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Showing papers on "Molybdenum published in 2020"


Journal ArticleDOI
TL;DR: In this article, a photocatalytic H2 production rate of MoxS@TiO2@Ti3C2 composite with an optimized hydrothermal treatment temperature (160 °C) was achieved.

177 citations


Journal ArticleDOI
TL;DR: In this article, the authors present a comprehensive and critical summary on the recent progress in the Mo-based electrodes for hydrogen evolution reaction (HER) including molybdenum alloys.

154 citations


Journal ArticleDOI
TL;DR: It is shown that a nickel-molybdenum nanoalloy with tetragonal MoNi4 phase can catalyze the ultrafast hydrogen oxidation reaction (HOR) efficiently in alkaline electrolytes and has the capability to tolerate carbon monoxide poisoning.
Abstract: Hydroxide exchange membrane fuel cells offer possibility of adopting platinum-group-metal-free catalysts to negotiate sluggish oxygen reduction reaction. Unfortunately, the ultrafast hydrogen oxidation reaction (HOR) on platinum decreases at least two orders of magnitude by switching the electrolytes from acid to base, causing high platinum-group-metal loadings. Here we show that a nickel-molybdenum nanoalloy with tetragonal MoNi4 phase can catalyze the HOR efficiently in alkaline electrolytes. The catalyst exhibits a high apparent exchange current density of 3.41 milliamperes per square centimeter and operates very stable, which is 1.4 times higher than that of state-of-the-art Pt/C catalyst. With this catalyst, we further demonstrate the capability to tolerate carbon monoxide poisoning. Marked HOR activity was also observed on similarly designed WNi4 catalyst. We attribute this remarkable HOR reactivity to an alloy effect that enables optimum adsorption of hydrogen on nickel and hydroxyl on molybdenum (tungsten), which synergistically promotes the Volmer reaction. The lack of efficient and cost-effective catalysts for hydrogen oxidation reaction (HOR) hampers the application of hydroxide exchange membrane fuel cells. Here, authors reported bimetallic MoNi4 and WNi4 nanoalloys with marked HOR activity in alkali, among which MoNi4 outperforms the Pt/C catalyst.

141 citations


Journal ArticleDOI
TL;DR: In this article, the authors showed that monolayer molybdenum disulfide (MoS2) is a potential alternative substrate to anchor transition metal (TM) SACs towards NRR.

132 citations


Journal ArticleDOI
TL;DR: In this article, three different types of new stainless steel samples were designed and developed by using Monte Carlo Simulation program Geant 4 code, and the neutron equivalent dose was measured using an average 4.5 MeV energy fast neutron source.

124 citations


Journal ArticleDOI
TL;DR: In this article, a novel environment friendly CMP slurry was developed, containing of silica, hydrogen peroxide (H2O2), malic acid and deionized water.

124 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of Mo content on the microstructure revolution and corrosion behavior of cast FeCoCrNiMoxhigh-entropy alloys in chloride environments were investigated.

91 citations



Journal ArticleDOI
TL;DR: In this article, a cage-confinement pyrolysis route is proposed to realize size-controllable synthesis of molybdenum-based catalysts ranging from isolated single Mo atoms to sub-nanometer clusters.

88 citations


Journal ArticleDOI
TL;DR: In this paper, the authors reported the synthesis of tungsten diselenide (WSe2) doped with various transition metals (Fe, Co, Nb, Ni and Zr).
Abstract: Layered transition metal dichalcogenides (TMDCs) are an emerging family of catalysts. Included in this group is tungsten diselenide (WSe2), which has attracted recent attention for electro-optical applications. Tungsten is opportune because it is the heaviest transition metal in the TMDC family and is widely abundant on Earth. Moreover, WS2 and WSe2 are more benign in nature than their molybdenum counterparts. Despite this, WSe2 has been relatively unexplored as a catalyst. We report the synthesis of WSe2 doped with various transition metals (Fe, Co, Nb, Ni and Zr). Among the doped catalysts, Ni–WSe2 has been found to be the most promising electrocatalyst for the hydrogen evolution reaction (HER) as it possesses the smallest charge transfer resistance and thus facilitates a faster catalytic reaction. Upon doping with Ni, catalytic enhancement results from improved hydrogen adsorption (Hads). Beyond this threshold of Ni loading, the improved activity in alkaline medium is due to the optimized interaction of the OH/surface active sites. Using density functional theory calculations, we identified that the catalytic sites are Se atoms either bound to a substitutional Ni dopant or constituting a small patch of NiSe grafted on the WSe2 surface.

