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Molybdenum sulphide (2D-MoS 2) promises great potential as a hydrogen evolution (HER) catalyst, especially, when combined with conductive carbon supports like graphene oxide (GO) and carbon nanotubes (CNT). However, the hydrophobic nature of these carbon supports limits the catalytic potential of MoS 2. To overcome this, we introduced hydrophilic Nickel Boride (Ni 2 B) into GO/CNT electrodes (Ni 2 B-GO/CNT), enhancing wettability (Contact angle-25.3°) and HER activity. By hydrothermally depositing MoS 2 onto the hydrophilic Ni 2 B-GO/CNT electrode, we fabricated a self-supporting MoS 2 @Ni 2 B-GO/CNT electrode. The MoS 2 deposition led to the formation of MoS 2 @Ni 2 B-GO/CNT heterostructure with multiple interfaces, favoring interfacial electronic redistribution (XPS) to significantly improve the HER activity. Thus, the proposed MoS 2 @Ni 2 B-GO/CNT electrode exhibited an excellent durability of 100 h (97%) and an overpotential of 224 mV at 10 mA cm−2 in acidic medium. [Display omitted] • Hydrothermal growth of MoS 2 on Ni 2 B-GO/CNT to form a self-supporting electrode. • Hydrophilic Ni 2 B was incorporated into the GO/CNT matrix to enhance electrode wettability. • Enhanced HER catalytic activity from a heterostructure of MoS 2 with Ni 2 B, GO and CNT. • Excellent durability of MoS 2 @ Ni 2 B-GO/CNT was achieved for 100 h in acidic medium. [ABSTRACT FROM AUTHOR]

Orthorhombic stable phase of MoO 3 and Ni-doped MoO 3 with different weight percentages (2 %,5 % and 10 %) were successfully synthesized by following a surfactant free acid-assisted chemical co-precipitation method under optimized experimental conditions. Structural and compositional investigation using tools like X-ray diffraction and Raman spectroscopy verified the orthorhombic phase and structure quality of the prepared samples with findings from Raman consistent with those from XRD. The optical characteristics analysed using UV–Vis diffused reflectance spectroscopy and photoluminescence spectroscopy revealed that Ni2+ may act as a shallow acceptor at lower doping concentrations. It was observed that the structure and characteristics of MoO 3 dramatically altered as a function of Ni doping concentration, suggesting that Ni ions migrated from lattice substitution to grain boundaries. Images from field emission scanning electron microscope revealed the formation of layer-by-layer growth of micro-plate like morphology of the prepared samples with increasing agglomeration influenced by grain boundaries. EDAX spectrum confirmed the presence of Mo, O and Ni and their compositional proportion. Based on the properties analysed, the photocatalytic properties of the synthesized samples were analysed for degradation of Alizarin Red dye and kinetic studies were conducted. The optical characterization revealed defect induced emissions and the feasibility of MoO 3 acting as a photodetector was studied along with Ni-doping proving the versatility of material for multifunctional applications. [ABSTRACT FROM AUTHOR]

The urgent development of economically practical and sustainable electrocatalysts to accelerate the hydrogen evolution reaction (HER) is critical for solving the pressing issues related to carbon dioxide emissions. Because of their platinum-like catalytic efficiency, excellent stability, and multidimensional structure of their crystal phases, molybdenum phosphides have emerged as extremely promising HER electrocatalysts. In this account, we begin with a meticulous explication of the hydrogen-generating process by water electrolysis, followed by an examination of the criteria used to assess HER catalytic activity. Also, the role of the phosphorus component and synthetic routes of molybdenum phosphides is presented in HER applications. Moreover, in recent years, various strategies designed to enhance the HER performance of molybdenum phosphides have been introduced, encompassing state-of-the-art techniques such as the fabrication of heterostructures, hetero-atom doping, hybrid structures involving carbon materials, and defect engineering. Furthermore, the theoretical studies based on density functional theory (DFT) are mentioned for HER. The paper concludes by emphasizing the current challenges and auspicious prospects in advancing electrocatalysts for hydrogen production, with a dedicated focus on catalysts based on molybdenum phosphides. • Outstanding features of molybdenum phosphides were presented. • Various methods were introduced in the fabrication of molybdenum phosphides. • Enhancement strategies in HER efficiency of molybdenum phosphides were discussed. • Current challenges and possible solutions on molybdenum phosphides-based HER electrocatalyst were provided. • DFT works of molybdenum phosphides on HER were presented. [ABSTRACT FROM AUTHOR]

Molybdenum disulphide (MoS 2) has been widely studied as a potential alternative to Pt/C catalysts for hydrogen evolution reactions (HER) in acidic conditions. However, the limited electron transfer capability and poor conductivity restrict further improvement of the HER activity. Herein, a novel bimetallic Ti 2 VC 2 T x MXene/MoS 2 heterojunction was fabricated by hydrothermal method. In addition, hydroxylated carbon nanotubes (CNTs) was incorporated to increase its conductivity and structural stability. The as-prepared Ti 2 VC 2 T x /MoS 2 -CNTs electrocatalyst was characterized and the HER performance were investigated in acidic media. The effects of different weight ratio of Ti 2 VC 2 T x to ammonium molybdate tetrahydrate (AMT), catalyst mass loading, and CNTs dosage on the HER activities of Ti 2 VC 2 T x /MoS 2 -CNTs were optimized. The optimal electrocatalyst exhibits superior HER properties in 0.5 M H 2 SO 4 electrolyte with an overpotential of 183 mV at a current density of 10 mA∙cm−2, a Tafel slope of 83 mV∙dec−1, a double-layer capacitance (C dl) value of 160 mF cm−2, as well as satisfactory long-term stability. This study provides an intentional exploration for developing bimetallic MXene based HER electrocatalysis application. [Display omitted] • A novel bimetallic Ti 2 VC 2 T x MXene/MoS 2 heterojunction was fabricated by hydrothermal method. • Hydroxylated carbon nanotubes was incorporated to increase the conductivity and structural stability. • The optimal catalyst exhibits superior HER activity in 0.5 M H 2 SO 4 electrolyte. • An overpotential of 183 mV at 10 mA∙cm−2, Tafel slope of 83 mV∙dec−1 and C dl of 160 mF cm−2 are achieved. [ABSTRACT FROM AUTHOR]

• The combined toxicity of Mo and Cd was evaluated in duck ovaries. • Mo and/or Cd led to trace element imbalance and ovarian injury. • Mo and/or Cd disturbed Th1/Th2 balance and polarized towards Th1. • Mo and/or Cd could activate ER stress-mediated necroptosis. • Mo and Cd could aggravate ovarian toxic damage. Cadmium (Cd) and excess molybdenum (Mo) pose serious threats to animal health. Our previous study has determined that Cd and/or Mo exposure can cause ovarian damage of ducks, while the specific mechanism is still obscure. To further investigate the toxic mechanism of Cd and Mo co-exposure in the ovary, forty 8-day-old female ducks were randomly allocated into four groups for 16 weeks, and the doses of Cd and Mo in basic diet per kg were as follows: control group, Mo group (100 mg Mo), Cd group (4 mg Cd), and Mo + Cd group (100 mg Mo + 4 mg Cd). Cadmium sulfate 8/3-hydrate (CdSO 4 ·8/3H 2 O) and hexaammonium molybdate ((NH 4) 6 Mo 7 O 24 ·4H 2 O) were the origins of Cd and Mo, respectively. At the 16th week of the experiment, all ovary tissues were collected for the detection of related indexes. The data indicated that Mo and/or Cd induced trace element disorders and Th1/Th2 balance to divert toward Th1 in the ovary, which activated endoplasmic reticulum (ER) stress and then provoked necroptosis through triggering RIPK1/RIPK3/MLKL signaling pathway, and eventually caused ovarian pathological injuries and necroptosis characteristics. The alterations of above indicators were most apparent in the joint group. Above all, this research illustrates that Mo and/or Cd exposure can initiate necroptosis through Th1/Th2 imbalance-modulated ER stress in duck ovaries, and Mo and Cd combined exposure aggravates ovarian injuries. This research explores the molecular mechanism of necroptosis caused by Mo and/or Cd, which reveals that ER stress attenuation may be a therapeutic target to alleviate necroptosis. [Display omitted] [ABSTRACT FROM AUTHOR]

