High Dispersion Research Articles

Size-dependent activity modulation of supported Ni nanocatalysts for efficient solid-state hydrogen storage in magnesium

The activity of Nickel (Ni)-based catalysts strongly depends on their particle size and dispersion; however, achieving controllable preparation of uniform particle size with high activity remains a great challenge for Ni-based catalysts to promote efficient hydrogen storage. Here, we employ a facile Carbothermal Shock (CTS) method to obtain carbon fiber-loaded Ni-based nanocatalysts (Ni@CC) with high dispersibility and size-dependent properties, which can exhibit superior catalytic effects for solid-state hydrogen storage in MgH2. It was found that the shorter the CTS duration, the smaller the size of the Ni nanoparticles, and the better the catalytic effect. Among these, the MgH2-Ni@CC with a CTS duration of 30 s showed the best hydrogen storage performance. Its activation energy for hydrogen release was significantly decreased from 158.3 kJ⋅mol−1 for milled MgH2 to 98.6 kJ⋅mol−1. More importantly, the retention rate of hydrogen absorption capacity is 95.1 % after 30 cycles, which far exceeds the 65.5 % retention rate observed in milled MgH2. These property enhancements can be attributed to the presence of nano-sized Ni and its in situ derived Mg2Ni intermediate phases, which create more channels for hydrogen atoms diffusion. Meanwhile, the close contact between nano-Ni and the Mg/MgH2 matrix can provide active catalytic sites and low-energy interfaces for facilitating hydrogen adsorption and desorption. Our study presents a promising approach to significantly improve the hydrogen storage performance of MgH2 by modulating size-dependent catalytic activity.

Improvement in the activity of Ru/ZrO2 for CO2 methanation by the enhanced hydrophilicity of zirconia

Increasing interests in the supported Ru catalysts for CO2 methanation can be recently found in the literature. In this work, we demonstrated that the enhanced surface hydrophilicity of ZrO2 via air plasma treatment has significant effects on the properties of Ru/ZrO2 catalyst for CO2 methanation. At the same CO2 conversions, the reaction temperature over the catalysts on ZrO2 with enhanced hydrophilicity is 20–70 °C lower than those on untreated ZrO2. The catalyst characterization confirms that the enhanced hydrophilicity leads to more hydroxyl groups and oxygen vacancies on the support, which further promotes CO2 adsorption and activation, facilitating the conversion of CO2 to HCO3* and HCOO* in formate pathway. The enhanced hydrophilicity also causes a high Ru dispersion with stronger electronic interaction between Ru and ZrO2, which forms more interfacial active sites and improves the adsorption and dissociation of H2, promoting the linear-CO-Ru0 adsorption in CO* pathway.

Integrating the 5-SENSE Score for Patient Selection in Vagus Nerve Stimulation for Drug-Resistant Epilepsy.

Addressing the challenge of drug-resistant epilepsy, our study offers a novel perspective by retrospectively applying the 5-SENSE score, initially created for stereoelectroencephalography (SEEG) planning, to evaluate its predictive value in patients undergoing vagus nerve stimulation (VNS) therapy. We conducted a comprehensive preoperative diagnostic work-up, including computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography-CT (PET-CT), video-electroencephalogram (video-EEG), and clinical semiology. We then stratified 76 patients into three groups - low, moderate, and high focality - based on the focality of the seizure-onset zone. Such stratification was made to check the scoring ability in predictingVNStherapy seizure reduction. Our findings demonstrate an association between the extent of focality at the seizure-onset zone and the effectiveness of VNS, which may help to define the role of the 5-SENSE score in patient selection for VNS. This high dispersion of responses in the group with high focality reinforces the idea that outcome estimation is difficult and argues for an individualized strategy in the treatment of drug-resistant epilepsy. A study at the level of the 5-SENSE score indicates the importance of detailed preoperative assessments that may better optimize selection for VNS therapy and further improve clinical outcomes.