84 citations




Journal ArticleDOI
TL;DR: The two-dimensional morphology of molybdenum oxycarbide nanosheets dispersed on silica is found vital for imparting high stability and catalytic activity in the dry reforming of methane, and the specific activity of 2D-Mo2COx/SiO2 exceeds that of other Mo2C catalysts by ca.
Abstract: The two-dimensional morphology of molybdenum oxycarbide (2D-Mo2COx) nanosheets dispersed on silica is found vital for imparting high stability and catalytic activity in the dry reforming of methane. Here we report that owing to the maximized metal utilization, the specific activity of 2D-Mo2COx/SiO2 exceeds that of other Mo2C catalysts by ca. 3 orders of magnitude. 2D-Mo2COx is activated by CO2, yielding a surface oxygen coverage that is optimal for its catalytic performance and a Mo oxidation state of ca. +4. According to ab initio calculations, the DRM proceeds on Mo sites of the oxycarbide nanosheet with an oxygen coverage of 0.67 monolayer. Methane activation is the rate-limiting step, while the activation of CO2 and the C–O coupling to form CO are low energy steps. The deactivation of 2D-Mo2COx/SiO2 under DRM conditions can be avoided by tuning the contact time, thereby preventing unfavourable oxygen surface coverages. The two-dimensional morphology of molybdenum oxycarbide (2D-Mo2COx) nanosheets dispersed on silica is found vital for the dry reforming of methane. Here the authors show that the specific activity of 2D-Mo2COx/SiO2 exceeds that of other Mo2C-based catalysts by ca. 3 orders of magnitude.

Journal ArticleDOI
TL;DR: In this article, the photocatalytic activity of molybdenum trioxide (MoO3) thin films was studied and the dependence of the physical properties of the metal oxides on the sputtering power and working pressure was investigated.

Journal ArticleDOI
TL;DR: In this article, the effect of oxygen incorporation (from synthesis, cat synthesis, and cat catalysts) on the ORR in acid was investigated and the results showed promising activity and stability for the oxygen reduction reaction in acid.
Abstract: Molybdenum nitride (Mo–N) catalysts have shown promising activity and stability for the oxygen reduction reaction (ORR) in acid. However, the effect of oxygen (O) incorporation (from synthesis, cat...

Journal ArticleDOI
TL;DR: In this article, the morphological and structural properties and chemical composition of the prepared materials have been analyzed by transmission electron microscopy, X-ray diffraction and Xray photoelectron spectroscopy.

Journal ArticleDOI
TL;DR: In this article, a series of 3D network aloe waste-derived carbon (3D-AWC)-supported molybdenum-based bimetallic oxide nanohybrid catalysts were synthesized via co-precipitation method.
Abstract: The development of highly efficient catalysts has attracted great attention in energy conversion field. In this work, a series of 3D network aloe waste-derived carbon (3D-AWC)-supported molybdenum-based bimetallic oxide nanohybrids (ZnMoO4/3D-AWC, Cu3Mo2O9/3D-AWC, and MnMoO4/3D-AWC) were synthesized via co-precipitation method. Benefiting from the synergistic effect of molybdenum-based bimetallic oxide and 3D-AWC, the catalytic activities of electrocatalysts for triiodide reduction reaction (IRR) and hydrogen evolution reaction (HER) were enhanced. Solar cell with ZnMoO4/3D-AWC obtained device efficiency of 7.65%, comparable to that with Pt (6.74%), while ZnMoO4/3D-AWC catalyst delivered a Tafel slope (54 mV dec−1) in 1.0 M KOH for HER, which demonstrated a comparable property to Pt/C. In addition, the 3D-AWC-supported molybdenum-based bimetallic oxide nanohybrid catalysts exhibited superior electrochemical stability in IRR and HER. The catalytic mechanism was illustrated from electronic structure and work function by first-principle DFT calculations. This research provides a reference in designing high-performance catalysts for multi-domain energy fields.

Journal ArticleDOI
TL;DR: In this paper, a 2D organ-like Mo2C MXene matrix derived from Mo2Ga2C crystals, coupled with MoS2 nanoflowers to explore the hydrogen evolution reaction (HER) of molybdenum carbides and disulfides was proposed.
Abstract: Two-dimensional molybdenum carbides belong to a novel family of 2D transition metal carbides/nitrides called MXenes, which have a wide range of electrochemical applications. However, the synergistic catalysis of transition metal carbides and disulfides has not been studied in depth. A strategy was proposed to prepare a 2D organ-like Mo2C MXene matrix derived from Mo2Ga2C crystals, coupled with MoS2 nanoflowers to explore the hydrogen evolution reaction (HER) of molybdenum carbides and disulfides. Compared with Mo2CTx (where Tx means F, O, and OH surface terminations) Mxene catalysts, MoS2@Mo2CTx nanohybrids showed significantly enhanced HER activity, with a low overpotential of 176 mV in alkaline media at a current density of 10 mA cm−2 and a very small overpotential of 26 Ω. Density functional theory calculations indicated that the reduction of the hydrogen adsorption energy of the MoS2@Mo2CTx nanohybrids could be attributed to fast electron transport ensured by Mo2CTx with intrinsic conductivity and a large number of hydrogen adsorption sites provided by MoS2 nanoflowers. The synthetic method is promising to tailor the specific properties by preparing organ-like molybdenum carbides coupled with MoS2 nanoflowers.