Green hydrogen has an audible echo in the clean energy field. In this piece of work, pure and Mo-doped CuO thin films were deposited at different substrate temperatures on the Indium Tin Oxide (ITO) by the DC/RF sputtering technique. The prepared samples were utilized to generate hydrogen gas within the photoelectrochemical water-splitting mechanism. Crystallographic planes (−111), and (200) were the preferred orientations for pure and Mo-doped CuO thin films. Moreover, the average crystallite size was doubled by Mo doping reaching 25.8 nm. FE-SEM microscopic image exhibits that the pure and Mo–CuO thin films have a regular distribution with a small size. The optical band gap has rosed by doping from 1.8 eV to 2.05 eV. Then, it increased to 2.3 eV and 2.4 eV at temperatures of 100 °C and 200 °C respectively. Pure and Mo–CuO thin films were applied as photocathodes for hydrogen generation with water water-splitting technique. The photoelectrochemical application revealed a photocurrent density of ∼2.25 mA/cm2 for Mo-doped CuO photoelectrode at room temperature. This optimum photoelectrode was studied for stability and electrochemical impedance. In addition, the incident photon to current efficiency (IPCE%) was 4.47 % at 500 nm. The applied bias photon to current conversion efficiency (ABPE%) was 4.25 % at −0.38V. As a result of the above, pure and Mo-doped CuO photoelectrodes are low-cost thin films and have a high-efficiency performance for green hydrogen generation industrially. • Mo-doped CuO thin films were carefully sputtered on an ITO substrate at different temperatures. • Effect of doping and temperature on structural and optical properties of CuO thin films has been studied. • The efficiency of Mo-doped CuO photoelectrode at room temperature outperforms the rest. • Photocurrent density ∼2.25 mA/cm2 and (ABPE%) 4.25 % at −0.38V were revealed. • Mo–CuO photoelectrodes have a high level performance for green hydrogen generation. [ABSTRACT FROM AUTHOR]

Layered oxide cathode materials have good structural stability and high capacity, making them ideal cathode materials of Na-ion batteries (SIBs). Nonetheless, the irreversible phase transitions and metal dissolution often result in poor cycling stability. Here, a simple strategy was developed to Na 2 MoO 4 and MoO 3 coated Na 0.67 Fe 0.15 Cu 0.1 Mn 0.65 Ni 0.1 O 2 (NFCMN-M) as cathode material of SIBs with ultrahigh cycling stability caused by the enhanced kinetic. The formed Na 2 MoO 4 layer on the surface of Na 0.67 Fe 0.15 Cu 0.1 Mn 0.65 Ni 0.1 O 2 (NFCMN) particles supplies a good conductive connection, and inhibits side effects between cathode material and electrolyte. Thanks to the unique component, the as-prepared NFCMN-M shows a good rate performance with a reversible discharge capacity of 132.4, 112.6, 102.3, 87.1 and 79.3 mAh g−1 at 0.1, 0.5, 1, 3 and 5C, respectively. The NFCMN-M also delivers an initial capacity of 73.7 mAh g−1 at 10C and an ultrahigh cycling stability with a capacity retention rate of about 80 % after 1000 cycles. The result confirms that the Na 2 MoO 4 modification is a direct and effective strategy to improve the capacity and enhance cycling stability of NFCMN at high charge-discharge rates. [ABSTRACT FROM AUTHOR]

Molybdenum carbide materials have demonstrated remarkable potential in catalyzing the hydrogen evolution reaction (HER). However, further modulation of their performance through simultaneously engineering the size and surface crystal facets remains challenging. Herein, we report the successful fabrication of N-doped carbon-supported monodisperse Mo 2 C nanoparticles with a size of ∼2.06 nm, exhibiting co-exposed (101)/(102) facets-heterojunction, derived from annealing glycine and ammonium molybdate tetrahydrate. The optimized Mo 2 C/NC-Amt catalyst exhibits a low overpotentials of 128 mV to achieve the current density of 10 mA cm−2 and a small Tafel slope of 72 mV dec−1 under alkaline solution. By changing the molybdate precursor, the phase and crystal facet composition of molybdenum carbide can be effectively tuned, which provides a good platform for studying their structure-activity in HER. The theoretical calculations reveal the synergistic effect of (101)/(102) facets-heterojunction accelerates electron transfer and regulates the d band center of Mo 2 C, reducing the reaction barriers of intermediates in the HER process, thus significantly boosting reaction activity. This work proposes a novel insight into the rational fabrication of efficient HER catalysts through facet engineering toward heterojunction construction under the 2.5 nm region. [Display omitted] • Monodisperse Mo 2 C nanoparticles (∼2.06 nm) on N-doped carbon are synthesized. • The formed surface heterojunction involves (101) and (102) facets of Mo 2 C. • DFT calculations reveal the synergistic mechanisms of the facet heterojunctions. • The optimized catalyst presents distinguished HER performance in 1 M KOH. [ABSTRACT FROM AUTHOR]

Molybdenum tailings (MTs) and kaolinite were used as the main materials in the fabrication ceramic foams (CFs) via the high-temperature sintering method, with the addition of SiC as a foaming agent. The effects of MT content on the basic physical properties, pore structure, and chemical characterization were investigated. Results showed that MT enhanced the foaming capability. When the MT content was 60% and the sintering temperature was 1170 °C, the optimum CFs obtained demonstrated bulk density, porosity, water absorption, and compressive strength of 0.55 g/cm3, 77.3%, 6.94%, and 6.74 MPa, respectively, and the pore structure was relatively homogeneous with an average pore diameter of 0.67 mm. The results revealed that SiO 2 –-Al 2 O 3 –-MgO–-CaO system CFs can be prepared from Ca–Mg-rich MT, which provided a feasible strategy for value-added utilization of Ca–Mg-rich MT. [ABSTRACT FROM AUTHOR]

In this study, BiMeVOx compounds (where Me: Co, Mo, Ce, Zr) were synthesized and characterized as potential photoelectrochemical materials for solar water splitting, the hydrogen evolution reaction (HER), and oxygen evolution reaction (OER). The analysis confirmed the successful formation of phase BiMeVOx compounds with the desired crystal structure. Among the tested materials, BiCoVOx(800) showed the highest photocurrent density (674 μA cm−2) and HER/OER activity (Tafel slope: HER = 100 mV dec−1 and OER = 75 mV dec−1), followed by BiMoVOx(800), BiCeVOx(800), and BiZrVOx(800). The superior photoelectrochemical performance of BiCoVOx(800) can be attributed to its unique electronic structure and optimized band alignment, which promote efficient charge separation and facilitate the water splitting and hydrogen evolution processes. The findings of this study highlight the promising potential of the synthesized BiMeVOx materials, particularly BiCoVOx, as efficient photoelectrochemical catalysts for water splitting. These results contribute to the advancement of renewable energy technologies and provide valuable insights for the design and development of novel photoactive materials. [Display omitted] • BiMeVOx (Me: Co, Ce, Mo, Zr) catalysts were synthesized for water electrolysis to produce hydrogen energy. • BiCoVOx(800) as a Bifunctional Catalyst for HER and OER. • The BiCoVOx photoanode shows a photocurrent density of Δj = 674 μA cm−2. • Multifunctional BiCoVOx Enhances Water Splitting. [ABSTRACT FROM AUTHOR]

