Ti3C2 MXene-derived Li4Ti5O12 nanoplates with in-situ formed carbon quantum dots for metal-ion battery anodes.

Two-dimensional (2D) material Ti3C2 MXenes have recently been used in electrode composites for lithium-ion batteries (LIBs) for their excellent electrical conductivity and accordion-like nanosheet morphology. However, Ti3C2 has low specific capacity and fast degradation rate upon cycling after inevitably coupling with surface species during synthesis. In this work, Ti3C2 is used as Ti-source for Li4Ti5O12 (LTO) and C-source for carbon quantum dots (CQDs) in a one-step hydrothermal process. The resultant LTO product (M-LTO) inherits the nanosheet morphology of Ti3C2 with uniformly anchored CQDs. The highly electronic conductive CQDs optimize the transmission path of ions which reduces the diffusion barrier of ions, and they further increase the density of states of the material which effectively improving the conductivity of M-LTO. Remarkable electrochemical performances including high initial specific capacity, long lifetime and excellent low temperature capacity are demonstrated for this type of electrode in LIBs, sodium ion batteries (SIBs) and lithium-magnesium ion hybrid batteries (LMIHBs). This paper offers a new strategy to the rapidly expanding research on the application of transition metal MXenes in electrodes for metal-ion batteries.

Tin Disulfide Nanosheets with Active-Site-Enriched Surface Interfacially Bonded on Reduced Graphene Oxide Sheets as Ultra-Robust Anode for Lithium and Sodium Storage.

Two-dimensional (2D) tin disulfide (SnS2) has attracted intensive research owing to its high specific capacity for Li and Na storage, natural abundance, as well as environmental friendliness. However, the poor reaction kinetics, low intrinsic electrical conductivity, and severe volumetric variation upon cycling processes of SnS2 impede its widespread application. In this work, SnS2 nanosheets with active-site-enriched surface intimately grown on reduced graphene oxide (rGO) via C-O-Sn chemical bonds are prepared. The aligning affords more active sites for electrode reaction and short transport pathways for Li+/Na+ and electrons. The strong chemical bonding enhances the interfacial affinity of SnS2 with rGO and inhibits the detachment of active SnS2 from rGO during repeated charge and discharge processes, which can ensure an integrated electrode structure. The 3D conductive and flexible rGO network improves the conductivity of the entire composite and buffers the volume change of SnS2 upon charge/discharge. These advantages enable the designed SnS2/rGO nanocomposite to have high specific capacity, superior rate capability, and outstanding long-cycling stability for both Li and Na storage.

(101) Plane-Oriented SnS2 Nanoplates with Carbon Coating: A High-Rate and Cycle-Stable Anode Material for Lithium Ion Batteries.

Tin disulfide is considered to be a promising anode material for Li ion batteries because of its high theoretical capacity as well as its natural abundance of sulfur and tin. Practical implementation of tin disulfide is, however, strongly hindered by inferior rate performance and poor cycling stability of unoptimized material. In this work, carbon-encapsulated tin disulfide nanoplates with a (101) plane orientation are prepared via a facile hydrothermal method, using polyethylene glycol as a surfactant to guide the crystal growth orientation, followed by a low-temperature carbon-coating process. Fast lithium ion diffusion channels are abundant and well-exposed on the surface of such obtained tin disulfide nanoplates, while the designed microstructure allows the effective decrease of the Li ion diffusion length in the electrode material. In addition, the outer carbon layer enhances the microscopic electrical conductivity and buffers the volumetric changes of the active particles during cycling. The optimized, carbon coated tin disulfide (101) nanoplates deliver a very high reversible capacity (960 mAh g-1 at a current density of 0.1 A g-1), superior rate capability (796 mAh g-1 at a current density as high as 2 A g-1), and an excellent cycling stability of 0.5 A g-1 for 300 cycles, with only 0.05% capacity decay per cycle.

Preparation of TiOxNy/TiN composites for photocatalytic hydrogen evolution under visible light.

TiOxNy/TiN heterojunction composites with tunable chamber structures were prepared through reduction and nitridation of organotitania obtained via solvothermal alcoholysis at 900 °C for 4 h in partially cracked NH3. Owing to the low synthesis temperature, TiOxNy/TiN duplicates the original structure of organotitania. It also demonstrates an outstanding activity toward hydrogen production as high as 34.9 µmol h(-1) g(-1), which is about 1.5 times higher than the highest value reported in the literature for the TiN material. The enhanced photoactivity can be ascribed to the heterojunction structure, which is beneficial for separating the photogenerated carriers in space.

B-doped 3C-SiC nanowires with a finned microstructure for efficient visible light-driven photocatalytic hydrogen production.

B-doped 3C-SiC nanowires have been synthesized via a facile and simple carbothermal reduction method at 1500 °C for 2 h in a flowing purified argon atmosphere. The obtained nanowires possess a single crystalline and finned microstructure with fins about 100-200 nm in diameter and 10-20 nm in thickness. The diameter of the inner core stem is about 80 nm on average. Due to the smaller band gap, the finned microstructure and the single crystalline nature, the B-doped 3C-SiC nanowires demonstrate efficient activity as high as 108.4 µmol h(-1) g(-1) for H2 production, which is about 20 times higher than that of 3C-SiC nanowhiskers and 2.6 times higher than the highest value reported in the literature for SiC materials.