Mo Doping Research Articles

Role of Mo doping and the interfacial interaction mechanism of Ni-Mo-S electrodes: experimental and computational study.

The metal element doping strategy is often used to optimize the electrode materials of supercapacitors as they can provide rich redox active sites and high conductivity; however, the synergistic effect between different metallic ions and the interfacial interaction mechanism during the energy storage process are still unclear. In this work, Mo-doped Ni-Mo-S (NMS) nanoflowers are prepared by one-step electrodeposition, and the ratios of Ni : Mo are tailored. Dynamics analysis shows that the Mo element occupies a prominent position in the capacitive behavior contribution. Meanwhile, density functional theory (DFT) reveals that Mo doping influences the electronic structure of the NMS materials and their affinity towards OH- in the electrolyte. All the electrodes (NMS-0, NMS-0.5, NMS-1, NMS-2, NMS-3, and NMS-4) exhibit excellent specific capacitance (1640.8, 1665.8, 1456.2, 1414.6, 1515.4 and 1214.6 F g-1, respectively) and good cycling stability (80.8%, 84.5%, 75.4%, 78.2%, 93.1% and 99.6%, respectively) for 5000 cycles. This work proposes an efficient method to synthesize NMS materials and theoretically studies the effect of the Mo element during the energy storage process.

Influence of Mo Doping on Electronic and Magnetic Properties of Monolayer Crx3: A First-Principles Study

Influence of Mo Doping on Electronic and Magnetic Properties of Monolayer Crx3: A First-Principles Study

High Strength and Ductility of an Additively Manufactured Crconi Medium-Entropy Alloy Achieved by Minor Mo Doping

High Strength and Ductility of an Additively Manufactured Crconi Medium-Entropy Alloy Achieved by Minor Mo Doping

High-valence Mo doping for highly promoted water oxidation of NiFe (oxy)hydroxide

The incorporation of high-valence Mo into NiFe (oxy)hydroxide stabilizes the active β-NiOOH phase and facilitates surface intermediate adsorption, thereby reducing the barrier energy and improving catalytic OER performance.

Boosting oxygen evolution by nickel nitrate hydroxide with abundant grain boundaries via segregated high-valence molybdenum

High-valence metal doping and abundant grain boundaries (GBs) have been proved to be effective strategies to promote the oxygen evolution reaction (OER). However, the reasonable design of the two to facilitate OER collaboratively is challenging. Herein, a convenient and novel one-step molten salt decomposition strategy is proposed to fabricate segregated-Mo doped nickle nitrate hydroxide with substantial GBs on MoNi foam (Mo-NNOH@MNF). When processed in molten salt, the Mo species on the conductive substrate migrates unevenly to the surface of Mo-NNOH@MNF, which not only induces the formation of abundant GBs to modulate electronic structure, but also improves the intrinsic activity as high-valence dopants, synergistically elevating OER activity. As verification, the optimized Mo-NNOH@MNF-10h exhibits low overpotential of 150 mV at 10 mA cm−2, which can be attributed to the reduced valence charge transition energy of Ni by high-valence Mo dopant, coupled with the fine-tuning of d-band center bond and corresponding local electron density by induced GBs and Mo doping, as DFT calculations revealed. Moreover, the intrinsic robustness and strong adhesion ensure the long-term stability of 6 h at 500 mA cm−2. This work provides a promising molten salt decomposition approach to synthesize advanced materials with unique structures.

Mo-modified band structure and enhanced photocatalytic properties of tin oxide quantum dots for visible-light driven degradation of antibiotic contaminants

Functional nanomaterials are desirable in the sustainable photocatalytic degradation of antibiotic contaminants, but the development of nanostructured photocatalysts is facing fatal challenges not only in synthesis strategies but also in property control. Herein, a facile synthesis strategy is accomplished by the green synthesis of SnO2 quantum dots (QDs) engineered by Mo modification. The effects of Mo incorporation on the microstructural, compositional, electrical and optical properties are discussed. The electronic band structure of SnO2 QDs is modified by Mo dopants, which reduce the band gap by changing the position of the conduction band edge. The Mo-modified band structure provides the SnO2 QDs with visible-light driven photocatalytic abilities in the removal of antibiotics as emerging organic contaminants. The nanostructured photocatalysts exhibit proficient performances in the degradation of tetracycline hydrochloride. The degradation efficiency is up to 96.5% when the antibiotic concentration is 25 mg/L and the rate constant is 0.033 min−1. The hydroxyl radicals, produced by the oxidation of water, are determined to be the main active species in the photocatalytic process. The valence band edge over 3 eV guarantees the strong oxidizing abilities of photogenerated holes to create highly active hydroxyl radicals for the efficient photocatalytic degradation. First principle calculations based on the density functional theory reveal the mechanism of Mo modification, illustrating that Mo 4d electrons extend the conduction band edge to the Fermi level. The present work provides a green synthesis strategy and mechanism insights for band structure modification of SnO2 QDs as proficient visible-light driven photocatalysts for environmental remediation.

