Unzipped Multiwalled Carbon Nanotube Oxide/Multiwalled Carbon Nanotube Hybrids for Polymer Reinforcement

Multiwalled carbon nanotubes (MWNTs) have been widely used as nanofillers for polymer reinforcement. However, it has been restricted by the limited available interface area of MWNTs in the polymer matrices. Oxidation unzipping of MWNTs is an effective way to solve this problem. The unzipped multiwalled carbon nanotube oxides (UMCNOs) exhibit excellent enhancement effect with low weight fractions, but agglomeration of UMCNOs at a relatively higher loading still hampered the mechanical reinforcement of polymer composites. In this paper, we interestingly found that the dispersion of UMCNOs in polymer matrices can be significantly improved with the combination of pristine MWNTs. The hybrids of MWNTs and UMCNOs (U/Ms) can be easily obtained by adding the pristine MWNTs into the UMCNOs aqueous dispersion, followed by sonication. With a π-stacking interaction, the UMCNOs were attached onto the outwalls of MWNTs. The morphologies and structure of the U/Ms were characterized by several measurements. The mechanical testing of the resultant poly­(vinyl alcohol) (PVA)-based composites demonstrated that the U/Ms can be used as ideal reinforcing fillers. Compared to PVA, the yield strength and Young’s modulus of U/M–PVA composites with a loading of 0.7 wt % of the U/Ms approached ∼145.8 MPa and 6.9 GPa, respectively, which are increases of ∼107.4% and ∼122.5%, respectively. The results of tensile tests demonstrated that the reinforcement effect of U/Ms is superior to the individual UMCNOs and MWNTs, because of the synergistic interaction of UMCNOs and MWNTs

Synergistically Constructed Electromagnetic Network of Magnetic Particle-Decorated Carbon Nanotubes and MXene for Efficient Electromagnetic Shielding

Lightweight polymer-based nanostructured aerogels are crucial for electromagnetic interference (EMI) shielding to protect electronic devices and humans from electromagnetic radiation. The construction of three-dimensional (3D) conductive networks is crucial to realize the excellent electromagnetic shielding performance of polymer-based aerogels. However, it is difficult to realize the interconnection of different conductive fillers in the polymer matrix, which limits the further improvement of their performance. Herein, 3D ordered hierarchical porous Fe3O4-decorated carbon nanotube (Fe3O4@CNT)/MXene/cross-linked aramid nanofiber (c-ANF)/polyimide (PI) aerogels were prepared via a unidirectional freezing strategy. Benefiting from the magnetic loss effect of Fe3O4 magnetic nanoparticles, the conductive and dielectric loss effects of CNTs, and the multiple reflections induced by the 3D ordered hierarchical porous structure, the Fe3O4@CNTs/MXene/c-ANFs/PI (FMCP) aerogels with the same contents of 8 wt % of Fe3O4@CNTs and MXene exhibit a high absolute EMI shielding effectiveness (SE) of up to 67.42 dB and a microwave reflection (SER) of 0.60 dB. More importantly, the phase transition of a small amount of MXene to TiO2 optimizes the impedance matching and transmission and then improves the microwave absorption. The FMCP aerogel has an outstanding normalized surface specific SE (SSE/t) which is up to 62,654 dB cm2·g–1. Meantime, the FMCP aerogels also show super-elasticity and could maintain 91.72% of the maximum stress after 1000 cycles of compression release under a fixed deformation of 60%

Reactive Aramid Nanofiber-Reinforced Polyvinyl-Alcohol-Based Solid Polymer Electrolyte for High-Performance Li Metal Batteries

Solid polymer electrolytes (SPEs) with high ionic conductivity and strong mechanical properties are preconditions for the stable cycling of high-performance Li metal batteries. However, single-polymer SPEs often have low ionic conductivity, which greatly limits their further application. Herein, a SPE composed of polyvinyl alcohol (PVA), reactive aramid nanofibers (RANFs), and lithium bistrifluoromethanesulfonimide (LiTFSI) is prepared using a simple solution-casting method. After introducing the RANFs, the SPE of RANFs/PVA-containing LiTFSI not only exhibits high mechanical properties but also has good thermal stability. The RANFs/PVA SPE constructed from the strong hydrogen bond interaction between rigid RANFs and flexible PVA shows high migration efficiency of lithium ions. When the loading amount of RANFs is 2 wt %, the ionic conductivity of RANFs/PVA reaches ∼7.7 × 10 –4 S·cm–1, and the lithium-ion migration number is ∼0.54 at 60 °C. Toward the Li|RANFs/PVA-2 wt %|LiFePO4 full cell, the discharge specific capacity could reach 162.5 mA h·g–1 at 60 °C and 0.1 C. Meanwhile, the Li|RANFs/PVA-2 wt %|LiFePO4 battery also shows outstanding long-term cycling performance and could maintain 81% of the initial capacity after 1200 cycles at 1 C. The solid-state Li|RANFs/PVA|LiFePO4 cell also exhibits excellent resilience in destructive tests such as cell bending, piercing, and cutting

Synergistic Effect of Co₃O₄ Nanoparticles and Graphene as Catalysts for Peroxymonosulfate-Based Orange II Degradation with High Oxidant Utilization Efficiency

Cobalt oxide and graphene nanocomposites (Co₃O₄/graphene) are fabricated as heterogeneous catalysts to accelerate sulfate radical generation in Orange II degradation. The Co₃O₄/graphene catalyst is characterized through X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy. Results show that the Co₃O₄/graphene catalysts are prepared successfully. Co₃O₄ or graphene solely exhibits slight catalytic activity, but their hybrid (Co₃O₄/graphene) efficiently degrades and removes Orange II from an aqueous solution in the presence of peroxymonosulfate (PMS). Orange II is completely removed or degraded (100%) within 7 min by using the composite catalysts; by contrast, Orange II is partially removed when Co₃O₄ or graphene is used alone under the same conditions. These phenomena suggest a synergistic catalytic activity of Co₃O₄ and graphene in the hybrid. To investigate the causes of the synergistic interactions of the Co₃O₄/graphene composites, we summarize previous studies and propose an electron transfer pathway between Co₃O₄ and graphene. We then perform density functional theory calculations to describe the specific features of the composite structures. The hybrid structure is more conductive than the individual semiconductor cobalt oxide clusters because of the hybridization between Co-4d orbital and graphene-p orbital. Fukui indices of electrophilic attack indicate that Co²⁺, not Co³⁺, is the active site. Therefore, the PMS activation processes and Orange II degradation pathways are involved in an electrochemical process. Graphene functions as a wire because of its excellent electrical conductivity during oxidation