Catalytic Upgrading of Bio-Oil over Cu/MCM-41 and Cu/KIT‑6 Prepared by β‑Cyclodextrin-Assisted Coimpregnation Method

Cu loaded MCM-41 and KIT-6 are prepared by β-cyclodextrin (CD) assisted coimpregnation method (Cu/MCM-41-CD and Cu/KIT-6-CD) for in situ catalytic upgrading of bio-oil derived from the fast pyrolysis of biomass. It is found that Cu/MCM-41-CD and Cu/KIT-6-CD exhibit higher catalytic activity for promoting the deoxygenation from the bio-oil when compared with those prepared by conventional impregnation method. 20 wt % of Cu loaded MCM-41-CD and KIT-6-CD shows the highest catalytic activity, by which the upgraded bio-oil is rich in monocyclic aromatic hydrocarbons such as benzene, toluene, and xylene with the total relative maximum hydrocarbon amounts of 73.2% and 86.1%. After reuse of the regenerated catalyst for four cycles, no serious reduction of total relative hydrocarbon amount is found. The possible upgrading mechanism is proposed. It is expected to provide a new direction with a green method for development of the catalyst for the upgrading of bio-oil

Exploration of the Active Center Structure of Nitrogen-Doped Graphene for Control over the Growth of Co₃O₄ for a High-Performance Supercapacitor

Nitrogen-doped graphene sheets with different active center structures, such as amine N, quaternary N, pyridinic N, or pyrrolic N atoms, were successfully fabricated using targeted nitrogen precursors and a designed annealing process. Then, the nitrogen-doped graphene with a different structure is used as the active center for the growth of Co₃O₄ nanoparticles. The investigation results reveal that the interaction between loaded Co₃O₄ particles and amine N atoms doped in graphene sheets is stronger than those of quaternary N, pyridinic N, or pyrrolic N atoms, and leads to a smaller particle size of Co₃O₄ and a high specific surface area of composite electrodes which perform with better electrochemical behavior. The Co₃O₄/N-RGO 550 °C dominated with amine N atoms exhibits the highest capacitance of 3553 and 1967 F g^–1 at 1 and 15 A g^–1, respectively, which are apparently higher values than those of the other Co₃O₄ composite grown on the nitrogen-doped graphene dominated with pyridinic N, pyrrolic N, or quaternary N atoms, respectively, and those of previously reported Co₃O₄ with different morphology or Co₃O₄ composite materials. Moreover, an electrode prepared from Co₃O₄/N-RGO 550 °C dominated with amine N atoms also has an excellent cycling stability with >90% capacity retention after 3000 cycles at 5 A g^–1. The stronger interaction between Co₃O₄ and amine N atoms doped in graphene sheets, which facilitate the formation of smaller Co₃O₄ particle sizes to form higher specific surface and desired pore size distribution to enhance the capacitance and make the Co₃O₄/N-RGO 550 °C extremely stable for capacitive energy storage, suggest the potential usage of the Co₃O₄/N-RGO 550 °C composite as high-supercapacitor electrode materials

An in Situ Potential-Enhanced Ion Transport System Based on FeHCF–PPy/PSS Membrane for the Removal of Ca²⁺ and Mg²⁺ from Dilute Aqueous Solution

An in situ potential-enhanced ion transport system based on the electrochemically switched ion permselectivity (ESIP) membrane was developed for the effective removal of Ca²⁺ and Mg²⁺ from dilute aqueous solution. In this system, uptake/release of the target ions can be realized by modulating the redox states of the ESIP membrane, and continuously permselective separation of the target ions through the ESIP membrane can be achieved by tactfully applying a pulse potential on the membrane and combining with an external electric field. In this study, iron hexacyanoferrate (FeHCF)–polypyrrole/polystyrenesulfonate (PPy/PSS) ESIP membrane with high conductivity and high flux was prepared by using stainless steel wire mesh (SSWM) as conductive substrate. The driving force for the ion transport was analyzed in detail by the equivalent circuit of the system. It is found that the FeHCF interlayer between the SSWM substrate and the PPy/PSS membrane played an important role in removing Ca²⁺ and Mg²⁺ from aqueous solutions, and markedly enhanced the separation performance of the membrane due to the improvement of the electroactivity as well as the change of the surface morphology. Influences of the applied cell voltage of the external electric field and the pulse (constant) potential across the membrane on the separation of Ca²⁺ and Mg²⁺ were investigated. It is demonstrated that the pulse potential was more beneficial for improving the removal efficiency than the constant potential applied on the membrane. The hardness of the treated water was reduced to 50 ppm (CaCO₃) by applying a pulse potential of ±2.0 V and an cell voltage of 5.0 V when the initial concentration of Ca²⁺ was 10 mM (1000 ppm (CaCO₃)). It is expected that the in situ potential-enhanced ion transport system based on the FeHCF–PPy/PSS membrane could be used as a novel water softening technology

Local Structure and Dynamics in the Na Ion Battery Positive Electrode Material Na₃V₂(PO₄)₂F₃

Na₃V₂(PO₄)₂F₃ is a novel electrode material that can be used in both Li ion and Na ion batteries (LIBs and NIBs). The long- and short-range structural changes and ionic and electronic mobility of Na₃V₂(PO₄)₂F₃ as a positive electrode in a NIB have been investigated with electrochemical analysis, X-ray diffraction (XRD), and high-resolution ²³Na and ³¹P solid-state nuclear magnetic resonance (NMR). The ²³Na NMR spectra and XRD refinements show that the Na ions are removed nonselectively from the two distinct Na sites, the fully occupied Na1 site and the partially occupied Na2 site, at least at the beginning of charge. Anisotropic changes in lattice parameters of the cycled Na₃V₂(PO₄)₂F₃ electrode upon charge have been observed, where <i>a</i> (= <i>b</i>) continues to increase and <i>c</i> decreases, indicative of solid-solution processes. A noticeable decrease in the cell volume between 0.6 Na and 1 Na is observed along with a discontinuity in the ²³Na hyperfine shift between 0.9 and 1.0 Na extraction, which we suggest is due to a rearrangement of unpaired electrons within the vanadium t_2g orbitals. The Na ion mobility increases steadily on charging as more Na vacancies are formed, and coalescence of the resonances from the two Na sites is observed when 0.9 Na is removed, indicating a Na1–Na2 hopping (two-site exchange) rate of ≥4.6 kHz. This rapid Na motion must in part be responsible for the good rate performance of this electrode material. The ³¹P NMR spectra are complex, the shifts of the two crystallograpically distinct sites being sensitive to both local Na cation ordering on the Na2 site in the as-synthesized material, the presence of oxidized (V⁴⁺) defects in the structure, and the changes of cation and electronic mobility on Na extraction. This study shows how NMR spectroscopy complemented by XRD can be used to provide insight into the mechanism of Na extraction from Na₃V₂(PO₄)₂F₃ when used in a NIB