Template synthesis of molybdenum-doped NiFe-layered double hydroxide nanotube as high efficiency electrocatalyst for oxygen evolution reaction

Oxygen evolution reaction (OER) with four proton–electron coupled transfer process is a half-reaction that restricts the development of rechargeable metal-air batteries and water splitting devices, and it is of great significance to develop inexpensive and efficient OER catalysts. Herein, Mo-doped NiFe-layered double hydroxide (Mo–NiFe-LDH) nanotubes are synthesized using a self-sacrificial template method. Benefitting from the unique nanostructure, Mo–NiFe-LDH-2 exhibits a large electrochemical surface area of 63.94 cm2. In addition, a strong electronic interaction occurs between Mo, Fe, and Ni after Mo doping, resulting in highly active Ni3+ sites. Consequently, the Mo–NiFe-LDH-2 shows high OER activity with an overpotential of 317 mV to deliver a current density of 20 mA cm−2 and a small Tafel slope of 44 mV dec−1. This work provides a feasible strategy to develop high efficiency electrocatalysts through transition metal doping and structural regulation.

Metal-organic framework-derived hierarchical flower-like Mo-doped Co3O4 for enhanced triethylamine sensing properties

Metal-organic frameworks (MOFs) derived oxide semiconductors have drawn more and more attention in many fields due to their unique structural merits. Herein, hierarchical flower-like Mo-doped Co3O4 derived Co-MOF has been synthesized through a solvothermal method and following annealing process. The gas sensing measurements show that the sensing properties of Mo-doped Co3O4 sample are far superior than that of pure Co3O4. In particular, 1 at% Mo-doped Co3O4 sample exhibits high response values of 92–50 ppm TEA at 180 °C, which are about 46 times than that of pure Co3O4 sample. In addition, it shows short recovery time (33 s), excellent gas selectivity, good repeatability and long-term stability. The improved gas sensing performance can be ascribed to Mo doping and hierarchical flower-like microstructure.

Creation of Mo active sites on indium oxide microrods for photocatalytic amino acid production

As an n-type semiconductor, In2O3 is considered a promising photocatalyst for producing amino acids using biomass derivatives as precursors. However, similar to other intrinsic semiconductors, In2O3 suffers from poor charge dynamics. Herein, we show the synthesis of Mo-doped In2O3 (Mo-In2O3) with a porous rod-shaped structure through a one-step solvothermal reaction followed by calcination. Under visible-light irradiation, Mo-In2O3 achieves a high conversion rate of 81% for the reaction that transforms lactic acid into alanine with a selectivity of 91%. Spectroscopic techniques and density functional theory calculations reveal that Mo doping introduces defect states slightly below the conduction band of In2O3, which improves the separation of photogenerated electron-hole pairs. In addition, Mo atoms on the surface form extra adsorption and reaction centers that greatly enhance the reaction rate. This work provides insights into the development of transition metal-doped semiconductor photocatalysts to produce amino acids.

Sustainable micro-activation of dissolved oxygen driving pollutant conversion on Mo-enhanced zinc sulfide surface in natural conditions

The activation of inert oxygen (O2) often consumes enormous amounts of energy and resources, which is a global challenge in the field of environmental remediation and fuel cells. Organic pollutants are abundant in electrons and are promising alternative electron donors. Herein, we implement sustainable microactivation of dissolved oxygen (DO) by using the electrons and adsorption energy of pollutants by creating a nonequilibrium microsurface on nanoparticle-integrated molybdenum (Mo) lattice-doped zinc sulfide (ZnS) composites (MZS-1). Organic pollutants were quickly removed by DO microactivation in the MZS-1 system under natural conditions without any additional energy or electron donor. The turnover frequency (TOF, per Mo atom basis) is 5 orders of magnitude higher than those of homogeneous systems. Structural and electronic characterization technologies reveal the change in the crystalline phase (Zn-S-Mo) and the activation of π-electrons on six-membered rings of ZnS after Mo doping, which results in the formation of a nonequilibrium microsurface on MZS-1. This is the key for the strong interfacial interaction and directional electron transfer from pollutants to MZS-1 through the delocalized π-π conjugation effect and from MZS-1 to DO via Zn-S-Mo, as demonstrated by electron paramagnetic resonance (EPR) techniques and density functional theory (DFT) calculations. This process achieves the efficient use of pollutants and the low-energy activation of O2 through the construction of a nonequilibrium microsurface, which shows new significance for water treatment.

