RESUMEN
Graphene is a potential candidate for achieving high-performance and multifunctional polypropylene (PP) composites. However, the complex manufacturing process and low dispersibility of graphene, as well as poor interfacial adhesion between graphene and polypropylene chains, stifle progress on large-scale production and applications of graphene/polypropylene composites. Here, we develop a strategy of maleic anhydride grafted polypropylene (MAPP) latex-assisted graphene exfoliation and melt blending to address the key challenges facing in industrial production. The surface property of the graphitic precursor is well-designed to achieve a high graphene exfoliation yield of â¼100% and induce abundant hydrogen bonding between the obtained mild-oxidized graphene (MOG) sheets and MAPP chains. Therefore, the MAPP-modified MOG can homogeneously disperse in the PP matrix and exhibits an excellent interfacial compatibility with the polymer. The addition of 5 wt % MOG results in simultaneous increase in the initial decomposition temperature, crystallization temperature, tensile strength, and Young's modulus by 43.2, 11.4 °C, 21.5, and 50.7%, respectively, and the electrical conductivity increases to 0.02 S·m-1. This work illustrates a practical solution to low-cost, eco-friendly, and feasible industrial production of graphene/PP composites through synchronous exfoliation and interfacial modification of graphene.
RESUMEN
Transition-metal compounds are attractive for catalysis and other fields but generally suffer from aggregating propensity, circuitous diffusion pathways and limited reaction activities. Two-dimensional (2D) quasi-nanosheets composed of nano-sized crystals with precisely controlled stoichiometric features can readily overcome these problems. We here construct a variety of interconnected 2D holey arrays composed of single-crystal nitrogen-doped nanoparticles through a coordination-driving deposition and sequential etching (CDSE) strategy, independent of the phases and stoichiometries of target crystals. The strong coordination between the empty orbits of metal ions and n-orbits of pyridine nitrogen in conjugated carbon nitride (CN) confines the growth of metal species in 2D form. Meanwhile, the eighteen-membered-rings of CN coupled with metal ions can be thermally etched preferentially as a result of weakened N[double bond, length as m-dash]C bonds caused by forming the TiO2+-N6 configuration. The as-obtained metal oxide quasi-nanosheets and their phosphatized counterparts show impressive activities in photocatalysis and electrocatalysis owing to the synergetic effect of geometric and compositional features. Our CDSE strategy offers a versatile platform, with which to explore the properties and functions of hierarchical architectures.
RESUMEN
The development of Li-S batteries is largely impeded by the complicated shuttle effect of lithium polysulfides (LiPSs) and sluggish reaction kinetics. In addition, the low mass loading/utilization of sulfur is another key factor that makes Li-S batteries difficult to commercialize. Here, a porous catalytic V2O3/V8C7@carbon composite derived from MIL-47 (V) featuring heterostructures is reported to be an efficient polysulfide regulator in Li-S batteries, achieving a substantial increase in sulfur loading while still effectively suppressing the shuttle effect and enhancing kinetics. Systematic mechanism analyses suggest that the LiPSs strongly adsorbed on the V2O3 surface can be rapidly transferred to the V8C7 surface through the built-in interface for subsequent reversible conversion by an efficient catalytic effect, realizing enhanced regulation of LiPSs from capture to conversion. In addition, the porous structure provides sufficient sulfur storage space, enabling the heterostructures to exert full efficacy with a high sulfur loading. Thus, this S-V2O3/V8C7@carbon@graphene cathode exhibits prominent rate performance (587.6 mAh g-1 at 5 C) and a long lifespan (1000 cycles, 0.017% decay per cycle). It can still deliver superior electrochemical performance even with a sulfur loading of 8.1 mg cm-2. These heterostructures can be further applied in pouch cells and produce stable output at different folding angles (0-180°). More crucially, the cells could retain 4.3 mAh cm-2 even after 150 cycles, which is higher than that of commercial lithium-ion batteries (LIBs). This strategy for solving the shuttle effect under high sulfur loading provides a promising solution for the further development of high-performance Li-S batteries.
RESUMEN
Graphene-based thermally conductive polymer composites are of great importance for the removal of the excess heat generated by electronic devices. However, due to the orientation of graphene sheets in the polymer matrix, the through-plane thermal conductivity of polymer/graphene composites remains far from satisfactory. We here demonstrate a confined liquid-phase expansion strategy to fabricate highly oriented confined expanded graphite (CEG) aerogels. After being incorporated into epoxy resin (EP), the resulting EP/CEG composites exhibit a high through-plane thermal conductivity (4.14 ± 0.21 W m-1 K-1) at a quite low filler loading of 1.75 wt % (0.91 vol %), nearly 10 times higher than that of neat EP resin and 7.5 times higher than the in-plane thermal conductivity of the composite, indicating that the CEG aerogel has a high through-plane thermal conductivity enhancement efficiency that outperforms those of many graphite/graphene-based fillers. The facile preparation method holds great industrial application potential in fabricating anisotropic thermally conductive polymer composites.
