Design and synthesis of NiCo-NiCoO2@C composites with improved lithium storage performance as the anode materials.

The rapid capacity decay severely limits the commercial applications of metal oxide-based electrodes. Exploring innovative materials with enhanced lithium storage performance is urgent and challenging. Herein, we propose a strategy for the synthesis of NiCo-NiCoO2@C composites using layered double hydroxide (LDH) precursors. When used as the anode materials, the composites deliver enhanced capacity throughout the continuous charge-discharge process. In our design, the electrochemically active NiCoO2 nanoparticles pulverize the NiCo phases via a conversion reaction. The NiCo phases can increase capacity by reacting with the Li2O yielded from the conversion of NiCoO2 and participating in the reversible transformation of solid-electrolyte interface (SEI) films, thus ensuring fast charge transfer. Voids that appear with the consumption of NiCo phases can provide abundant channels for Li+ transportation. Carbon matrices can effectively alleviate the stress generated during repeated cycles of expansion and shrinkage. Benefiting from these features, NiCo-NiCoO2@C anode delivers a highly enhanced reversible capacity of 961.6 mAh g-1 after 300 cycles at 200 mA g-1. This LDH-based strategy may be extended to the design and synthesis of various enhanced anode materials for lithium-ion batteries (LIBs).

Rational design of heterointerface between MoO2 and N-doped carbon with tunable electromagnetic interference shielding capacity.

Exploring highly efficient electromagnetic interference (EMI) shielding filler is urgently desired for next-generation wireless communication and integrated electronics. In this regard, a series of heterogeneous MoO2/N-doped carbon (MoO2/NC) nanorods with tunable conductivity have been successfully synthesized by regulating the pyrolysis temperature within 600, 700 and 800 °C. Profiting from the rational design of heterointerface and low-dimensional structure, the MoO2/NC powder achieves stronger EMI shielding capacity with the incremental temperature. It is found that the MoO2/NC-800 nanorods exhibit the optimal average EMI shielding effectiveness (SE) of 57.2 dB at a thickness of ∼0.3 mm in the X band. Meanwhile, the corresponding shielding mechanisms of MoO2/NC nanorods are also elaborately explained. More interestingly, the increase of sintering temperature makes an obvious effect on absorption loss but has little influence on reflection loss, demonstrating that adjusting the pyrolysis temperature is an effective strategy to strengthen the electromagnetic energy dissipation.

Hierarchical porous Co-CoO@NC hollow microspheres with capacity growth by reactivation of solid-electrolyte interface films.

Transition metal oxide (TMO)-based electrodes exhibit increased capacities, yet the mechanism behind the true cause of capacity in such materials remains unclear. Herein, hierarchical porous and hollow Co-CoO@NC spheres assembled by nanorods with refined nanoparticles and amorphous carbon have been synthesized by a two-step annealing approach. A temperature gradient-driven mechanism is revealed for the evolution of the hollow structure. Compared with the solid CoO@NC spheres, the novel hierarchical of Co-CoO@NC can fully utilize the interior active material by exposing both ends of each nanorod into electrolyte. The hollow interior provides extra space for the volume variation, leading to an up-trend capacity of 919.3 mAh g-1 at 200 mA g-1 over 200 cycles. Differential capacity curves disclose that solid electrolyte interface (SEI) films reactivation partly contributes to increasing reversible capacity. The introduction of nanosized Co particles benefits the process by participating in the transformation of SEI components. This study provides a guide for constructing anodic material with exceptional electrochemical performance.

Catalytic graphitization assisted synthesis of Fe3C/Fe/graphitic carbon with advanced pseudocapacitance.