Journal ArticleDOI
TL;DR: In this paper, the influence of molybdenum tailings on the concrete properties, reinforced concrete columns and concrete-filled steel tubular columns was investigated, and the environmental impact of these structural concrete products with molybin-dimentional tailings was also assessed.

Journal ArticleDOI
TL;DR: Molybdenum in enzymes as catalytic center has chemical adaptability which is valuable to biological systems, in physiological conditions as discussed by the authors, and is used as a catalytic centre in enzymes.
Abstract: Molybdenum in enzymes as catalytic center has chemical adaptability, which is valuable to biological systems, in physiological conditions...

Journal ArticleDOI
TL;DR: In this paper, an amorphous molybdenum sulphide functionalized dipicolyamine exchanger was prepared and ultilised to scavenge toxic heavy metal ions from both synthetic and real acid mine waste water (copper mining industry).

Journal ArticleDOI
TL;DR: In this paper, a room temperture (RT) gas sensor was constructed by means of reactive RF magnetron co-sputtering at 400 °C and the structural, morphology, topography, optical, and electrical characterizations of the prepared sensors were carried out by XRD Rietveld structure refinement analyses.

Journal ArticleDOI
TL;DR: A porous nanoplate composed of small MoP flakes confined in thin N, P, S-triple-doped carbon (MoP@NPSC) was prepared by the assembly of phosphomolybdic acid and egg white and phosphorization to obtain a lamellar hybrid precursor via a hydrogen bond.
Abstract: Molybdenum phosphide is one of the most potential electrocatalysts for the hydrogen evolution reaction (HER), whereas it is still challenging to achieve an efficient molybdenum phosphide-based catalyst that performs well over a wide pH range. Herein, a porous nanoplate composed of small MoP flakes confined in thin N, P, S-triple-doped carbon (MoP@NPSC) was prepared by the assembly of phosphomolybdic acid (H3PMo12O40·nH2O, {PMo12}) and egg white, followed by phosphorization. Given its small size (ca. 1 nm) in favor of deriving small particles and the oxygen-rich surface with strong coordination ability, the {PMo12} cluster was selected to combine with egg white to obtain a lamellar hybrid precursor via a hydrogen bond. Through controllable phosphating, a nanoplate organized by interconnected MoP particles was generated, accompanied by the in situ formation of the N, P, S-doped carbon thin layer and pores from the pyrolysis of egg white. The plentiful pores, thin carbon coating, and multielement doping bring about promoted electrolyte/bubble diffusion, enhanced conductivity and stability, and lowered adsorption energy of hydrogen/hydroxyl, respectively. All of the above merits endow MoP@NPSC with prominent activity with low overpotentials of 50, 76, and 71 mV at 10 mA cm-2 toward the HER in alkaline, neutral, and acid media, respectively, and nearly no attenuation after 40 h of testing. Especially, compared with commercial Pt/C, MoP@NPSC exhibits similar low onset potential and even better at large current density in 1 M KOH. The electrolyzer equipped with the MoP@NPSC cathode and the NiFe-LDH anode requires only 1.52 V to deliver 10 mA cm-2 and can be powered by a solar cell (1.524 V) charged by sunlight.

Journal ArticleDOI
TL;DR: In this article, a composite of zeolite Y type -graphene as a support doped with molybdenum-cobalt and cobalt or nickel (active phase and promoter) was synthesized and evaluated as hydrodesulfurization catalysts.
Abstract: A composite of zeolite Y type -graphene as a support doped with molybdenum-cobalt and molybdenum-nickel (active phase and promoter) was synthesized and evaluated as hydrodesulfurization (HDS) catalysts. The ZGMoCo was found to have the ability to reduce the sulfur content by ≈98 % after a 5 h reaction time which is higher compared to the ZMoCo or ZMoNi. This activity can be ascribed to the improved surface area and better distribution of the active phases (molybdenum and cobalt or nickel) on the zeolite Y type -graphene surface. SEM images showed enhanced dispersion of the active phases on the support surface. As per the BET measurements, the surface area was improved due to the introduction of graphene to be 323.6 m2/g ZGMoCo compared to 257.3 m2/g ZMoCo; and 312.5 m2/g for ZGMoNi compared to 245.7 m2/g for ZMoNi. The work offers a convenient approach to prepare an effective HDS catalyst.