The mechanism of the water gas shift reaction (WGSR) catalyzed by Mo(CO) 6 in both gaseous and aqueous phases were analyzed using the density functional theory (DFT) method. This study indicates that aqueous phase slightly increased every energy barrier for each step along the reaction path. The turnover frequency (TOF) of the reaction was determined using the energy span model (ESM). The TOF value in the aqueous phase (2.48 × 10−16 s−1) is slightly lower than in the gas phase (6.08 × 10−16 s−1). Actually, the advantages of aqueous phase may be attributed to high solubility and concentration of H 2 O, CO, OH−. The study of temperature (300–900 K) on energy profile shows that the reaction rate of WGSR can be increased with the increase of temperature. This research filled the gap in understanding the mechanism for the WGSR in aqueous phase, provides a reasonable theoretical foundation for molybdenum-based catalysts development. • Mechanisms of gaseous phase and aqueous phase carbonyl complexes Mo(CO) 6 catalyzed WGSR are reported. • The energetic span model is applied to reveal the kinetic behavior of the catalytic cycles. • The increase in temperature is beneficial for accelerating the reaction rate. [ABSTRACT FROM AUTHOR]

To address the urgent need for non-precious metal-based catalysts in the industrial preparation and application of hydrogen energy, we present a secondary hydrothermal strategy to prepare a Mo-modified cobalt carbonate precursor, resulting in the Mo–Co/Co 2 N 0.67 catalyst. The cobalt-based materials exhibit a layered flake structure due to molybdenum modification, exposing more active sites, while molybdenum oxide modification enhances hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR). In alkaline HER measurements, Mo–Co/Co 2 N 0.67 achieves a remarkable current density of 10 mA cm−2 at only 27 mV. The overall water splitting of Mo–Co/Co 2 N 0.67 + RuO 2 can reach 10 mA cm−2 at 1.52 V voltage. In alkaline HOR measurements, it exhibits the current density of 2.92 mA cm−2@0.1 V vs. RHE and an exchange current density (J 0) of 2.96 mA cm−2. This work highlights the effective regulation of non-noble metal-based electrocatalysts through Mo modification, providing valuable insights for the development of efficient non-precious metal-based hydrogen electrocatalysis within the context of anion exchange membrane unitized reversible fuel cells (AEM-URFC). [Display omitted] • The surface modification by molybdenum optimizes the hydrogen reaction. • Flake Mo–Co/Co 2 N 0.67 provides more reaction channels and electrochemical active area. • Mo–Co/Co 2 N 0.67 exhibits −10 mA cm−2 at −27 mV and Tafel slope of 58.63 mV dec−1. [ABSTRACT FROM AUTHOR]

Methane release from marine sediments strongly influences the local seafloor environment and ecosystems, and may impact Earth's climate system. Recent studies revealed anomalous molybdenum (Mo) enrichment in seep sediments, which was linked to methane release events. Marine seep sediments are a potential sink of Mo for the global ocean, while the mechanisms leading to local Mo enrichment are not fully understood. The sediments from a gas hydrate-bearing area of the South China Sea analyzed herein reveal authigenic Mo (Mo auth) contents ranging from 0 and 31.4 µg/g and δ98Mo auth values ranging from 0.18 ‰ to 3.31 ‰. The range of δ98Mo auth values of seep sediments is therefore similar to values of modern iron-rich sediments with low concentrations of dissolved porewater hydrogen sulfide and sediments deposited under weakly euxinic sediments. Among the obtained South China Sea data, the more positive δ98Mo auth values (>ca. 1.5 ‰) are interpreted to reflect diffusion of seawater Mo into the sediment at moderate seepage rates and Mo isotope fractionation during the formation of thiomolybdates in the sulfidic seep environment. The lower δ98Mo auth values (

Among the major challenges facing the hydrogen economy is the issue of hydrogen storage. In terms of "future energy needs", electrochemical hydrogen storage in solid-state materials is an accepted perspective that could mitigate the discontinuation of primary energy sources. In this study, we demonstrate the electrochemical properties of a complex metal oxide that contains the molybdate group, Dy 2 Mo 3 O 12. Wet-chemical synthesis of nanostructured Dy 2 Mo 3 O 12 is primarily carried out using ultrasound-assisted wet-chemical methods in the presence of a variety of surfactants. The structural and morphological observations of the samples confirm a pure and highly crystalline structure obtained in the presence of CTAB surfactant at 900 °C and 30 min of sonication, with an average crystalline size of 29 nm. Based on the FTIR spectrum of this sample, it can be concluded that there are significant absorptions indicating the formation of oxygen-metal bonds. The specific surface area and pore volume of the selected sample are 4.543 m2/g and 0.0284 cm3/g, respectively, demonstrating its porous structure. Electrochemical studies of this sample at various temperatures have revealed an enhanced discharge capacity (5100 mAh/g at 65 °C) with a capacity retention rate of 97%. Based on these findings, mixed metal oxides containing at least one active charge transfer species (Red./Ox.) are suitable for use in solid-state hydrogen storage devices. [Display omitted] • Pioneering technique for creating Dy 2 Mo 3 O 12 -Dy 2 O 3 nanocomposites. • Showcasing a unique material that holds potential for enhanced electrochemical hydrogen storage. • Significant strides in achieving enhanced electrochemical hydrogen storage. • Foundational step in the exploration of materials designed for harvesting hydrogen storage systems. [ABSTRACT FROM AUTHOR]

Among the various molybdenum oxide (MoO x) films, molybdenum dioxide (MoO 2) has gained significant attention as a promising electrode material for metal-insulator capacitors owing to its exceptional crystalline properties and high work function (WF). However, achieving precise atomic layer deposition of MoO 2 films requires careful selection of molybdenum (Mo) precursors and oxidants, given the metastable nature of MoO 2. Furthermore, film properties can vary depending on the oxidation potential of the reactant. In this study, we successfully deposited MoO 2 films by utilizing Mo (NMe 2) 4 as the Mo source, which reacted with an O source (oxygen gas or ozone). MoO x (O 2) and MoO x (O 3) films exhibited significantly different growth rates, measuring approximately 0.23 and 1.36 Å/cycle, respectively. Additionally, MoO x (O 2) and MoO x (O 3) exhibited high WFs of 4.81 and 5.12 eV, respectively. Finally, hydrogen (H 2) annealing induced a monoclinic phase in MoO 2. By contrast, MoO x (O 3) exhibited an orthorhombic structure after both H 2 and O 2 annealing, suggesting that the crystal structure was independent of the annealing atmosphere. These findings highlight the possibility that when a MoO 2 layer that is well crystallized through H 2 treatment is applied as an electrode for dynamic random-access memory(DRAM) capacitors, high-k crystal-inducing effects can be functionalized, and the leakage current can be reduced through the Schottky emission barrier. [ABSTRACT FROM AUTHOR]

Nowadays, the application scenarios of rare earth doped luminescent materials tend to be refined and complicated. The optical properties of rare earth doped materials are difficult to precisely control via the traditional design and synthesis methods, namely, changing doping concentration or preparative conditions. The aim of this study is to tune the optical transition properties of Er3+ in tungsto-molybdate NaY(Mo x W 1- x O 4) 2 (x = 0, 0.01, 0.1, 0.3, 0.5, 0.7, 0.9, 0.99 and 1.0) phosphors by changing the host matrix. The Er3+ doped continuous tungsto-molybdate solid solution NaY(Mo x W 1- x O 4) 2 phosphors were prepared via a solid state reaction technique at optimized calcination temperatures. The refractive indexes of the obtained solid solution samples were confirmed according to different models and compared. Subsequently, the optical transition intensity parameters, radiative transition rates and intrinsic radiative lifetimes of Er3+ in these solid solution phosphors were calculated in the framework of Judd-Ofelt theory. It was confirmed that the optical transition properties of Er3+ can be greatly tuned by the solid solution composition, and the tuning effects for different transitions are different. To validate the reliability of the Judd-Ofelt calculations, the temperature-dependent emission spectra of two green emissions of Er3+ for different solid solution samples were studied. It was found that the radiative transition rate ratios between two green emissions derived from theoretical calculations and experimental measurements are in reasonable agreement, thus proving that the optical transition calculations are reliable and the optical transition properties of Er3+ in the tungsto-molybdates can be tuned in a large range. This work reminds us of a new route for developing novel luminescence materials based on practical demands. [ABSTRACT FROM AUTHOR]

