices and these do not provide direct pictures of the defects during carrier transport. In this investigation, we employed the discharging current analysis method to attain quantitative information involving the defect densities of amorphous hafnium–indium–zinc–oxide (a-HIZO) TFT. We were able to estimate the number of defect sites of a-HIZO TFT as being of the order of 1018/cm3, although this is dependent on the Hf content. We believe that this method can be widely used to estimate the defect density of oxide TFTs. [ABSTRACT FROM AUTHOR]

[Display omitted] • The restructuring and degradation of OD-Cu during CO 2 reduction were revealed. • The C 2 + FE of OD-Cu decreased from 39.4% at 1 h to 26.0% at 5 h at −1.5 V vs. RHE. • Cu defect sites are easily dissolved during electrochemical CO 2 reduction. • Low-coordinated Cu defect sites are responsible for CO 2 reduction to C 2+ products. • The degradation can be circumvented and the FE of C 2+ products maintained at ca. 47.2% with the Cu redeposition process. Renewable energy produced through electrochemical CO 2 reduction is promising for mitigating the energy crisis and environmental issues. Notably, oxide-derived copper (OD-Cu) has attracted considerable attention owing to its unique ability to catalyze CO 2 electroreduction to >2e− products, especially C 2+ products, which are the key feedstocks for the chemical process. However, Cu under operating conditions usually leads to structure reconstruction and degradation, which hinders understanding the origin of its activity. Understanding the restructuring and degradation of OD-Cu catalyst to form C 2+ products is critical for understanding the active sites and, thus for designing effective and durable catalysts for CO 2 reduction. This paper describes that Cu defect sites are easily dissolved during electrochemical CO 2 reduction, and the presence of defect sites is strongly related to the catalytic performance of C 2+ products. Here, the C 2+ products Faradaic efficiency (FE) of OD-Cu decreased from 39.4% at 1 h to 26.0% at 5 h at −1.5 V vs. RHE, along with a decrease in low-coordinated defect sites. The low-coordinated defect sites facilitate CO adsorption and help to increase the CO coverage, thus promoting CO–CO coupling. The decrease in the number of defect sites and activity degradation is circumvented by promoting the Cu redeposition process. The C 2+ products FE of OD-Cu can be maintained at ca. 47.2% without an obvious decrease in CO 2 -saturated 0.1 M KHCO 3 with 1 mM Cu2+. The results of this study help in understanding the activity of OD-Cu and reveal its deactivation mechanism. This knowledge will aid in designing highly active and stable catalysts for CO 2 reduction. [ABSTRACT FROM AUTHOR]

Copper-ceria mixed oxides are widely considered promising catalysts for oxidation reactions, especially when the participation of lattice oxygen is required. However, the mechanistic understanding of these catalytic systems is still incomplete, due to their considerable complexity. In fact, copper doping of ceria results in the formation of a significant number of different interacting sites in continuous evolution during the catalytic processes. In the present study, pure and Cu-doped ceria samples were deeply investigated through combined spectroscopic techniques, i.e. XPS, EPR, and in situ FTIR and Raman spectroscopy. Through this systematic approach, the copper sites and lattice defects responsible for the enhanced CO oxidation activity of doped ceria were elucidated. Superficial Cu+ species and small Cu0 clusters promote the adsorption of CO at low temperature, while isolated Cu2+ monomers and dimers well-dispersed in the ceria matrix foster lattice oxygen mobility, involving the sub-surface in the redox phenomena. Consequently, the structure of Cu-doped ceria undergoes substantial modifications throughout CO oxidation in the absence of O 2 , with the formation of oxygen vacancy clusters. Anyway, these changes are reversible, and structural reorganization in the presence of O 2 can occur even at room temperature. The excellent performance of Cu-doped ceria eventually stems from the effective cooperation among the different catalytic sites in the mixed oxide. [Display omitted] • The different defects and Cu sites in doped ceria are complementarily investigated. • Cu+ sites and small Cu0 clusters at the catalyst surface enhance CO adsorption. • Isolated Cu2+ monomers and dimers in the CeO 2 matrix foster lattice oxygen mobility. • Clusters of oxygen vacancies may form when the oxygen demand at the surface is high. • The effective cooperation of the different sites promotes ceria catalytic activity. [ABSTRACT FROM AUTHOR]

Electrocatalysts with strong stability and high electrocatalytic activity have received increasing interest for oxygen reduction reactions (ORRs) in the cathodes of energy storage and conversion devices, such as fuel cells and metal-air batteries. However, there are still several bottleneck problems concerning stability, efficiency, and cost, which prevent the development of ORR catalysts. Herein, we prepared bimetal FeCo alloy nanoparticles wrapped in Nitrogen (N)-doped graphitic carbon, using Co-Fe Prussian blue analogs (Co3[Fe(CN)6]2, Co-Fe PBA) by the microwave-assisted carbon bath method (MW-CBM) as a precursor, followed by dielectric barrier discharge (DBD) plasma treatment. This novel preparation strategy not only possessed a fast synthesis rate by MW-CBM, but also caused an increase in defect sites by DBD plasma treatment. It is believed that the co-existence of Fe/Co-N sites, rich active sites, core-shell structure, and FeCo alloys could jointly enhance the catalytic activity of ORRs. The obtained catalyst exhibited a positive half-wave potential of 0.88 V vs. reversible hydrogen electrode (RHE) and an onset potential of 0.95 V vs. RHE for ORRs. The catalyst showed a higher selectivity and long-term stability than Pt/C towards ORR in alkaline media.

