Construction of Binder-Free, Self-Supported, Hetero-Core-Shell Honeycomb Structured CuCo2 O4 @Ni0.5 Co0.5 (OH)2 with Abundant Mesopores and High Conductivity for High-Performance Energy Storage.

Clever and rational design of structural hierarchy, along with precise component adjustment, holds profound significance for the construction of high-performance supercapacitor electrode materials. In this study, a binder-free self-supported CCO@N0.5 C0.5 OH/NF cathode material is constructed with hierarchical hetero-core-shell honeycomb nanostructure by first growing CuCo2 O4 (CCO) nanopin arrays uniformly on highly conductive nickel foam (NF) substrate, and then anchoring Ni0.5 Co0.5 (OH)2 (N0.5 C0.5 OH) bimetallic hydroxide nanosheet arrays on the CCO nanopin arrays by adjusting the molar ratio of Ni(OH)2 and Co(OH)2 . The constructed CCO@N0.5 C0.5 OH/NF electrode material showcases a wealth of multivalent metal ions and mesopores, along with good electrical conductivity, excellent electrochemical reaction rates, and robust long-term performance (capacitance retention rate of 87.2%). The CCO@N0.5 C0.5 OH/NF electrode, benefiting from the hierarchical structure of the material and the exceptional synergy between multiple components, demonstrates an excellent specific capacitance (2553.6 F g-1 at 1 A g-1 ). Furthermore, the assembled asymmetric CCO@N0.5 C0.5 OH/NF//AC/NF supercapacitor demonstrates a high energy density (70.1 Wh kg-1 at 850 W kg-1 ), and maintains robust capacitance cycling stability performance (83.7%) after undergoing 10 000 successive charges and discharges. It is noteworthy that the assembled supercapacitor exhibits an operating voltage (1.7 V) that is well above the theoretical value (1.5 V).

Spontaneous Molecule Aggregation for Nearly Single-Ion Conducting Sol Electrolyte to Advance Aqueous Zinc Metal Batteries: The Case of Tetraphenylporphyrin.

Zn metal as a promising anode of aqueous batteries faces severe challenges from dendrite growth and side reactions. Here, tetraphenylporphyrin tetrasulfonic acid (TPPS) is explored as an electrolyte additive for advanced Zn anodes. It is interesting to note that TPPS spontaneously assembles into unique aggregates. As they adsorb on the Zn anode, the aggregates enhance the resistance to electrolyte percolation and dendrite growth compared to single molecules. Meanwhile, TPPS facilitates anion association in the solvation sheath of Zn2+, and boosts the transference number of Zn2+ up to 0.95. Therefore, anion-related side reactions and anion-induced electrode overpotentials are reduced accordingly. In this context, the electrolyte containing TPPS exhibits excellent electrochemical performance. Even under a high loading of MnO2 (25 mg cm-2), a limited Zn supply (N/P ratio=1.7), and a lean electrolyte (15 µL mAh-1), the full cells still represent a higher cumulative capacity compared to the reported data. The advantages of this electrolyte are also adapted to other cathode materials. The pouch cells of Zn||NaV3O8 ⋅ 1.5H2O realize a capacity of ~0.35 Ah at 0.4 C under harsh conditions.

Metal-Organic Frameworks and Their Derivatives-Based Nanostructure with Different Dimensionalities for Supercapacitors.

With the urgent demand for the achievement of carbon neutrality, novel nanomaterials, and environmentally friendly nanotechnologies are constantly being explored and continue to drive the sustainable development of energy storage and conversion installations. Among various candidate materials, metal-organic frameworks (MOFs) and their derivatives with unique nanostructures have attracted increasing attention and intensive investigation for the construction of next generation electrode materials, benefitting from their unique intrinsic characteristics such as large specific surface area, high porosity, and chemical tunability as well as the interconnected channels. Nevertheless, the poor electrochemical conductivity severely limits their application prospects, hence a variety of nanocomposites with multifarious structures have been designed and proposed from different dimensionalities. In this review, recent advances based on MOFs and their derivatives in different dimensionalities ranging from 1D nanopowders to 2D nanofilms and 3D aerogels, as well as 4D self-supporting electrodes for supercapacitors are summarized and highlighted. Furthermore, the key challenges and perspectives of MOFs and their derivatives-based materials for the practical and sustainable electrochemical energy conversion and storage applications are also briefly discussed, which may be served as a guideline for the design of next-generation electrode materials from different dimensionalities.

Three-Dimensional Architecture Reduced Graphene Oxide-LiFePO4 Composite: Preparation and Excellent Microwave Absorption Performance.

