An ordered porous Mn3O4@N-doped carbon/graphene (MCG) composite has been synthesized through a facile carbonization of Mn-based metal–organic frameworks (Mn-MOFs) using the poly(styrene-co-AA) spheres as the template. Because of the periodic arrangement of metal nodes and organic ligands in the Mn-MOFs, the Mn3O4 nanoparticles with an average diameter of 7 nm are uniformly distributed and the carbon is formed in situ in the MCG composite. The MCG exhibits a specific surface area of 326 m2 g−1 with a total pore volume of 1.02 cm3 g−1, which is much higher than that of the Mn3O4-based composites reported to date. In addition, the MCG displays excellent electrochemical performances in an aqueous 1 M Na2SO4 electrolyte with a maximum specific capacitance of 456 F g−1 at 1 A g−1 and 246 F g−1 at 20 A g−1. The MCG also owns a good cycling stability with 98.1 % of the initial capacitance remaining after 2000 cycles at 5 A g−1.

•ZnO/N-doped porous carbon composite is prepared by a facile solvent-free method.•ZIF-8 in-situ grow on the surface of ZnO nanorod.•ZnO/NC-Z exhibits high discharge capacity and superior cycling stability.•The ZnO/NC-Z can serve as precursor to synthesize carbon tube.The N-doped carbon coated ZnO nanorods (ZnO/NC-Z NRDs) are synthesized through a simple solvent-free method, in which the N-doped carbon is derived from thermal treatment of the in-situ grown zeolitic imidazolate framework-8 (ZIF-8) on the surface of ZnO NRDs. The in-situ coated N-doped carbon layer can not only enhance the electrical conductivity of ZnO NRDs and thus increasing the diffusion rate of Li ions, but also serve as a buffer layer to impede the volume expansion during the charge-discharge processes. When utilized as anodes for lithium-ion batteries (LIBs), the as-synthesized ZnO/NC-Z NRDs deliver a high capacity of 1011 mA h g−1 at 200 mA g−1 after 200 cycles and remain 544 mA h g−1 at 1000 mA g−1 after 850 cycles, holding a capacity retention of as high as 87.7%. In addition, the as-synthesized ZnO/NC-Z NRDs can also act as a precursor for the preparation of high performance N-doped carbon tube (1001.1 mA h g−1 at 200 mA g−1 with the retention of 99.1% after 100 cycles) with an ultrathin wall thickness. Such solvent-free synthetic method can not only simplify the synthesis process, but also pave a new strategy to synthesize Zn-based materials for the application of energy storage devices.

The C–ZnCo2O4–ZnO nanorod arrays (NRAs), which consist of MOF-derived carbon coating on ZnCo2O4–ZnO NRAs, are rational designed and synthesized via a facile template-based solution route on Ti foil and used as high-performance anode for lithium-ion batteries (LIBs). The uniform coated MOF-derived carbon layers on the ZnCo2O4–ZnO nanorods surface can serve as a conductive substrate as well as buffer layer to restrain volume expansion during charge–discharge process. When tested as anodes for LIBs, the C–ZnCo2O4–ZnO NRAs show high reversible capacity of 1318 mA h g−1 at 0.2 A g−1 after 150 charge–discharge cycles. Furthermore, C–ZnCo2O4–ZnO NRAs also exhibit brilliant rate performance of 886.2, 812.8, 732.2 and 580.6 mA h g−1 at 0.5, 1, 2 and 5 A g−1, respectively. The outstanding lithium storage performance of C–ZnCo2O4–ZnO NRAs could be ascribed to the stimulated kinetics of ion diffusion and electron transport originated from the shortened lithium-ion diffusion pathway and improved electronic conductivity benefit from uniformly coating MOF-derived carbon.

A series of semi-fluorinated sulfonated polyimides (6F-SPIs) are designed and synthesized via a one-step high-temperature polycondensation reaction. The sulfonation degrees of 6F-SPIs are controlled through changing the ratio of sulfonated diamine to non-sulfonated diamine in the casting solution. The physico-chemical properties and single cell performance of 6F-SPI membranes are thoroughly evaluated and compared to a non-fluorinated SPI membrane (6H-SPI-50) and a Nafion 115 membrane. The results show that the designed 6F-SPI membrane with a 50% sulfonation degree (6F-SPI-50) possesses the highest proton selectivity (1.613 × 105 S min cm−3) among all tested membranes. Besides, the 6F-SPI-50 membrane exhibits a promising performance for vanadium redox flow batteries (VRFBs), showing higher coulombic efficiencies (96.90–99.20%) and energy efficiencies (88.25–64.80%) than the Nafion 115 membrane (with coulombic efficiencies of 90.60–96.70% and energy efficiencies of 81.04–60.10%) at the current densities ranging from 20 to 100 mA cm−2. Moreover, the 6F-SPI-50 membrane shows excellent chemical stability in the VRFB system. This work paves the way for the development of a new class of 6F-SPI membranes for the VRFB application.

