Facile synthesis of defect-rich interfacial Mo/MoO2 for efficient peroxymonosulfate activation and refractory pollutants degradation.

Peroxymonosulfate-based advanced oxidation process (PMS-AOP) has shown great potential in sewage purification, and catalyst development capable of efficient PMS activation is a key while challenging element. Herein we reported a facile electro-explosive route to synthesize the oxygen vacancy (Vo)-enriched Mo/MoO2 without using chemical reagents. The detailed studies suggested that the synergy of Mo active site and Vo in the catalyst significantly boosted the activation kinetics of PMS. Evidently, the Mo site of different oxidation states contributed to chemical activation of PMS, while the Vo favored the activation of PMS and the generation of non-radical 1O2 species. As a result, the Mo/MoO2-10 h/PMS system delivered a complete removal of acid orange 7 (AO7) within 4 min, significantly exceeding the activity of Mo/PMS (16%), MoO2-H/PMS (25%) and most of other PMS-based systems. Moreover, the current system showed high potential for removal of different pollutants including antibiotics and organic dyes. Radical quenching experiments and electron paramagnetic resonance (EPR) studies revealed that the 1O2 species was significant for AO7 decomposition. This work provided a novel strategy to a batch-scale synthesis of high-performance PMS activator for water remediation in practice.

Controlled Fabrication of Metallic MoO2 Nanosheets towards High-Performance p-Type 2D Transistors.

Two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDCs) are extensively employed as channel materials in advanced electronic devices. The electrical contacts between electrodes and 2D semiconductors play a crucial role in the development of high-performance transistors. While numerous strategies for electrode interface engineering have been proposed to enhance the performance of n-type 2D transistors, upgrading p-type ones in a similar manner remains a challenge. In this work, significant improvements in a p-type WSe2 transistor are demonstrated by utilizing metallic MoO2 nanosheets as the electrode contact, which are controllably fabricated through physical vapor deposition and subsequent annealing. The MoO2 nanosheets exhibit an exceptional electrical conductivity of 8.4 × 104 S m‒1 and a breakdown current density of 3.3 × 106 A cm‒2. The work function of MoO2 nanosheets is determined to be ≈5.1 eV, making them suitable for contacting p-type 2D semiconductors. Employing MoO2 nanosheets as the electrode contact in WSe2 transistors results in a notable increase in the field-effect mobility to 92.0 cm2 V‒1 s‒1, which is one order of magnitude higher than the counterpart devices with conventional electrodes. This study not only introduces an intriguing 2D metal oxide to improve the electrical contact in p-type 2D transistors, but also offers an effective approach to fabricating all-2D devices.

Bifunctional CdS-MoO2 catalysts for selective oxidation of lactic acid coupled with photocatalytic H2 production.

The persistent hurdles of charge rapid recombination, inefficient use of light and utilization of sacrificial reagents have plagued the field of photocatalytic hydrogen evolution (PHE). In this research, tiny MoO2 nanoparticles of 10 nm in diameter were prepared through a straightforward solvothermal approach with a specific ratio of oleylamine and oleic acid as stabilizers. The critical factor in the synthesis process was found to be the ratio of oleylamine to oleic acid. Moreover, a two-phase interface assembly method facilitated the uniform deposition of MoO2 onto CdS nanorods. Due to the localized plasmonic-thermoelectric effect on the surface of MoO2 along with its abundant oxygen vacancies, the composite catalyst exhibited outstanding photo-utilization efficiency and an abundance of active sites. The CdS-MoO2 composite displayed a unique photochemical property in transforming lactic acid into pyruvic acid and generating hydrogen simultaneously. After exposure to artificial sunlight for 4 h, significant values of 4.7 and 3.7 mmol⋅g-1⋅h-1 were achieved for hydrogen production and pyruvic acid formation, respectively, exceeding CdS alone by 3.29 and 4.02-fold, while the selectivity of pyruvic acid was 95.68 %. Furthermore, the S-Scheme electron transport mechanism in the composites was elucidated using Electron Paramagnetic Resonance (EPR) spectroscopy, radical trapping experiments, energy band structure analysis, and the identification of critical intermediates in the process of selective oxidation. This work sheds light on the design and preparation of high-performance photocatalysts for biorefining coupled with efficient hydrogen evolution.

