Solvent-free synthesis of N-doped carbon coated ZnO nanorods composite anode via a ZnO support-induced ZIF-8 in-situ growth strategy

Synthesis of copper naphthalocyanine/graphene oxide composites as anode materials for lithium-ion batteries

Naphthalocyanine and its derivatives are new types of functional materials with wide application prospects. This paper discusses the synthesis of copper tetra tert-butyl-naphthalocyanine (CuNc) and analyses its molecular and electronic structure. Next, CuNc is combined with graphene oxide (GO) through π-π interaction and then pyrolyzed to form a CuNc/GO composite. A systematic investigation of the morphology, structure, composition and properties of CuNc/GO revealed that N-doped graphene is decorated with CuO particles. The electrochemical properties of CuNc/GO are compared with those of directly pyrolysed CuNc. The prepared CuNc/GO (1 : 1) electrode shows a large specific capacity (655.1 mA h g-1) after 100 cycles at 100 mA g-1. Its high capacity, enhanced cycling stability and strong rate performance are attributed to the synergetic effect of N-doped graphene and CuO particles. Besides expanding the use of naphthalocyanine compounds, this work presents a promising candidate material for lithium-ion battery anodes.

In Situ Construction of Zn2Mo3O8/ZnO Hierarchical Nanosheets on Graphene as Advanced Anode Materials for Lithium-Ion Batteries

Transition-metal oxides as anodes for lithium-ion batteries (LIBs) have attracted enormous interest because of their high theoretical capacity, low cost, and high reserve abundance. Unfortunately, they commonly suffer from poor electronic and ionic conductivity and relatively large volume expansion during discharge/charge processes, thereby triggering inferior cyclic performance and rate capability. Herein, a molybdenum-zinc bimetal oxide-based composite structure (Zn₂Mo₃O₈/ZnO/rGO) with rectangular Zn₂Mo₃O₈/ZnO nanosheets uniformly dispersed on reduced graphene oxide (rGO) has been prepared by using a simple and controllable cyanometallic framework template method. The Zn₂Mo₃O₈/ZnO rectangular nanosheets with desirable porous features are composed of nanocrystalline subunits, facilitating the exposure of abundant active sites and providing sufficient contact with the electrolyte. Benefiting from the composition and structural merits as well as the induced synergistic effects, the Zn₂Mo₃O₈/ZnO/rGO composite as LIB anodes delivers superior electrochemical properties, including high reversible capacity (960 mA h g^-1 after 100 cycles at 200 mA g^-1), outstanding rate performance (417 mA h g^-1 at 10,000 mA g^-1), and admirable long-term cyclic stability (862 mA h g^-1 after 400 cycles at 1000 mA g^-1). The mechanism of lithium storage and the formation of SEI film are systematically elucidated. This work provides an effective strategy for synthesizing promising Mo-cluster compound-based anodes for high-performance LIBs.

Bimetal-MOF and bacterial cellulose-derived three-dimensional N-doped carbon sheets loaded Co/CoFe nanoparticles wrapped graphite carbon supported on porous carbon nanofibers: An efficient multifunctional electrocatalyst for Zn-air batteries and overall water splitting

In this work, a three-dimensional (3D) multifunctional Co/CoFeNC@N-CNF electrocatalyst was first synthesized by the pyrolysis of a CoFe bimetal-centred metal-organic framework (MOF) and bacterial cellulose (BC). The initial potential and half-wave potential of Co/CoFeNC@N-CNF can reach 0.99 V and 0.8 V. Low overpotentials of 320 mV and 155 mV are purely required for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) at a current density of 10 mA cm^-2, respectively. The electrochemical performance of Co/CoFeNC@N-CNF exceeds most bimetal-MOF-derived electrocatalysts reported to date. The superior electrochemical performance is mainly due to abundant active sites, high-efficiency electrochemical performance, and high electron transport efficiency. In addition, the theoretical calculation results show that the synergistic effect of the CoFe bimetal can optimize the adsorption energy for intermediates of the oxygen reduction reaction (ORR), OER and HER. Furthermore, we assembled a mold and solid Zn-air battery using the catalyst as an air cathode catalyst, demonstrating the maximum power densities of 292 mW cm^-2 and 178 mW cm^-2. The 3D structure electrocatalysts derived from the MOF and bacterial cellulose provide an innovative and instructive approach for the design of diverse energy nanomaterials.

