Solvothermal Method Research Articles

Self-Reconstructed Metal–Organic Framework-Based Hybrid Electrocatalysts for Efficient Oxygen Evolution

Refining synthesis strategies for metal–organic framework (MOF)-based catalysts to improve their performance and stability in an oxygen evolution reaction (OER) is a big challenge. In this study, a series of nanostructured electrocatalysts were synthesized through a solvothermal method by growing MOFs and metal–triazolates (METs) on nickel foam (NF) substrates (named MET-M/NF, M = Fe, Co, Cu), and these electrocatalysts could be used directly as OER self-supporting electrodes. Among these electrocatalysts, MET-Fe/NF exhibited the best OER performance, requiring only an overpotential of 122 mV at a current density of 10 mA cm−2 and showing remarkable stability over 15 h. The experimental results uncovered that MET-Fe/NF underwent an in situ structural reconstruction, resulting in the formation of numerous iron/nickel (oxy)hydroxides with high OER activity. Furthermore, in a two-electrode water-splitting setup, MET-Fe/NF only required 1.463 V to achieve a current density of 10 mA cm−2. Highlighting its potential for practical applications. This work provides insight into the design and development of efficient MOF-based OER catalysts.

Selective CO2 Photoreduction into CH4 Triggered by the Synergy between Oxygen Vacancy and Ru Substitution under Near-Infrared Light Irradiation.

Near-infrared (NIR) light powdered CO2 photoreduction reaction is generally restricted to the separation efficiency of photogenerated carriers and the supply of active hydrogen (*H). Herein, the study reports a retrofitting hydrogenated MoO3-x (H-MoO3-x) nanosheet photocatalysts with Ru single atom substitution (Ru@H-MoO3-x) fabricated by one-step solvothermal method. Experiments together with theoretical calculations demonstrate that the synergistic effect of Ru substitution and oxygen vacancy can not only inhibit the recombination of photogenerated carriers, but also facilitate the CO2 adsorption/activation as well as the supply of *H. Compared with H-MoO3-x, the Ru@H-MoO3-x exhibit more favorable formation of *CHO in the process of *CO conversion due to the fast *H generation on electron-rich Ru sites and transfer to *CO intermediates, leading to the preferential photoreduction of CO2 to CH4 with high selectivity. The optimized Ru@H-MoO3-x exhibits a superior CO2 photoreduction activity with CH4 evolution rate of 111.6 and 39.0µmol gcatalyst -1 under full spectrum and NIR light irradiation, respectively, which is 8.8 and 15.0 times much higher than that of H-MoO3-x. This work provides an in-depth understanding at the atomic level on the design of NIR responsive photocatalyst for achieving the goal of carbon neutrality.

Mechanochemical Synthesis of Boroxine-linked Covalent Organic Frameworks.

We report a rapid, room-temperature mechanochemical synthesis of 2- and 3-dimensional boroxine covalent organic frameworks (COFs), enabled by using trimethylboroxine as a dehydrating additive to overcome the hydrolytic sensitivity of boroxine-based COFs. The resulting COFs display high porosity and crystallinity, with COF-102 being the first example of a mechanochemically prepared 3D COF, exhibiting a surface area of ca.2,500m2g-1. Mechanochemistry enabled a >20-fold reduction in solvent use and ~100-fold reduction in reaction time compared with solvothermal methods, providing target COFs quantitatively with no additional work-up besides vacuum drying. Real-time Raman spectroscopy permitted the first quantitative kinetic analysis of COF mechanosynthesis, while transferring the reaction design to Resonant Acoustic Mixing (RAM) enabled synthesis of multi-gram amounts of the target COFs (tested up to 10 g).

Regulating Catalytic Oxidation Enantiomers Behavior by Imparting Chiral Microenvironment in Zr-Based Metal-Organic Frameworks.

