As the desired sulfur host of lithium-sulfur battery, the strong polarity and fast electron migration capability are indispensable for achieving effective adsorption and conversion of lithium polysulfides (LiPSs), that is, restricting the shuttle effect. Herein a porous microdisk Ti 4 O 7 /TiN/C heterojunction with strong polar N-Ti-O covalent bonds is precisely constructed. Compared with O-Ti-O or N-Ti-N bond in single Ti 4 O 7 or TiN , the N-Ti-O bond with stronger polarity could adsorb and bond with S and Li atoms in LiPSs, which is beneficial for LiPSs adsorption. Beside, the Ti 4 O 7 /TiN heterostructure favors the electron transfer , which could promote the conversion of LiPSs. The design strategy is to construct abundant polar N-Ti-O bonds at Ti 4 O 7 /TiN heterogeneous interface that would realize the associative process of LiPSs adsorption, trapping, and conversion, thereby restraining the shuttle effect efficiently. In the current study, as the host of the sulfur cathode, the porous microdisk TiN/Ti 4 O 7 /C heterojunction exhibits a high specific capacity of 1204.5 mAh g −1 at 0.2 C, and a high specific capacity of 616.5 mAh g −1 at an ultrahigh current density of 4 C. In addition, 86.4% and 116.9% capacity are retained over 1000 cycles at 1 C and 2 C, respectively. This strategy provides an insight into developing lithium-sulfur battery with extraordinary performance, and opens promising routes to design the next-generation electrochemical energy storage devices.
A systematic study was performed on PM2.5 filtration and photodegradation performance of polyacrylonitrile @TiO 2 / zeolitic imidazolate framework-8（PTZ）hybrid membrane. The hybrid membrane was prepared by electrospinning technique and in situ Metal-organic frameworks (MOFs) synthesis. The optimized membrane maintained a good PM2.5 capture efficiency (greater than 99%) and a pressure drop of 34 Pa. The larger specific surface area and higher pore structure enhance the filter interception effect and electrostatic interaction, which can have high applications for the filtering of PM2.5. In addition, zeolitic imidazolate framework-8 (ZIF-8) is uniformly coated on the surface of polyacrylonitrile @ TiO 2 (PT) nanofiber to form N -Ti-O bonds, thus reducing the reorganization of electron-hole pairs and improving the efficiency of photodegradation. Compared with PT, the hybrid structure formed by PTZ has a higher degradation efficiency for PM2.5 (increased from 66% to 85%). The produced PTZ membrane exhibits a promising future in the collection and green degradation of PM2.5.
Highly efficient and stable photocatalysts were synthesized at room temperature by modifying MIL-125(Ti) with N-doped carbon quantum dots (N/CM(Ti)). The N/CM(Ti) with 2.5 vol % N doped carbon quantum dots (N/CQDs) had the best light absorption and visible-light photocatalytic nitrogen oxide (NO) removal efficiency (approximately 49%). It was found through X-ray photoelectron spectroscopy analysis that a N–Ti–O bond was formed in the 2.5 vol % N/CM(Ti), which is more conducive to charge transfer. Photocurrent and electrochemical impedance data also showed that the carrier separation efficiency of 2.5 vol % N/CM(Ti) was significantly superior to that of MIL-125(Ti). In addition, the TiIII–TiIV of MIL-125(Ti) acts as the active center for photocatalytic removal of NO. Two possible electron migration paths were proposed: electron transfer from N/CQDs to TiIII–TiIV center of MIL-125(Ti) due to the photoinduced electron transfer property of N/CQDs, and absorption of UV light generated from the N/CQDs by the terephthalic acid ligand followed by electron transfer to metal active sites for photocatalytic removal of NO.
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