Journal ArticleDOI
TL;DR: In this paper, the surface structure characteristics of drinking water treatment residuals before and after activation were investigated, and the effects of different factors on molybdenum(VI) adsorption and the adsorsption mechanism were also analyzed.

Journal ArticleDOI
TL;DR: The most highly resolved structure of vanadium nitrogenase to date is reported at 1.0 Å resolution, with CO bound to the active site cofactor after catalytic turnover, in a binding mode that is in line with previous reports on the CO complex of molybdenum nitrogenase.
Abstract: Nitrogenases reduce N2 , the most abundant element in Earth's atmosphere that is otherwise resistant to chemical conversions due to its stable triple bond. Vanadium nitrogenase stands out in that it additionally processes carbon monoxide, a known inhibitor of the reduction of all substrates other than H+ . The reduction of CO leads to the formation of hydrocarbon products, holding the potential for biotechnological applications in analogy to the industrial Fischer-Tropsch process. Here we report the most highly resolved structure of vanadium nitrogenase to date at 1.0 A resolution, with CO bound to the active site cofactor after catalytic turnover. CO bridges iron ions Fe2 and Fe6, replacing sulfide S2B, in a binding mode that is in line with previous reports on the CO complex of molybdenum nitrogenase. We discuss the structural consequences of continued turnover when CO is removed, which involve the replacement of CO possibly by OH- , the movement of Q176D and K361D , the return of sulfide and the emergence of two additional water molecules that are absent in the CO-bound state.

Reference EntryDOI
21 May 2020
TL;DR: In this article, the authors present a survey of the Molybdenum chemistry and its application in various areas of industry, such as mining, automotive, agriculture, and economic aspects.
Abstract: The article contains sections titled: 1. Introduction 2. Properties 3. Occurrence 3.1. Minerals 3.2. Deposits 4. Production 4.1. Concentration 4.2. Processing of Concentrate 4.3. Recovery from Spent Petroleum Catalysts 4.4. Recovery during Production of Tungsten Ores 4.5. Production of Molybdenum Metal Powder 4.6. Production of Compact Molybdenum Metal 4.7. Processing of Molybdenum 4.8. Molybdenum-Base Alloys 5. Uses 6. Production of Ferromolybdenum 6.1. Ferromolybdenum Grades 6.2. Raw Materials 6.3. Submerged Arc Furnace Carbothermic Reduction 6.4. Metallothermic Reduction 7. Molybdenum Compounds 7.1. Overview of Molybdenum Chemistry 7.2. Molybdenum Oxides 7.3. Molybdenum Chalcogenides 7.4. Molybdenum Halides 7.5. Molybdates, Isopolymolybdates, and Heteropolymolybdates 7.6. Other Molybdenum Compounds 8. Uses of Molybdenum Compounds 8.1. Catalysis 8.2. Lubrication 8.3. Corrosion Inhibition 8.4. Flame Retardancy and Smoke Suppression 8.5. Pigments 8.6. Agriculture 9. Analysis 10. Economic Aspects 11. Environmental Aspects 12. Toxicology and Occupational Health

Journal ArticleDOI
TL;DR: A half-sandwich molybdenum(II) thiolate complex with a η2-MeCN ligand was found to catalyze transfer hydrogenation of nitriles efficiently with ammonia as discussed by the authors.
Abstract: A half-sandwich molybdenum(II) thiolate complex with a η2-MeCN ligand, Cp*Mo(1,2-Ph2PC6H4S)(η2-NCMe) (1(η2-NCMe)), was found to catalyze transfer hydrogenation of nitriles efficiently with ammonia ...

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a transition metal selenide supported on three-dimensional metal foams for water splitting using a simple one-step hydrothermal approach, which achieved a low overpotential of 113mV to achieve the current density of 10 µm−2, and a small Tafel slope of 85.7mV dec−1.

Journal ArticleDOI
Zhiwei Liu1, Han Wei1, Dawei Hu1, Shuling Sun1, Hu Anpeng1, Wang Zhen1, Jia Yanzi1, Xinqiang Zhao1, Qinghe Yang1 
TL;DR: In this paper, a series of NiMo/γ-Al2O3 hydrodesulfurization (HDS) catalysts with different metal-support interactions were first prepared by a conventional impregnation method through changing the calcination temperature.