Showing papers on "Molybdenum published in 2023"

A molybdenum-based nanoplatform with multienzymes mimic capacity for oxidative stress-induced acute liver injury treatment

Abstract: Excessive levels of ROS is one of the important causes of acute liver injury. Here, we report a simple and economical method to synthesize MoS2-PEG@BSA (MPB) nanosheets. Due to the...

Catalytic production of ammonia from dinitrogen employing molybdenum complexes bearing N-heterocyclic carbene-based PCP-type pincer ligands

Abstract: Abstract Mechanistic insight into the catalytic production of ammonia from dinitrogen is needed to improve the synthesis of this vital molecule. Here we study the use of samarium diiodide (SmI 2 ) and water in the presence of molybdenum complexes that bear PCP-type pincer ligands to synthesize ammonia. The proton-coupled electron transfer during the formation of a N–H bond on the molybdenum imide complex was found to be the rate-determining step at high catalyst concentrations. Additionally, the dimerization step of the catalyst became the rate-determining step at low catalyst concentrations. We designed PCP-type pincer ligands with various substituents at the 5- and 6-positions and observed that electron-withdrawing groups promoted the reaction rate, as predicted by density functional theory calculations. A molybdenum trichloride complex that bears a trifluoromethyl group functioned as the most effective catalyst and produced up to 60,000 equiv. ammonia based on the molybdenum atom of the catalyst, with a molybdenum turnover frequency of up to 800 equiv. min −1 . The findings reported here can contribute to the development of an environmentally friendly next-generation nitrogen-fixation system.

High Resolution Electrochemical Imaging for Sulfur Vacancies on 2D Molybdenum Disulfide

Abstract: Molybdenum disulfide (MoS2) is considered as one of the most promising non‐noble‐metal catalysts for hydrogen evolution reaction (HER). To achieve practical application, introducing sulfur (S) vacancies on the inert basal plane of MoS2 is a widely accepted strategy to improve its HER activity. However, probing active sites at the nanoscale and quantitatively analyzing the related electrocatalytic activity in electrolyte aqueous solution are still great challenges. In this work, utilizing high‐resolution scanning electrochemical microscopy, optimized electrodes and newly designed thermal drift calibration software, the HER activity of the S vacancies on an MoS2 inert surface is in situ imaged with less than 20‐nm‐radius sensitivity and the HER kinetic data for S vacancies, including Tafel plot and onset potential, are quantitatively measured. Additionally, the stability of S vacancies over the wide range of pH 0−13 is investigated. This study provides a viable strategy for obtaining the catalytic kinetics of nanoscale active sites on structurally complex electrocatalysts and evaluating the stability of defects in different environments for 2D material‐based catalysts.

In Situ Synthesis of Two-Dimensional Lateral Semiconducting-Mo:Se//Metallic-Mo Junctions Using Controlled Diffusion of Se for High-Performance Large-Scaled Memristor.

Abstract: Two-dimensional (2D) materials are favorable candidates for resistive memories in high-density nanoelectronics owing to their ultrathin scaling and controllable interfacial characteristics. However, high processing temperatures and difficulties in mechanical transfer are intriguing challenges associated with their implementation in large areas with crossbar architecture. A high processing temperature may damage the electrical functionalities of the bottom electrode, and mechanical transfer of 2D materials may introduce undesirable microscopic defects and macroscopic discontinuities. In this study, an in situ fabrication of an electrode and 2D-molybdenum diselenide (MoSe2) is reported. The controlled diffusion of selenium (Se) in the predeposited molybdenum (Mo) produces Mo//Mo:Se stacks with a few layers of MoSe2 on top and MoSex on the bottom. Diffusion-assisted Mo//Mo:Se fabrication is observed over a large area (4 in. wafer). Additionally, a 5 × 5 array of crossbar memristors (Mo//Mo:Se//Ag) is fabricated using the diffusion of Se in patterned Mo. These memristors exhibit a small switching voltage (∼1.1 V), high endurance (>250 cycles), and excellent retention (>15 000 s) with minimum cycle-to-cycle and device-to-device variation. Thus, the proposed nondestructive in situ technique not only simplifies the fabrication but also minimizes the number of required stages.