Effect of the Thermo-Mechanical Processing on the Impact Toughness of a 12% Cr Martensitic Steel with Co, Cu, W, Mo and Ta Doping

This paper presents the results of an experimental investigation of a 12% Cr steel where a significant increase in Charpy impact toughness and a slight decrease in ductile-brittle transition temperature (DBTT) from 70 °C to 65 °C were obtained through thermo-mechanical processing, including interim hot forging at 1050 °C with long-term annealing at 1000 °C, as compared with conventional heat treatment. At lower temperatures ranging from −20 °C to 25 °C, the value of impact toughness comprised ~40 J cm−2 in the present 12% Cr steel subjected to thermo-mechanical processing. The amount of δ-ferrite decreased to 3.8%, whereas the size of prior austenite grains did not change and comprised about 40–50 μm. The boundaries between δ-ferrite and martensitic laths were decorated by continuous chains of Cr- and W-rich carbides. M23C6 carbides also precipitated along the boundaries of prior austenite grains, packets, blocks and martensitic laths. Thermo-mechanical processing increased the mean size of M23C6 carbides and decreased their number particle densities along the lath boundaries. Moreover, the precipitation of a high number of non-equilibrium V-rich MX particles was induced by hot forging and long-term normalizing at 1000 °C for 24 h.

Controlled moderative sulfidation-fabricated hierarchical heterogeneous nickel sulfides-based electrocatalyst with tripartite Mo doping for efficient oxygen evolution

An electrocatalyst with heterogeneous nanostructure, especially the hierarchical one, generally shows a more competitive activity than that of its single-component counterparts for oxygen evolution reaction (OER), due to the synergistically enhanced kinetics on enriched active sites and reconfigured electronic band structure. Here this work introduces hierarchical heterostructures into a NiMo@NiS/MoS2@Ni3S2/MoOx (NiMoS) composite by one-pot controlled moderative sulfidation. The optimal solvent composition and addition of NaOH enable NiMoS to own loose and porous structures, smaller nanoparticle sizes, optimal phase composition and chemical states of elements, improving the OER activity of NiMoS. To achieve current densities of 50 and 100 mA cm−2, small overpotentials of 275 and 306 mV are required respectively, together with a minor Tafel slope of 58 mV dec−1, which outperforms most reported sulfide catalysts and IrO2. The synergistic effects in the hierarchical heterostructures expose more active sites, adjust the electronic band structure, and enable the fast charge transfer kinetics, which construct an optimized local coordination environment for high OER electrocatalytic activity. Furthermore, the hierarchical heterostructures suppress the distinct lowering of electrical conductivity and collapse of pristine structures resulted from the metal oxidation and synchronous S leaching during OER, yielding competitive catalytic stability.

Design heterostructure of NiS–NiS2 on NiFe layered double hydroxide with Mo doping for efficient overall water splitting

NiFe layered double hydroxide (LDH)-based materials arouse great attention because of their outstanding catalytic activity for oxygen evolution reaction (OER) under alkaline conditions. However, its catalytic activity for hydrogen evolution reaction (HER) under alkaline conditions is relatively poor. Herein, to improve the HER catalytic activity of NiFe LDH under alkaline conditions, we design a heterostructure of NiS and NiS2 on NiFe LDH and successfully achieve Mo element doping. The catalyst named NiFe-LDH@Mo–NiS–NiS2/NF possesses a three-dimensional nano-flower-like structure and shows an outstanding catalytic performance for both HER and OER. Specifically, in 1 M KOH solution, it requires the low overpotentials of 261 and 120 mV to achieve the current density of 50 and 10 mA cm−2 for OER and HER, respectively. Simultaneously, when NiFe-LDH@Mo–NiS2–NiS/NF is used as the bifunctional catalysts, it only needs a low voltage of 1.63 V to achieve a current density of 10 mA cm−2. The outstanding catalytic performance is attributed to its special heterostructure and the synergy between Mo and NiSx, resulting in comparability with most reported non-noble metal-based catalysts. The doping of metal elements and the construction of heterostructures provide new ideas for the structure regulation and performance improvement of bifunctional electrocatalysts.

