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Overall hydrazine splitting (OHzS) is a promising alternative for overall water splitting (OWS) towards hydrogen production due to the anodic hydrazine oxidation reaction (HzOR) involving less electrons and faster kinetics than oxygen evolution reaction (OER). However, it still remains a challenge to synthesis bifunctional electrocatalyst for hydrogen evolution reaction (HER) and HzOR with low overpotentials. Herein, we report two-dimensional multifunctional layered double hy [Detail] ...
Download coverIn this study, Mn-Na2WO4/γ-Al2O3 catalysts with varying ratios of Mn/W were prepared using the dry impregnation method. These catalysts were then tested for their suitability in the oxidative coupling of methane reaction. The X-ray photoelectron results revealed the presence of the tetrahedral WO42– phase in all prepared catalysts. It is believed that the presence of this phase is associated with high catalyst activity, indicating the potential of the catalysts for the desired reaction. The activity results show that the catalyst with a high Mn/W ratio exhibited higher activity at 800 °C, whereas the catalyst with a low Mn/W ratio showed greater activity at 850 °C. This suggests that the Mn/W ratio influences the reaction temperature at which the catalyst is most active. Furthermore, the X-ray diffraction results of the treated catalysts revealed that the catalyst with a high Mn/W ratio exhibited more MnAl2O4 at 800 °C, whereas the catalyst with a low Mn/W ratio contained more MnWO4 at 850 °C. The results suggest that the presence of MnAl2O4 sites may promote a more facile Mn2+ ↔ Mn3+ cycle at lower temperatures than the MnWO4 site, potentially contributing to the enhanced catalyst activity in the oxidative coupling of methane reaction at 800 °C.
Titanium and its alloys have numerous biomedical applications thanks to the composition and morphology of their oxide film. In this study, the colorful oxide films were formed by anodizing cast Ti-6Al-4V and Ti-6Al-7Nb alloys in a 10% oxalic acid solution for 30 s at different voltages (20–80 V) of a direct current power supply. Atomic force microscopy was used as an accurate tool to measure the surface roughness of thin films on the nanometer scale. Scanning electron microscopy and X-ray diffraction were performed to analyze surface morphology and phase structure. According to the results, the produced titanium oxide layer showed high surface roughness, which increased with increasing anodizing voltage. The impact of anodizing voltages on the color and roughness of anodized layers was surveyed. The corrosion resistance of the anodized samples was studied in simulated body fluid at pH 7.4 and a temperature of 37 °C utilizing electrochemical impedance spectroscopy and the potentiodynamic polarization method. The anodized samples for both alloys at 40 V were at the optimal voltage, leading to a TiO2 layer formation with the best compromise between oxide thickness and corrosion resistance. Also, findings showed that TiO2 films produced on Ti-6Al-7Nb alloys had superior surface roughness properties compared to those of Ti-6Al-4V alloys, making them more appropriate for orthopedic applications. From the obtained data and the fruitful discussion, it was found that the utilized procedure is simple, low-cost, and repeatable. Therefore, anodization in 10% oxalic acid proved a viable alternative for the surface finishing of titanium alloys for biomedical applications.
The cycloaddition reaction between epoxides and CO2 is an effective method to utilize CO2 resource. Covalent organic frameworks (COFs) provide a promising platform for the catalytic CO2 transformations on account of their remarkable chemical and physical properties. Herein, a family of novel vinylene-linked ionic COFs named TE-COFs (TTE-COF, TME-COF, TPE-COF, TBE-COF) has been facilely synthesized from N-ethyl-2,4,6-trimethylpyridinium bromide and a series of triphenyl aromatic aldehydes involving different numbers of nitrogen atoms in the central aromatic ring. The resulting catalyst TTE-COF with excellent adsorption capacity (45.6 cm3·g–1, 273 K) exhibited outstanding catalytic performance, remarkable recyclability and great substrate tolerance. Moreover, it was also observed that the introduction of nitrogen atom in the precursor led to a great improvement in the crystallinity and CO2 adsorption capacity of TE-COFs, thus resulting to a progressively improved catalytic performance. This work not only illustrated the influence of monomer nitrogen content on the crystallinity and CO2 adsorption capacity of TE-COFs but also provided a green heterogeneous candidate for catalyzing the cycloaddition between CO2 and epoxides, which shed a light on improving the catalytic performance of the CO2 cycloaddition reaction by designing the covalent organic frameworks structures.
