Synthesis of microflower-like vacancy defective copper sulfide/reduced graphene oxide composites for highly efficient lithium-ion batteries.

Copper sulfide (CuS) is considered a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical capacity and good electrical conductivity. However, the inferior cycle performance and low coulombic efficiency of CuS caused by structure detoriation and degradation and the 'shuttling effect' of polysulfide intermediates are restricting its practical application. In this work, we report a facile method to generate S vacancies (Vs) in CuS nanoflowers by thermal annealing in Ar. The obtained CuS was composited with reduced graphene oxide (rGO) to prepare an anode for LIBs. The existence of vacancy defects in CuS leads to electron delocalization and excitation, which is responsible for the conductivity improvement and fast charge transport kinetics. Meanwhile, the graphene coating layer ensures fast pathways for Li+ ion diffusion and provides strong physical adsorption of the polysulfides. Furthermore, hierarchical CuS spheres composed of ultrathin nanosheets provide large void spaces to accommodate the volume expansion of CuS. The synthesized composite exhibited a high initial discharge capacity of 882 mAh g-1 and demonstrated stable cyclability along with around 99% coulombic efficiency over 100 cycles. The results of this work reveal that Vs-CuS/rGO composites are promising anodes to enhance the performance of next-generation lithium-ion batteries.

Stability of Sn-Pd-Kaolinite catalyst during heat treatment and nitrate reduction in continuous flow reaction.

In this study, a novel and highly reactive Sn-Pd catalyst supported by environmentally benign kaolinite (Sn-Pd-kaolinite) was developed and evaluated for stability for effective nitrate (NO3-) reduction in batch and continuous mode. Complete NO3- removal with fast reduction kinetics (k = 18.16 × 10-2 min-1) and 71% selectivity toward N2 were achieved by the Sn-Pd-kaolinite catalyst during batch reactions. During continuous tests, 100% NO3- removal and 80% N2 was achieved for 60 h. However, NO3- removal efficiency gradually decreased to 80% in170 h. The catalyst was then successfully regenerated in the system by increasing H2 flow which achieved a complete NO3- removal again. The metal leaching from catalyst surface was negligible (Sn 0.01% and Pd 0.006%) and the structure was stable during the continuous test, confirming that the Sn-Pd-Kaolinite catalyst had a superior reaction kinetics and operational durability.

Biomass Waste Inspired Highly Porous Carbon for High Performance Lithium/Sulfur Batteries.

The synthesis of highly porous carbon (HPC) materials from poplar catkin by KOH chemical activation and hydrothermal carbonization as a conductive additive to a lithium-sulfur cathode is reported. Elemental sulfur was composited with as-prepared HPC through a melt diffusion method to form a S/HPC nanocomposite. Structure and morphology characterization revealed a hierarchically sponge-like structure of HPC with high pore volume (0.62 cm³âˆ™g −1 ) and large specific surface area (1261.7 m²âˆ™g −1 ). When tested in Li/S batteries, the resulting compound demonstrated excellent cycling stability, delivering a second-specific capacity of 1154 mAh∙g −1 as well as presenting 74% retention of value after 100 cycles at 0.1 C. Therefore, the porous structure of HPC plays an important role in enhancing electrochemical properties, which provides conditions for effective charge transfer and effective trapping of soluble polysulfide intermediates, and remarkably improves the electrochemical performance of S/HPC composite cathodes.