Constructing MoO2@MoS2 heterostructures anchored on graphene nanosheets as a high-performance anode for sodium ion batteries

Stable Structure and Fast Ion Diffusion: A Flexible MoO2@Carbon Hollow Nanofiber Film as a Binder-Free Anode for Sodium-Ion Batteries with Superior Kinetics and Excellent Rate Capability

Designing innovative anode materials that exhibit excellent ion diffusion kinetics, enhanced structural stability, and superior electrical conductivity is imperative for advancing the rapid charge-discharge performance and widespread application of sodium-ion batteries. Hollow-structured materials have received significant attention in electrode design due to their rapid ion diffusion kinetics. Building upon this, we present a high-performance, free-standing MoO2@hollow carbon nanofiber (MoO2@HCNF) electrode, fabricated through facile coaxial electrospinning and subsequent heat treatment. In comparison to MoO2@carbon nanofibers (MoO2@CNFs), the MoO2@HCNF electrode demonstrates superior rate capability, attributed to its larger specific surface area, its higher pseudocapacitance contribution, and the enhanced diffusion kinetics of sodium ions. The discharge capacities of the MoO2@HCNF (MoO2@CNF) electrode at current densities of 0.1, 0.2, 0.5, 1.0, 2.0 and 5.0 A g-1 are 195.55 (155.49), 180.98 (135.20), 163.81 (109.71), 144.05 (90.46), 121.16 (71.21) and 88.90 (44.68) mAh g-1, respectively. Additionally, the diffusion coefficients of sodium ions in the MoO2@HCNFs are 8.74 × 10-12 to 1.37 × 10-12 cm2 s-1, which surpass those of the MoO2@CNFs (6.49 × 10-12 to 9.30 × 10-13 cm2 s-1) during the discharging process. In addition, these prepared electrode materials exhibit outstanding flexibility, which is crucial to the power storage industry and smart wearable devices.

Nanoarchitected graphene/copper oxide nanoparticles/MoS2 ternary thin films as highly efficient electrodes for aqueous sodium-ion batteries

Sodium-ion batteries (SIBs) operating in aqueous electrolyte are an emerging technology that promises to be safer, cheaper, more sustainable and more efficient than their lithium-based counterparts. One of the great challenges associated with this technology is the development of advanced materials with high specific capacity to be used as electrodes. Herein, we describe an ingenious strategy to prepare unprecedented tri-component nanoarchitected thin films with superior performance when applied as anodes in aqueous SIBs. Taking advantage of the broadness and versatility of the liquid-liquid interfacial route, three transparent nanocomposite films comprising graphene, molybdenum sulphide and copper oxide nanoparticles have been prepared. The samples were characterized using several techniques, and the results demonstrated that depending on the specific experimental strategy, different nanoarchitectures are achieved, resulting in different and improved properties. An astonishing capacity of 1377 mA h g-1 at 0.1 A g-1 and a degree of recovery of 100% were observed for the film in which the interactions among the components were optimized. This is among the highest capacity values reported in the literature and demonstrates the potential of these tri-component materials to be used as anodes in aqueous sodium-ion batteries.

Self-supporting network-structured MoS2/heteroatom-doped graphene as superior anode materials for sodium storage

Layered graphene and molybdenum disulfide have outstanding sodium ion storage properties that make them suitable for sodium-ion batteries (SIBs). However, the easy and large-scale preparation of graphene and molybdenum disulfide composites with structural stability and excellent performance face enormous challenges. In this study, a self-supporting network-structured MoS₂/heteroatom-doped graphene (MoS₂/NSGs-G) composite is prepared by a simple and exercisable electrochemical exfoliation followed by a hydrothermal route. In the composite, layered MoS₂ nanosheets and heteroatom-doped graphene nanosheets are intertwined with each other into self-supporting network architecture, which could hold back the aggregation of MoS₂ and graphene effectively. Moreover, the composite possesses enlarged interlayer spacing of graphene and MoS₂, which could contribute to an increase in the reaction sites and ion transport of the composite. Owing to these advantageous structural characteristics and the heteroatomic co-doping of nitrogen and sulfur, MoS₂/NSGs-G demonstrates greatly reversible sodium storage capacity. The measurements revealed that the reversible cycle capacity was 443.9 mA h g^-1 after 250 cycles at 0.5 A g^-1, and the rate capacity was 491.5, 490.5, 453.9, 418.1, 383.8, 333.1, and 294.4 mA h g^-1 at 0.1, 0.2, 0.5, 1, 2, 5 and 10 A g^-1, respectively. Furthermore, the MoS₂/NSGs-G sample displayed lower resistance, dominant pseudocapacitive contribution, and faster sodium ion interface kinetics characteristic. Therefore, this study provides an operable strategy to obtain high-performance anode materials, and MoS₂/NSGs-G with favorable structure and excellent cycle stability has great application potential for SIBs.

One-step preparation of MoOx/ZnS/ZnO composite and its excellent performance in piezocatalytic degradation of Rhodamine B under ultrasonic vibration

This paper synthesized a new type of ternary piezoelectric catalyst MoO_x/ZnS/ZnO (MZZ) by a one-step method. The catalytic degradation of Rhodamine B (RhB) solution (10 µg/g, pH = 7.0) shows that the composite catalyst has excellent piezoelectric catalytic activity under ultrasonic vibration (40 kHz). The piezoelectric degradation rate of the optimal sample reached 0.054 min^-1, which was about 2.5 times that of pure ZnO. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS) technologies were used to analyze the structure, morphology, and interface charge transfer properties of the MZZ piezocatalysts. The results showed that the composite catalyst may have a core-shell structure. ZnS is coated on the surface of ZnO, while MoO_x adheres to the surface of ZnS. This structure endowed MZZ larger specific surface area than ZnO, which benefits the RhB adsorption. More importantly, the formed heterojunction structure between ZnS and ZnO promotes the separation of positive and negative charges induced by the piezoelectric effect. MoO_x species may act as a charge trap to further promote more carriers to participate in the reaction. In addition, MoO_x may also be beneficial in adsorbing dyes. Active species capture experiments show that superoxide radicals and holes are the main active species in piezoelectric catalytic reactions on MZZ catalysts.