Chiral inversions of enantiomers have significantly different biological activities, so it is important to develop simple and effective methods to efficiently identify optically pure compounds. Inspired by enzyme catalysis, the construction of chiral microenvironments resembling enzyme pockets in the pore space structure of metal-organic frameworks (MOFs) to achieve asymmetric enantioselective recognition and catalysis has become a new research hotspot. Here, a super-stable porphyrin-containing material PCN-224 is constructed by solvothermal method and a chiral microenvironment around the existing catalytic site of the material is created by post-synthesis modifications of the histidine (His) enantiomers. Experimental and theoretical calculations results show that the modulation of chiral ligands around Zr oxide clusters produces different spatial site resistances, which can greatly affect the adsorption and catalytic level of the enantiomeric molecules of tryptophan guests, resulting in a good enantioselective property of the material. It provides new ideas and possibilities for future chiral recognition and asymmetric catalysis.

Superoxide radicals dominated hydrogen peroxide activation using BiOI for boosting Fenton-like catalytic degradation of bisphenol A

Herein, flower-like BiOI micro-spherulites were successfully prepared via a solvothermal method, and it exhibited a remarkably Fenton-like catalytic efficacy in the degradation of BPA under dark condition without additional energy input. BiOI can function as an electron-poor center, facilitating the activation of H2O2 into •O2−, while simultaneously serving as an electron-rich center to reduce dissolved O2 to •O2−. This electron-rich and electron-poor centers of BiOI synergistically enhance the •O2− generation for highly Fenton-like catalytic performance. Moreover, the removal performance of BPA demonstrated a significant pH dependency, and the presence of low concentrations of halide ions and humic acid did not exhibit noticeable inhibitory effect on the degradation of BPA. Additionally, several intermediates have been identified to propose a comprehensive degradation mechanism for BPA. This study presents a novel BiOI Fenton-like catalytic system for the purification of recalcitrant organic pollutants in wastewater.

Excellent electrochemical performance of N and Mn doped NiCo2O4 functional nanostructures: an effective approach for symmetric supercapacitor application

In supercapacitors (SCs), cobaltite spinel is considered as an excellent electrode material because it is abundant on earth, cost-effective, and theoretically capable of achieving high capacitance values. However, there are number of factors that prevent spinel cobaltite from achieving its maximum theoretical specific capacitance, including low electrical conductivity, insufficient active sites, and slow charge transport. For these reasons, it is necessary to simplify the structural and compositional design to overcome these limitations. An efficient solvothermal method followed by pyrolysis was successfully used to shape NiCo2O4 nanoflowers doped with N (Nitrogen) and Mn (Manganese). In addition to increasing the ion diffusion resistance and charge transfer resistance, N and Mn-doped NiCo2O4 provides an electrical conductivity system. The optimized N, Co, and Mn4 (NCoMn4) nanoflowers (4 wt% Mn-doped NiCo2O4) exhibits maximum specific capacitance of 269Fg−1 at 1Ag−1 current density with an exceptional retention of capacitance 92% after 5,000 uninterrupted cycles in the Na2SO4 media. The electrokinetic analysis of NCoMn4 further indicates that overall charge is stored predominantly through capacitance, as compared with other electrodes. It is also worth noting that the as-fabricated symmetric supercapacitor delivers the maximum energy density of 36.11 Whkg−1 at a power density of 1.04 kWkg−1 at 1 Ag−1 current density. This work opens a new path to develop hybrid electrodes for enhanced supercapacitor applications and will specify an efficient method for improving the charge transfer capability.

In situ generation of turbostratic nickel hydroxide as a nanozyme for salivary glucose sensor.