Highly Sensitive Room-Temperature Detection of Ammonia in the Breath of Kidney Disease Patients Using Fe2Mo3O8/MoO2@MoS2 Nanocomposite Gas Sensor.

A novel Fe2Mo3O8/MoO2@MoS2 nanocomposite is synthesized for extremely sensitive detection of NH3 in the breath of kidney disease patients at room temperature. Compared to MoS2, α-Fe2O3/MoS2, and MoO2@MoS2, it shows the optimal gas-sensing performance by optimizing the formation of Fe2Mo3O8 at 900 °C. The annealed Fe2Mo3O8/MoO2@MoS2 nanocomposite (Fe2Mo3O8/MoO2@MoS2-900 °C) sensor demonstrates a remarkably high selectivity of NH3 with a response of 875% to 30 ppm NH3 and an ultralow detection limit of 3.7 ppb. This sensor demonstrates excellent linearity, repeatability, and long-term stability. Furthermore, it effectively differentiates between patients at varying stages of kidney disease through quantitative NH3 measurements. The sensing mechanism is elucidated through the analysis of alterations in X-ray photoelectron spectroscopy (XPS) signals, which is supported by density functional theory (DFT) calculations illustrating the NH3 adsorption and oxidation pathways and their effects on charge transfer, resulting in the conductivity change as the sensing signal. The excellent performance is mainly attributed to the heterojunction among MoS2, MoO2, and Fe2Mo3O8 and the exceptional adsorption and catalytic activity of Fe2Mo3O8/MoO2@MoS2-900 °C for NH3. This research presents a promising new material optimized for detecting NH3 in exhaled breath and a new strategy for the early diagnosis and management of kidney disease.

Observation of Linear Magnetoresistance in MoO2.

Magnetoresistance, the change in resistance with applied magnetic fields, is crucial to the magnetic sensor technology. Linear magnetoresistance has been intensively studied in semimetals and semiconductors. However, the air-stable oxides with a large linear magnetoresistance are highly desirable but remain to be fully explored. In this paper, we report the direct observation of linear magnetoresistance in polycrystalline MoO2 without any sign of saturation up to 7 T under 50 K. Interestingly, the linear magnetoresistance reaches as large as 1500% under 7 T at 2 K. The linear field dependence is in great contrast to the parabolic behavior observed in single-crystal MoO2, probably due to phonon scattering near the grain boundaries. Our results pave the way to comprehending magneto-transport behavior in oxides and their potential applications in magnetic sensors.

Nitrogen and Sulfur Co-Doped Carbon-Coated Ni3S2/MoO2 Nanowires as Bifunctional Catalysts for Alkaline Seawater Electrolysis.

Bifunctional catalysts have inherent advantages in simplifying electrolysis devices and reducing electrolysis costs. Developing efficient and stable bifunctional catalysts is of great significance for industrial hydrogen production. Herein, a bifunctional catalyst, composed of nitrogen and sulfur co-doped carbon-coated trinickel disulfide (Ni3S2)/molybdenum dioxide (MoO2) nanowires (NiMoS@NSC NWs), is developed for seawater electrolysis. The designed NiMoS@NSC exhibited high activity in alkaline electrolyte with only 52 and 191 mV overpotential to attain 10 mA cm-2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Significantly, the electrolyzer (NiMoS@NSC||NiMoS@NSC) based on this bifunctional catalyst drove 100 mA cm-2 at only 1.71 V along with a robust stability over 100 h in alkaline seawater, which is superior to a platinum/nickel-iron layered double hydroxide couple (Pt||NiFe LDH). Theoretical calculations indicated that interfacial interactions between Ni3S2 and MoO2 rearranged the charge at interfaces and endowed Mo sites at the interfaces with Pt-like HER activity, while Ni sites on Ni3S2 surfaces at non-interfaces are the active centers for OER. Meanwhile, theoretical calculations and experimental results also demonstrated that interfacial interactions improved the electrical conductivity, boosting reaction kinetics for both HER and OER. This study presented a novel insight into the design of high-performance bifunctional electrocatalysts for seawater splitting.

