Boosting cobalt ditelluride quantum-rods anode materials for excellent potassium-ion storage via hierarchical physicochemical encapsulation

The exploration of anode materials that can store large-sized K-ion to solve the poor kinetics and large volume expansion issues has become the key scientific bottlenecks hindering the development of potassium-ion batteries (PIBs). Herein, ultrafine CoTe₂ quantum rods physiochemically encapsulated by graphene and nitrogen-doped carbon (CoTe₂@rGO@NC) are regarded as anode electrodes for PIBs. Dual physicochemical confinement and quantum size effect not only enhance electrochemical kinetics but also restrain large lattice stress during repeated K-ion insertion/extraction process. Superior electronic conductivity, K-ion adsorption, and diffusion ability can be acquired for CoTe₂@rGO@NC, confirmed through first-principles calculations and kinetics study. K-ion insertion/extraction proceeds via a typical conversion mechanism relying on Co as the redox site, where the robust chemical bond of COCo plays an important role in maintaining the electrode stability. Accordingly, CoTe₂@rGO@NC contributes a high initial capacity of 237.6 mAh·g^-1 at 200 mA·g^-1, a long lifetime over 500 cycles with low-capacity decay of 0.10% per cycle. This research will lay the materials science foundation for the construction of quantum-rod electrodes.

Boosting the zinc ion storage capacity and cycling stability of interlayer-expanded vanadium disulfide through in-situ electrochemical oxidation strategy

Metallic vanadium dichalcogenides with high conductivity and large layer spacing are fantastically potential to be cathode candidates for aqueous zinc ion batteries. However, simply reliance on the reversible Zn²⁺ intercalation/deintercalation process in the layer structure of vanadium dichalcogenides makes it suffer from low specific capacity and limited cycling number. Here we report a facile in-situ electrochemical oxidation strategy to boost the zinc ion storage capacity of interlayer-expanded vanadium disulfide (VS₂·NH₃) hollow spheres with satisfying cyclic stability. The hydrated vanadium oxide (V₂O₅·nH₂O) generated from oxidized VS₂·NH₃, are endowed with reduced nanosheet size and subordinated porous structure, which provides abundant accessible sites and accelerates the zinc ion diffusion process. As a result, the VS₂·NH₃ derived cathode after the electrochemical oxidation process delivers a high reversible capacity of 392 mA h g^-1 at 0.1 A g^-1 and long cyclic stability (110% capacity retention at 3 A g^-1 after 2000 cycles). The efficient oxidation process of VS₂·NH₃ cathode and the storage mechanism in the subsequent cycles are schematically investigated. This work not only reveals the zinc ion storage mechanism of the oxidized VS₂·NH₃ but also sheds light on advanced design for high-performance Zn ion cathode materials.

Possibility of methane conversion into heavier hydrocarbons using nanosecond lasers

Effect of nanosecond lasers on the methane dissociation is experimentally studied by using three different laser wavelengths at 248 nm, 355 nm and 532 nm. C2H2 generation is measured as a major reaction product in experiments and the energy consumptions in production of this component are measured as 5.8 MJ/mol, 3.1 MJ/mol and 69.0 MJ/mol, for 355 nm, 532 nm and 248 nm wavelengths, respectively. The mechanism of conversion and production of new stable hydrocarbons is also theoretically investigated. It is found that in theoretical calculations, the ion-molecule reactions should be included and this leads to a unique approach in proper explanation of the experimental measurements.