Universal construction of sulfur doped molybdenum-based nanosheets for enhanced hydrogen evolution in a wide pH range

Abstract: Rational designing and fabricating catalysts with abundant exposed active sites and optimized electronic structure is of essential to boost electrocatalytic performance. In this study, well-organized porous nanosheets of sulfur-doped molybdenum-based compounds on carbon cloth (S-MoX n /CC, S-MoX n = S-MoP, S-Mo 2 C, S-MoN, and S-MoO 3 ) are universally constructed via in situ topological transformation from the MoS 2 nanosheets as self-supported electrodes for pH-universal hydrogen evolution reaction (HER). Various structural characterizations show that the S-MoX n nanosheets with abundant nanopores and edges endowing them with plentiful exposed active sites, high mass transfer efficiency, and good conductivity. As a result, these S-MoX n /CC electrodes, especially S-MoP/CC exhibits superior HER performance with low overpotentials of 75, 75, and 127 mV at 10 mA cm -1 in acidic, alkaline, and neutral electrolytes, superior to the MoX n /CC counterparts. Theoretical calculations reveal that the synergy between S dopant and MoX n can effectively alter the electronic structure of S-MoX n , thus enhancing the HER performance. A series of novel porous nanosheets of sulfur-doped molybdenum-based compounds S-MoX n (S-Mo 2 C, S-MoP, S-MoN, and S-MoO 3 ) derived from MoS 2 nanosheets on carbon cloth were constructed via in situ a topological transformation method as self-supported monolithic electrodes for hydrogen evolution reaction (HER). The self- supported porous nanosheet structure endows the S-MoX n /CC with plentiful exposed active sites, high mass transfer efficiency, and good electrical conductivity. The electronic coupling effect between MoX n and S dopant facilitates to promote the electron transfer, optimize the hydrogen adsorption free energy of S-MoX n and lower d-band center of Mo. Therefore, the S-MoX n /CC electrodes exhibit enhanced HER performance. • A series of 3D self-supported porous S-MoX n nanosheets electrodes are fabricated. • The S-MoP/CC electrode exhibits superior HER performance in a wide pH range. • The electronic interaction between S dopant and MoX n results in an enhanced HER performance. • The mechanism of HER over S-MoX n /CC electrodes is clarified by DFT calculations.

Rational Design of Molybdenum Doped Cobalt nitrides Nanowire Arrays for Robust Overall Water Splitting.

Abstract: Rational design of efficient bifunctional electrocatalysts is highly imperative but still a challenge for overall water splitting. Herein, we construct novel self-supported Co3N nanowire arrays with different Mo doping contents by the hydrothermal and nitridation processes, serving as bifunctional electrocatalysts for overall water splitting. The optimal Co3N-Mo0.2/NF electrode delivers the low overpotential of 97 mV at the current density of 50 mA cm-2 as well as high stability for HER. DFT calculations prove that Mo doping can effectively modulate the electronic structure and surface adsorption energies of H2O and hydrogen intermediates of Co3N, leading to improved reaction kinetics with high catalytic activity. Furthermore, the modification of FeOOH species on the surface of Co3N-Mo0.2/NF can further improve the OER performance benefiting from the synergistic effect of dual Co-Fe catalytic centers. As a result, the Co3N-Mo0.2@FeOOH/NF catalysts display outstanding OER catalytic performance with low overpotentials of 250 mV at 50 mA cm-2. The constructed Co3N-Mo0.2/NF||Co3N-Mo0.2@FeOOH/NF water electrolyzer exhibits a small voltage of 1.48 V to achieve a high current density of 50 mA cm-2 at 80 oC, which is superior to most of the reported electrocatalysts. This work provides a new approach to developing robust electrode materials for electrocatalytic water splitting.

1T and 2H phase molybdenum disulfide as a counter electrode for Pt free dye-sensitized solar cells

Abstract: Thin films of 1T and 2H mixed-phase MoS2 on FTO substrate by hydrothermal technique with altering reaction time (24 (12) 60 h) was made. Raman and XRD analysis confirm the coexistence of 2H and 1T phase of MoS2. Transformation of nanoplatelets into nanobelts with reaction time was witnessed in SEM and UV–Vis-NIR absorbance pattern shows characteristic absorption peaks of MoS2 at 291 nm and 680 nm. Due to the change in morphology, the bandgap of MoS2 increased from 1.82 eV (nanoplatelets) to 1.97 eV (nanobelts). Fabrication of MoS2 CE based DSSCs with assembly of (TiO2/N719/I3-I-/MoS2) was made and photoconversion efficiency follows the order MoS2-36 > MoS2-24 > MoS2-48 > MoS2-60. MoS2-36 electrode (7.96 %) based DSSC exhibits higher photoconversion efficiency than Pt (6.8 %) based DSSC. Thus, mixed-phase of MoS2 nanobelts stand superior and can be used as a potential candidate for counter electrodes compared to cost-effective Pt free DSSC.