Eco-friendly sustainable fluorescent coal-based carbon dots as a highly selective probe for Cu2+detection

Carbon dots as fluorescent probes exhibit brilliant sensitivity and selectivity in copper ion detection, which greatly depends on their microstructure. Herein, a mild oxidation method was adopted to tailor the organic macromolecules of coal and its derivatives for preparing coal-based carbon dots. Such coal-based carbon dots comprise a carbonaceous center dominated by sp2 microcrystalline carbon, surface defects formed by sp3 amorphous carbon, and oxygen/nitrogen-containing functional groups. The coal-based humic acid-based carbon dots (HA-CDs) exhibit high dispersity (∼7.6 nm), high sp2 microcrystalline carbon (61.73 %), abundant carboxyl groups (2.09 %), hydroxy groups (8.93 %), and pyridinic nitrogen (1.06 %). Due to their unique microstructure, the HA-CDs in aqueous solutions exhibit prominent fluorescence stability under different pH conditions and show superior selectivity and sensitivity to Cu2+ even in the existence of other metal ions. Within the concentration range of 0–40 µmol/L, the fluorescence intensity of HA-CDs linearly correlates with the concentration of Cu2+. The limit of detection is 0.014 µmol/L, allowing for tracing the Cu2+ concentration in flowing water. This work affords a novel idea for the microstructure design of high-sensitivity carbon dots for Cu2+ detection in the water environment.

Promoting metal oxides–zeolite electron interaction on MnCeOx/HY catalyst for boosting nitrogen oxides reduction

The MnOx-CeO2 metal oxides are considered as promising alternative catalysts for selective catalytic reduction with NH3 (NH3-SCR) to remove NOx due to its excellent low temperature performance. However, their strong oxidative ability can lead to NH3 over-oxidation, narrowing the active temperature range and reducing N2 selectivity. Moreover, their weak surface acidity hampers medium to high-temperature activity and alkali metal resistance. Hence, in this study, MnCeOx metal oxides were coupled with HY zeolite to create MnCeOx/HY, demonstrating excellent NH3-SCR performance. The high dispersion of metal oxides on the zeolite surface and their close integration promoted strong electron interaction, effectively reducing oxygen vacancies and surface adsorbed oxygen concentrations. Consequently, the oxidative ability of active metal oxides was appropriately weakened, suppressing undesirable side reactions. MnCeOx/HY also notably suppressed NO adsorption and nitrate formation, promoting the catalytic reaction solely through the E-R mechanism and enhancing N2 selectivity. The abundant strong acid sites on the zeolite surface facilitates NH3 adsorption at moderate to high temperatures, notably expanding the active temperature window. Furthermore, the acid sites of HY zeolite serve as sacrificial sites, preferentially reacting with alkali metals, thus exhibiting excellent resistance to alkali metal poisoning on MnCeOx/HY. Combining with the DFT results, the structure-activity relationships in this study also reveal the importance of the effective synergy between acid sites and redox sites for optimal catalytic performance, offering valuable insights into the development of highly active and alkali-resistant denitrification catalysts.

Novel N-ZnO/p-BN adsorption-photocatalytic composites with interfacial bonding for efficient synergistic degradation of pollutants in water

Exploring green methods for removing organic pollutants from water bodies has attracted significant attention. In this research, N-ZnO/p-BN adsorption-photocatalytic composites were prepared by a simple solvothermal method, and various analytical characterizations confirmed the formation of B-O-Zn bonds at the heterojunction interface that facilitated the separation of photogenerated carriers and revealed a type-II mechanism of charge transfer in the heterostructure. The photodegradation efficiency for oxytetracycline (OTC) by composites with different N-ZnO loadings was investigated under simulated sunlight, and the degradation efficiency of the optimal sample (50 wt% N-ZnO/p-BN) for 50 mg/L OTC reached 92.2 % at 120 min. Efficient pollutant enrichment, broadened light absorption range, high dispersion of the photocatalysts, and effective charge migration are all important factors for improving photocatalytic activity. Furthermore, the photocatalytic process was further investigated, experiments showed that the N-ZnO/p-BN composites were universally applicable under a variety of conditions and possessed the characteristics of low dosage and high degradable concentration. Finally, a rational photocatalytic mechanism was proposed for the degradation system and the degradation pathways of the main degradation model OTC were analyzed and deduced. Therefore, this study provides new ideas for designing high-performance adsorption-photocatalytic composites.

The NOAH HSQC-COSY module revisited: A theoretical and practical comparison of pulse sequences

NMR supersequences, as exemplified by the NOAH (NMR by Ordered Acquisition using 1H detection) technique, are a powerful way of acquiring multiple 2D data sets in much shorter durations. This is accomplished through targeted excitation and detection of the magnetisation belonging to specific isotopologues (‘magnetisation pools’). Separately, the HSQC-COSY experiment has recently seen an increase in popularity due to the high signal dispersion in the indirect dimension and the removal of ambiguity traditionally associated with HSQC-TOCSY experiments. Here, we describe how the HSQC-COSY experiment can be integrated as a ‘module’ within NOAH supersequences. The benefits and drawbacks of several different pulse sequence implementations are discussed, with a particular focus on how sensitivities of other modules in the same supersequence are affected.