Preparation of Progressive Driving Bilayer Polymer-Dispersed Liquid Crystals Possessing a PDLC-PVA-PDLC Structure.

In this paper, the bilayer polymer-dispersed liquid crystals possessing a PDLC-PVA-PDLC structure were prepared by integrating two monolayer PDLCs. The effect of the polymer mesh size on the electro-optical properties of a bilayer PDLC was investigated by comparing the micro-morphology and electro-optical curves under different polymerization conditions. In addition, the impact of doping MoO2 nanoparticles with surface modification on the comprehensive performance of the bilayer PDLC was further researched. The contrast ratio of the bilayer PDLC prepared under the optimal conditions was improved by more than 90% and still maintained excellent progressive driving performance. Therefore, the development of a bilayer PDLC with optimal electro-optical properties will significantly enhance the technological prospects for the application of PDLC-based devices in smart windows, displays, and flexible devices.

Converting formaldehyde in methanol with MoO2 under irradiation: A pollution-free strategy for cleaning air.

Direct photocatalytic reduction of toxic formaldehyde (HCHO) in value-added chemicals and fuels is promising because that not only abates the environmental pollution, but also solves the energy shortage. Herein, self-supported MoO2 and MoO3 nanoparticles growing on Mo meshes were comparatively applied to the photocatalytic conversion of HCHO. Under UV-visble lights, MoO2 reduces HCHO in methanol (CH3OH) while MoO3 oxidizes HCHO in carbon oxide and water. Their contrary photocatalytic capacities were revealed. Compared with MoO3, the lower work function of MoO2 enables an electron-rich interface, realizing a complete reduction of 30 ppm HCHO to CH3OH in 30 min. Theoretical calculations clarify that a large number of delocalized electrons on MoO2 attracts HCHO molecule and activates its CO bond, facilitating subsequent hydrogenation and reduction of HCHO to CH3OH. As for MoO3, the wider bandgap and higher potential of valence band govern the photocatalytic oxidation of HCHO.

Strategically Designed Pd-Induced Changes in Alkaline Hydrogen Evolution Reaction and Oxygen Evolution Reaction Performances of Electrochemical Water Oxidation by the Galvanically Synthesized MoO2/MoO3 Composite Thin Film.

Electrochemical water oxidation is believed to be an effective pathway to produce clean, carbon-free, and environmentally sustainable green energy. In this work, we report a simple, easy-to-construct, facile, low-cost, and single-step galvanic technique to synthesize a Pd-supported temperature-assisted MoOx thin film nanocomposite for effective water oxidation. The most suitable nanocomposite exhibits very low overpotential at 10 mA/cm2 with smaller Tafel slope values for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) processes in an alkaline medium. The formation of a metal oxide-metal junction accelerates the growth of more active sites, promoting induced electronic synergism at the MoOx-Pd interface. This endows higher electrical conductivity and faster electron transfer kinetics, thus accelerating the faster water dissociation reaction following the Tafel-Volmer mechanism to boost the HER process in an alkaline medium. The excellent electrochemical HER and OER performances of our electrocatalyst even supersede the accomplishments of the benchmark catalysts Pt/C and RuO2. Moreover, neither of these two catalysts demonstrates both catalytic reactions, i.e., HER and OER at the same time, which have been observed for our synthesized catalyst. Our findings illustrate the potential of a thin-film MoOx-Pd nanocomposite to be an exceedingly effective electrocatalyst developed by interface engineering strategies. This also provides insight into designing several other semiconductor composite catalysts using simple synthesis techniques for highly efficient HER/OER processes that could be alternatives to benchmark electrocatalysts for water electrolysis.

Understanding How the Suppression of Insertion-Induced Phase Transitions Leads to Fast Charging in Nanoscale LixMoO2.

