Shang Jiang

Mesoporous NiCo2O4 nanospheres with a high specific surface area as electrode materials for high-performance supercapacitors

Ternary nickel cobaltite (NiCo2O4) has attracted more and more attention as a promising electrode material for high performance supercapacitors (SCs) due to its high theoretical capacity, unique crystal structure and excellent electronic conductivity. In this study, a template-free chemical co-precipitation method as a general strategy has been easily developed to fabricate mesoporous NiCo2O4 nanospheres with a high specific surface area of 216 m2 g−1, which can be further self-assembled into 3D frameworks. The key to the formation of mesoporous NiCo2O4 nanospheres with a desired pore-size distribution centered at ∼2.4 nm is a unique preparation method assisted with sodium bicarbonate as a complex agent. When tested as electrode materials for SCs, the NiCo2O4 electrodes delivered excellent electrochemical performances with high specific capacitance (842 F g−1 at a current density of 2 A g−1), superior cycling stability with no capacity decrease after 5000 cycles (103% initial capacity retention), and great rate performance at a 10-time current density increase (79.9% specific capacitance retention). Furthermore, as expected in a NiCo2O4-based asymmetric supercapacitor device, a superior energy density as high as 29.8 W h kg−1 at a power density of 159.4 W kg−1 could be achieved. These results highlight a general, eco-friendly, template-free strategy for the scale-up fabrication of a promising mesoporous NiCo2O4 electrode material for high-performance SC applications.

N-Methyl-2-pyrrolidone assisted synthesis of hierarchical ZSM-5 with house-of-cards-like structure

Development of facile, economic and green routes towards the synthesis of hierarchical zeolites with high catalytic activity still remains a challenge in modern industrial catalysis. In this paper, we report on a novel synthesis of house-of-cards-like ZSM-5 (HCL-ZSM-5) via the introduction of N-methyl-2-pyrrolidone into a template-free zeolite synthesis system. Importantly, the HCL-ZSM-5 presents much better catalytic performances in the cracking of cumene and 1,3,5-triisopropylbenzene (TIPB) than conventional porous catalysts (ZSM-5, Y zeolite and Al-MCM-41).

Synthesis and properties of MFI zeolites with microporous, mesoporous and macroporous hierarchical structures by a gel-casting technique

The comparatively small micropore dimensions of bulk ZSM-5 zeolites often limit both the adsorption and catalytic conversion of large organic molecules. Here, we report that ZSM-5 zeolites were prepared by a gel-casting technique with microporous, mesoporous and macroporous hierarchical structures. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption, temperature-programmed-desorption of ammonia (TPD-NH3) and Fourier transform infrared spectroscopy (FTIR) measurements. The hierarchical structured ZSM-5 zeolites were used to carry out catalytic cracking of 1,3,5-triisopropyl benzene and n-hexadecane. The results show that, compared with traditional ZSM-5, Beta or Al-MCM-41, this modified ZSM-5 displayed preferable catalytic activity and selectivity.

A novel, efficient and facile method for the template removal from mesoporous materials

A new catalytic-oxidation method was adopted to remove the templates from SBA-15 and MCM-41 mesoporous materials via Fenton-like techniques under microwave irradiation. The mesoporous silica materials were treated with different Fenton agents based on the template’s property and textural property. The samples were characterized by powder X-ray diffraction(XRD) measurement, N2 adsorption-desorption isotherms, infrared spectroscopy, 29Si MAS NMR and thermo gravimetric analysis(TGA). The results reveal that this is an efficient and facile approach to the thorough template-removal from mesoporous silica materials, as well as to offering products with more stable structures, higher BET surface areas, larger pore volumes and larger quantity of silanol groups.

Designed fabrication of three-dimensional δ-MnO2-cladded CuCo2O4 composites as an outstanding supercapacitor electrode material

Three-dimensional δ-MnO2-cladded CuCo2O4 composites are designed and grown in situ on Ni foam via a simple hydrothermal reaction and subsequent one-pot chelation-mediated aqueous processes. The electrode architecture can take good advantage of the synergistic effects contributed by both the porous CuCo2O4 nanoflake core and the δ-MnO2 shell layer. When δ-MnO2-cladded CuCo2O4 composites, along with porous Ni foam, are employed as a binder-free electrode for supercapacitors, the hybrid electrode shows higher specific capacitances and a better rate capability than the single CuCo2O4 nanoflake electrode. A maximum specific capacitance of 1180 F g−1 is achieved at a current density of 1 A g−1 and 81.7% of this value remains at a high current density of 10 A g−1. Moreover, the δ-MnO2-cladded CuCo2O4 electrode also delivers an excellent cycling stability, maintaining 93.2% at 15 A g−1 after 5000 galvanostatic charge–discharge cycles. Moreover, according to electrochemical impedance spectroscopy (EIS) analysis, the δ-MnO2-cladded CuCo2O4 electrode possesses a lower equivalent series resistance of 0.78 Ω and a charge transfer resistance of 0.09 Ω. In view of its cost-effective fabrication process and excellent energy storage properties, this unique integrated nanoarchitecture would hold great promise in the field of electrochemical energy storage.