Antihepatoma activity of Marsdenia tenacissima polysaccharide-decorated selenium nanoparticles by regulating the Bax/Bcl-2/caspases and p21/Akt/cyclin A2 signaling pathways

Combining selenium nanoparticles (SeNPs) with bioactive polysaccharides is one of the effective ways to overcome the shortcomings of SeNPs and polysaccharides and obtain novel antitumor drug candidates. In this study, a heteropolysaccharide (MTP70) with moderate antihepatoma activity was isolated from the stems of Marsdenia tenacissima (Roxb.) Wight et Arn. To further improve the antihepatoma activity of MTP70 and the application of SeNPs, a novel stable nanoparticle (MTP-SeNP) was designed and fabricated. MTP-SeNPs (Se content of 8.25 %) were characterized as monodisperse spherical nanoparticles (50 nm) with MTP70 wrapped on the surface of the SeNPs by the formation of CO⋯Se bonds and possessed high stability and good dispersion in water for almost a month. In addition, MTP-SeNPs showed higher inhibitory effect compared with MTP70. MTP-SeNPs could effectively inhibit the proliferation, invasion, and metastasis of HepG2 cells by inducing apoptosis and arresting the cell cycle at the S phase, which were closely related to the activation of the Bax/Bcl-2/Caspases and p21/Akt/Cyclin A2 signaling pathways. Our results provide a theoretical basis for further development and application of M. tenacissima polysaccharide, and show that MTP-SeNPs could be explored as a promising anti-hepatoma agent in the pharmaceutical and biomedical industries.

Producing a siliceous ferroalloy from a mixture of amorphous rocks

The main silicon-containing component in a charge during ferrosilicon smelting is quartzite. The carbothermic reduction rate of the crystalline structure SiO2 has a limitation associated with a fixed energy reserve of silicon-oxygen bond. The reactive capacity of silica can be increased by using its amorphous form instead of the crystalline SiO2. The amorphous form of silica has a higher dispersion, greater free surface energy, and, consequently, a more active degree of entering into a reaction. Such silica-containing materials include amorphous rocks: diatomite, opoka, tripoli. The article presents the results of experimental studies of electrothermal ferrosilicon production from a mixture of amorphous rocks (tripoli, opoka, diatomite with a mass ratio of 1:1:1).It is established that when smelting the mixture of amorphous rocks containing 77 % SiO2, 7.9 % Al2O3, 5.2 % Σ CaO and MgO, 4 % Σ K2O Na2O, 3.3 % Fe2O3, 1.3 % CaCO3, 0.9 % CaSO4, 0.4 % others, three ferrosilicon grades are formed: FeSi25 (22–29 % Si), FeSi45 (41–47 % Si), FeSi50 (47–52 % Si) with the extraction degree of 70–87.6 % silicon into the alloy. Moreover, the ferrosilicon grade decreases with an increase in steel shavings in the charge from 21.9-31.4 % to 33–35 %. In comparison with ferrosilicon smelting from a standard charge containing quartzite with the crystalline form of SiO2, steel shavings and coke, ferrosilicon production from the mixture of amorphous rocks allows to increase the process rate by 17.5–21.6 %. It is possible to increase the silicon extraction degree into the alloy from 80-85 %–94.5 % if its final stage is carried out in the resistance mode. Widespread occurrence in nature, favorable conditions of occurrence, low cost, high reactive capacity are favorable factors for using amorphous rocks in the production of ferroalloys.