Fast-charging Li-ion batteries are technologically important for the electrification of transportation and the implementation of grid-scale storage, and additional fundamental understanding of high-rate insertion reactions is necessary to overcome current rate limitations. In particular, phase transformations during ion insertion have been hypothesized to slow charging. Nanoscale materials with modified transformation behavior often show much faster kinetics, but the mechanism for these changes and their specific contribution to fast-charging remain poorly understood. In this work, we combine operando synchrotron X-ray diffraction with electrochemical kinetics analyses to illustrate how nanoscale crystal size leads to suppression of first-order insertion-induced phase transitions and their negative kinetic effects in MoO2, a tunnel structure host material. In electrodes made with micrometer-scale particles, large first-order phase transitions during cycling lower capacity, slow charge storage, and decrease cycle life. In medium-sized nanoporous MoO2, the phase transitions remain first-order, but show a considerably smaller miscibility gap and shorter two-phase coexistence region. Finally, in small MoO2 nanocrystals, the structural evolution during lithiation becomes entirely single-phase/solid-solution. For all nanostructured materials, the changes to the phase transition dynamics lead to dramatic improvements in capacity, rate capability, and cycle life. This work highlights the continuous evolution from a kinetically hindered battery material in bulk form to a fast-charging, pseudocapacitive material through nanoscale size effects. As such, it provides key insight into how phase transitions can be effectively controlled using nanoscale size and emphasizes the importance of these structural dynamics to the fast rate capability observed in nanostructured electrode materials.

Mo2 C-Based Ceramic Electrode with High Stability and Catalytic Activity for Hydrogen Evolution Reaction at High Current Density.

Developing robust electrodes with high catalytic performance is a key step for expanding practical HER (hydrogen evolution reaction) applications. This paper reports on novel porous Mo2 C-based ceramics with oriented finger-like holes directly used as self-supported HER electrodes. Due to the suitable MoO3 sintering additive, high-strength (55 ± 6 MPa) ceramic substrates and a highly active catalytic layer are produced in one step. The in situ reaction between MoO3 and Mo2 C enabled the introduction of O in the Mo2 C crystal lattice and the formation of Mo2 C(O)/MoO2 heterostructures. The optimal Mo2 C-based electrode displayed an overpotential of 333 and 212 mV at 70 °C under a high current intensity of 1500 mA cm-2 in 0.5 m H2 SO4 and 1.0 m KOH, respectively, which are markedly better than the performance of Pt wire electrode; furthermore, its price is three orders of magnitude lower than Pt. The chronopotentiometric curves recorded in the 50 - 1500 mA cm-2 range, confirmed its excellent long-term stability in acidic and alkaline media for more than 260 h. Density functional theory (DFT) calculations showed that the Mo2 C(O)/MoO2 heterostructures has an optimum electronic structure with appropriate *H adsorption-free energy in an acidic medium and minimum water dissociation energy barrier in an alkaline medium.

Synergistically Stabilizing Zinc Anodes by Molybdenum Dioxide Coating and Tween 80 Electrolyte Additive for High-Performance Aqueous Zinc-Ion Batteries.

Recently, aqueous zinc-ion batteries (ZIBs) have become increasingly attractive as grid-scale energy storage solutions due to their safety, low cost, and environmental friendliness. However, severe dendrite growth, self-corrosion, hydrogen evolution, and irreversible side reactions occurring at Zn anodes often cause poor cyclability of ZIBs. This work develops a synergistic strategy to stabilize the Zn anode by introducing a molybdenum dioxide coating layer on Zn (MoO2@Zn) and Tween 80 as an electrolyte additive. Due to the redox capability and high electrical conductivity of MoO2, the coating layer can not only homogenize the surface electric field but also accommodate the Zn2+ concentration field in the vicinity of the Zn anode, thereby regulating Zn2+ ion distribution and inhibiting side reactions. MoO2 coating can also significantly enhance surface hydrophilicity to improve the wetting of electrolyte on the Zn electrode. Meanwhile, Tween 80, a surfactant additive, acts as a corrosion inhibitor, preventing Zn corrosion and regulating Zn2+ ion migration. Their combination can synergistically work to reduce the desolvation energy of hydrated Zn ions and stabilize the Zn anodes. Therefore, the symmetric cells of MoO2@Zn∥MoO2@Zn with optimal 1 mM Tween 80 additive in 1 M ZnSO4 achieve exceptional cyclability over 6000 h at 1 mA cm-2 and stability (>700 h) even at a high current density (5 mA cm-2). When coupling with the VO2 cathode, the full cell of MoO2@Zn∥VO2 shows a higher capacity retention (82.4%) compared to Zn∥VO2 (57.3%) after 1000 cycles at 5 A g-1. This study suggests a synergistic strategy of combining surface modification and electrolyte engineering to design high-performance ZIBs.