Molybdenum doped bilayer photoanode nanotubes for enhanced photoelectrochemical water splitting

Conversion of solar energy into hydrogen energy via photoelectrochemical (PEC) water splitting is one of the most promising approaches for generation of clean and sustainable hydrogen energy in order to address the alarming global energy crisis and environmental problems. To achieve superior PEC performance and solar to hydrogen efficiency (STH), identification, synthesis, and development of efficient photoelectrocatalysts with suitable band gap and optoelectronic properties along with high PEC activity and durability is highly imperative. With the aim of improving the performance of our previously reported bilayer photoanode of WO3 and Nb and N co-doped SnO2 nanotubes i.e. WO3-(Sn0.95Nb0.05)O2:N NTs, herein, we report a simple and efficient strategy of molybdenum (Mo) doping into the WO3 lattice to tailor the optoelectronic properties such as band gap, charge transfer resistance, and carrier density, etc. The Mo doped bilayer i.e. (W0.98Mo0.02)O3-(Sn0.95Nb0.05)O2:N revealed a higher light absorption ability with reduced band gap (1.88 eV) in comparison to that of the undoped bilayer (1.94 eV). In addition, Mo incorporation offered improvements in charge carrier density, photocurrent density, with reduction in charge transfer resistance, contributing to a STH (∼3.12%), an applied bias photon-to-current efficiency (ABPE ∼ 8% at 0.4 V), including a carrier density (Nd ∼ 7.26 × 1022 cm−3) superior to that of the undoped bilayer photoanode (STH ∼2%, ABPE ∼ 5.76%, and Nd ∼5.11 × 1022 cm−3, respectively). The substitution of Mo6+ for W6+ in the monoclinic lattice, forming the W–O–Mo bonds altered the band structure, realizing further enchantments in the PEC reaction and charge transfer kinetics. Additionally, doped bilayer photoanode revealed excellent long term PEC stability under illumination, suggesting its robustness for PEC water splitting. The present work herein provides a simple and effective Mo doping approach for generation of high performance photoanodes for PEC water splitting.

Achieving synergistic performance through highly compacted microcrystalline rods induced in Mo doped GeTe based compounds

Among the lead-free thermoelectric material, germanium telluride (GeTe) has been extensively investigated due to its high thermoelectric performance (ZT) in mid-temperature; however, high p-type carrier density (∼1021 cm−3) hinder its suitability for higher ZT. To enhance the thermoelectric performance of the environmentally favorable GeTe, we explored the Mo doping significantly optimizes the carrier concentration along with uniquely unveiled microcrystalline rods accompanying compact grain boundaries, high-density planar defects, and point defects effectuating all-frequency phonon scattering yields to lower down the thermal conductivity. Furthermore, Sb/Bi co-doping with Mo at the Ge sites predominantly reduces the carrier concentration and thermal conductivity to attain a higher ZT. The co-doping of Bi manifested a more prominent role in achieving the highest ZT of ∼2.3 at 673 K for the sample composition with Ge0.89Mo0·01Bi0.1Te. This study demonstrates an exciting hidden aspect of microstructural modification by forming highly dense microcrystalline rods through Mo doping to achieve high performance in the GeTe system.

Synergy Strategy of Electrical Conductivity Enhancement and Vacancy Introduction for Improving the Performance of VS4 Magnesium-Ion Battery Cathode

The development of cathode materials with a high electric conductivity and a low polarization effect is crucial for enhancing the electrochemical properties of magnesium-ion batteries (MIBs). Herein, Mo doping and nitrogen-doped tubular graphene (N-TG) introduction are carried out for decorating VS4 (Mo-VS4/N-TG) via the one-step hydrothermal method as a freestanding cathode for MIBs. The results of characterizations and density functional theory (DFT) reveal that rich sulfur vacancies are induced by Mo doping, and N-TG as a high conductive skeleton material serves to disperse the active material and forms a tight connection, all of which collectively improved the electrical conductivity of electrode and increased the adsorption energy of Mg2+ (-6.341 eV). Furthermore, the fast reaction kinetics is also confirmed by the galvanostatic intermittent titration technique (GITT) and the pesudocapacitance-like contribution analysis. Benefiting from the synergistic effect of electrical conductivity enhancement and rich vacancy introduction, Mo-VS4/N-TG delivers a steady Mg2+ storage specific capacity of about 140 mAh g-1 at 50 mA g-1, outstanding cycle stability (80.6% capacity retention ratio after 1200 cycles under 500 mA g-1), and excellent rate capability (specific capacity reaches 77.1 mAh g-1 when the current density reaches 500 mA g-1). In addition, the reversible reaction process, intercalation mechanism, and structural stability during the Mg2+ insertion/extraction process are confirmed by a series of ex situ characterizations. This research provides a sustainable and scalable strategy to spur the development of MIBs.