We report an environmentally friendly strategy for the synthesis of Fe3C/Fe/graphitic carbon based on hydrothermal carbonization and graphitization of carbon spheres with potassium ferrate (K2FeO4) at 800 °C. The obtained sample consisting of Fe3C/Fe nanoparticles and graphitic carbon (FC-1-8) delivered an enhanced pseudocapacitance of 428.0 F g-1 at a current density of 1 A g-1. After removal of the Fe3C/Fe electroactive materials, the graphitic carbon (FC-1-8-HCl) possessed a large specific surface area (SSA) up to 2813.6 m2 g-1 with a capacity of 243.3 F g-1 at 1 A g-1, far outweighing the other amorphous carbon electrodes of FC-0-8 (carbon spheres annealed at 800 °C without the treatment of K2FeO4). The graphitic material with a porous structure could offer more electroactive sites and improved conductivity of the sample. This method provided guidelines for the synthesis of superior performance supercapacitors with synchronous graphitic carbon and electroactive species.

Eu3+-doped layered gadolinium hydroxides as drug carriers and their bactericidal behavior.

Layered rare earth hydroxides (LRHs) due to outstanding photoluminescence (PL) properties and anion exchangeability are extensively reported in multiple fields. In this work, the drug-loaded and bactericidal behaviors of Eu3+-doped layered gadolinium hydroxides (LGdHs:Eu) as optical carriers were explored through intercalation and release of cephalexin (CE). In the intercalation state, the PL intensity of CE--LGdHs:Eu obviously decreased because of the quenching effect of CE-. And the PL intensity of LGdHs:Eu was restored with the release of CE- ions in phosphate buffer solutions (PBS). A significant functional relationship between the drug releasing amount and PL intensity ratio was found, providing a novel optical method to specify the drug dosage. And CE--LGdHs:Eu showed the excellent bactericidal properties in both in vivo and in vitro experiments.

Soft-chemistry synthesis, solubility and interlayer spacing of carbon nano-onions.

Carbon nano-onions (CNOs), as one of the allotropes of carbon, have attracted great attention because of their excellent performance in many fields, especially in capacitors. Developing soft-chemistry synthesis methods is critically of importance, while the forming mechanism in this area is not clear. In this paper, we present a critical review of CNOs regarding the structure, especially interlayer spacing, and synthesis processes, elaborating the recent progress on soft-chemistry methods. Hansen solubility parameter theory is applied to predict and regulate the solubility of CNOs. This article would be inspirational and give new insights into understanding the formation and properties of CNOs.

Hydrothermal Synthesis of Carbon Nano-Onions from Citric Acid.

Carbon nano-onions with concentric fullerene-like carbon shells were synthesized by hydrothermal carbonization of citric acids at 180 °C and formed through the intermediates of graphene quantum dots, graphitic nano-sheets and graphitic hollow polyhedrons. The graphene quantum dots were firstly formed by the dehydration of citric acids and then grew and stacked into graphitic nano-sheets, which curved into graphitic hollow polyhedrons due to the interface energy. The graphitic hollow polyhedrons eventually transformed into spherical carbon nano-onions with the lowest interface energy in the hydrothermal solution by disordering and rearrangement of the carbon shell.

Excellent Microwave Absorption and Electromagnetic Interference Shielding Based on Reduced Graphene Oxide@MoS2 /Poly(Vinylidene Fluoride) Composites.

Reduced graphene oxide (rGO)@MoS2 composites with a loose structure were prepared and added to poly(vinylidene fluoride) (PVDF) to form composites that showed superior microwave absorption and excellent electromagnetic interference shielding performances. The maximum reflection loss of the rGO@MoS2 /PVDF composites, with a low filling rate (only 5.0 wt %), can reach -43.1 dB at 14.48 GHz, and the frequency bandwidth below -10 dB is 3.6-17.8 GHz (in the frequency range of 2-18 GHz) with a thickness of 1-5 mm. Furthermore, rGO@MoS2 /PVDF composites with a higher filling rate (25 wt %) also exhibit outstanding electromagnetic interference shielding effectiveness, reaching a maximum at 27.9 dB. The mechanism of enhanced absorption and electromagnetic interference shielding performances were also studied in detail.