Morphology effects of CeO2 on the performance of CaO-Cu/ CeO2 for integrated CO2 capture and conversion to CO

CeO2 support inhibits CaO sintering, and oxygen vacancy influences CO2 hydrogenation performance, making CeO2 widely applied in Integrated CO2 capture and in-situ conversion technology for reverse water–gas shift (ICCC-RWGS). Oxygen vacancy concentration was dependent on the morphology of CeO2, which would affect metal dispersion and CO2 hydrogenation conversion. However, Very little is known about the morphology effect of CeO2 on the carbon capture and in-situ hydrogenation performance of DFMs. Here, Cu/CeO2 with different CeO2 morphologies was synthesized, and high Cu dispersion was achieved on Cu/CeO2-R, exhibiting the best CO2 hydrogenation performance. Integrated Cu/CeO2 with CaO by physical mixing method, CaO-Cu/CeO2 was used to investigate the morphology effects of CeO2 on the performance of CaO-Cu/CeO2 for integrated CO2 capture and conversion to CO. CaO-Cu/CeO2-R exhibited the best capture-hydrogenation performance (CO2 conversion rate of 75 %, CO production rate of 9.72 mmol/g). The CeO2-R provided more surface oxygen vacancies, enhancing carbonate hydrogenation. The larger specific surface area and {110} crystal plane of CeO2-rod enhanced Cu dispersion, and the smaller particle size of CeO2-R enhanced its interaction with CaO, improving the cyclic stability of CaO-Cu/CeO2-R. The hydrogenation performance of CaO-Cu/CeO2 was dependent on the morphology of CeO2, providing insights into the design of high-activity metal catalytic components in ICCC-RWGS.

Direct conversion of biogas to syngas over bimetallic nickel–cobalt supported on α-alumina catalysts

Syngas is an essential feedstock for many valuable chemicals, produced primarily by steam reformation of methane. Recently, dry reformation (reaction between methane and carbon dioxide) has gained importance as both the reactants are greenhouse gases (GHGs). However, dry reformation (DRM) produces syngas with a low H2/CO (<1.0). The DRM requires catalyst such as nickel supported on alumina, which results in higher coke. In this study, 6Ni–6Co/α-Al2O3 and 12Ni/α-Al2O3 catalysts were prepared by wetness impregnation. The catalysts were characterized using FESEM, XRD, XPS, BET, H2-TPR, NH3-TPD and H2-Chemisorption. The catalyst performance under DRM conditions were carried out in a fixed bed reactor at 20,000 ml/gcat.hr GHSV, between 600 °C and 700 °C, at atmospheric pressure. The performance of the catalysts was compared based on conversion of methane and carbon dioxide, hydrogen to carbon monoxide and coke deposition. The rates of consumption of methane carbon dioxide were found to be equal, and higher rates were observed for 6Ni–6Co/α-Al2O3, which is attributed to NiAl2O4/CoAl2O4 phase of active metals, higher surface area, smaller crystallite size and higher dispersion. This active phase of catalyst also responsible for higher rate of CO2 adsorption and reduced coke deposition. Highest H2/CO was found to be 1.26 for 6Ni–6Co/α-Al2O3.

Comparative Genomics Supports Ecologically Induced Selection as a Putative Driver of Banded Penguin Diversification.

The relative importance of genetic drift and local adaptation in facilitating speciation remains unclear. This is particularly true for seabirds, which can disperse over large geographic distances, providing opportunities for intermittent gene flow among distant colonies that span the temperature and salinity gradients of the oceans. Here, we delve into the genomic basis of adaptation and speciation of banded penguins, Galápagos (Spheniscus mendiculus), Humboldt (Spheniscus humboldti), Magellanic (Spheniscus magellanicus), and African penguins (Spheniscus demersus), by analyzing 114 genomes from the main 16 breeding colonies. We aim to identify the molecular mechanism and genomic adaptive traits that have facilitated their diversifications. Through positive selection and gene family expansion analyses, we identified candidate genes that may be related to reproductive isolation processes mediated by ecological thermal niche divergence. We recover signals of positive selection on key loci associated with spermatogenesis, especially during the recent peripatric divergence of the Galápagos penguin from the Humboldt penguin. High temperatures in tropical habitats may have favored selection on loci associated with spermatogenesis to maintain sperm viability, leading to reproductive isolation among young species. Our results suggest that genome-wide selection on loci associated with molecular pathways that underpin thermoregulation, osmoregulation, hypoxia, and social behavior appears to have been crucial in local adaptation of banded penguins. Overall, these results contribute to our understanding of how the complexity of biotic, but especially abiotic, factors, along with the high dispersal capabilities of these marine species, may promote both neutral and adaptive lineage divergence even in the presence of gene flow.