Among the 3d-transition metal hydroxide series, nickel hydroxide is a well-studied electroactive catalyst. In particular, nickel hydroxide and its composite materials are well-suited for non-enzymatic glucose sensing. The electrocatalytic efficiency of nickel hydroxide is attributed to the thickness or to be precise, the thinness of the electroactive layer. Herein, we have successfully prepared metallic nickel@nickel hydroxide nanosheets through a straightforward one-pot solvothermal method. We were able to electrochemically generate a highly sensitive α-Ni(OH)2 on the nanosheets. The dynamic generation and synergy between α- and β-Ni(OH)2, imparts a glucose oxidase enzyme-like ability to the catalyst. Our proposed nickel nanozyme exhibits a good sensitivity of 683 μA mM-1 cm-2 for glucose. The sensor operates in the range of 0.001-3.1 mM, with a lower limit of detection (LOD) of 9.1 μM and exhibits a response time of ≈00.1 s. Nickel-nanozyme demonstrated better selectivity for glucose in the presence of interfering compounds. Notably, the sensor does not suffer from an interfering oxygen evolution reaction. This greatly improves sensitivity in glucose detection in lower concentrations making the sensor viable to measure salivary glucose levels. In this study, we demonstrate that our sensor can detect glucose in human saliva. The real sample analysis was carried out with saliva samples from three healthy human volunteers and one prediabetic volunteer. Our proposed sensor measurements show excellent agreement with calculated salivary glucose levels with 98% accuracy in sensing glucose in real saliva samples.

Solvothermal synthesis of micro-pillar shaped Ag2Se and its thermoelectric potential

Solvothermal method can synthesize ultralarge and high-performance thermoelectric powders with controllable structure, morphology, composition, and grain size. Here, we have developed a facile and surfactant-free solvothermal method for the synthesis of ultralarge Ag2Se powders. The as-synthesized Ag2Se powders exhibit the morphology of micro-pillar with the length ranging from several to hundreds of microns, and the average length-diameter ratio of ∼4.9. In as-synthesized Ag2Se micro-pillars, regardless of the high crystallinity and closely perfect Ag/Se ratio of ∼2, the highly localized lattice distortions and strain fields might indicate partial superionicity of room-temperature orthorhombic Ag2Se. Compositional and structural analysis after spark plasma sintering indicates the formation of additional Se vacancies due to Se sublimation during the sintering process, which leads to high carrier concentration of ∼1.3 × 1019 cm−3 and limits the room-temperature dimensionless figure of merit to ∼0.46. Further optimizing the carrier concentration to ∼1 × 1018 cm−3 can theoretically lead to high room-temperature dimensionless figure of merit of ∼1.4. Our study not only renders a facile solvothermal method for the synthesis of Ag2Se micro-pillars with extensive thermoelectric application potentials.

Designed Growth of Covalently Bonded WO3/PEDOT Hybrid Nanorods Array with Enhanced Electrochromic Performance

A covalently bonded WO3/PEDOT hybrid nanorods array has been prepared through solvothermal, oil bath, and electrochemical deposition methods using KH57 as a coupling agent. The obtained WO3/PEDOT shows substantially increased electrochromic performance with an increased response speed (3.4 s for coloring and 1.2 s for bleaching), excellent optical modulation (86.7% at 633 nm), high coloration efficiency (122.0 cm2/C at 633 nm), and distinguished cyclic stability. It was found that the covalent bond interaction between WO3 and PEDOT plays an essential role in property enhancement. The covalently bonded inorganic/organic hybrid nanorods array may promise great potential in developing smart-display and energy-efficient materials and devices featuring low energy consumption, cost effectiveness, and environmental protection.

Iron metal organic framework decorated carbon nanofiber-based electrode for electrochemical sensing platform of chlorpyrifos in fruits and vegetables

Chlorpyrifos, a prime insecticide encountered in numerous agricultural products, is associated with an array of adverse health implications, notably endocrine disturbances and carcinogenic tendencies. Monitoring the environment and controlling quality requires a rapid and simple method for determining the organophosphate insecticide. Overcome the universal challenge postured by this contaminant, this study presents a novel strategy to fabricate an electrochemical sensor based on Iron MOFs, synthesized using 3,5-pyrazoledicarboxylic acid (PyDA) using one-pot solvothermal method with carbon nanofiber matrix for sensing the chlorpyrifos. Notably, this MOF anchored electrode owns important fundamental features such as an expansive surface area, abundant active sites, a vast operational spectrum linear range (1.0–150 μM), a minimal detection threshold (15.1 nM), and an amplified sensitivity towards chlorpyrifos. This Fe-PyDA/CNF/GCE electrode not only showcased more extraordinary electrochemical attributes, but its broad linear detection range and low detection threshold emphasize its ability for real-world applications with reasonable recoveries.