Development of Porous MoO2 Pellet Target for 99Mo/99mTc Generator.

Technetium-99m(99mTc) is used worldwide in 85% of nuclear medicine diagnostic imaging procedures. We developed porous MoO2 pellets as an alternative to reactor-based targets in an (n,γ) reaction for producing Technetium-99m (99mTc) in nuclear medicine. The pellets, formed through a manufacturing process involving mixing, sintering, eluting, and drying, offer advantages such as selective dissolution and improved yield. This research offers a potential solution for stable 99mTc production, focusing on porous molybdenum dioxide (MoO2) as a target material due to its insolubility in water. Using potassium molybdate (K2MoO4) as a pore former, we developed porous MoO2 pellets that facilitate efficient technetium extraction and target recycling. This approach offers control over pore formation and shows promise in addressing supply challenges and enhancing 99mTc production.

Highly Uniform Spherical MoO2-MoO3/Polypyrrole Core-Shell Nanocomposite as an Optoelectronic Photodetector in UV, Vis, and IR Domains.

A highly uniform spherical MoO2-MoO3/polypyrrole core-shell nanocomposite has been successfully synthesized as an optoelectronic photon sensing material, capable of detecting light in the UV, Vis, and IR domains. The nanocomposite is prepared through the oxidation of pyrrole using Na2MoO4, resulting in a uniform spherical morphology that has been confirmed by TEM, theoretical modeling, and SEM analyses. This morphology contributes to its promising optical behavior, characterized by a small bandgap of 1.36 eV. The optoelectronic photosensing capability of the nanocomposite has been evaluated across the UV, Vis, and IR spectra, demonstrating high efficiency. The photoresponsivity R values indicate the ability of the nanocomposite to generate hot electrons in response to incident photons. With an R value of 4.15 mA·W-1 at 440 nm, this optoelectronic device exhibits considerable promise for integration into an advanced technological apparatus. The detection (D) value of 9.30 × 108 Jones at 440 nm further confirms the high sensitivity in the Vis region. The excellent stability of the device can be attributed to the inherent MoO2-MoO3 oxide and Ppy polymer materials. This stability has been demonstrated through reproducibility studies and current-voltage measurements under various optical conditions. The combination of stability, efficiency, and sensitivity makes this optoelectronic device well suited for light sensing applications in both industrial and commercial settings. Its promising performance opens up opportunities for advancements in various fields requiring accurate and reliable light detection.

N-doped carbon sheets supported P-Fe3O4-MoO2 for freshwater and seawater electrolysis.

Electric-driven freshwater/seawater splitting is an attractive and sustainable route to realize the generation of H2 and O2. Molybdenum-based oxides exhibit poor activity toward freshwater/seawater electrolysis. Herein, we adjusted the electronic structure of MoO2 by constructing N-doped carbon sheets supported P-Fe3O4-MoO2 nanosheets (P-Fe3O4-MoO2/NC). P-Fe3O4-MoO2/N-doped carbon sheets were precisely prepared by pyrolysis of Schiff base Fe complex and MoO3 nanosheets through phosphorization. Benefiting from the unique structures of the samples, it required 119/145 mV to drive freshwater/seawater reduction reaction at 10 mA/cm2. P-Fe3O4-MoO2/NC catalysts exhibited superior freshwater/seawater oxidation reactivity with 180/189 mV at 10 mA/cm2 compared with commercial RuO2. The low cell voltages for P-Fe3O4-MoO2/NC were 1.47 and 1.59 V towards freshwater and seawater electrolysis, respectively. Our work might shed light on the structural modulation of Mo-based oxides for enhancing freshwater and seawater electrolysis activity.

