Molybdenum-based Oxides Research Articles

Defect engineering synergistically boosts the catalytic activity of Fe-MoOv for highly efficient breast mesh antitumor therapy

The demand for breast mesh with antitumor properties is critical in post-mastectomy breast reconstruction to prevent local tumor recurrence. Molybdenum-based oxide (MoOx) exhibits enzyme-like activities by catalyzing endogenous hydrogen peroxide to produce reactive oxygen species for inducing tumor cell apoptosis. However, its catalytic activity is limited by insufficient active sites. Herein, a defect engineering strategy is proposed to create redox nanozymes with multiple enzymatic activities by incorporating Fe into MoOx (Fe-MoOv). Fe-MoOv is subsequently integrated into polycaprolactone (PCL) to fabricate breast meshes for establishing an enzyme-catalyzed antitumor platform. The doping of Fe into MoOx formed numerous defect sites, including oxygen vacancies (OV) and Fe substitution sites, synergistically boosting the binding capacity and catalytic activity of Fe-MoOv. Density functional theory calculations demonstrated that the outstanding peroxidase-like catalytic activity of Fe-MoOv resulted from the synergy between OV and Fe sites. Additionally, OV contributes to the localized surface plasmon resonance effect, enhancing the photothermal capability of the PCL/Fe-MoOv mesh. Upon near-infrared laser exposure, the catalytic activity of the PCL/Fe-MoOv mesh is further improved, leading to increased generation of reactive oxygen species and enhanced antitumor efficacy, achieving 86.7% tumor cell mortality, a 264% enhancement compared to the PCL/MoOx mesh.

Photo-enhanced electrocatalytic methanol oxidation of carbon black-modified Pt and Mo-based oxide for acidic and basic solutions

Pt nanoparticles were electrodeposited on a molybdenum-based oxide (e.g., molybdenum oxide (MoO3) and bismuth molybdate (Bi2MoO6)) modified carbon black (CB) support to study the enhancement of methanol oxidation in acidic and basic solutions with the assistance of visible light illumination. Morphology studies showed that Bi2MoO6 nanoparticles were initially anchored on the CB matrix with round 2.2 nm Pt nanoparticle decoration, resulting in a large extension of the specific active catalytic surface area (SSA) for Pt/Bi2MoO6/CB. It was found that the Pt/Bi2MoO6/CB composite catalyst offered the highest electrocatalytic activity with visible light support, showing 2 (in an acidic solution) and 18 (in a basic solution) times higher reactivity than the electrodeposited Pt/CB. Moreover, the electrocatalytic activity and stability of the prepared catalyst toward methanol oxidation with the aid of visible light were noticeably improved in both acidic and basic solutions, and the oxidation improvement was greatest in basic solutions. Therefore, the improved oxidation performance of the prepared catalysts was mostly a result of the combination of both photocatalytic and electrocatalytic procedures on Pt-based catalysts with metal oxides, resulting in enhanced catalytic activity and stability for the oxidation of methanol and CO under visible light.

Regeneration of copper catalysts mediated by molybdenum-based oxides

Cu catalysts, known for their unparalleled catalytic capabilities due to their unique electronic structure, have faced inherent challenges in maintaining long-term effectiveness under harsh hydrogenation conditions. Here, we demonstrate a molybdenum-mediated redispersion behavior of Cu under high-temperature oxidation conditions. The oxidized Cu nanoparticles with rich metal-support interfaces tend to dissolve into the MoO3 support upon heating to 600 °C, which facilitates the subsequent regeneration in a reducing atmosphere. A similar redispersion phenomenon is observed for Cu nanoparticles supported on ZnO-modified MoO3. The modification of ZnO significantly improves the performance of the Cu catalyst for CO2 hydrogenation to methanol, with the high activity being well maintained after four repeated oxidation-reduction cycles. In situ spectroscopic and theoretical analyses suggest that the interaction involved in the formation of the copper molybdate-like compound is the driving force for the redispersion of Cu. This method is applicable to various Mo-based oxide supports, offering a practical strategy for the regeneration of sintered Cu particles in hydrogenation applications.