Spray drying induced engineering a hierarchical reduced graphene oxide supported heterogeneous Tin dioxide and Zinc oxide for Lithium-ion storage

In this work, a hierarchical reduced graphene oxide (RGO) supportive matrix consisting of both larger two-dimensional RGO sheets and smaller three-dimensional RGO spheres was engineered with ZnO and SnO₂ nanoparticles immobilized. The ZnO and SnO₂ nanocrystals with controlled size were in sequence engineered on the surface of the RGO sheets during the deoxygenation of graphene oxide sample (GO), where the zinc-containing ZIF-8 sample and metal tin foil were used as precursors for ZnO and SnO₂, respectively. After a spray drying treatment and calcination, the final ZnO@SnO₂/RGO-H sample was obtained, which delivered an outstanding specific capacity of 982 mAh·g^-1 under a high current density of 1000 mA·g^-1 after 450 cycles. Benefitting from the unique hierarchical structure, the mechanical strength, ionic and electric conductivities of the ZnO@SnO₂/RGO-H sample have been simultaneously promoted. The joint contributions from pseudocapacitive and battery behaviors in lithium-ion storage processes bring in both large specific capacity and good rate capability. The industrially mature spray drying method for synthesizing RGO based hierarchical products can be further developed for wider applications.

Review of ZnO Binary and Ternary Composite Anodes for Lithium-Ion Batteries

To enhance the performance of lithium-ion batteries, zinc oxide (ZnO) has generated interest as an anode candidate owing to its high theoretical capacity. However, because of its limitations such as its slow chemical reaction kinetics, intense capacity fading on potential cycling, and low rate capability, composite anodes of ZnO and other materials are manufactured. In this study, we introduce binary and ternary composites of ZnO with other metal oxides (MOs) and carbon-based materials. Most ZnO-based composite anodes exhibit a higher specific capacity, rate performance, and cycling stability than a single ZnO anode. The synergistic effects between ZnO and the other MOs or carbon-based materials can explain the superior electrochemical characteristics of these ZnO-based composites. This review also discusses some of their current limitations.

Synergistic effects of flake-like ZnO/SnFe2O4/nitrogen-doped carbon composites on structural stability and electrochemical behavior for lithium-ion batteries

In order to improve the electrochemical performance and relieve volume expansion of pure SnFe₂O₄ anode for lithium-ion batteries (LIBs), we synthesized a novel ZnO/SnFe₂O₄/nitrogen-doped carbon composites (ZSFO/NC) with flake-like polyhedron morphology by using ZIF-8 as a sacrificial template. Remarkably, it exhibited an initial charge/discharge capacities of 1078.3/1507.5 mAh g^-1 with a high initial coulombic efficiency (ICE) of 71.2%, and maintained a steady charge/discharge capacities of 1495.7/1511.8 mAh g^-1 at 0.2 A g^-1 after 300 cycles. The excellent rate performance of 435.6 mAh g^-1 at a higher current density of 10.0 A g^-1 and superior reversible capacity of 532.3/536.2 mAh g^-1 after 500 cycles at 2.0 A g^-1 were obtained. It revealed that the nitrogen-doped carbon matrix and peculiar structure of ZSFO/NC not only effectively buffered large volume expansion upon (de)lithiation through the synergistic interface action between ZnO, SnFe₂O₄ and NC, but also improved capacity of the composite by large contribution of surface pseudo-capacitance. The excellent charge-discharge performance showed that ZSFO/NC composite has a great potential for LIBs due to the synergistic effect of the multi-components.

Visible light driven photocatalytic degradation of aqueous acetamiprid over nitrogen and graphene oxide doped ZnO composites

The present investigation focused on the photocatalytic degradation of acetamiprid in aqueous solutions under visible light over bare ZnO as well as N- and N-GO-doped photocatalysts. The synthesised materials were characterised using SEM, TEM, XRD, nitrogen sorption, photoluminescence, UV-Vis, FTIR and electrochemical impedance spectroscopy techniques. The obtained results pointed out the high photocatalytic performances of the N-GO-ZnO allowing complete degradation of the acetamiprid after 5 hours of reaction at ambient temperature. Under otherwise the same operating conditions, 12, 38 and 68% conversion were reached in the absence of any photocatalyst, over the bare ZnO and N-doped ZnO materials, respectively.