The present work reports preparation of 3D composites of reduced graphene oxide (RGO) with coral-like LiFePO4 particles in two steps, which involves the fabrication of LiFePO4 particles by the solvothermal method and the subsequent preparation of RGO/coral-like LiFePO4 composites by the etching method. The microwave absorption properties of LiFePO4 particles, coral-like LiFePO4 particles, and the RGO/coral-like LiFePO4 composites were studied. Our results show that the as-prepared RGO/coral-like LiFePO4 composites exhibit significantly improved microwave absorption properties compared with the pure LiFePO4 particles and coral-like LiFePO4 particles. The RGO/coral-like LiFePO4 composite (S-60) possesses optimized reflection loss (RL) performance with an RL value of -61.4 dB and a broad effective absorption bandwidth of 4 GHz (from 11.36 to 14.88 GHz and 16.32 to 16.8 GHz) at the matching thickness of only 2.4 mm. This demonstrates that the RGO/coral-like LiFePO4 composites can be superior candidates for lightweight and high-efficiency microwave absorbers.

Facile Synthesis of Flowerlike LiFe5O8 Microspheres for Electrochemical Supercapacitors.

Facile synthesis of porous and hollow spinel materials is very urgent due to their extensive applications in the field of energy storage. In present work, flowerlike porous LiFe5O8 microspheres etched for 15, 30, and 45 min (named as p-LFO-15, p-LFO-30, and p-LFO-45, respectively) are successfully synthesized through a facile chemical etching method based on bulk LiFe5O8 (LFO) particles as precursors, and they are applied as electrode materials for high-performance electrochemical capacitors. In particular, the specific surface area of p-LFO-45 reaches 46.13 m2 g-1, which is 112 times greater than that of the unetched counterpart. Therefore, the p-LFO-45 electrode can achieve a higher capacitance of 278 F g-1 at a scan rate of 5 mV s-1 than the unetched counterpart. Furthermore, the p-LFO-45 electrode presents a good cycling stability with 78.3% of capacitive retention after 2000 cycles, which is much higher than that of the unetched LFO particles (66%). Therefore, the flowerlike porous LFO microspheres are very promising candidate materials for supercapacitor applications.

Embedding of conductive Ag nanoparticles among honeycomb-like NiMn layered double hydroxide nanosheet arrays for ultra-high performance flexible supercapacitors.

Layered double hydroxides are considered promising electrode materials for the preparation of high-energy-density supercapacitors owing to their suitable microstructure and significant electrochemical properties. In this study, honeycomb-like NiMn-layered double-hydroxide (NiMn-LDH) nanosheet arrays with numerous electron/ion channels, a large number of active sites, considerable redox reversibility, and significant electrical conductivity were synthesized by combining Co2(OH)2CO3 nanoneedle arrays with NiMn-LDH nanosheet arrays and Ag nanoparticles on a carbon cloth (CC) substrate through a hydrothermal strategy (CC@Co2CH/NM-LDH-Ag). The fabricated CC@Co2CH/NM-LDH-Ag binder-free electrode exhibited a high specific capacitance of 10,976 mF cm-2 (3092F/g, 1391.4C g-1) at 2 mA cm-2 (1 A/g), and a high capacitance retention of 93.2 % after 10,000 cycles at a current density of 20 mA cm-2. In addition, a solid-state asymmetric supercapacitor (ASC) device assembled using CC@Co2CH/NM-LDH-Ag as the cathode possessed an ultrahigh energy density of 68.85 Wh kg-1 at a power density of 722.6 W kg-1, and two fabricated ASC units in series were able to power a multifunctional display for more than 30 min. Therefore, this study provides a new approach for the design and synthesis of high-performance flexible electrodes.

In Situ Generation of Vertically Crossed P-Cu3Se2 Ultrathin Nanosheets Derived from Cu2S Nanorod Arrays for High-Performance Supercapacitors.

Transition-metal selenides (TMSs) have great potential in the synthesis of supercapacitor electrode materials due to their rich content and high specific capacity. However, the aggregation phenomenon of TMS materials in the process of charging and discharging will cause capacity attenuation, which seriously affects the service life and practical applications. Therefore, it is of great practical significance to design simple and efficient synthesis strategies to overcome these shortcomings. Hence, P-doped Cu3Se2 nanosheets are loaded on vertically aligned Cu2S nanorod arrays to synthesize CF/Cu2S@Cu3Se2/P nanocomposites with a unique core-shell heterostructure. Notably, the Cu2S precursors can be rapidly converted into Cu3Se2 nanorod arrays in situ in just 30 min at room temperature. The unique core-shell heterostructure effectively avoids the aggregation phenomenon, and the doped P elements further enhance the electrochemical properties of the electrode materials. Therefore, the as-prepared CF/Cu2S@Cu3Se2/P electrode exhibits a high areal capacitance of 5054 mF cm-2 (1099 C g-1) at 3 mA cm-2 and still retains 90.2% capacitance after 10 000 galvanostatic charge-discharge (GCD) cycles. The asymmetric supercapacitor (ASC) device assembled from synthetic CF/Cu2S@Cu3Se2/P and activated carbon (AC) possesses an energy density of 41.1 Wh kg-1 at a power density of 480.4 W kg-1. This work shows that the designed CF/Cu2S@Cu3Se2/P electrode has broad application prospects in the field of electrochemical energy storage.