Exploring the Capability of Cu-MoS2 Catalysts for Use in Electrocatalytic Overall Water Splitting

Herein, we prepare MoS2 and Cu-MoS2 catalysts using the solvothermal method, a widely accepted technique for electrocatalytic overall water-splitting applications. TEM and SEM images, standard tools in materials science, provide a clear view of the morphology of Cu-MoS2. HRTEM analysis, a high-resolution imaging technique, confirms the lattice spacing, lattice plane, and crystal structure of Cu-MoS2. HAADF and corresponding color mapping and advanced imaging techniques reveal the existence of the Cu-doping, Mo, and S elements in Cu-MoS2. Notably, Cu plays a crucial role in improving the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) of the Cu-MoS2 catalyst as compared with the MoS2 catalyst. In addition, the Cu-MoS2 catalyst demonstrates significantly lower overpotential (167.7 mV and 290 mV) and Tafel slopes (121.5 mV dec−1 and 101.5 mV dec−1), standing at −10 mA cm−2 and 10 mA cm−2 for HER and OER, respectively, compared to the MoS2 catalyst. Additionally, the Cu-MoS2 catalyst displays outstanding stability for 12 h at −10 mA cm−2 of HER and 12 h at 10 mA cm−2 of OER using chronopotentiaometry. Interestingly, the Cu-MoS2‖Cu-MoS2 cell displays a lower cell potential of 1.69 V compared with the MoS2‖MoS2 cell of 1.81 V during overall water splitting. Moreover, the Cu-MoS2‖Cu-MoS2 cell shows excellent stability when using chronopotentiaometry for 18 h at 10 mA cm−2.

Construction of Rod-Like Bi4O5I2/NaYF4:Yb,Tm Composite and its Improved Photocatalytic Degradation Performance Under Near-Infrared Light

Photocatalytic technology exhibits promising prospects in environmental remediation owing to its sustainable and environmentally friendly advantages. Among the bismuth-rich halide oxides, Bi4O5I2 has demonstrated remarkable efficacy in dye degradation due to its favorable valence band and conduction band positions. In this study, we successfully synthesized Bi4O5I2/NaYF4:Yb,Tm composites through a solvothermal method. When exposed to visible light, the Bi4O5I2/NaYF4:Yb,Tm composite achieved an impressive degradation rate of 86.7% for RhB solution after 60[Formula: see text]min of light-induced reaction. Moreover, the incorporation of NaYF4:Yb,Tm into Bi4O5I2 extended the utilization of near-infrared (NIR) spectroscopy. Under 980[Formula: see text]nm NIR light irradiation, the degradation rate of Rhodamine B (RhB) solution by the Bi4O5I2/NaYF4:Yb,Tm composite reached 43.0% after 240[Formula: see text]min of light reaction. Free radical capture experiments confirmed that h[Formula: see text] and •[Formula: see text] O[Formula: see text] played a significant role as the primary active species in the degradation process of RhB by the Bi4O5I2/NaYF4:Yb,Tm composites. Furthermore, we explored the mechanism behind the photocatalytic degradation of RhB solution using the Bi4O5I2/NaYF4:Yb,Tm composites. Bi4O5I2/NaYF4:Yb,Tm holds great potential as a promising candidate for utilization of NIR light for photocatalytic reactions.