Two-dimensional titanium carbides (Ti 3 C 2 T x) are part of the novel family of transition metal carbides/nitrides known as MXenes, which exhibit a broad range of photo-electrocatalytic applications. In this study, we present a facile hydrothermal synthesis method for Ti 3 C 2 T x decorated on molybdenum diselenide (MoSe 2) nanoflower composites, serving as an enhanced catalyst for hydrogen (H 2) evolution. Ti 3 C 2 T x , acting as a 2D conductive substrate, facilitates electron transfer, preventing MoSe 2 agglomeration, while MoSe 2 offers abundant active sites. The characterizations of surface analysis, optical properties, morphological nanostructure, and elemental composition performance of Ti 3 C 2 T x nanosheets, MoSe 2 nanoflowers, and Ti 3 C 2 T x /MoSe 2 nanoflower composites was conducted using FTIR, XRD, UV–Visible spectroscopy, SEM, EDS Mapping, TEM, and XPS techniques. The catalyst with optimal performance, the Ti 3 C 2 T x /MoSe 2 nanoflower composite demonstrates excellent functional properties in the H 2 evolution, showing a lower overpotential of 135 mV and smaller Tafel slope of 72 mV/dec at 10 mA/cm2 compared to Ti 3 C 2 T x nanosheets and MoSe 2 nanoflowers. The Ti 3 C 2 T x /MoSe 2 nanoflower composite forms heterojunctions to inhibit the rapid recombination rate of photo-induced electrons and holes. In comparison to MoSe 2 nanoflowers and Ti 3 C 2 T x catalysts (where T x = F, and O surface terminations), the optimized Ti 3 C 2 T x /MoSe 2 nanoflower composite exhibits significantly enhanced photocatalytic activity in H 2 production, with a H 2 production rate of 2146 μmolg−1h−1 superior than the Ti 3 C 2 T x nanosheets (1367 μmolg−1h−1) and MoSe 2 nanoflowers (986 μmolg−1h−1), respectively. Through this design, effective separation of photogenerated charge carriers is achieved, improving the activity of photocatalytic H 2 production and demonstrating the promise of the cocatalyst strategy for photocatalysis. [ABSTRACT FROM AUTHOR]

Cardiac pacing with temporary epicardial pacing wires (TEPW) is used to treat rhythm disturbances after cardiac surgery. Occasionally, TEPW cannot be mechanically extracted and remain in the thorax, where they may rarely cause serious complications like migration and infection. We aim to develop bioresorbable TEPW that will dissolve over time even if postoperative removal is unsuccessful. In the present study, we demonstrate a completely bioresorbable design using molybdenum (Mo) as electric conductor and the resorbable polymers poly(D, L-lactic-co-glycolic acid) (PLGA) and polycaprolactone (PCL) for electrically insulating double-coating. We compared the pacing properties of these Mo TEPW demonstrators to conventional steel TEPW in Langendorff-perfused rat hearts and observed similar functionality. In vitro , static immersion tests in simulated body fluid for up to 28 days elucidated the degradation behaviour of uncoated Mo strands and the influence of polymer coating thereon. Degradation was considerably reduced in double-coated Mo TEPW compared to the uncoated and the PLGA-coated condition. Furthermore, we confirmed good biocompatibility of Mo degradation products in the form of low cytotoxicity in cell cultures of human cardiomyocytes and cardiac fibroblasts. Temporary pacing wires are routinely implanted on the heart surface to treat rhythm disturbances in the days following cardiac surgery. Subsequently, these wires are to be removed. When removal attempts are unsuccessful, wires are cut at skin level and the remainders are left inside the chest. Retained fragments may migrate within the body or become a centre of infection. These complications may be prevented using resorbable pacing wires. We manufactured completely resorbable temporary pacing wires using molybdenum as electrical conductor and assessed their function, degradation and biological compatibility. Our study represents an important step in the development of a safer approach to the treatment of rhythm disturbances after cardiac surgery. [Display omitted] [ABSTRACT FROM AUTHOR]

Molybdenum based phosphides have gradually become the investigation frontier of hydrogen evolution catalysts due to the platinum like electronic structure. In this paper, N, P double-doped graphite carbon layers wrapped with MoP nanoparticles (P–MoP@NPC), is directly compounded by one-step high-temperature carboning PMo 12 -APP@ZIF-8 precursor. P–MoP@NPC possesses splendid hydrogen production reactive, in two kinds of electrolytes, when the overpotentials of P–MoP@NPC are 132 mV and 161 mV, the slope of current density reaching 10 mA cm−2, Tafel slope are 67 and 79 mV dec−1, respectively. In the bargain, P–MoP@NPC displays satisfactory durability in acid and alkaline mediums and can continue to work for more than 24 h. The wonderful hydrogen production ability of P–MoP@NPC is ascribed to the synergistic effect of MoP nanoparticles, hierarchical porous structure as well as N, P double-doped carbon layers. The confinement effect of ZIF-8 makes most of the synthesized MoP nanoparticles evenly distributed. The hierarchical porous structure caused by the volatilization of Zn atoms with high temperature can expose more active centers. The N, P double-doped graphitic carbon layers not only protect the catalyst but also adjust the electronic structure of MoP, promoting the hydrogen production capacity. This work may provide a general way to study molybdenum phosphide catalysts synthesized by APP as a green phosphorus source for energy conversion. Molybdenum phosphide catalyst (P–MoP@NPC) was synthesized by simple solution mixing and high temperature calcination. The synthesized P–MoP@NPC has good catalytic activity and stability at 0.5 M H 2 SO 4 and 1 M KOH. [Display omitted] • APP is used as a green phosphorus source for phosphatization. • N, P dual-doped catalyst (P–MoP@NPC) was constructed with high efficiency hydrogen evolution activity; • Zn ions volatilization in ZIF-8 causes multistage pores to expose more active sites; • The confinement effect of ZIF-8 makes MoP nanoparticles evenly distributed. [ABSTRACT FROM AUTHOR]

The two-dimensional molybdenum carbide (Mo 2 CT x) has a similar electronic structure to platinum, which has the potential to be one of non-precious metals catalysts for hydrogen evolution reaction (HER). However, the preparation of Mo 2 CT x by conventional HF and LiF–HCl etching method inevitably introduces the –F and –Cl terminations on the surface, which adversely affect activity and stability. In this study, the LiCl–KCl–Li 3 N molten salt was used to treat Mo 2 CT x at 600 °C and atmospheric pressure and introduce nitrogen heteroatoms. After treated in LiCl–KCl–Li 3 N molten salt, the HER performance of nitrogen-doped Mo 2 CT x is improved compared with that of un-doped Mo 2 CT x , which should be attributed to the optimization of the electronic structure of N–Mo 2 CT x and lower hydrogen adsorption energy barrier. This simple molten salt method provides a way to modify non-precious metal HER catalyst and introduce nitrogen heteroatoms. The LiCl–KCl–Li 3 N molten salt was used to treat Mo 2 CT x at 600 °C and atmospheric pressure and introduce nitrogen heteroatoms. After treatment in LiCl–KCl–Li 3 N molten salt, the HER performance of nitrogen-doped Mo 2 CT x is improved compared with that of un-doped Mo 2 CT x , which should be attributed to the optimization of the electronic structure of N–Mo 2 CT x and lower hydrogen adsorption energy barrier. [Display omitted] • N-modified Mo 2 CT x MXene was prepared via molten salt modification strategy. • The N doping optimizes the electronic structure of Mo 2 CT x. • The improved catalytic performance and stability for Mo 2 CT x. • The molten salt method is simple, efficient, cost-effective, and environmentally friendly for modification. [ABSTRACT FROM AUTHOR]