MoO2 Nanoclusters Embedded in Hierarchical Nitrogen Doped Carbon Nanoflower as Electrocatalytic Mediators in Aqueous Zinc-Tellurium Batteries: Enhancing Electrochemical Kinetics of Tellurium Redox Reaction.

Aqueous zinc-ion batteries (AZIBs) are considered to be one of the most promising devices for large-scale energy storage systems owing to their high theoretical capacity, environmental friendliness, and safety. However, the ionic intercalation or surface redox mechanisms in conventional cathode materials generally result in unsatisfactory capacities. Conversion-type aqueous zinc-tellurium (Zn-Te) batteries have recently gained widespread attention owing to their high theoretical specific capacities. However, it remains an enormous challenge to improve the slow kinetics of the aqueous Zn-Te batteries. Here, MoO2 nanoclusters embedded in hierarchical nitrogen-doped carbon nanoflower (MoO2 /NC) hosts are successfully synthesized and loaded with Te in aqueous Zn-Te batteries. Benefitting from the highly dispersed MoO2 nanoclusters and hierarchical nanoflower structure with a large specific surface area, the electrochemical kinetics of the Te redox reaction are significantly improved. As a result, the Te-MoO2 /NC electrode exhibits superior cycling stability and a high specific capacity of 493 mAh g-1 at 0.1 A g-1 . Meanwhile, the conversion mechanism is systematically explored using a variety of ex situ characterization methods. Therefore, this study provides a novel approach for enhancing the kinetics of the Te redox reaction in aqueous Zn-Te batteries.

Construction of Ni4Mo/MoO2 heterostructure on oxygen vacancy enriched NiMoO4 nanorods as an efficient bifunctional electrocatalyst for overall water splitting.

Despite great efforts over the past decade, rational design of bifunctional electrocatalysts with low cost and high efficiency still remains a challenge to achieve industrial water splitting. Herein, we synthesized the nickel-molybdenum nanorod array catalyst supported on NF (NMO@NM/MO) by a two-step process of hydrothermal and reductive annealing. Partial reduction of the NiMoO4 induces the structural reconstruction and formation of the Ni4Mo/MoO2 heterostructure on oxygen vacancy enriched nanorod, which bring out sufficient active sites, large specific surface area and favorable interfacial charge transfer. Thanks to the unique core-shell structure with the heterostructured Ni4Mo/MoO2 surface and defect-rich NiMoO4 core, the obtained electrocatalyst shows greatly improved hydrogen evolution reaction (HER) activity with an ultralow overpotential of 63 mV at 100 mA cm-2 (vs. 314 mV for the NiMoO4). Density function theory calculations reveal that the construction of the Ni4Mo/MoO2 heterostructure effectively accelerates H2O dissociation kinetics, while the defective NiMoO4 facilitates H* adsorption/desorption. Moreover, the heterostructure catalyst also displays excellent oxygen evolution reaction (OER) performance with the low overpotential of 274 mV at 100 mA cm-2. When coupling HER and OER by using NMO@NM/MO as both the cathode and anode, the alkaline electrolyzer delivers a current density of 10 mA cm-2 at only 1.50 V as well as good robustness. The synergistic effect of the hetero-interface and the defect engineering endows the electrocatalyst with excellent bifunctional catalytic activity for HER and OER. This work may provide a route for rational design of heterostructure electrocatalysts with multiple active components.

CVD Synthesis of MoS2 Using a Direct MoO2 Precursor: A Study on the Effects of Growth Temperature on Precursor Diffusion and Morphology Evolutions.