Covalent Organic Framework Catalyzed Amide Synthesis Directly from Alcohol Under Red Light Excitation

The dehydrogenative coupling of alcohols and amines to form amide bonds is typically catalysed by homogeneous transition metal catalysts at high temperatures ranging from 130‐140 °C. In our pursuit of an efficient and recyclable photocatalyst capable of conducting this transformation at room temperature, we report herein a COF‐mediated dehydrogenative synthesis. The TTT‐DHTD COF was strategically designed to incorporate a high density of functional units, specifically dithiophenedione, to trap photogenerated electrons and effectively facilitate hydrogen atom abstraction reactions. The photoactive TTT‐DHTD COF, synthesized using solvothermal methods showed high crystallinity and moderate surface area, providing an ideal platform for heterogeneous amide synthesis. Light absorption by the COF across the entire visible range, narrow band gap, and valence band position make it well‐suited for the efficient generation of excitons necessary for targeted dehydrogenation. Utilizing red light irradiation and employing extremely low loading of the COF, we have successfully prepared a wide range of amides, including challenging secondary amides, in good to excellent yields. The substrate's functional group tolerance, very mild reaction conditions, and the catalyst's significant recyclability represent substantial advancements over prior methodologies.

FeCo@hydrochar nanocomposites as efficient peroxymonosulfate activator for organic pollutant degradation.

Sulfate radical-based advanced oxidation processes (SR-AOPs) are renowned for their exceptional capacity to degrade refractory organic pollutants due to their wide applicability, cost-effectiveness, and swift mineralization and oxidation rates. The primary sources of radicals in AOPs are persulfate (PS) and peroxymonosulfate (PMS) ions, sparking significant interest in their mechanistic and catalytic aspects. To develop a novel nanocatalyst for SR-AOPs, particularly for PMS activation, we synthesized carbon-coated FeCo nanoparticles (NPs) using solvothermal methods based on the polyol approach. Various synthesis conditions were investigated, and the NPs were thoroughly characterized regarding their structure, morphology, magnetic properties, and catalytic efficiency. The FeCo phase was primarily obtained at [OH-] / [Metal] = 26 and [Fe] / [Co] = 2 ratios. Moreover, as the [Fe]/[Co] ratio increased, the degree of xylose carbonization to form a carbon coating (hydrochar) on the NPs also increased. The NPs exhibited a spherical morphology with agglomerates of varying sizes. Vibrating-sample magnetometer analysis (VSM) indicated that a higher proportion of iron resulted in NPs with higher saturation magnetization (up to 167.8 emu g-1), attributed to a larger proportion of FeCo bcc phase in the nanocomposite. The best catalytic conditions for degrading 100ppm Rhodamine B (RhB) included 0.05g L-1 of NPs, 2mM PMS, pH 7.0, and a 20-min reaction at 25°C. Notably, singlet oxygen was the predominant specie formed in the experiments in the SR-AOP, followed by sulfate and hydroxyl radicals. The catalyst could be reused for up to five cycles, retaining over 98% RhB degradation, albeit with increased metal leaching. Even in the first use, dissolved Fe and Co concentrations were 0.8 ± 0.3 and 4.0 ± 0.5mg L-1, respectively. The FeCo catalyst proved to be effective in dye degradation and offers the potential for further refinement to minimize Co2+ leaching.

A novel hybrid lanthanide metal-organic frameworks based on porphyrin for rapid detection of iron ions