Crystallographic, electronic and magnetic properties of Sr2FeW1-xMoxO6 double perovskite oxides

The structural, electronic and magnetic properties of Sr2FeW1-xMoxO6 with 0 ≤ x ≤ 0.3 are studied. Powder samples have been elaborated using the conventional solid - state reaction at 1300 °C. At room temperature our systems are single phase and crystallized in the tetragonal structure with the P4 space group. The Sr2FeWO6 possesses the metallicity ground state and antiferromagnetic ordering. Sr2FeW0.5Mo0.5O6 possesses the half metallicity ground state and ferromagnetic ordering. The difference energy ΔE between the magnetic configurations EFM and EAFM was calculated for x = 0, x = 0.25 and x = 0.5. The Mo doping in W atom leads to the half metallicity and ferromagnetic behavior. This result is confirmed by experimental. Magnetization measurements and calculations exhibit a paramagnetic-ferromagnetic transition. Sr2FeWO6 is antiferromagnetic at low temperature. The Curie temperature and spontaneous magnetization increase with increasing the value of x. The experiments results obtained are comparable with those obtained by simulations.

Heterojunction photoanode of SnO2 and Mo-doped BiVO4 for boosting photoelectrochemical performance and tetracycline hydrochloride degradation

The photoelectrochemical (PEC) method has a potential to harvest solar energy for sustainable energy and degrade contaminants. Herein, we fabricated cauliflower-like SnO2 and porous Mo-doped BiVO4 (SnO2/Mo:BiVO4) photoelectrodes by a sol-gel spin-coating method for better PEC performance and higher degradability of tetracycline hydrochloride (TC-HCl). The SnO2 layer plays a crucial role in attaining a smooth and uniform surface of the photoanodes for blocking holes to defect trap sites and preventing charge recombination with improved light utilization. Mo dopants serve as nuclei for the crystallization of BiVO4 and for making charge-adjustable porous structures for PEC performance. Thus, the content-optimized SnO2/Mo:BiVO4 photoanode film presents the highest photocurrent density of 0.59 mA cm−2 at 1.23 VRHE of 82.1% TC-HCl decomposition efficiency within 120 min at a rate constant of 1.49 × 10−2 min−1, providing a promising method for green environmental applications.

Visible light photocatalytic degradation of sulfanilamide enhanced by Mo doping of BiOBr nanoflowers

Design of high-efficiency visible light photocatalysts is critical in the degradation of antibiotic pollutants in water, a key step towards environmental remediation. In the present study, Mo-doped BiOBr nanocomposites are prepared hydrothermally at different feed ratios, and display remarkable visible light photocatalytic activity towards the degradation of sulfanilamide, a common antibacterial drug. Among the series, the sample with 2% Mo dopants exhibits the best photocatalytic activity, with a performance 2.3 times better that of undoped BiOBr. This is attributed to Mo doping that narrows the band gap of BiOBr and enhances absorption in the visible region. Additional contributions arise from the unique materials morphology, where the highly exposed (102) crystal planes enrich the photocatalytic active sites, and facilitate the adsorption of sulfanilamide molecules and their eventual attack by free radicals. The reaction mechanism and pathways are then unraveled based on theoretical calculations of the Fukui index and liquid chromatography/mass spectrometry measurements of the reaction intermediates and products. Results from this study indicate that deliberate structural engineering based on heteroatom doping and morphological control may serve as an effective strategy in the design of highly active photocatalysts towards antibiotic degradation.

In-situ Mo doped ZnIn2S4 wrapped MoO3 S-scheme heterojunction via Mo-S bonds to enhance photocatalytic HER

The construction of ZnIn2S4 based heterogeneous structure combined with in-situ relatively metal doping remains a great challenge. A direct Step-scheme (S-scheme) of in-situ Mo doped ZnIn2S4 wrapped MoO3 (MoO3@Mo-ZIS) was prepared in this work based on the thermal solubility properties of MoO3. The optimized photocatalyst of MoO3@Mo-ZIS exhibits superior H2 evolution rate of 5.5 mmol/g/h without co-catalysts, which is the 6.5 and 1.3 times of ZIS and 40 Mo doped ZIS (40 Mo-ZIS), respectively. The excellent photocatalytic activity was attributed to the Mo doping and formation of Mo-S species. The density functional theory (DFT) calculations demonstrate that the Mo-S species would form a new hybridized state near the Fermi level, reducing the ΔGH* to enhance photocatalytic hydrogen evolution reaction (HER). Furthermore, the direct S-scheme heterojunction of MoO3@Mo-ZIS confirmed by Electron paramagnetic resonance (EPR) and Kelvin probe force microscopy (KPFM) promotes photogenerated carrier separation, thus enhancing the performance of photocatalytic HER.