The Support and Bimetallic Synergy Effects in Cu‐Ni/SiO2 Catalysts for Hydrogenation of Furfural

AbstractHerein, a series of Cu, Ni catalysts were synthesized using mesoporous SiO2 (MCM‐41) and fumed SiO2 as supports for the catalytic hydrogenation of furfural (FF). The MCM‐41 support facilitated the high dispersion of Cu, Ni nanoparticles (NPs), and the hydrogenation products are primarily in the form of alcohols. For fumed SiO2, the proper amounts of acid sites contributed to the better selectivity of 2‐methyltetrahydrofuran(2‐MTHF). Hydrogenation results showed that the 10Cu10Ni/MCM‐41 catalyst afforded a 93.6 % yield of tetrahydrofurfuryl alcohol (THFA), while the 10Cu10Ni/SiO2 catalyst afforded a 61.73 % yield of 2‐MTHF and a 31.63 % yield of THFA. Meanwhile, it is also found that impregnating nickel salt before copper salt is more likely to promote the formation of deep hydrogenation products. Cyclic experiments indicate that developing a one‐step hydrogenation process with selective production of fully hydrogenated products is still a daunting and challenging task.

Designing affective workplace environments: The impact of typology, contour, ceiling and partition height on cognitive and aesthetic appraisal

Up to 90 % of our time is spent indoors, with 40 % of a full-time employee's waking hours spent at work, underscoring the critical importance of workplace environments in promoting health and well-being. While there is substantial knowledge about the impact of spatial design on environmental satisfaction and productivity, there is a gap in understanding its effect on employees' aesthetic and cognitive experiences. This study addresses these gaps by investigating how variations in typical workplace design elements—such as partition height, ceiling height, and contour shape—across three workplace typologies (Open plan, Cellular, and Bürolandschaft) influence both aesthetic (beauty, attention, pleasure) and cognitive (safety, distraction, interaction) appraisals. Thirty-six virtual models of workplace environments were generated using parametric modeling methods, and a total of 713 participants provided ratings and rankings for these dimensions. Our findings indicate that higher partitions are associated with greater perceived safety and reduced distractions, while curved contours are perceived as more aesthetically pleasing and enjoyable compared to angular designs. The Bürolandschaft typology significantly enhances perceived safety and interaction. Moreover, isovist analysis revealed that spatial features such as isovist compactness and circularity positively correlate with beauty, pleasure, and attention, while higher dispersion is linked to lower safety perceptions. These insights are crucial for designing affective workplace environments that balance openness and privacy, enhance safety, and support a science-informed approach to workplace design that promotes positive cognitive and aesthetic experiences.

Preparation and application of single-atom nanozymes in oncology: a review.

Single-atom nanozymes (SAzymes) represent a cutting-edge advancement in nanomaterials, merging the high catalytic efficiency of natural enzymes with the benefits of atomic economy. Traditionally, natural enzymes exhibit high specificity and efficiency, but their stability are limited by environmental conditions and production costs. Here we show that SAzymes, with their large specific surface area and high atomic utilization, achieve superior catalytic activity. However, their high dispersibility poses stability challenges. Our review focuses on recent structural and preparative advancements aimed at enhancing the catalytic specificity and stability of SAzymes. Compared to previous nanozymes, SAzymes demonstrate significantly improved performance in biomedical applications, particularly in tumor medicine. This progress positions SAzymes as a promising tool for future cancer treatment strategies, integrating the robustness of inorganic materials with the specificity of biological systems. The development and application of SAzymes could revolutionize the field of biocatalysis, offering a stable, cost-effective alternative to natural enzymes.

Synergistic combination of Mn/Fe bimetal-doped carbon nitride and peroxymonosulfate for efficient photocatalytic degradation of antibiotics

The widespread of antibiotics has resulted in potential threats to the aquatic environment and human health. The visible light-assisted peroxymonosulfate (PMS) activation method is considered to be an effective way to remove antibiotics in wastewater. In this study, Mn/Fe bimetal doped graphitic carbon nitride (MnFe-CN-x) was first synthesized for PMS activation under visible light towards tetracycline (TC) removal. The optimized MnFe-CN-50 possessed the excellent photocatalytic activity, PMS activation performance and photo-Fenton-like synergistic effect. In the photo-Fenton-like system, TC (20 mg L−1) was degraded by 99 % in 50 min and the kinetic constant was 0.074 min−1. The high dispersion of Mn and Fe in carbon nitride inhibited the recombination of charge carriers in MnFe-CN-x, increased its photocurrent density and charge mobility, effectively optimized the electronic structure, and promoted the generation of 1O2. Based on the analytical results of predictive toxicity evaluation software (TEST), it was confirmed that MnFe-CN-x could effectively reduce the environmental risks associated with antibiotic contamination. This study provided new insights into synthesizing bimetal-doped graphitic carbon nitride and the use of synergistic effects of photocatalysis and PMS activation to remove organic pollutants from wastewater.