BackgroundIron ion (Fe3+) is essential for the environment and human health. Detecting Fe3+ in water is crucial, making high-performance detection a key objective. Lanthanide metal-organic frameworks with abundant functional sites have been deemed a promising fluorescence sensor for Fe3+ detection. Currently, most metal-organic framework-based sensors for Fe3+ detection have cumbersome and time-consuming synthesis procedures and long detection times, which greatly limits their practical application. This study aims to construct a hybrid lanthanide metal-organic frameworks-based fluorescence sensor for Fe3+ detection that promises simple and rapid iron ion quantification in water. ResultsA novel hybrid lanthanide metal-organic frameworks (ECTMNs) was synthesized in one step using a solvothermal method with only 4 h. The frameworks comprise two metal ions, cerium and europium, serving as metal centers, and 4,4,4,4-(Porphine-5,10,15,20-tetrayl) tetrakis (TCPP) as an organic ligand. With the addition of Fe3+, the host-guest reaction occurred between Fe3+ and ECTMNs probe, leading to the gradual fluorescence burst of ECTMNs probe. A strong linear correlation between ECTMNs fluorescence intensity and Fe3+ concentration (1-90 μM) makes it a reliable sensor for Fe3+ monitoring with a detection limit of 0.3 μM. Moreover, the method was used to analyze real samples (tap water and river water), showing good recoveries (92-98%) and low relative standard deviations (3.96-6.11%), making it a promising option for rapidly detecting Fe3+. Significance and NoveltyA rapid synthesis protocol for hybrid lanthanide metal-organic frameworks is proposed in this study. The obtained ECTMNs exhibits good water solubility, high stability, and specificity for Fe3+. Based on ECTMNs, an innovative fluorescence sensor is established for selectively detecting Fe3+ in water, which is a simple operation method with a low detection limit and short sensing time. It provides a novel method for accurately and rapidly detecting Fe3+ in environmental pollution and water safety monitoring.

Appraising the structural and magnetic properties in template assisted neodymium based metal organic frameworks

This study demonstrates synthesis of two novel lanthanide-based metal-organic frameworks, namely [{NdIII(5 N3-H2isa)2(H2O)2}(H2O)2}]∞ (1) and [{NdIII(5 N3-H2isa)2(H2O)2}(H2O)(1,2-PE)}]∞ (2), synthesized via solvothermal methods using 5-azidoisophthalic acid (5 N3-H2isa) and NdCl3. Both compounds were extensively characterized using single crystal X-ray diffraction, as well as other physicochemical techniques such as IR, TGA, PXRD, and elemental analysis. Structural differences were observed in both compounds depending on the nature of the template molecule used. Compound 1 exhibits an infinite 2D architecture with lattice-occluded water molecules within the 2D layers. In contrast, compound 2, where 1-(-2-pyridyl)-2-(4-pyridyl)ethylene (1,2-PE) was used as the template, shows replacement of interstitial water molecules by the template molecule, resulting in significant changes in overall pore topology which is further corroborated by BET analysis. These structural variations were further supported by magnetic behaviour analyses, indicating an antiferromagnetic behaviour for both compounds.

Synthesis of amorphous titanium isophthalic acid catalyst with hierarchical porosity for efficient oxidative desulfurization of model feed with minimum oxidant

Deep desulfurization is an indispensable technique for obtaining clean fuel and the preparation of novel materials for upgrading desulfurization efficiency is highly pursued. Herein, we develop a novel amorphous titanium isophthalic acid (Ti-IPA) catalyst with hierarchical porosity and highly dispersion of Ti-OH defect sites via solvothermal method. Ti-IPA is suitable for a variety of oxidant desulfurization (ODS) reaction systems due to its amphiphilic nature. The optimal Ti-IPA reveal extraordinary ODS performance for oxidizing 1000 ppm sulfur of dibenzothiophene-to-dibenzothiophene sulfone in model feed within 12 min at 40 ℃ with minimum oxidant/sulfur molar ratio of 2 (the sulfur oxidation efficiency reached 99.5 %), and the reaction time can be altered to 5 min at 50 ℃. The activity per unit mass of Ti-IPA reaches 52.2 mmol h−1g−1 at 50 ℃, outperforming all the reported Ti-based organic materials. Quenching and EPR tests indicate that Ti-IPA adopts non-free-radical ODS mechanism. Experimental and characterization results verify that the terminal OH capped on the Ti defect sites can easily react with oxidant to form peroxo-titanium intermediates, which manipulate the sulfur oxidation efficiency.