Zeolite beta, especially heteroatomic zeolite beta, has been widely used in the industries of fine chemicals and petroleum refining because of its outstanding thermal stability, acid resistance, and unique 3-D open-frame structure. In this paper, aluminum-free Mn-β zeolite was hydrothermally synthesized in the SiO2–MnO2–(TEA)2O–NaF–H2O system. The effect of the chemical composition of the precursor mixture to the crystallization of the Al-free Mn-β zeolite was investigated. The synthesized Al-free Mn-β zeolite was characterized by inductively coupled plasma (ICP), XRD, thermogravimetric/differential thermal analysis (TG/DTA), N2 adsorption–desorption, FT-IR, UV–vis, X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM). The results show that the synthesized zeolite has a structure of β zeolite with good crystallinity and Mn ions present in the framework of the zeolite. The synthesized Al-free Mn-β zeolite shows great catalytic activity toward the phenol hydroxylation reaction using H2O2 as the oxidant. Approximately 35% of phenol conversion and ∼98% of dihydroxybenzene selectivity can be obtained under the optimal conditions.Keywords: Al-free; beta zeolite; catalytic activity; hydrothermal synthesis; phenol hydroxylation

•TiO2 nanotube arrays decorated with Sb2Se3 particles were successfully fabricated by electrodeposition.•The deposition potential plays a major role on the chemical composition and morphologies of Sb2Se3/TNAs.•Sb2Se3/TNAs obtained at −0.7 V exhibited the highest catalytic performance for the reduction of p-nitrophenol to p-aminophenol.•The formation of Sb2Se3 was confirmed to follow a co-deposition mechanism.Titanium dioxide (TiO2) nanotube arrays (TNAs) decorated with antimony selenide (Sb2Se3) particles were successfully fabricated through a simple and efficient electrodeposition strategy, which exhibited excellent catalytic performance for the reduction of p-nitrophenol. The electrodeposition mechanism was investigated by electrochemical methods. The microstructure, chemical composition and morphologies of the Sb2Se3/TNAs prepared at different deposition potentials were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The formation of Sb2Se3 was confirmed to follow a co-deposition mechanism. It was found that Sb2Se3/TNAs with homogeneous morphology could be obtained at −0.7 V, which exhibited the highest catalytic performance for the reduction of p-nitrophenol to p-aminophenol. The conversion rate of p-nitrophenol reached as high as 93.5% within 80 min. Such good catalytic performance could be attributed to the large surface area of TNAs that facilitate electrodeposition of Sb2Se3 and hence improve its catalytic performance.TiO2 nanotube arrays decorated with Sb2Se3 particles were successfully fabricated through a simple and efficient electrodeposition strategy, which exhibited excellent catalytic performance for the reduction of p-nitrophenol. The formation of Sb2Se3 was confirmed to follow a co-deposition mechanism.

Effects of methanesulfonic acid (MSA) and aminomethylsulfonic acid (AMSA) as additives for positive electrolyte on thermal stability and electrochemical performance are investigated. Both additives can improve the thermal stability of V(V) electrolyte, and AMSA has better effect, especially. The electrochemical results show that V(IV)/V(V) exhibits superior electrochemical activity and reversibility with additives, and the diffusion coefficient of V(IV) species, exchange current density and reaction rate constant become larger with additives in positive electrolyte. Among the two additives, AMSA has better effect for improvement of electrochemical activity and kinetics. The cell using positive electrolyte with additive of AMSA was assembled and the charge–discharge performance was evaluated. The assembled cell using AMSA as positive electrolyte additive shows good cycling performance, with higher energy efficiency (81.5%) and larger discharge capacity retention (40 cycles: 82.7%). The improved electrochemical performance may be ascribed to more active sites provided by NH2 group and the enhanced hydrophilicity of the electrode provided by NH2 and SO3H groups.

Carbon nanofibers grown on the surface of graphite felt by chemical vapour deposition was investigated for the first time in vanadium redox flow batteries. The electrochemical activity and reversibility of the carbon nanofibers modified graphite felt electrode are enhanced. A catalytic mechanism for electrochemical reaction of V(IV)/V(V) couple is proposed.

•A branched side-chain-type sulfonated polyimide membrane (6F-s-bSPI) is prepared.•The 6F-s-bSPI membrane possesses a very low vanadium ion permeability.•The 6F-s-bSPI membrane shows excellent proton selectivity and chemical stability.•The VRFB assembled with the 6F-s-bSPI membrane exhibits high efficiencies.•The 6F-s-bSPI membrane maintains a stable cycle performance in VRFB applications.A novel branched side-chain-type sulfonated polyimide (6F-s-bSPI) membrane with accessible branching agents of melamine, hydrophobic trifluoromethyl groups (CF3), and flexible sulfoalkyl pendants is prepared by a high-temperature polycondensation and post-sulfonation method for use in vanadium redox flow batteries (VRFBs). The chemical structure of the 6F-s-bSPI membrane is confirmed by ATR-FTIR and 1H NMR spectra. The physico-chemical properties of the as-prepared 6F-s-bSPI membrane are systematically investigated and found to be strongly related to the specially designed structure. The 6F-s-bSPI membrane offers a reduced cost and possesses a significantly lowered vanadium ion permeability (1.18 × 10−7 cm2 min−1) compared to the linear SPI (2.25 × 10−7 cm2 min−1) and commercial Nafion 115 (1.36 × 10−6 cm2 min−1) membranes, prolonging the self-discharge duration of the VRFBs. In addition, the VRFB assembled with a 6F-s-bSPI membrane shows higher coulombic (98.3%–99.7%) and energy efficiencies (88.4%–66.12%) than that with a SPI or Nafion 115 membrane under current densities ranging from 20 to 100 mA cm−2. Moreover, the VRFB with a 6F-s-bSPI membrane delivers a stable cycling performance over 100 cycles with no decline in coulombic and energy efficiencies. These results show that the branched side-chain-type structure is a promising design to prepare excellent proton conductive membranes.