3D hollow NiCo LDH nanocages anchored on 3D CoO sea urchin-like microspheres: A novel 3D/3D structure for hybrid supercapacitor electrodes

Engineering intervention to disrupt the evolution of ZIF-67: Ultra-fast synthesis of arrayed Co(OH)2@ZIF-L in dozens of seconds for high-energy charge storage

Designing rational heterostructures of high-performance electroactive materials on conductive substrates with hierarchical structures is critical for advancing electrochemical energy storage technologies. In this study, a unique spatial structure is fabricated by vertically aligning two-dimensional (2D) structures of Co-ZIF-L on conductive nickel foam (NF) substrate through interruption of ZIF-67 formation. This is followed by an innovative electrochemical synthesis method that disrupts unstable surface coordination bonds in Co-ZIF-L, enabling the in-situ generation of Co(OH)2. The resulting Co(OH)2@ZIF-L/NF binder-free electrodes feature a hierarchical spatial structure and are synthesized in approximately 30 s. These electrodes showcase exceptional area capacity of 3.1 C cm-2 at 1 mA cm-2, attributed to their high specific surface area and layered architecture that promotes electrolyte penetration. Density Functional Theory (DFT) calculations reveal that the Co(OH)2@ZIF-L nanostructures have superior electrical conductivity compared to the individual components. Furthermore, a hybrid supercapacitor (HSC) based on Co(OH)2@ZIF-L/NF//AC exhibits an impressive energy density of 42 Wh kg-1 at a power density of 184.7 W kg-1. This research provides new insights into the efficient synthesis of high-performance electroactive materials with unique spatial structures and expands the potential applications of ZIF materials.

Strategy for predicting catalytic activity of catalysts with hierarchical nanostructures

Three-dimensional hierarchical nanostructures have been employed as electrodes of solid oxide fuel cells (SOFCs) to notably improve the catalytic performance. Hierarchical nanoscale porous electrodes face a trade-off: macroscale pores enhance mass transfer but reduce the number of active sites, while microscale pores increase the number of active sites at the cost of higher transport resistance. Careful design of these structures is crucial for balancing mass transfer and reaction dynamics. A three-dimensional multiphysics model is developed in this paper to examine the influence of different hierarchical geometrical nanostructures on catalytic performance. Additionally, the effects of different diffusion coefficients are also investigated in this study to present the changes in catalytic activity in diffusion, mixed, and reaction-controlled regimes. The model shows good alignment with the experimentally obtained data. An improved Thiele modulus is formulated to quantitatively evaluate the efficiencies of complex hierarchical nanostructures by considering the detailed characteristics of the main and secondary structures.

2D-on-2D Al-Doped NiCo LDH Nanosheet Arrays for Fabricating High-Energy-Density, Wide Voltage Window, and Ultralong-Lifespan Supercapacitors

Battery-type electrode materials with high capacity, wide potential windows, and good cyclic stability are crucial to breaking through energy storage limitations and achieving high energy density. Herein, a novel 2D-on-2D Al-doped NiCo layered double hydroxide (NiCoAlx LDH) nanosheet arrays with high-mass-loading are grown on a carbon cloth (CC) substrate via a two-step hydro/solvothermal deposition strategy, and the effect of Al doping is employed to modify the deposition behavior, hierarchical morphology, phase stability, and multi-metallic synergistic effect. The optimized NiCoAl0.1 LDH electrode exhibits capacities of 5.43, 6.52, and 7.25 C cm-2 (9.87, 10.88, and 11.15 F cm-2) under 0-0.55, 0-0.60, and 0-0.65 V potential windows, respectively, illustrating clearly the importance of the wide potential window. The differentiated deposition strategy reduces the leaching level of Al3+ cations in alkaline solutions, ensuring excellent cyclic performance (108% capacity retention after 40 000 cycles). The as-assembled NiCoAl0.1 LDH//activated carbon cloth (ACC) hybrid supercapacitor delivers 3.11 C cm-2 at 0-2.0 V, a large energy density of 0.84 mWh cm-2 at a power density of 10.00 mW cm-2, and excellent cyclic stability with ≈135% capacity retention after 150 000 cycles.

Green Synthesis of ZnO Nanoparticles and Ag-Doped ZnO Nanocomposite Utilizing Sansevieria trifasciata for High-Performance Asymmetric Supercapacitors

This study provides a comprehensive analysis of a biofabricated nanomaterial derived from Sansevieria trifasciata root extract, evaluating its structural, morphological, and optical properties for use in asymmetric supercapacitors. The nanomaterial comprises pristine ZnO nanoparticles (ZnO NPs) and a 1% Ag-doped ZnO nanocomposite (Ag@ZnO NC), synthesized through a green-assisted sol-gel autocombustion method. Employing techniques such as X-ray diffraction, ultraviolet-visible near-infrared, scanning electron microscopy-energy-dispersive X-rayspectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and transmission electron microscopy, the study confirms a hexagonal wurtzite structure and nanocrystallites with spherical and hexagonal shapes (30 nm). Optical analysis reveals a red shift in the band gap with Ag doping, indicating improved conductivity. The material shows potential applications in solar cells, optoelectronics, spintronics, wastewater treatment, and high-performance asymmetric supercapacitors. Raman spectra validate the wurtzite phase and identify intrinsic defects. Electrochemical tests demonstrate remarkable supercapacitive behavior with a 94% capacitance retention after 10,000 cycles, highlighting its promise as advanced asymmetric supercapacitors.