In this study, molybdenum (Mo)-doped nickel titanate (NiTiO 3 ) materials were successfully synthesized as a function of Mo content through a modified Pechini method followed by a solvothermal treatment process. Various characterization methods were employed to investigate the optical and structural properties of the materials. XRD patterns clearly showed that the NiTiO 3 structure maintained a single phase with no observed crystalline structure transformations, even after the addition of 10 wt.% Mo. In the Raman spectra and XRD patterns, peak positions shifted with a change in Mo content, confirming that the NiTiO 3 lattice was doped with Mo. On the other hand, Mo doping of NiTiO 3 materials changed their optical properties. DRS-UV demonstrated that the addition of Mo increased photon absorption within the UV region. Relaxation processes were inhibited by Mo doping, which was evident in the PL spectra. Structural properties of the prepared materials were studied via FE-SEM and HR-TEM. The measured surface area increased proportionally with Mo content due to a reduction in grain size of the materials. [ABSTRACT FROM AUTHOR]

Pd-Ir mesocrystals with rough surface and highly branched structure were synthesized through a facile co-reduction method. The morphology evolution shows the mesocrystals were formed by oriented attachment of nanoparticles, and abundant defects sites as well as synergetic effect between building units were formed during mesocrystals oriented attachment process. Therefore, the supported Pd-Ir mesocrystals show a significant enhancement in catalytic performance in hydrogenation of 2-ethylanthraquinone compared with conventional Pd-Ir nanoparticles. The high activity can be ascribed to high densities of defect sites in Pd-Ir MCs catalyst, which facilitated H activation. In addition, the geometric effect of Pd-Ir MCs catalyst was responsible for inhibiting further hydrogenation of eAQH to undesired consecutive byproducts. Graphical Abstract: [ABSTRACT FROM AUTHOR]

The cooperative effects of secondary mesoporosity and defects on the coke formation and deactivation of zeolite were investigated in n -pentane aromatization using model Ga/ZSM-5 catalysts. Mesoporosity was introduced to a commercial ZSM-5 by alkaline desilication, while the defects sites ( i.e. , internal silanols) in zeolites were annealed by the treatment with ammonium hexafluorosilicate. Aromatization after supporting Ga showed that the mesopore generation retarded catalyst deactivation via the suppression of internal coke formation while facilitating the external coke formation due to the enhanced diffusion of coke precursors (e.g ., alkylaromatics) out of zeolite micropores. Internal coke can cause a more severe deactivation than external coke because the acid sites are mainly located in the zeolite micropores. However, the mesopore generation alone could not efficiently reduce the total amount of coke deposition (it mainly changed the location of coke). In contrast, the annealing of internal silanols could suppress the overall coke formation. This phenomenon could be explained by the fact that coke precursors are initially generated at the zeolite internal defects, and then deposited as coke at either the internal or the external surfaces of the zeolite depending on the relative kinetics of coke precursor diffusion and its polymerization. Consequently, the catalyst with mesoporosity and annealed internal silanols exhibited the slowest catalyst deactivation due to the suppression of both internal and external coke depositions. [ABSTRACT FROM AUTHOR]

Ceria (CeO 2 ) and sodium-modified ceria (Ce-Na) were prepared through combustion synthesis. Palladium was deposited onto the supports (Pd/CeO 2 and Pd/Ce-Na) and their activity for the aqueous-phase transfer hydrogenation of phenol using 2-propanol under liquid flow conditions was studied. Pd/Ce-Na showed a marked increase (6×) in transfer hydrogenation activity over Pd/CeO 2 . Material characterization indicated that water-stable sodium species were not doped into the ceria lattice, but rather existed as subsurface carbonates. Modification of ceria by sodium provided more adsorption and redox active sites (i.e. defects) for 2-propanol dehydrogenation. This effect was an intrinsic property of the Ce-Na support and independent of Pd. The redox sites active for 2-propanol dehydrogenation were thermodynamically equivalent on both supports/catalysts. At high phenol concentrations, the reaction was limited by 2-propanol adsorption. Thus, the difference in catalytic activity was attributed to the different numbers of 2-propanol adsorption and redox active sites on each catalyst. [ABSTRACT FROM AUTHOR]