In this study, a MoSi 2 coating was prepared on the surface of a molybdenum (Mo) substrate using the molten salt electrodeposition method, and the oxidation behavior of the coating over a wide temperature range from 773 K to 1673 K was studied in detail. The phase composition, surface and cross-sectional morphologies of the MoSi 2 coatings after oxidation at various temperatures were characterized, and the evolution of the phase and microstructure were analyzed to elucidate the oxidation mechanism. The experimental results showed that the MoSi 2 coating exhibited excellent oxidation resistance at lower temperatures (773 K) and did not experience the pesting phenomenon. When exposed to medium and high temperatures, a continuous and dense SiO 2 layer was formed on the surface of the MoSi 2 coating, which effectively prevented further oxidation inside the coating, thereby protecting the Mo substrate. Meanwhile, at higher temperatures, especially at 1473 K and 1673 K, the solid-phase diffusion of Si towards the substrate gradually transformed the MoSi 2 into Mo 5 Si 3 with a lower Si content. Notably, the thickness of the Mo 5 Si 3 layer that was distributed between the original MoSi 2 coating and the Mo substrate increased with the oxidation time and temperature. At 1673 K, a Mo 3 Si layer with a low Si content was formed beneath the Mo 5 Si 3 layer. Thus, the diffusion of Si was an important factor restricting the service life of MoSi 2 coating. [ABSTRACT FROM AUTHOR]

Improving the charge diffusion length and water oxidation kinetics of bismuth vanadate (BiVO 4) is essential to achieve better photoelectrochemical catalytic ability for water oxidation. Establishing heterojunctions and incorporating co-catalysts with BiVO 4 create facile charge transfer paths and generate more water oxidation reactions. In this work, nickel molybdenum oxide (NM) and carbon quantum dot (CQD) are firstly deposited on BiVO 4 by hydrothermal and soaking processes to design an efficient co-catalyst/photocatalyst system for water oxidation. The depositing amount of CQD is optimized to balance contributions of CQD and NM as the hole sink and the light-to-electron generator, respectively. The highest photocurrent densities of 2.2 and 3.9 mA/cm2 are achieved for BiVO 4 /NM/CQD in the electrolyte without and with hole scavenger, respectively. The BiVO 4 electrode only shows a photocurrent density of 1.2 mA/cm2 in the electrolyte without hole scavenger. The best photoelectrochemical catalytic ability of BiVO 4 /NM/CQD is approached by the reduced charge-transfer resistance and charge recombination as well as the enhancement on carrier densities. The excellent long-term stability with the photocurrent retention of 90% under illumination for 24 h is also obtained for BiVO 4 /NM/CQD. This study opens a blueprint on designing efficient catalysts for water oxidation by incorporating heterojunction and co-catalyst materials simultaneously. [Display omitted] • Nickel molybdenum oxide (NM) and carbon quantum dot (CQD) are deposited on BiVO 4. • BiVO 4 /NM/CQD acts as efficient co-catalyst/photocatalyst for water oxidation. • BiVO 4 /NM/CQD shows a photocurrent density of 3.9 mA/cm2 without hole scavenger. • BiVO 4 /NM/CQD shows a photocurrent retention of 90% under illumination for 24 hr. [ABSTRACT FROM AUTHOR]

Bismuth vanadate with suitable band edges is one of the efficient photocatalysts for water oxidation. Establishing heterojunction can improve electron diffusion lengths and photocatalytic ability of BiVO 4. In this work, nickel molybdenum oxide (Ni–Mo–O) and BiVO 4 heterojunction is established by the hydrothermal process with different nickel to molybdenum precursor ratios. The Ni–Mo–O/BiVO 4 electrode is applied as photoanodes for water oxidation. The growth mechanism of Ni–Mo–O on BiVO 4 surface is proposed. The Ni–Mo–O deposition amount is optimized regarding to light absorbance and charger transportation. The largest photocurrent density of 1.72 mA/cm2 at 1.23 V RHE is obtained for the optimal NiMoO 4 /BiVO 4 electrode (NM12) in the electrolyte without hole scavenger, while the pure BiVO 4 electrode only shows a photocurrent density of 0.90 mA/cm2. The NM12 electrode even presented an impressive photocurrent density of 5.39 mA/cm2 at 1.23 V RHE in the electrolyte with the hole scavenger, owing to the abundant active sites and higher light absorbance as well as the favorable synergistic effects from its suitable Ni to Mo ratio. The NM12 electrode also shows excellent long-term stability with the photocurrent retention of 83% after illumination for 6500 s. This work opens a blueprint for establishing a novel heterojunction with the adjustable metal ratio and coverage on BiVO 4. [Display omitted] • Nickel molybdenum oxide (Ni–Mo–O) and BiVO 4 heterojunction is made by hydrothermal. • Ni–Mo–O/BiVO 4 photoanode with varied Ni to Mo ratios is used for water oxidation. • The growth mechanism of Ni–Mo–O on BiVO 4 surface is proposed. • Photocurrent density of 5.39 mA/cm2 at 1.23 V RHE is got for optimal NM12 electrode. • The NM12 electrode shows an excellent photocurrent retention of 83 % after 6500 s. [ABSTRACT FROM AUTHOR]

Porphyry-type ore deposits are closely associated with subduction zones, but the ultimate source of the metals in these deposits is still uncertain. To test whether aqueous fluids from the subducted slab may contribute to the metal enrichment, we investigated the partitioning of Cu, Zn, Mo, and W between saline aqueous fluids and the subducted basaltic crust at 2.5–3.0 GPa and 650–670 °C by experiments in piston cylinder presses. The bulk fluid/solid partition coefficients (Dfluid/solid) of Cu and Zn increase significantly with fluid salinity. For Cu, Dfluid/solid is less than 1 in a salt-free aqueous fluid, but at a salinity of 10 wt% NaCl, Dfluid/solid approaches 10. On the other hand, the Dfluid/solid of Zn is still below 0.4 even at the same salinity. Dfluid/solid of Mo is always relatively high (>4), with only a very slight enhancement by salinity at 2.5 GPa. The fluid/solid partition coefficient of W is close to 1 for a chloride-free fluid, but slightly decrease with increasing salinity. Overall, these experimental data show that saline aqueous fluids released from the basaltic layer of the subducted oceanic slab can effectively transport Cu and Mo and therefore enrich these two metals in the mantle wedge. This enrichment does not contradict the observation that Cu concentrations in primitive arc magmas and MORB are similar, since these concentrations may be controlled by a buffering sulfide phase. The enrichment of copper in the source then does not necessarily increase Cu concentrations in the melt, but it ensures that the copper-bearing sulfide phase is not exhausted during repeated melting events. For molybdenum, our data suggest that aqueous fluids from the slab are the major source of Mo in arc magmas. Due to the high pre-enrichment of Mo in some sediments, there may be a direct link between the types of subducted sediment and the location of porphyry Mo deposits. On the other hand, the contribution of slab fluids to the Zn budget of these magmas is likely negligible. The W partitioning data are consistent with isotopic evidence for the mobility of W in subduction fluids. Moreover, the behavior of Mo and W is strongly affected by the abundance of rutile in the solid residue. In a rutile-free lithology, not only Mo, but also W would strongly partition into the fluid. As some sediments may be highly enriched in W relative to the average mantle, fluids from such sediments may also produce a significant W enrichment in the mantle wedge, provided that the sedimentary residue is free of rutile. [ABSTRACT FROM AUTHOR]