Controllable synthesis of nickel doped hierarchical zinc MOF with tunable morphologies for enhanced supercapability.

Metal-organic frameworks (MOFs) are attracting tremendous research interest because of their rich redox sites and high specific area which are beneficial for the energy storage applications. Nevertheless, the poor conductivity, low mechanical strength and unsatisfactory capacity severely hinder their wide application. Hence, it is of practical significance to design highly efficient and facile strategy to solve these issues. Herein, vertically oriented ZnO nanorod arrays are applied as precursor to synthesize laminated scale-like and highly-oriented Ni/Zn-MOF/ZnO nanocomposite. Owing to the desirable conductivity resulting from the doping nickel ions and the interaction between ZnO and its relative MOF, the fabricated 0.3Ni/Zn-MOF/ZnO@CC electrode exhibits an electrochemical capacitance of 1693 mF cm-2 at 1 mA cm-2. Moreover, the electrochemical capacitance retention of 80.7 % after 2500 cycling numbers is obtained under the constant current density of 10 mA cm-2 and the low internal resistance Rs of 0.89 Ω is observed. For practical application, the as-synthesized laminated scale-like Ni/Zn-MOF/ZnO@CC nanocomposite is served as positive electrode to fabricate solid-state asymmetric supercapacitor device. Moreover, a 2.5 V indicator could be powered for 8 min when the prepared supercapacitor units are connected. This work demonstrates the promising potential of the synthesized scale-like Ni/Zn-MOF composites for electrochemical energy storage applications.

Specific sensing of resorcin based on the hierarchical porous nanoprobes constructed by cuttlefish-derived biomaterials through differential pulse voltammetry.

The specific detection of resorcin from its isomers is a current research hotspot. Thus in our work, a ternary hierarchical porous nanoprobe has been constructed based on the combination of cuttlefish ink and bimetallic Au@Ag nanoclusters for the specific sensing of resorcin. Briefly, through electrostatic interaction, Au@Ag core-shell nanoclusters are immobilized on the surface of polydopamine extracted from cuttlefish, which is turned into nitrogen-doped porous carbon functionalized by bimetallic Au@Ag by topological transformation subsequently. Afterward, an electrochemical sensor is fabricated based on the nanoprobes for specifically determining resorcin in solution by differential pulse voltammetry, and the linear detection ranges of the sensor are 1-100 µM and 1.2-4 mM while the detection limit reaches 0.06 µM. Meanwhile, the sensing mechanism of resorcin by the pre-fabricated sensor is detailedly studied by density functional theory to obtain a clear electrochemical process. Besides, the selectivity, stability, plus reproducibility of the pre-fabricated sensor have been also tested, and the determinations for resorcin in real environmental water samples have also been performed with good recoveries, revealing the auspicious application potential in the environmental monitoring.

In situ-derived carbon nanotube-decorated nitrogen-doped carbon-coated nickel hybrids from MOF/melamine for efficient electromagnetic wave absorption.

Carbon nanotube-decorated nitrogen-doped carbon-coated nickel (CNT/Ni@N-C) microspheres have been fabricated by pyrolyzing the mixture of nickel-based metal organic framework (Ni-MOF) and melamine. The resultant composite is assembled from CNTs and spherical Ni@N-C composite. Besides, the CNT/Ni@N-C composite contains abundant nitrogen (N) dopants that contribute to defect dipole polarization. The melamine content is important for controlling the amount of N element and N dopant state in the composite. The optimized CNT/Ni@N-C composite with high content of pyridinic N exhibits strong absorption of -55.1 dB at 10.56 GHz with the thickness of 2.5 mm, and the effective absorbing bandwidth (reflection loss < -10 dB) is 11.2 GHz (6.0-17.2 GHz) with the thickness range of 1.5-4.0 mm. These results indicate that the N content and N dopant state have a great influence on electromagnetic wave absorption properties. This strategy will contribute to fabricate the carbon hybrid network consisting of metal organic frameworks derived metal/carbon hybrid and CNTs for electromagnetic wave absorption.