Impact of Graphene Oxide on SERS Enhancement of Arylated Gold Nanospheres: Mechanistic Insight.

The performance of gold nanospheres as substrates for surface-enhanced Raman spectroscopy (SERS) investigation has been compromised by their low adsorption efficiency, high colloidal dispersibility, and diminishing hot spots. However, gold nanosphere substrates modified using aryldiazonium gold(III) chemistry via durable gold-carbon bonds are promising for SERS enhancement due to their controlled organic layer density. In this study, arylated gold nanospheres AuNSs-COOH have shown SERS enhancement when incorporated into graphene oxide (GO) to form nanocomposites (NCs) labeled AuNSs-COOH/GO (AuNCs). Our investigation using X-ray photoelectron spectroscopy (XPS) surface analysis showed that the gold-aryl nanospheres reached their maximum SERS enhancement with an optimal coating. The evaluation included the Au 4f chemical environment and compact graphitic layers for the SERS substrate optimization. The fabricated AuNC substrates demonstrated superior efficiency and reproducibility. A broad linear range of 10-3-10-7 M 4-nitrophenol detection was obtained with exceptional repeatability, as evidenced by the relative standard deviation (RSD) of 9.32%. A detailed investigation of the energy profiles, particularly the valence band maximum (VBM) and band gap values of the substrate and analyte, depicted the electromagnetic (EM) and charge-transfer-induced enhancement and the role of GO inclusion in substrate efficiency in SERS enhancement mechanisms. The finite-difference time domain (FDTD) simulation results revealed that AuNCs incorporated with graphitic nanostructures exhibited the most substantial SERS effect through an EM field enhancement mechanism. This study demonstrated significant SERS enhancement using gold-aryl nanospheres when modified with GO, in contrast to the typical reliance on anisotropic nanostructures.

Efficient Electrochemical Reduction through Flow Cells Using Spherical-Polymer Based Carbon Supported Catalysts as Fixed-Bed Electrode

The transition to economically friendly feedstocks and the electrification of chemical synthesis reactions gained much attention in the recent years. To be able to compete with the conventional processes, it is crucial not only to concentrate on the electrochemical reactions itself but also to constantly improve the reactor concepts. A vast variety of designs are imaginable and already well-described – from a simple, undivided beaker cell setup to a divided flow cell with separate electrolytes at cathode and anode. [1] As electrode material not only flat metal electrodes are studied, but also the concept of using carbon supported metal nanoparticles is well-known to employ high dispersion to lower the total amount of required metal. [2,3] While there are already commercial flow reactors and electrodes available for electrosynthesis with flat standard electrodes, reactors using a fixed-bed of porous carbon with nanodispersed metals as electrode just recently started to attract attention. [4] Dealing with the pressure drop over the catalyst bed, while the electrical contact is still ensured, are key challenges for this reactor design. Spherical polymer-based carbons (SPBC) combine porous carbons properties with a high purity and especially spherical character. [5] While these advantages led already to commercial products for chromatographic applications (e.g. Carboxen®) the potential regarding flow-electrochemistry has not been leveraged. Key developments for this are reproducible synthesis procedures to deposit active metal on the SPBCs and the design of an electrochemical flow cell using these catalysts in a fixed-bed electrode configuration.The first part of this work presents the deposition of Cu through different impregnation and reduction procedures on a SPBC (Carboxen® 1032, 50 µm, Merck). The carbon was characterized by physisorption, TPD-MS, TPO, Raman and SEM. The resulting metal-impregnated carbon catalysts were additionally investigated regarding the metal loading. Using the applied impregnation and reduction parameters targeted metal loadings (3 – 20 wt%) could be well achieved. The second part focuses on the design and commissioning of a flow-cell for the application of the SPBC-supported catalysts as a fixed-bed at the cathode side. Electrochemical synthesis reactions are targeted in the cell and the reduction of 5-HMF to BHMF was chosen as the test reaction in this work. In the framework of the cell development multiple aspects not only regarding the construction but also reaction engineering issues had to be considered: material stability of the pump, fixation and pressure drop of catalyst bed, choice of electrolyte, effect of dissolved oxygen in the catholyte, optimal flow rate, reliable electrochemical protocol and selection of contact material. The latter has to be a compromise between chemical inertness and an enhanced electron transfer between the catalyst bed and the contact material (e.g. soft foil vs. hard metal). Figure 1A shows the current voltage characteristics of two possible contact materials (graphite foil, boron-doped diamond (BDD)) in the targeted electrolyte (0.5M borate buffer with 0.25M potassium chloride). Here, the graphite foil clearly shows a higher activity towards the hydrogen evolution reaction which may result in a less effective electrolysis later on. The comparison of BDD as contact material without and with a catalyst bed (Carboxen® 1032 loaded with 20 wt% Cu) resulted in a significant shift in the current voltage characteristic to lower overpotentials. Therefore, the electronic contact with the carbon bed is clearly enabled and the carbon spheres loaded with copper catalyze the reaction. Figure 1B presents the results of the test reaction with the conversion of the educt 5-HMF as well as the selectivity to the targeted product BHMF over the reaction time with BDD as contact material without and with a fixed bed of Cu/SPBC catalyst. The experiments prove full 5-HMF conversion within 23 h on stream in combination with a high selectivity towards BHMF with the catalyst bed. The mass-based productivity reaches values of up to 1.78 mmol h-1 gCu -1 and is therefore about 15 times higher compared to the use of conventional Cu foil (Pliterature = 0.11 mmol h-1 gCu -1 [6]). It is possible that due to the metal-support approach in the fixed-bed configuration, the copper is leveraged more efficiently and small amounts allow to provide sufficient metal surface area for the catalytic reaction.