Advances in metal-organic framework coatings: versatile synthesis and broad applications

Metal-organic frameworks (MOFs) as a new kind of porous crystalline materials have attracted much interest in many applications due to their high porosity, diverse structures, and controllable chemical structures. However, the specific geometrical morphologies, limited functions and unsatisfactory performances of pure MOFs hinder their further applications. In recent years, an efficient approach to synthesize new composites to overcome the above issues has been achieved, by integrating MOF coatings with other functional materials, which have synergistic advantages in many potential applications, including batteries, supercapacitors, catalysis, gas storage and separation, sensors, drug delivery/cytoprotection and so on. Nevertheless, the systemic synthesis strategies and the relationships between their structures and application performances have not been reviewed comprehensively yet. This review emphasizes the recent advances in versatile synthesis strategies and broad applications of MOF coatings. A comprehensive discussion of the fundamental chemistry, classifications and functions of MOF coatings is provided first. Next, by modulating the different states (e.g. solid, liquid, and gas) of metal ion sources and organic ligands, the synthesis methods for MOF coatings on functional materials are systematically summarized. Then, many potential applications of MOF coatings are highlighted and their structure-property correlations are discussed. Finally, the opportunities and challenges for the future research of MOF coatings are proposed. This review on the deep understanding of MOF coatings will bring better directions into the rational design of high-performance MOF-based materials and open up new opportunities for MOF applications.

N-doped Carbon Coated CoO Nanowire Arrays Derived from Zeolitic Imidazolate Framework-67 as Binder-free Anodes for High-performance Lithium Storage

To realize large lithium storage capacity and excellent rate capability lithium ion batteries, highly electrochemically active materials and rational design of structure are desirable. Here, we successfully synthesized CoO@N-doped carbon nanowire arrays derived from zeolitic imidazolate frameworks-67 (ZIF-67) on Ni foam (denoted as CoO@N-C/NF). Each CoO@N-C nanowire was built up of numerous ordered in-situ nitrogen-doped carbon coated CoO nanoparticles (around 20 nm) after annealing treatment. Benefited from the unique structural features, when served as anode for lithium ion batteries, the CoO@N-C/NF exhibit superior initial Coulombic efficiency of 78.04%, and excellent electrochemical cyclability (1884.1 mAh g⁻¹ at 1 A g⁻¹ after 100 cycles) and good rate capability (1169.2 mAh g⁻¹ at the rate of 5000 mA g⁻¹). To our knowledge, this is the highest capacity with similar electric current density that has been reported for CoO-based materials. Our results indicate that the CoO@N-C/NF electrode without any auxiliary materials are expected to open up new opportunities for CoO-based material to power electronic devices.

Selective edge etching to improve the rate capability of Prussian blue analogues for sodium ion batteries

Prussian blue analogues prefer to be etched along the edge in HCl solution, resulting in much enhanced ionic diffusions and thus rate capability.

Plasma-Induced Oxygen Vacancies in Urchin-Like Anatase Titania Coated by Carbon for Excellent Sodium-Ion Battery Anodes

The incorporation of oxygen vacancies in anatase TiO₂ has been studied as a promising way to accelerate the transport of electrons and Na⁺ ions, which is important for achieving excellent electrochemical properties for anatase TiO₂. However, wittingly introducing oxygen vacancies in anatase TiO₂ for sodium-ion anodes by a facile and effective method is still a challenge. In this work, we report an innovative method to introduce oxygen vacancies into the urchin-like N-doped carbon coated anatase TiO₂ (NC-DTO) by a facile plasma treatment. The superiorities of the oxygen vacancies combined with the conductive N-doped carbon coating enable the obtained NC-DTO of greatly improved sodium storage performance. When served as the anode for sodium-ion batteries, the NC-DTO electrode shows superior electrochemical performance (capacity: 272 mA h g^-1 at 0.25 C, capacity retention: 98.8% after 5000 cycles at 10 C, as well as ultrahigh capacity: 150 mA h g^-1 at 15 C). Density functional theory calculations combined with experimental results suggest that considerably improved sodium storage performance of NC-DTO is due to the enhanced electronic conductivity from the N-doped carbon layer as well as narrowed band gap and lowered sodiation energy barrier from the introduction of oxygen vacancies. This work highlights that introducing oxygen vacancies into TiO₂ by plasma is a promising method to enhance the electrochemical property of TiO₂, which also can be applied to different metal oxides for energy storage devices.