In terms of green energy, it is critical to investigate the carrier stability and hydrogen evolution reaction activity of atomic catalysts. On the (111) and (101) surfaces of MoP, we investigate how single and double atom interactions affect HER activity. According to the results, the Ru/Ni@MoP(111) catalyst's energy barrier and hydrogen evolution free energy are 0.012 eV and 0.129 eV, respectively, during hydrolysis. In contrast, Pt/Ni@MoP(101) requires only 0.087 eV energy to absorb in order to produce OH∗ and H∗, demonstrating how effectively the diatom can increase the activity of the catalyst surface. Additionally, the localized surface plasmon resonance effect, which benefits double-atom catalysts, can be induced by precious metals. Ni has good HER activity in general, which can significantly lower the price of precious metals. Homoplastically, it is demonstrated that the MoP stable surface has outstanding hydrogen evolution activity and functions well as a carrier. A research foundation for expanding the synergistic law of the novel electrocatalyst system and multi-atomic loads is provided by the study's revelation of the structure-activity link of catalysts. [Display omitted] • MoP can effectively serve as a catalyst carrier for single and double atom. • The acidic and alkaline oxygen evolution reactions of DACs and SACs were analyzed. • When Ni and transition metal form double atom, HER activity is significant. [ABSTRACT FROM AUTHOR]

Strategy to improve single-stage photofermentative hydrogen productivity of photosynthetic bacteria (PSB) by efficient use a formulated lignocellulosic substrate through suitable supplement of iron and molybdenum as enhancers of microbial activity of R. palustris was proposed. The maximum hydrogen production rate of 48.1 ml h−1 L−1 was obtained using response surface methodology as the result of accelerated bioreaction of proton reduction under inoculum density of 118.1 mg L−1, Fe2+ of 13.2 mg L−1 and Mo6+ of 2.65 μg L−1. Biokinetic analysis revealed the enhanced microbial activities in biomass synthesis and H 2 production. Suitable metal addition enabled PSB to act in whole as biocatalyst to facilitate assimilation of the formulated electron-rich carbon source from wheat straw through the efficient electron transfer needed for both cell growth and enzyme function of nitrogenase. Therefore, higher kinetic values of k c in 0.146 h−1 and R m in 59.4 ml h−1 L−1, accompanied with improved performances of H 2 yield in 1.56 mol mol−1 carbon and substrate degradation in 93.6% were attained. [Display omitted] • Enhancement strategy of lignocellulosic photofermentation was developed. • A higher production rate of 48.1 ml H 2 h−1 l−1 from wheat straw was attained by R. palustris. • Synergistic effect of metal Fe and Mo addition stimulated nitrogenase-catalyzed H 2 reaction. [ABSTRACT FROM AUTHOR]

In fabrication of metal-reinforced ceramics, metallic powders are used as one of the raw materials, however, they hinder obtaining nanometallic particles in the matrix. The use of metallic nanopowders is inefficient, because they are highly flammable and require special storage and handling conditions (cool, dry inert gas, tightly sealed). Replacing metallic powders with coordination complexes allows to obtain nanocomposites in harmless manufacturing processes. The use of coordination complex of molybdenum (molybdenyl acetylacetonate) allowed to fabricate ZrO 2 /Mo composites by slip casting and gelcasting. The increase in fracture toughness (ca. 25%) was observed with the little concentration of the metallic phase (up to 1.5 wt%) in a composite. It results from gaining fine metallic particles (ca. 62 nm) in the ceramic matrix. SEM analysis revealed that crack propagation is inhibited by nano-sized metallic particles according to three mechanisms: crack deflection, crack blocking by plastic deformation and interface debonding. [Display omitted] • Coordination complexes are good substitutes for metal powders in CMCs fabrication. • Molybdenyl acetylacetonate is the beneficial precursor of Mo phase in ZrO 2 matrix. • ZrO 2 -Mo composites showed increased fracture toughness (27%) at low Mo content (1.5%). • Precursors decompose to fine metallic grains (ca. 62 nm) visible in composite microstructure. [ABSTRACT FROM AUTHOR]

The development of stable electrocatalysts for the catalysis of the electrochemical water-splitting process has become an area of particular interest in recent years. In this study, a simple interfacial method is proposed to fabricate a novel molybdenum (Mo)-substituted Co 3 O 4 with N-doped reduced graphene oxide (N-rGO) composite for application as a high-performance oxygen evolution reaction (OER) electrocatalyst in a typical alkaline solution. Various efficient characterization methods are used to examine its structure, morphology, elemental composition, and surface area. The optimized 20MoCo/NRG composite exhibits improved electrocatalytic performance with robust electronic interfacial bonding, improved intrinsic activity, and high ECSA values. Furthermore, it exhibits remarkable electrocatalytic OER activity with a lower overpotential of 378 mV and minor Tafel slope value of 143 mV dec−1 at a current density of 10 mA cm−2 in a 1 M KOH solution compared with the other as-synthesized catalysts. Notably, the 20MoCo/NRG composite catalyst demonstrates exceptional durability for 15 h. Consequently, this effective interfacial nanostructure provides novel insights into the development of high-performance, long-lasting electrocatalysts for the water oxidation process. [Display omitted] • Developed Mo-substituted Co 3 O 4 /NRG nanomaterial composite as a potential catalyst. • As-prepared 20MoCo/NRG composite electrocatalyst exhibits excellent OER performance. • Exhibits low overpotential, minor Tafel slope in 1 M KOH, and good OER stability. • Mo/Co 3 O 4 and N-rGO present a strong synergistic coupling effect. • Thus, Mo ions in 20MoCo/NRG produce more electrochemically active sites. [ABSTRACT FROM AUTHOR]

Numerous studies have reported the development of Pd-based catalyst for the anode direct formic acid fuel cell (DFAFC) that improves the electrocatalytic activities. We have now developed a carbon nanofiber embedded with carbon black (Vulcan) and molybdenum sulfide (MoS 2) nanoparticles as the Pd support for the FAOR catalyst. The MoS 2 -Vulcan embedded carbon nanofiber (MoS-VECNF) was first prepared by electrospinning and heat treatment. The MoS-VECNF was prepared with different weight ratios of MoS 2 to polyacrylonitrile (PAN). The prepared support was then loaded with 20 wt% Pd nanoparticles by the polyol method. The Pd/MoS-VECNF catalyst demonstrated a better FAOR activity and stability as compared to the Pd/VECNF catalyst with 0.10 as the optimum weight ratio. The achieved peak current density was 1.46 times higher than that of the Pd/VECNF catalyst. The presence of MoS 2 nanoparticles in the carbon support produced a strong metal-support interaction which improved the FAOR activity and stability of the catalyst. Therefore, the Pd/MoS-VECNF catalyst is suggested to be promising for DFAFC applications. • Molybdenum-containing carbon nanofiber supported Pd catalyst was synthesized. • Pd/MoS-VECNF catalysts were tested for formic acid oxidation. • Formic acid oxidation activity is improved by the addition of molybdenum. • Superior stability is achieved by the molybdenum-containing catalyst. • Pd/MoS-VECNF catalyst is promising for direct formic acid fuel cells application. [ABSTRACT FROM AUTHOR]

