ABSTRACT
CoMnOx catalysts were prepared using a microwave (MW)/ultrasonic (US)-assisted method. Amorphous/crystalline regions in CoMnOx (MW = 250 W US = 300 W) increased the oxygen vacancy content and CoMnOx exhibited excellent activity for methane oxidation (T90 = 330 °C). A new approach is provided here to improve the activity of transition metal catalysts.
ABSTRACT
By using low-temperature scanning tunneling microscopy and spectroscopy (STM/STS), we observe in-gap states induced by Andreev tunneling through a single impurity state in a low carrier density superconductor (NaAlSi). The energy-symmetric in-gap states appear when the impurity state is located within the superconducting gap. In-gap states can cross the Fermi level, and they show X-shaped spatial variation. We interpret the in-gap states as a consequence of the Andreev tunneling through the impurity state, which involves the formation or breakup of a Cooper pair. Due to the low carrier density in NaAlSi, the in-gap state is tunable by controlling the STM tip-sample distance. Under strong external magnetic fields, the impurity state shows Zeeman splitting when it is located near the Fermi level. Our findings not only demonstrate the Andreev tunneling involving single electronic state but also provide new insights for understanding the spatially dependent in-gap states in low carrier density superconductors.
ABSTRACT
Metal-Organic Frameworks (MOFs) are a very promising material in the fields of energy and catalysis due to their rich active sites, tunable pore size, structural adaptability, and high specific surface area. The concepts of "carbon peak" and "carbon neutrality" have opened up huge development opportunities in the fields of energy storage, energy conversion, and catalysis, and have made significant progress and breakthroughs. In recent years, people have shown great interest in the development of MOFs materials and their applications in the above research fields. This review introduces the design strategies and latest progress of MOFs are included based on their structures such as core-shell, yolk-shell, multi-shelled, sandwich structures, unique crystal surface exposures, and MOF-derived nanomaterials in detail. This work comprehensively and systematically reviews the applications of MOF-based materials in energy and catalysis and reviews the research progress of MOF materials for atmospheric water harvesting, seawater uranium extraction, and triboelectric nanogenerators. Finally, this review looks forward to the challenges and opportunities of controlling the synthesis of MOFs through low-cost, improved conductivity, high-temperature heat resistance, and integration with machine learning. This review provides useful references for promoting the application of MOFs-based materials in the aforementioned fields.
ABSTRACT
In recent years, it has been found that adjusting the organizational structure of Co3O4 through solid solution and other methods can effectively improve its catalytic performance for the oxidation of low concentration methane. Its catalytic activity is close to that of metal Pd, which is expected to replace costly noble metal catalysts. Therefore, the in-depth research on the mechanism and methods of Co3O4 microstructure regulation has very important academic value and economic benefits. In this paper, we reviewed the catalytic oxidation mechanism, microstructure regulation mechanism, and methods of nano-Co3O4 on methane gas, which provides reference for the development of high-activity Co3O4-based methane combustion catalysts. Through literature investigation, it is found that the surface energy state of nano-Co3O4 can be adjusted by loading of noble metals, resulting in the reduction of Co-O bond strength, thus accelerating the formation of reactive oxygen species chemical bonds, and improving its catalytic effect. Secondly, the use of metal oxides and non-metallic oxide carriers helps to disperse and stabilize cobalt ions, improve the structural elasticity of Co3O4, and ultimately improve its catalytic performance. In addition, the performance of the catalyst can be improved by adjusting the microstructure of the composite catalyst and optimizing the preparation process. In this review, we summarize the catalytic mechanism and microstructure regulation of nano-Co3O4 and its composite catalysts (embedded with noble metals or combined with metallic and nonmetallic oxides) for methane combustion. Notably, this review delves into the substance of measures that can be used to improve the catalytic performance of Co3O4, highlighting the constructive role of components in composite catalysts that can improve the catalytic capacity of Co3O4. Firstly, the research status of Co3O4 composite catalyst is reviewed in this paper. It is hoped that relevant researchers can get inspiration from this paper and develop high-activity Co3O4-based methane combustion catalyst.
ABSTRACT
Here we use low-temperature and variable-temperature scanning tunneling microscopy to study the pnictide superconductor, Ba1-xSrxNi2As2. In the low-temperature phase (triclinic phase) of BaNi2As2, we observe the unidirectional charge density wave (CDW) with Q = 1/3 on both the Ba and NiAs surfaces. On the NiAs surface of the triclinic BaNi2As2, there are structural-modulation-induced chain-like superstructures with distinct periodicities. In the high-temperature phase (tetragonal phase) of BaNi2As2, the NiAs surface appears as the periodic 1 × 2 superstructure. Interestingly, in the triclinic phase of Ba0.5Sr0.5Ni2As2, the unidirectional CDW is suppressed on both the Ba/Sr and NiAs surfaces, and the Sr substitution stabilizes the periodic 1 × 2 superstructure on the NiAs surface, which enhance the superconductivity in Ba0.5Sr0.5Ni2As2. Our results provide important microscopic insights for the interplay among the unidirectional CDW, structural modulation, and superconductivity in this class of pnictide superconductors.
ABSTRACT
WO3/Ag3PO4 with different weight ratios were prepared by ultrasonic assisted two-step deposition method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence spectroscopy (PL) and transmission electron microscopy (TEM). The photocatalytic activities of all samples were evaluated by the degradation of rhodamine B (RhB) under visible light irradiation. WA-60 shows the highest photocatalytic activity in the WA-x series composite, while the photocatalytic activity of WAA-60 is the best among all samples. The free radical trapping experiments show that photogenerated holes (h+) are the main active species. The Ag nanoparticles produced by the decomposition of Ag3PO4 are located at the interface of Ag3PO4/WO3, which promotes the separation efficiency of photogenerated electrons and holes. To further explain the photocatalytic mechanism, electrochemical and physical tests are introduced to explore the flow of electrons inside the catalyst.
ABSTRACT
Different nuclear [(Eu(1 - x)Pr(x))(DPSO)(phen)3(ClO4)2]ClO4 x nH2O (x = 0.000-0.200, DPSO as the abbreviation for diphenyl sulfoxide and phen for 1,10-phenanthroline, n = 1-6) coordination compounds were synthesized, and were studied by means of composition analysis, conductance, IR spectra and fluorescence excitation and emission spectra. In the fluorescence spectra it was found that Pr3+ has a great influence on the luminescence of Eu3+. The fluorescence emission intensity of europium perchlorate was enhanced when doped with 0.001-->0.100 mol Pr3+. The local symmetry of Eu3+ site is low in this coordination compounds.