Self-Assembly of Antisite Defectless nano-LiFePO4@C/Reduced Graphene Oxide Microspheres for High-Performance Lithium-Ion Batteries

LiFePO4@C/rGO hierarchical microspheres with superior electrochemical activity and high tap density were first synthesized using a Fe-based single inorganic precursor (LiFePO4OH@RF/GO) obtained from a template-free self-assembly synthesis, following with direct calcination. The synthesis process requires no physical mixing step. The phase transformation path way from tavorite LiFePO4OH to olivine LiFePO4 upon calcination was determined by the in situ high temperature XRD technique. Benefitted from the unique structure of the material, these microspheres can be densely packed together, giving a high tap density of 1.3 g cm, and simultaneously, the defectless LiFePO4 primary nanocrystals modified with highly conductive surface carbon layer and ultrathin rGO provide good electronic and ionic kinetics for fast electron/Li ion transport. Lithium-ion batteries (LIBs), as one important technology for electric energy storage, have revolutionarily extend the battery life of portable electronic devices (e.g. smart phones, wearable devices, and laptop computers), and now stand as a promising candidate for high-power and long-life battery applications, typically for the electric transportation off the grid and the clean energy back-up and storage systems. [1-3] To date, olivine (e.g. LiFePO4), layer-type (e.g. LiNi1-x-yMnxCoyO2), and spinel (e.g. LiMn2O4) electrode materials are the three mostly used cathodes for high power LIBs. [1, 2, 4] Among them, LiFePO4 is more stable in thermodynamics and reaction kinetics than the other two owing to the presence of a robust polyanionic framework. [5-7] Moreover, LiFePO4 prevails in terms of natural abundance, cost, and environmental friendliness. The major issue to this material is the negative transport kinetics in both Li ion diffusion and electron delivery. Size tailoring, in conjunction with surface carbon (i.e. graphitic carbon, graphene, et al.) coatings to form LiFePO4/C nanocomposite is acknowledged as a technology of choice to alleviate this issue effectively. [6-9] However, when the particle size of LiFePO4/C is decreased down to nanoscale, thermodynamic instability and high risk of side reactions with the organic electrolyte become into new hazards needed to be faced with. [10] In addition, the processability and tap density (less than 1.0 g cm ) of the powders also require improvements when it comes to a practical point of view. [11] For that, small LiFePO4/C nanoparticles assembled into hierarchical architectures, ideally with a microsphere morphology, would naturally become more easily free-flowing and can be densely packed together, giving a higher tap density and hence a higher volumetric energy density. [12-14] Hydrothermal and solvothermal synthesis technologies or a combination of them are the methods commonly used to create LiFePO4/C microsphere with hierarchical architectures, the vast majority of which, however, required the use of instable and costly ferrous iron (Fe) salts as the raw material, and simultaneously a reducing agent and/or inert gas to avoid the oxidation of Fe ions during reactions. [13, 15] On top of that, most attempts to develop new routes, especially through ferric iron (Fe) based approaches, focused either on the “one-pot synthesis” or “in-situ carbon coating”, rather than considering both two concepts together. [12-14] Thus exploring a simpler synthesis scheme to produce LiFePO4/C microspheres with ideal structural features will be of great interest. In this communication, reduced GO-modified LiFePO4/C (i.e. LiFePO4@C/rGO) hierarchical microspheres were synthesized for the first time by a one-pot mixed-solvothermal process to form a ferric three-component precursor of LiFePO4OH@RF/GO, followed by direct calcination at high temperature, during which tedious physical mixing and grinding step can be totally avoided. The final LiFePO4@C/rGO microspheres created can be densely packed together, giving a high tap density of 1.3 g cm, and simultaneously, the small primary LiFePO4 nanoparticles (65 nm), in conjunction with the integrated carbonous conductive network can provide an adequate electrochemically available surface for enhancing the high-rate capability. The phase transformation mechanism from tavorite LiFePO4OH to the olivine LiFePO4 upon calcination was also determined by the in situ high temperature X-ray diffraction (XRD). [a] Dr. H. Wang, Dr. L. Liu, Prof. R. Wang, Dr. S. Jiang, L. Ni, H. Tang, Prof. Z. Zhang, Prof. S. Qiu State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, International Joint Research Laboratory of Nano-Micro Architecture Chemistry Jilin University Changchun 130012, P. R. China E-mail: zzhang@jlu.edu.cn [b] Dr. H. Wang, Dr. Z. Wang, J. Hu, Dr. H. Chen, Prof. F. Pan School of Advanced Materials Peking University Shenzhen Graduate School Shenzhen 518055, P. R. China E-mail: panfeng@pkusz.edu.cn [c] Dr. H. Qiu, Prof. Y. Wei, Prof. Z. Zhang Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education) Jilin University Changchun 130012, P. R. China [d] Dr. X. Yan School of Chemistry and Materials Science Jiangsu Normal University Xuzhou 221116, P. R. China Supporting information for this article is given via a link at the end of the document. 10.1002/cssc.201800786 A cc ep te d M an us cr ip t ChemSusChem This article is protected by copyright. All rights reserved.LiFePO4 @C/reduced graphene oxide (rGO) hierarchical microspheres with superior electrochemical activity and a high tap density were first synthesized by using a Fe3+ -based single inorganic precursor (LiFePO4 OH@RF/GO; RF=resorcinol-formaldehyde, GO=graphene oxide) obtained from a template-free self-assembly synthesis followed by direct calcination. The synthetic process requires no physical mixing step. The phase transformation pathway from tavorite LiFePO4 OH to olivine LiFePO4 upon calcination was determined by means of the in situ high-temperature XRD technique. Benefitting from the unique structure of the material, these microspheres can be densely packed together, giving a high tap density of 1.3 g cm-3 , and simultaneously, defectless LiFePO4 primary nanocrystals modified with a highly conductive surface carbon layer and ultrathin rGO provide good electronic and ionic kinetics for fast electron/Li+ ion transport.