Noble Metal‐Free High Entropy Perovskite Oxide with High Cationic Dispersion Enhanced Oxygen Redox Reactivity

AbstractHigh entropy perovskite oxide (HEPO) materials have received significant interest as efficient electrocatalysts owing to their chemical and structural stability, effective interaction of multiple metal active sites with the reaction intermediate species resulting in enhanced catalytic activity. The effect of high‐entropy strategy could achieve the regulation of the structural durability by tailoring the composition. Herein, we design a novel transition metal and rare‐earth metal based high entropy perovskite oxide (Co0.11Mn0.11Ni0.11Fe0.14La0.13Nd0.13Gd0.13Pr0.13)O3, showing superior catalytic activity in the oxygen reduction reaction (ORR) and also promising electrocatalyst in oxygen evolution reaction (OER). High degree of cationic dispersion in the lattice and multiple electrocatalytic active sites enhance the oxygen ion migration at the surface and facilitate electron transfer, manifesting good ORR performance. Notably, the as‐prepared high entropy material exhibits onset and half‐wave potential of 1.02 V and 0.89 V versus RHE, respectively, exceeding the performance of the benchmarked Pt/C catalyst in the ORR process with reasonable redox kinetics. Moreover, the material also presents faster kinetics with reasonably low overpotential and excellent electrochemical stability in the OER process as well. This study shows the viability of designing non‐precious high entropy materials as highly efficient oxide electrocatalyst by utilizing its broad compositional space.

Construction of heterojunctions with in situ growth of ZnIn2S4 nanosheets on the surface of atomically dispersed Cu-modified MOFs for high-performance visible-light photocatalytic antibiotic degradation

Metal-organic frameworks (MOFs) are ideal candidates for obtaining composites with excellent photocatalytic properties due to their reasonable band gaps and high specific surface area. In this study, Cu@UiO-66-NH2@ZnIn2S4 nanocomposites were prepared by a two-step photoinduction method and hydrothermal method. The prepared catalysts in a range of ratios showed high visible light degradation of tetracycline hydrochloride (TC). Among them, 10%-Cu@UIO-66-NH2/ZnIn2S4 showed the best catalytic activity and photoelectrochemical performance. In this catalytic system, the high specific surface area and porosity of UIO-66-NH2 provide sites for the high dispersion of Cu. In addition, the introduction of Cu also reduces the band gap, which is conducive to the electron transfer between the interfaces, which results in the formation of type II heterojunctions with a unique and highly efficient electron transfer mechanism, and also enables the photocatalytic process to generate more active radicals (O2–, OH, h+). In addition, the stability of the catalyst was tested, as well as the possible degradation pathways were hypothesized to evaluate its toxicity. Thus, this study provides a strategy for the preparation of stable and efficient photocatalysts..