In Situ Synthesis of Nanorod Arrays of Nickel–Molybdenum Nitrides as Stable Electrocatalysts for Hydrogen Evolution Reactions

Abstract: The development of cheap and highly active electrocatalysts for efficient water splitting is crucial for the production of green hydrogen at a low cost. In this work, we proposed a two-step method including hydrothermal and nitridation reactions to in situ synthesize NiMoN nanorod arrays with abundant active sites and a fast electron transfer rate on nickel foam substrate. The optimal tailoring of the Ni/Mo ratio leads to a high concentration of active Mo3+ species and suitable Ni doping content in the NiMoN catalyst, which shows superior hydrogen evolution reaction performance. The overpotentials at the current densities of 10 and 100 mA/cm2 are only 20 and 46 mV, which are better than those of the most reported NiMoN-based catalysts and even the commercial benchmark material of Pt/C. Additionally, the electrocatalyst also shows excellent long-term stability after 24 h tests at densities of 10 and 100 mA/cm2, possessing great potential for industrial applications for water splitting to produce hydrogen.

Photodeposition of molybdenum sulfide on MTiO3 (M: Ba, Sr) perovskites for photocatalytic hydrogen evolution

Abstract: Photocatalytic hydrogen evolution using semiconductor materials have been studied effectively by converting solar energy into the chemical energy. Perovskite based materials have been widely used as semiconductor catalysts for the photocatalytic hydrogen production. Herein, molybdenum sulfide photodeposited onto MTiO3 (M: Ba, Sr) perovskites (MTiO3/MoSx) have been investigated on the photocatalytic hydrogen evolution under solar light irradiation in the presence of triethanolamine (TEOA) and eosin Y (EY) as an electron donor and photosensitizer, respectively. Compared to pristine MTiO3, BaTiO3/MoSx and SrTiO3/MoSx show a remarkable improvement in the hydrogen production efficiency and stability. Photocatalytic hydrogen evolution activities found in the order of SrTiO3/MoSx > BaTiO3/MoSx > MoSx > SrTiO3 > BaTiO3. In addition, photocatalytic hydrogen activity of SrTiO3/Pt was evaluated for comparison with SrTiO3/MoSx under the same conditions and SrTiO3/MoSx produced higher hydrogen activity than SrTiO3/Pt due to the high active sites created by MoSx on the catalyst surface which is originated from Mo–S and S–S bonds.

Optical, Optoelectronic, and Third‐Order Nonlinear Photonics of Ultrathin Molybdenum Oxide Film Deposited by Atomic Layer Deposition

Abstract: The atomic layer deposition (ALD) technique has attracted significant attention because it enables the control of film synthesis at the subnanometre scale. Herein, molybdenum oxide (MoO3) ultrathin films using the ALD system through Bis(t‐butylimido)bis(dimethylamino)molybdenum (VI) as a molybdenum (Mo) source are prepared. To understand the effect of deposition temperature, thin films are prepared at three different temperatures 100, 150, and 250 °C. The morphological and elemental properties are assessed using a field emission scanning electron microscope, scanning transmission electron microscopy, and energy‐dispersive X‐ray spectroscopy techniques. It is observed that the film thicknesses increase with the increase in the deposition temperature. It is found that the film growth at 150 °C is the most potential one for UV optoelectronic applications with high stability even under low applied bias voltages. Moreover, these films show interesting nonlinear optical behaviors as investigated with the z‐scan technique applying open and closed aperture methods. The calculated nonlinear optical parameters including nonlinear absorption coefficient (β), nonlinear refractive index (n 2), nonlinear refractive coefficient (γ), and third‐order nonlinear susceptibility (χ (3)) are 10−11 m W−1, 10−16 cm2 W−1, 10−11 cm2 W−1, and 10−11 esu, respectively.