Due to the positive conduction band of MoO 3 , it is typically unable to generate hydrogen under photocatalysis. In this work, we reported direct photocatalytic hydrogen evolution from substoichiometric MoO 3-x ultrathin nanowire using sacrificial triethanolamine. By incorporating trace amounts of oleylamine and the ligand polyvinyl pyrrolidone, blue ultrathin MoO 3-x nanowires with the diameter of approximately 2 nm were effectively created through a simple hydrothermal method. These one-dimensional MoO 3-x ultrathin nanowires boast a modified energy band structure, which promotes an elevated shift in the conduction band and favors the availability of more active sites. These factors jointly contribute to direct photocatalytic hydrogen evolution by MoO 3-x ultrathin nanowires. Moreover, we introduced MXene Ti 3 C 2 T x as a cocatalyst, enabling the fabrication of MXene Ti 3 C 2 T x -MoO 3-x composites via a simple two-phase composite method. The implementation of MXene Ti 3 C 2 T x as a substrate effectively isolates photogenerated electron-hole duos, resulting in boosted performance in generating hydrogen and oxygen through photocatalysis. The optimized MXene Ti 3 C 2 T x -MoO 3-x composites demonstrate exceptional photocatalytic performance, with hydrogen and oxygen evolution rates reaching 36.1 and 1044.2 μmol·h-1g-1, respectively. These values signify a remarkable 6 and 3.2-fold increase over raw material. This method of synthesizing size-tunable MoO 3-x nanowires and MXene Ti 3 C 2 T x -MoO 3-x composites presents a promising avenue for research in energy and allied fields. [Display omitted] • MoO 3-x ultrathin nanowires with a diameter of 2 nm were prepared with trace of oleylamine. • The more negative conduction band position permits the direct hydrogen evolution of MoO 3-x. • Seamless contact Mxene Ti 3 C 2 T x -MoO 3-x is acquired through a two-phase assembling method. • Mxene Ti 3 C 2 T x -MoO 3-x composite exhibits excellent photocatalytic performance and stability. • Hydrogen evolution and oxygen production of Mxene Ti 3 C 2 T x -MoO 3-x is 6 and 3.2-fold of pure MoO 3-x. [ABSTRACT FROM AUTHOR]

In recent years, there has been an increasing interest in using small organic molecules to convert chemical fuels into electrical energy. In this context, ethylene glycol (EG) is a potential feedstock due to its high energy density, which makes this molecule suitable for direct alcohol fuel cells. Thus, combining Pt atoms with other oxophilic elements, such as Mo, is a promising strategy based on the unrivaled importance of developing efficient electrocatalysts for this application. Herein, we report the engineering of PtMo nanoparticles (NPs) as the active phase for EG electrooxidation. Interestingly, a self-assembly process occurred during their manufacturing, and a simple NPs synthesis process (a modified one-pot polyol method) afforded nanostructures with virtually all Mo atoms inside the particles for different PtMo ratios. By preparing three PtMo ratios, we obtained the following NPs sizes: 2.74 ± 2.34 nm (Pt 90 Mo 10), 2.16 ± 1.92 nm (Pt 80 M 20), and 2.47 ± 2.09 nm (2.47 ± 2.09 nm). After immobilizing the NPs onto Vulcan XC-72 carbon black, we got different onset potentials/current densities (at 25 °C): Pt 90 Mo 10 /C (0.33 V/189.0 μA/cm2), Pt 80 Mo 20 /C (0.19 V/132.0 μA/cm2), and Pt 70 Mo 30 /C (0.24 V/95.0 μA/cm2) for the EG electrooxidation. However, essential understandings were raised regarding the studied systems: density-functional tight-binding-based (DFTB) calculations addressed the configuration of the metals in the obtained nanostructures; also, such an approach brought insights regarding the emergence of electronic properties of the different PtMo ratios and mechanistic insights corroborating analytical analyses performed by liquid chromatography. Hence, the best results could be attributed to tailored electronic effects based on a Mo-optimized quantity (Pt 80 Mo 20 /C electrocatalyst). Therefore, we believe we cooperated in better understanding PtMo-based systems, and how the metal ratio decisively can affect their performance, opening new opportunities for practical fuel cell applications. [Display omitted] • Preparation of self-assembled PtMo nanoparticles. • Optimization of the PtMo ratio for ethylene glycol electrooxidation with improved performance. • Association of electronic properties with the catalytic process. • Mechanistic insights regarding the ethylene glycol electrooxidation for the optimized bimetallic system. [ABSTRACT FROM AUTHOR]

We have analyzed concentrations of Mo, Re and U in the suspended particles, water column, underlying carbonate-dominated sediments and pore waters of two contrasting marine lakes situated on the Adriatic Coast of Croatia. Our data are the first for Re in these lakes. Rogoznica Lake is mainly euxinic, but subject to occasional oxygenation events, whereas Mljet Island's Malo Jezero is currently oxic year around but historically was seasonally euxinic. These characteristics make the lakes useful testing grounds for redox proxies. We devote particular attention to Re/Mo ratios, which have great promise as redox proxies. In marine sediments, the range of log[Re auth /Mo auth ] exceeds 2, and typical analytical uncertainty is ±0.05, providing resolving power similar to δ98Mo. Authigenic [Re s /Mo s ] ratios in sediments depend on varying supplies of three components: FeMo,Re)S 4 coprecipitates, Fe(III) oxyhydroxides (plus Mn(III,IV) oxyhydroxides in some cases) and a still-uncharacterized Re-rich, Mo-poor component possibly of biological origin. Removal of the latter component explains a 50% depletion of Re aq without Mo aq from Rogoznica's oxic waters. Water column concentrations of Mo aq and Re aq , as well as [Re s /Mo s ] ratios in Rogoznica's suspended particles are predicted successfully by a model that attributes these elements' removal from sulfidic seawater solely to coprecipitation in Fe(Mo,Re)S 4 , assuming a partition coefficient of 0.6. However, to predict sediment compositions, additional authigenic Mo supplied by mainly Fe(III) oxyhydroxides during sporadic oxygenation events must be considered. In Malo Jezero, sulfide concentrations are too low even in pore waters for precipitation of Fe(Mo,Re)S 4. Consistent with earlier work, U aq profiles are best explained by eddy diffusive transport to the sediment rather than capture by a precipitate in the water column. In Rogoznica pore waters, Mo aq extracted through 0.45 μm pore size filters exceeds by 50-fold concentrations predicted by the model and measured previously with 0.15 μm filters. This observation implies presence of ferrothiomolybdate colloids, which could be important, overlooked participants in the sedimentary geochemistry of Mo. [ABSTRACT FROM AUTHOR]

Sedimentary molybdenum (Mo) and uranium (U) enrichments have been widely used as a proxy for redox conditions in oxygen-depleted marine paleo-environments. However, in a dynamic upwelling system the seasonal fluctuations from oxic to completely anoxic-sulfidic bottom waters and lateral sediment transport can modify the primary Mo and U signal of the sediment, which in turn may impact paleo-redox interpretations. In this study we present pore water and solid phase data collected at two cross shelf transects during the 'more oxygenated' austral winter and 'anoxic' austral summer to study the influence of spatially and seasonally contrasting redox conditions on the formation of authigenic Mo and U enrichments in organic carbon (TOC) rich mud belt sediments on the Namibian shelf. A mass balance was established for each element based on diffusive fluxes and element mass accumulation rates to evaluate the respective mechanisms of trace metal delivery, accumulation and recycling. Mo is delivered to the sediment in its dissolved form via diffusion across the sediment–water interface, especially during austral summer when bottom waters are anoxic and surface sediments are highly sulfidic. In the center of the inner shelf mud belt, the benthic Mo fluxes of up to 37 nmol cm−2 yr−1 into sulfidic surface sediments are the highest ever reported for reducing sulfidic systems and agree with the rate of Mo accumulation in the solid phase. Concurrently, high sedimentation rates and low terrigenous input limit solid phase Mo accumulation on the Namibian shelf. In ancient marine sediments, this mode of Mo cycling can be identified by low Mo/TOC ratios of ∼2 similar to those found in sediments deposited below the perennial oxygen minimum zone on the Peruvian shelf and to those found in deposits of the Cretaceous Oceanic Anoxic Event 2. Diffusive U fluxes into the sediment are generally too low to account for the sedimentary enrichment leading to the conclusion that U is delivered mainly in particulate form. In areas with anoxic bottom water, shallow dissolved U maxima directly below the sediment water interface and rather low sedimentary U content indicate that particulate U is recycled and largely released back into the bottom water. At sites where bottom water oxygen concentrations vary from anoxic to completely oxic on seasonal timescales, the depth at which Mo and U are removed from pore waters moves vertically within the sediment column thus defining a layer between the sediment surface and ∼20 cm depth, in which Mo and U accumulate in the solid phase. Our results emphasize the importance of short-term redox fluctuations in the bottom waters and underlying sediments, as well as lateral sediment transport for the authigenic enrichment of redox-sensitive trace metals in reducing shelf sediments. The relative enrichment patterns identified might be useful for the reconstruction of open marine anoxia in the geological past. [ABSTRACT FROM AUTHOR]

