Jingyu Sun

Facile fabrication of novel BiVO4/Bi2S3/MoS2 n-p heterojunction with enhanced photocatalytic activities towards pollutant degradation under natural sunlight

The novel three-component BiVO4/Bi2S3/MoS2 heterojunction was successfully fabricated through a facile in-situ hydrothermal method based on the formation of the intermediate Bi2S3 by coupling BiVO4 and MoS2 precursor. The Bi2S3 was easily formed attributing to the strong interaction between Bi3+and S2- ions with the aid of the hydrothermal reaction. The photocatalytic performances of samples were systematically investigated via the photocatalytic degradation of Rhodamine B (RhB), methylene blue (MB) and malachite green (MG) under solar light irradiation. As a result, the photocatalytic degradation rate of BM-10 for RhB, MB and MG are 97%, 93% and 94%, respectively. The enhanced photocatalytic activities could be due to the suppression of charge recombination and the enhanced the visible light absorption of BiVO4/Bi2S3/MoS2 heterojunction.

Rational and green synthesis of novel two-dimensional WS2/MoS2 heterojunction via direct exfoliation in ethanol-water targeting advanced visible-light-responsive photocatalytic performance

Two-dimensional transition metal dichalcogenides (2D TMDs) and their heterostructures have by far stimulated growing research interests in the field of optoelectronics and photocatalysis. In this regard, scalable fabrication of 2D TMDs at an environmentally-benign and cost-effective manner via liquid phase exfoliation is a particularly fascinating concept. Herein we report a facile and green strategy to produce few-layered WS2 suspensions at a large scale by a direct exfoliation of commercial WS2 powders in water-ethanol mixtures. In turn, by making full use of the features of 2D layered WS2, a novel 2D WS2/MoS2 composite was constructed for the first time via an in-situ hydrothermal reaction to grow MoS2 nanoflakes onto few-layered WS2 basal planes. The as-obtained WS2/MoS2 heterostructure was investigated for photocatalytic applications. Such a hybrid material demonstrated superior photocatalytic activity in the photocatalysis of organic dye molecules relative to that of pristine 2D WS2, MoS2 and their physical mixtures. This enhancement was associated with the 2D WS2/MoS2 heterostructuring effect. In addition, comparisons of the photocatalytic performances of our heterojunctions with those of recently reported 2D TMD-based hybrid materials manifested a significantly higher efficiency.

Synchronous immobilization and conversion of polysulfides on a VO2–VN binary host targeting high sulfur load Li–S batteries

Lithium–sulfur (Li–S) batteries are deemed as one of the most promising next-generation energy storage systems. However, their practical application is hindered by existing drawbacks such as poor cycling life and low Coulombic efficiency due to the shuttle effect of lithium polysulfides (LiPSs). We herein present an in situ constructed VO2–VN binary host which combines the merits of ultrafast anchoring (VO2) with electronic conducting (VN) to accomplish smooth immobilization–diffusion–conversion of LiPSs. Such synchronous advantages have effectively alleviated the polysulfide shuttling, promoted the redox kinetics, and hence improved the electrochemical performance of Li–S batteries. As a result, the sulfur cathode based on the VO2–VN/graphene host exhibited an impressive rate capability with ∼1105 and 935 mA h g−1 at 1C and 2C, respectively, and maintained long-term cyclability with a low capacity decay of 0.06% per cycle within 800 cycles at 2C. More remarkably, favorable cyclic stability can be attained with a high sulfur loading (13.2 mg cm−2). Even at an elevated temperature (50 °C), the cathodes still delivered superior rate capacity. Our work emphasizes the importance of immobilization–diffusion–conversion of LiPSs toward the rational design of high-load and long-life Li–S batteries.