In this study, the influence of growth temperature variation on the synthesis of MoS2 using a direct MoO2 precursor was investigated. The research showed that the growth temperature had a strong impact on the resulting morphologies. Below 650 °C, no nucleation or growth of MoS2 occurred. The optimal growth temperature for producing continuous MoS2 films without intermediate-state formation was approximately 760 °C. However, when the growth temperatures exceeded 800 °C, a transition from pure MoS2 to predominantly intermediate states was observed. This was attributed to enhanced diffusion of the precursor at higher temperatures, which reduced the local S:Mo ratio. The diffusion equation was analyzed, showing how the diffusion coefficient, diffusion length, and concentration gradients varied with temperature, consistent with the experimental observations. This study also investigated the impact of increasing the MoO2 precursor amount, resulting in the formation of multilayer MoS2 domains at the outermost growth zones. These findings provide valuable insights into the growth criteria for the effective synthesis of clean and large-area MoS2, thereby facilitating its application in semiconductors and related industries.

Constructing Hierarchical Porous MoO2 @Mo2 N@C Composite via a Confined Pyrolysis Synthetic Strategy Towards Lithium-Ion Battery Anodes.

Molybdenum dioxide (MoO2 ) demonstrates a big potential toward lithium-ion storage due to its high theoretical capacity. The sluggish reaction kinetics and large volume change during cycling process, however, unavoidably lead to inferior electrochemical performance, thus failing to satisfy the requirements of practical applications. Herein, we developed a molybdenum-based oxyacid salt confined pyrolysis strategy to achieve a novel hierarchical porous MoO2 @Mo2 N@C composite. A two-step successive annealing process was proposed to obtain a hybrid phase of MoO2 and Mo2 N, which was used to further improve the electrochemical performance of MoO2 -based anode. We demonstrate that the well-dispersed MoO2 nanoparticles can ensure ample active sites exposure to the electrolyte, while conductive Mo2 N quantum dots afford pseudo-capacitive response, which conduces to the migration of ions and electrons. Additionally, the interior voids could provide buffer spaces to surmount the effect of volume change, thereby avoiding the fracture of MoO2 nanoparticles. Benefiting from the aforesaid synergies, the as-obtained MoO2 @Mo2 N@C electrode demonstrates a striking initial discharge capacity (1760.0 mAh g-1 at 0.1 A g-1 ) and decent long-term cycling stability (652.5 mAh g-1 at 1.0 A g-1 ). This work provides a new way for the construction of advanced anode materials for lithium-ion batteries.

Preparation and Photocatalytic Performance of MoS2/MoO2 Composite Catalyst.

Solar energy is an inexhaustible clean energy providing a key solution to the dual challenges of energy and environmental crises. Graphite-like layered molybdenum disulfide (MoS2) is a promising photocatalytic material with three different crystal structures, 1T, 2H and 3R, each with distinct photoelectric properties. In this paper, 1T-MoS2 and 2H-MoS2, which are widely used in photocatalytic hydrogen evolution, were combined with MoO2 to form composite catalysts using a bottom-up one-step hydrothermal method. The microstructure and morphology of the composite catalysts were studied by XRD, SEM, BET, XPS and EIS. The prepared catalysts were used in the photocatalytic hydrogen evolution of formic acid. The results show that MoS2/MoO2 composite catalysts have an excellent catalytic effect on hydrogen evolution from formic acid. By analyzing the photocatalytic hydrogen production performance of composite catalysts, it suggests that the properties of MoS2 composite catalysts with different polymorphs are distinct, and different content of MoO2 also bring differences. Among the composite catalysts, 2H-MoS2/MoO2 composite catalysts with 48% MoO2 content show the best performance. The hydrogen yield is 960 µmol/h, which is 1.2 times pure 2H-MoS2 and two times pure MoO2. The hydrogen selectivity reaches 75%, which is 22% times higher than that of pure 2H-MoS2 and 30% higher than that of MoO2. The excellent performance of the 2H-MoS2/MoO2 composite catalyst is mainly due to the formation of the heterogeneous structure between MoS2 and MoO2, which improves the migration of photogenerated carriers and reduces the possibilities of recombination through the internal electric field. MoS2/MoO2 composite catalyst provides a cheap and efficient solution for photocatalytic hydrogen production from formic acid.