CO2 capture is one of the key technologies for dealing with the global warming and implementing low-carbon development strategy. The emergence of ionic metal-organic frameworks (I-MOFs) has diversified the field of porous materials, which have been extensively applied for gas adsorption and separation. In this work, amino-functionalized imidazolium ionic liquid as organic monodentate ligand was used for one step synthesis microporous Cu based I-MOFs. Precise tuning of the adsorption properties was obtained by incorporating aromatic anions, such as phenoxy, benzene carboxyl, and benzene sulfonic acid group into the I-MOFs via a facile ion exchange method. The new I-MOFs showed high thermal stability and high capacity of 5.4 mmol·g–1 under atmospheric conditions for selective adsorption of CO2. The active sites of microporous Cu-MOF are the ion basic center and unsaturated metal, and electrostatic attraction and hydroxyl bonding between CO2 and modified functional sulfonic groups are responsible for the adsorption. This work provides a feasible strategy for the design of I-MOF for functional gas capture.
Decalin is considered as an important compound of high-energy-density endothermic fuel, which is an ideal on-board coolant for thermal management of advanced aircraft. However, decalin contains two isomers with a tunable composition, and their effects on the pyrolysis performance, such as the heat sink and coking tendency have not been demonstrated. Herein, we investigated the pyrolysis of decalin isomers, i.e., cis-decalin, trans-decalin and their mixtures (denoted as mix-decalin), in order to clarify the effects of the cis-/trans-structures on the pyrolysis performance of decalin fuels. The pyrolysis results confirmed that conversion of the tested fuels (600–725 °C, 4 MPa) decreased in the order cis-decalin > mix-decalin > trans-decalin. Detailed analyses of the pyrolysis products were used to compare the product distributions from cis-decalin, mix-decalin and trans-decalin, and the yields of some typical components (such as cyclohexene, 1-methylcyclohexene, benzene and toluene) showed significant differences, which could be ascribed to deeper cracking of cis-decalin. Additionally, the heat sinks and coking tendencies of the decalins decreased in the order cis-decalin > mix-decalin > trans-decalin. This work demonstrates the relationship between the cis/trans structures and the pyrolysis performance of decalin, which provides a better understanding of the structure-activity relationships of endothermic hydrocarbon fuels.
Layered double hydroxides have demonstrated great potential for the oxygen evolution reaction, which is a crucial half-reaction of overall water splitting. However, it remains challenging to apply layered double hydroxides in other electrochemical reactions with high efficiency and stability. Herein, we report two-dimensional multifunctional layered double hydroxides derived from metal-organic framework sheet precursors supported by nanoporous gold with high porosity, which exhibit appealing performances toward oxygen/hydrogen evolution reactions, hydrazine oxidation reaction, and overall hydrazine splitting. The as-prepared catalyst only requires an overpotential of 233 mV to reach 10 mA·cm–2 toward oxygen evolution reaction. The overall hydrazine splitting cell only needs a cell voltage of 0.984 V to deliver 10 mA·cm–2, which is far more superior than that of the overall water splitting system (1.849 V). The appealing performances of the catalyst can be contributed to the synergistic effect between the metal components of the layered double hydroxides and the supporting effect of the nanoporous gold substrate, which could endow the sample with high surface area and excellent conductivity, resulting in superior activity and stability.