Switching Vertical to Horizontal Graphene Growth Using Faraday Cage‐Assisted PECVD Approach for High‐Performance Transparent Heating Device

Plasma-enhanced chemical vapor deposition (PECVD) is an applicable route to achieve low-temperature growth of graphene, typically shaped like vertical nanowalls. However, for transparent electronic applications, the rich exposed edges and high specific surface area of vertical graphene (VG) nanowalls can enhance the carrier scattering and light absorption, resulting in high sheet resistance and low transmittance. Thus, the synthesis of laid-down graphene (LG) is imperative. Here, a Faraday cage is designed to switch graphene growth in PECVD from the vertical to the horizontal direction by weakening ion bombardment and shielding electric field. Consequently, laid-down graphene is synthesized on low-softening-point soda-lime glass (6 cm × 10 cm) at ≈580 °C. This is hardly realized through the conventional PECVD or the thermal chemical vapor deposition methods with the necessity of high growth temperature (1000 °C-1600 °C). Laid-down graphene glass has higher transparency, lower sheet resistance, and much improved macroscopic uniformity when compare to its vertical graphene counterpart and it performs better in transparent heating devices. This will inspire the next-generation applications in low-cost transparent electronics.

Vanadium Dioxide-Graphene Composite with Ultrafast Anchoring Behavior of Polysulfides for Lithium–Sulfur Batteries

The lithium-sulfur (Li-S) battery has been deemed as one of the most promising energy-storage systems owing to its high energy density, low cost, and environmental benignancy. However, the capacity decay and kinetic sluggishness stemming from polysulfide shuttle effects have by far posed a great challenge to practical performance. We herein demonstrate the employment of low-cost, wet-chemistry-derived VO2 nanobelts as the effective host additives for the graphene-based sulfur cathode. The VO2 nanobelts displayed an ultrafast anchoring behavior of polysulfides, managing to completely decolor the polysulfide solution in 50 s. Such a fast and strong anchoring ability of VO2 was further investigated and verified by experimental and theoretical investigations. Benefitting from the synergistic effect exerted by VO2 in terms of chemical confinement and catalytic conversion of polysulfides, the Li-S batteries incorporating VO2 and graphene manifested excellent cycling and rate performances. Notably, the batteries delivered an initial discharge capacity of 1405 mAh g-1 when cycling at 0.2 C, showed an advanced rate performance of ∼830 mAh g-1 at 2 C, and maintained a stable cycling performance at high current densities of 1, 2, and 5 C over 200 cycles, paving a practical route toward cost-effective and environmentally benign cathode design for high-energy Li-S batteries.

Caging Nb2O5 Nanowires in PECVD-Derived Graphene Capsules toward Bendable Sodium-Ion Hybrid Supercapacitors

Sodium-ion hybrid supercapacitors (Na-HSCs) by virtue of synergizing the merits of batteries and supercapacitors have attracted considerable attention for high-energy and high-power energy-storage applications. Orthorhombic Nb2 O5 (T-Nb2 O5 ) has recently been recognized as a promising anode material for Na-HSCs due to its typical pseudocapacitive feature, but it suffers from intrinsically low electrical conductivity. Reasonably high electrochemical performance of T-Nb2 O5 -based electrodes could merely be gained to date when sufficient carbon content was introduced. In addition, flexible Na-HSC devices have scarcely been demonstrated by far. Herein, an in situ encapsulation strategy is devised to directly grow ultrathin graphene shells over T-Nb2 O5 nanowires (denoted as Gr-Nb2 O5 composites) by plasma-enhanced chemical vapor deposition, targeting a highly conductive anode material for Na-HSCs. The few-layered graphene capsules with ample topological defects would enable facile electron and Na+ ion transport, guaranteeing rapid pseudocapacitive processes at the Nb2 O5 /electrolyte interface. The Na-HSC full-cell comprising a Gr-Nb2 O5 anode and an activated carbon cathode delivers high energy/power densities (112.9 Wh kg-1 /80.1 W kg-1 and 62.2 Wh kg-1 /5330 W kg-1 ), outperforming those of recently reported Na-HSC counterparts. Proof-of-concept Na-HSC devices with favorable mechanical robustness manifest stable electrochemical performances under different bending conditions and after various bending-release cycles.