Engineering Ag nanoparticles and amorphous MoOx on three dimensional N-doped carbon networks for enhanced lithium storage performance

Molybdenum-based oxides have been widely investigated as promising material for lithium ion batteries owing to their unique physical and chemical properties as well as the large specific capacities. However, the fast capacity fading and poor cyclability originated from the large volume expansion and the sluggish electrode kinetics still inhibit their practical application. Herein, Ag nanoparticles combined with amorphous MoOx-in-plane nanoconfined on three dimensional N-doped porous carbon networks (3DNC) are designed and synthesized through salt-template strategy accompanied by annealing treatment and hydrothermal method (3DNC-MoOx-Ag). The synergistic effect of Ag nanoparticles and amorphous MoOx can inhibit the “dead volume” and aggregation of the electrode, accommodate the volume change, accelerate the diffusion kinetics during the lithium ion intercalation and de-intercalation processes. As a result, the designed 3DNC-MoOx-Ag delivers prominent cycling stability (834 mAh g−1 after 100 cycles at 200 mA g−1) and excellent rate performance (419 mAh g−1 after 70 cycles at 5000 mA g−1). Even at 5000 mA g−1, a specific capacity as high as 369 mAh g−1 can be achieved after 500 cycles.

Rechargeable Aqueous Lithium-Ion Batteries with Molybdenum-Based Oxides As Negative Electrode Materials

Organic electrolytes used for commercial lithium-ion batteries, like EC or DMC, are flammable, often resulting in causes of fire accidents. In 1994, an aqueous lithium-ion battery using nonflammable water as electrolyte was reported for the first time, and attention has been paid for the improved safety.1 However, the conventional aqueous electrolyte solution has a narrow electrochemical window, and improvement in energy density was, therefore, needed. In recent years, highly concentrated LiTFSA (TFSA; bis(trifluoromethyl-sulfonyl)amide) aqueous solution has been proposed as aqueous electrolyte solutions with a wider electrochemical window.2,3 In this study, we report electrochemical properties of Mo-based oxides as negative electrode materials for aqueous batteries with the concentrated aqueous electrolyte, and 21 mol kg-1 LiTFSA aqueous solution was used as electrolyte. The Mo-based oxide, Li y Nb2/7Mo3/7O2, 4 is used as a negative electrode for aqueous lithium-ion batteries with spinel-type manganese-based oxide, Li1.05Mn1.95O4, as a positive electrode. Charge/discharge curves of full cells, consisting of Li1.05Mn1.95O4 and Li y Nb2/7Mo3/7O2, are shown in Figure 1. For comparison 1 M LiPF6/EC:DMC = 3/7 by volume and 21 mol g-1 LiTFSA/H2O are used as electrolyte solutions. Both cells show good cyclability at a rate of 1000 mA g-1 and are operable as 2 V-class full cells as shown in Figure 1. Capacity retention of both cells for 1000 cycle test is also shown in Figure 2, and the full cell with the concentrated aqueous electrolyte shows comparable reversibility with aprotic electrolyte solution with similar Coulombic efficiently. From these results, we will further discuss the possibility of Mo-based oxide as potential negative electrode materials for aqueous lithium-ion batteries.References(1)Wu Li, J. R. Dahn, D. S. Wainwright, Science, 264, 1115 (1994).(2)Suo, L. et al., Science 350, 938 (2015).(3)Yamada. et al., Nat. Energy, 1, 16129 (2016).(4)Hoshino et al., and N. Yabuuchi, ACS Energy Lett., 2, 733 (2017). Figure 1

A new layered sodium molybdenum oxide anode for full intercalation-type sodium-ion batteries

A new layered Na0.3MoO2 exhibits a reversible capacity of 146 mA h g−1, remarkable cycling stability and good rate capability for sodium half-cells. And a Na0.3MoO2//Na0.8Ni0.4Ti0.6O2 full intercalation-type sodium-ion cell is fabricated and it displays an excellent cycling stability. These results indicate that molybdenum-based oxide is a promising anode material for sodium-ion batteries.