To enhance the yields of benzene, toluene, and xylene in tetralin hydrocracking, the effect of the support acid properties of NiMo catalysts on hydrocracking performance of tetralin were investigated in this study. NaY zeolites were modified by hydrothermal treatment to form USY zeolites at different temperatures and adjust the type and amount of acid. In addition, H-Beta was loaded into the USY to further adjust the acidic properties of the catalysts. The result shows that when the total B acid content of the catalyst is maintained between 150 and 200 μmol·g–1, the total acid amount is maintained between 1.7 and 1.9 mmol·g–1, and the L/B (L and B acids) ratio is maintained between 1.5 and 2, the catalysts have favorable performances on tetralin hydrocracking. Under this condition, the catalysts have a yield of benzene, toluene, and xylene higher than 30 wt % and a selectivity for benzene, toluene, and xylene higher than 35%. The tetralin conversion is greater than 85 wt %. The AB6 catalyst obtains the best hydrocracking effect with the conversion of tetralin reaching 90.24 wt %, the yields of benzene, toluene, and xylene reaching 33.58 wt %, and the selectivity of benzene, toluene, and xylene reaching 37.21%, respectively.
In a dual-chamber photocatalytic fuel cell device, polyvinyl alcohol degradation and H2 evolution were concurrently achieved. The setup involved commercial P25 as the photoanode and Ag@Fe2O3 nanoparticles as the cathode. Additionally, the feasibility of a Fenton-like reaction in the cathode, utilizing Fe2+ ions and pumped O2, was demonstrated. Different cathode materials, polyvinyl alcohol types, and pH values’ effects were assessed on device performance. Quenching tests highlighted photoinduced holes (h+) and OH· radicals as pivotal contributions to polyvinyl alcohol degradation. Long-term stability of the device was established through cycling experiments.
In this study, we synthesize a catalyst comprising cobalt nanoparticles supported on MXene by pyrolyzing a composite in a N2 environment. Specifically, the composite comprises a bimetallic Zn/Co zeolitic imidazole framework grown in situ on the outer surface of MXene. The catalytic efficiency of the catalyst is tested for the self-coupling of 4-methoxybenzylamine to produce value-added imine, where atmospheric oxygen (1 atm) is used as the oxidant. Based on the results, the catalyst displayed impressive catalytic activity, achieving 95.4% yield of the desired imine at 383 K for 8 h. Furthermore, the catalyst showed recyclability and tolerance toward benzylamine substrates with various functional groups. The outstanding performance of the catalyst is primarily attributed to the synergetic catalytic effect between the cobalt nanoparticles and MXene support, while also benefiting from the three-dimensional porous structure. Additionally, a preliminary investigation of potential reaction mechanisms is conducted.
Biomass-derived carbon materials for lithium-ion batteries emerge as one of the most promising anodes from sustainable perspective. However, improving the reversible capacity and cycling performance remains a long-standing challenge. By combining the benefits of K2CO3 activation and KMnO4 hydrothermal treatment, this work proposes a two-step activation method to load MnO2 charge transfer onto biomass-derived carbon (KAC@MnO2). Comprehensive analysis reveals that KAC@MnO2 has a micro-mesoporous coexistence structure and uniform surface distribution of MnO2, thus providing an improved electrochemical performance. Specifically, KAC@MnO2 exhibits an initial charge-discharge capacity of 847.3/1813.2 mAh·g–1 at 0.2 A·g–1, which is significantly higher than that of direct pyrolysis carbon and K2CO3 activated carbon, respectively. Furthermore, the KAC@MnO2 maintains a reversible capacity of 652.6 mAh·g–1 after 100 cycles. Even at a high current density of 1.0 A·g–1, KAC@MnO2 still exhibits excellent long-term cycling stability and maintains a stable reversible capacity of 306.7 mAh·g–1 after 500 cycles. Compared with reported biochar anode materials, the KAC@MnO2 prepared in this work shows superior reversible capacity and cycling performance. Additionally, the Li+ insertion and de-insertion mechanisms are verified by ex situ X-ray diffraction analysis during the charge-discharge process, helping us better understand the energy storage mechanism of KAC@MnO2.