This research proposes the utilization of molybdenum tailings (MT) to toughen fly ash-based geopolymers. To fully understand the effect of MT on the fracture performance and damage behavior of fly ash-based geopolymers, the effect of mode I fracture toughness and fracture energy of fly ash-based geopolymers with different MT contents were researched by using semi-circular bending (SCB) tests. The damage and strain behavior of the semi-circular bending with notches (NSCB) specimens during the fracture process were evaluated by acoustic emission (AE) technology and digital image correlation (DIC) technology, and finally the micromorphology of the fracture surface of NSCB specimens after the loading finished were observed by scanning electron microscopy (SEM). The results show that the tensile strength, fracture toughness and fracture energy of fly ash-based geopolymers were significantly increased with the addition of MT, and the peak value was reached at 30 wt% MT contents, with the increase amplitude reaching 77%, 31% and 45% respectively. This was attributed to the filling effect of MT, which made the structure of fly ash-based geopolymers more dense, reduced the formation and expansion of internal microcracks, shifted the growth direction of microcracks from the pore structure to the gel phase and the interface between the gel phase and glassy microspheres during the fracture process, improved the stability of the structure and the fracture resistance. [ABSTRACT FROM AUTHOR]

Porous ceramics with more than 99% mullite (3Al 2 O 3 ·2SiO 2) content were fabricated at the low sintering temperature of 800 °C using silicon debris and mesoporous aluminum oxide (Al 2 O 3) obtained from calcining aluminium hydroxide (Al(OH) 3) as silicon source and aluminium source, respectively. The study found that adding ammonium molybdate tetrahydrate (AMT) as sintering additive allowed the complete mullitization reaction temperature of the raw materials to be reduced to approach the melting point of molybdenum trioxide (MoO 3). Specifically, the silicon debris is continuously oxidized to silicon dioxide (SiO 2) in the sintering process, prompting the formation of a silicon-rich liquid phase in the molten MoO 3. Meanwhile, a large number of mesopores in the Al 2 O 3 contributed to the dissolution of aluminum source in the silicon-rich liquid phase. Resultantly, synthesizing mullite can be performed at a temperature as low as 800 °C. Additionally, the research showed that the porous mullite ceramics sintered at this temperature had a flexural strength of 22.07 MPa, an open porosity of 52.58%, a linear shrinkage rate of 0.9%, and a bulk density of 1.49 g/cm3. This study not only presents a novel low-cost method for preparing porous mullite ceramics at low temperatures but also provides a simple method for the complete recycling of waste silicon debris. [ABSTRACT FROM AUTHOR]

Several studies have revealed that the glass transition temperature (T g) of polymer nanocomposites (PNCs) may change upon the loading of even a small number of nanoparticles (NPs). However, the exact phenomenon behind such shifting in T g is still not well known. This study uses experimental and MD simulation approaches to explore the physics of the T g of polyaniline (PANI) nanocomposite with molybdenum carbide (Mo 2 C) nanoparticles at different weight percentage loading of NPs. The experimental study shows that, at a lower wt-% loading of NPs, the T g of the resulting PNCs decreases slowly, and above a particular loading wt-%* (30 wt-%), the depression in T g becomes more serious. The SEM images show that for wt-% < wt-%*, NPs remain diffuse in the polymer matrix, and for wt-%t > wt-%* a large number of NPs surround the polymer. The MD simulation reveals a slow increase in the diffusion of polymer and NPs for wt-% < wt-%* and a sudden increase for wt-%t > wt-%*. The measurement of the radius of gyration of the polymer reveals swelling of the polymer for wt-% < wt-%* and contraction of the polymer for wt-%t > wt-%*. Moreover, the variations of the diffusion constants and the radius of gyration of the polymer are consistent with the T g behaviour of PNCs. [ABSTRACT FROM AUTHOR]

Molybdenum (Mo) is extracted predominantly from magmatic-hydrothermal ore deposits, and knowledge of the thermodynamic properties of aqueous Mo complexes over a wide range in pressures (P) and temperatures (T) is required to predict the transport and deposition of Mo in ore-forming environments. These properties are usually derived from experimental studies conducted over a limited P-T range, with uncertainties increasing as temperature and pressure increase, because of inherent technical difficulties and decreasing number of studies. There is a discrepancy between numerous experimental studies at T < 400 °C and a handful of studies at magmatic-hydrothermal conditions. The low T (<400 °C) experiments suggested that Mo(VI) chloride complexes are unlikely to play a significant role in nature, whereas some studies in magmatic-hydrothermal conditions showed the predominance of Mo(VI) chloride complexes. In an attempt to resolve these inconsistencies, we investigated Mo(VI)-Cl complexations from 350 to 750 °C (500 to 2000 bar) using ab initio molecular dynamics (MD) simulations. The simulations reveal that in high-temperature magmatic-hydrothermal fluids (750 °C, 2000 bar), a tetrahedral Mo(VI) chloride complex, MoO 2 (OH)Cl(aq), becomes stable; this coordination differs from the octahedral Mo(VI)-chloride complexes identified in highly acidic sub-critical fluids. The ab initio thermodynamic integration method was employed to calculate the equilibrium constants of the reaction. MoO 2 (OH)Cl(aq) + H 2 O = MoO 2 (OH) 2 (aq) + HCl(aq) Thermodynamic modelling of the speciation using the calculated equilibrium constants shows that at lower temperatures (350 °C, 500 bar), Mo(VI)-chloro complexes are only important at highly acidic conditions (pH < 1), in accordance with previous studies. However, the MD results show that at higher temperatures, Mo-chloro-complexes may be important in transporting Mo in mildly acidic conditions up to the quartz-muscovite-K-feldspar buffered pH. Hence, Mo(VI) chloro-complexes could play an important role in the formation of magmatic-hydrothermal Mo deposits (e.g., Climax-type Mo deposits). We conclude that the mode of metal transport can change dramatically at high temperatures as a result of coordination changes caused by changes in the solvation properties of water; and that quantitative MD is an important tool to support the interpretation of scant experimental results available for magmatic-hydrothermal systems. [ABSTRACT FROM AUTHOR]

The Mesoproterozoic ocean was previously proposed to be characterized by low oxygen concentrations that may have resulted in a stasis in eukaryotic evolution. Recent studies reveal several pluses of oxygenation during this period that may have facilitated eukaryote evolution. However, few quantitative constraints on the global oxygenation events have hindered the comprehensive understanding of interactions between eukaryotes and environments. Here we present new molybdenum isotope (δ98/95Mo, simplified as δ98Mo) data coupled with sulfur and carbon isotope compositions and trace element contents from the carbonates and mudstones of the Gaoyuzhuang Formation (ca. 1.60–1.54 Ga) in two-well preserved sections in the North China Craton. The δ98Mo data from the two sections show similar trends in stratigraphic variation, with a prominent positive excursion in the Gaoyuzhuang Member III and peak values reaching up to 2.03‰ and 1.92‰, respectively. We developed a revised isotope mass balance model with high manganese (Mn) (hydr)oxide burial rate due to higher manganese concentration in the Mesoproterozoic oceans. Model calculation suggests that at least more than half of global seafloor (>54%) was covered with oxygenated seawater during the deposition of the Gaoyuzhuang Member III. Our estimation points to a significant oxygenation event in the early Mesoproterozoic with magnitude and extent much higher than previously thought. Further, a simple mass-balance calculation suggests that the atmospheric oxygen level was at least > 4% PAL (present atmospheric level) and likely up to 30% PAL at ca. 1.57 Ga. This oxygenation event, together with other environmental and/or developmental factors, may have facilitated a short and rapid evolution of eukaryotes in the early Mesoproterozoic. [ABSTRACT FROM AUTHOR]