Insights into the formation and growth of high entropy PdPtSnPbNi nanowires to obtain catalysts with high alcohol electrocatalytic oxidation activity

High-entropy alloys have raised great interest in recent years because of their potential applications for multi-electron reactions owing to their diverse active sites and multielement tunability. However, the difficulty of synthesis is an obstacle to their development due to phase separation often exists. In addition, it’s a challenge to precisely control morphology in harsh conditions, thus leading to nanoparticles in many cases. We report a facile method to obtain PdPtPbSnNi HEA NWs by solvothermal synthesis method that no existing phase separation. PdPb nucleation plays a role in the formation of the high-entropy structure that serves as a PdPb nucleus for Sn, Ni, and Pt reduction subsequently, thus forming a single phase and an orderly-arranged nanowire structure. Significantly, the optimized PdPtPbSnNi NWs exhibit excellent catalytic activity and stability for both EOR and MOR which is 4.36 A mgPd+Pt-1 and 4.34 A mgPd+Pt-1, respectively. This study highlights a novel strategy for morphology tuning, providing a prospect for designing superior high-entropy nano-catalysts for multi-step reactions.

Hollow Co9S8-carbon fiber hierarchical heterojunction with Schottky contacts for tunable microwave absorption

Heterogeneous interface engineering of hollow hierarchical structures with Schottky contacts is an attractive approach for designing light weight and efficient microwave absorption (MA) materials. Herein, hollow Co9S8-carbon fiber (CF) composites were prepared by solvothermal, electrostatic spinning, and pyrolysis methods. CF was used as the main chain and hollow Co9S8 derived from metal-organic frameworks (MOFs) was homogeneously embedded in it, which overcame the difficulties of the traditional template method and effectively avoided the particle agglomeration problem. The interface polarization relaxation process is improved by the construction of Co9S8-CF heterojunction with Schottky contacts, which effectively modulates the dielectric loss. The internal hollow macroporous cavity and CF with lightweight properties enhance the reflection attenuation of the internal cavity. In addition, the electromagnetic characteristics can be flexibly adjusted to achieve the tunable MA performance by varying the reaction parameters. As a result, the Co9S8-CF-3–700 exhibits optimum MA performance, with a reflection loss (RL) of −60.83 dB at 10.85 GHz and a thickness of 2.76 mm. The effective absorption bandwidth (EAB) extends to 5.6 GHz at a thickness of 2.19 mm. This research provides a promising approach to creating light weight and efficient MA materials with potential applications in radar and communication systems.

Tailoring the interfacial electron redistribution of ball-in-ball structured CuO-Co3O4 nanocomposites for synergistic enhancement in hydrolytic dehydrogenation of ammonia borane

Construction of high-efficiency and affordable catalysts for hydrogen production from hydrolysis of ammonia borane is highly desirable, but significant challenges still exist. In this study, a series of ball-in-ball hollow structured CuO-Co3O4 nanocomposites with varied Cu/Co molar ratio were constructed via simple solvothermal method combined with a post-calcination. The CuO-Co3O4 composite featuring a Cu/Co molar ratio of 1: 2 displayed the highest catalytic efficiency, achieving a turnover frequency (TOF) value of 25.0 molH2 molcat.−1 min−1 for AB hydrolysis. An evident synergistic enhancement in catalytic activity was confirmed between CuO and Co3O4. Experimental and theoretical researches uncovered that the enhancement of activity is originated from the electron transfer between Cu and Co ingredients, which is beneficial for the adsorption and activation of H2O and ammonia borane. In addition, the DFT calculations results revealed that the actual active sites for AB hydrolysis in CuO-Co3O4 composite catalyst is the Co site. These findings should provide some insightful recommendations for designing robust and cost-effective composite catalysts for the hydrolytic dehydrogenation of ammonia borane.