Two series of one dimensional coordination polymers, {Na[Ln( sal ) 4 ]} n (Ln=Eu, Tb, Er, Y) and {Na[Ln( msal ) 4 ]} n (Ln=Er) and a new series of trinuclear complexes Na[Ln 2 ( nsal ) 7 (CH 3 OH) 2 ] (Ln=Pr, Eu, Er) have been synthesized, structurally characterized and their luminescence and decay dynamical properties studied. This in order to explore the potential of sal -type ligands to yield compounds with various dimensionalities and probe the impact of defect sites on their unique photoluminescence behaviour. The Eu 3+ compounds, {Na[Eu( sal ) 4 ]} n and Na[Eu 2 ( nsal ) 7 (CH 3 OH) 2 ] are bright red luminophores having Eu 3+ ( 5 D 0 ) emission spectra dominated by the 5 D 0 → 7 F 2 transition. Eu 3+ substitutional defects, possibly arising from the swapping of Na + with Eu 3+ ions and the replacement of sal - with methanol, are evident from luminescence and decay dynamical data on both complexes. Decay data also indicate that energy migration on the Eu 3+ sub-lattice in one dimensional chains of {Na[Eu( sal ) 4 ]} n is multidimensional and dynamic but is less efficient than energy migration in Na[Eu 2 ( nsal ) 7 (CH 3 OH) 2 ] which features a H-bonded network of trinuclear molecules. The results of this comparative exploration of structure and luminescence can be manipulated to direct dimensionality in crystal engineering of these compounds. [ABSTRACT FROM AUTHOR]

The combination of introducing mesopores and minimizing framework defects in zeolite catalysts has been proved to be highly effective in improving their catalytic lifetime in the MTH reaction. However, there is currently a lack of simple method to realize these two purposes at the same time. In this work, we report a simple one-step approach which not only completed the introduction of abundant mesopores into zeolite catalyst but also simultaneously realized the reduction of framework defects. Secondary template, fluoride media and post-treatment technology were not used during the synthetic process. As an example, a hierarchical ZSM-5 zeolite catalyst with low defect density was successfully synthesized. In the MTH reaction, the synergy effect of the hierarchical pore structure and the less framework defects endowed the prepared zeolite catalyst with a very long lifetime, which is 7.1 times that of the reference catalyst. [Display omitted] • A simple one-step approach for preparing hierarchical ZSM-5 zeolites with low defect density. • Secondary template, fluoride media and post-treatment technology are not used. • The prepared zeolite catalyst shows an extremely long lifetime during catalyzing MTH reaction. • The approach and the prepared catalyst are suitable for large-scale industrial applications. [ABSTRACT FROM AUTHOR]

Precise configurations of isolated metal atoms in nitrogen-doped carbon materials with 2D single or multilayers and 3D nanoarchitectures are gaining attention owing to their good stability and activity at high current densities. Atomic metal-N x moieties, which utilize maximum atoms to attain high intrinsic activity and novel electronic architecture of support materials, facilitate strong interaction between the central metal atom and support matrix. However, resource consumption is considerably high due to the inferior atomic utilization of active sites. Therefore, energy-efficient electrochemical processes are needed to develop advanced isolated single-atom architecture, which would provide high atom-utilization and good durability. Herein, the concepts of atomically dispersed metal sites in single-atom and alloy architectures and their electronic features associated with structural evolution are discussed. Opportunities and challenges associated with the use of isolated single-atoms in 2D materials are discussed based on their unique electronic defects, low-valence central metals, mechanical flexibility, and maximum access to metal sites. This insightful revisit into the engineering of single-atom and alloy architectures would provide a profound understanding of electronic modulations and regulation of geometric characteristics, and unravels potential directions for electrochemical energy conversion, charge storage, and sensing processes., (© 2023 Wiley-VCH GmbH.)

To simultaneously achieve thorough purification of acetylene and maximum ethene increment, a sea urchinlike trimetallic PdAuAg mesocrystal catalyst as targeting sample and cuboctahedral trimetallic PdAuAg x and bimetallic catalyst as control samples were prepared by a co-reduction method, immobilized on MgAl hydrotalcite. Compared with bimetallic PdAu and PdAg catalysts, trimetallic PdAuAg x catalyst gave prior selectivity due to the positive synergetic effect. Significantly, PdAuAg 2 mesocrystal catalyst exhibited a turnover frequency of 0.063 s −1 , 46.5% higher than that of cuboctahedral PdAuAg 2 catalyst. A 76.2% ethene selectivity was achieved for the thorough purification of acetylene over PdAuAg mesocrystal catalyst with H 2 :C 2 H 2 of 2:1. Further improving H 2 :C 2 H 2 to 3, 76.5% yield can be maintained at 140 °C. Enhanced activity of the mesocrystal catalyst could be attributed to a high concentration of defect sites and a low activation barrier. Improved ethene selectivity could be ascribed to the increase in the (1 1 1)/(1 0 0) facets ratio and the formation of a Pd-C phase. [ABSTRACT FROM AUTHOR]