Ultra-thin nanosheets decorated in-situ S-doped 3D interconnected carbon network as interlayer modified Li-S batteries separator for accelerating adsorption-catalytic synergistic process of LiPSs

The shuttle effect of soluble lithium polysulfides (LiPSs) is primarily responsible for the unstable performance of lithium-sulfur (Li-S) batteries, which has severely impeded their continued development. In order to solve this problem, a special strategy is proposed. Specifically, ultra-thin NiCo based layered double hydroxides (named LDH or NiCo-LDH) nanosheets are implanted into a pre-designed 3D interconnected carbon networks (SPC) to obtain porous composite materials (named SPC-LDH).During the operation of the battery, the 3D interconnected porous carbon mesh was the first to rapidly adsorb LiPSs, and then the LDH on the surface of the carbon mesh was used to realize the catalytic conversion of LiPSs. This facilitates the electrochemical conversion reaction between S substances while addressing the "shuttle effect". As a result, the battery maintains a discharge capacity of 1401.9, 1114.3, 975.5, 880.7, 760.4 and 679.6 mAh g-1 at the current densities of 0.1, 0.2, 0.5, 1, 2 and 3C, respectively. After 200 cycles at 2C, the battery's capacity stays at 732.9 mAh g-1, meaning that the average rate of capacity decay is only 0.007 % per cycle. Moreover, in-situ XRD demonstrates the critical function of PP/SPC-LDH separators in inhibiting LiPSs and encouraging Li2S transformation. The strong affinity of SPC-LDH for Li2S6 is also confirmed by density functional theory (DFT) calculation, offering more theoretical support for the synergistic adsorption process. This work offers a compelling method to develop modified separator materials that can counteract the "shuttle effect" in Li-S batteries.

Ultrafast Microwave-Assisted Synthesis of Porous NiCo Layered Double Hydroxide Nanospheres for High-Performance Supercapacitors

Currently, new clean energy storage technology must be effective, affordable, and ecologically friendly so as to meet the diverse and sustainable needs of the energy supply. In this work, NiCo-LDH containing intercalated EG was successfully prepared within 210 s using an ultrafast microwave radiation technique. Subsequently, a series of characterization and systematic electrochemical tests were conducted to analyze the composition, structure, and energy storage mechanism of the NiCo-LDH material. The Ni:Co ratio of 5:5 results in the highest capacitance value of 2156 F/g at 1 A/g and an outstanding rate performance of 86.8% capacity retention rate at 10 A/g. The results demonstrated that the unique porous structure of NiCo-LDH and large layer spacing were conducive to more electrochemical reactions. Additionally, an electrochemical test was carried out on the NiCo-LDH as a hybrid supercapacitor electrode material, with NiCo-LDH-5:5 serving as the positive electrode and activated carbon as the negative electrode, the asymmetric supercapacitor can achieve a maximum energy density of 82.5 Wh kg-1 and power density of 8000 W kg-1. The NiCo-LDH-5:5//AC hybrid supercapacitors own 81.5% cycle stability and 100% coulombic efficiency after 6000 cycles at 10 A/g.

NiCo-LDH coupled with 2D ZIF-derived Co nitrogen doped carbon nanosheet arrays as a self-supporting electrocatalyst for detection of formaldehyde

Formaldehyde is susceptible to illegal addition to foodstuffs to extend their shelf life due to its antimicrobial, preservative and bleaching properties. In this study, a self-supporting "nanosheet on nanosheet" arrays electrocatalyst with core-shell heterostructure was prepared in situ by coupling NiCo layer double hydroxide with 2D ZIF derived Co-nitrogen-doped porous carbon on carbon cloth (Co-N/C@NiCo-LDH NSAs/CC). Co-N/C nanosheet arrays act as a scaffold core with good electrical conductivity, providing more NiCo-LDH nucleation sites to avoid NiCo-LDH agglomeration, thus having fast mass/charge transfer performance. While the NiCo-LDH nanosheet arrays shell with high specific surface area provide more active sites for electrochemical reactions. As an electrocatalytic sensing electrode, Co-N/C@NiCo-LDH NSAs/CC has a wide linear range of 1 μM to 13 mM for formaldehyde detection, and the detection limit is 82 nM. Besides, the sensor has been applied to the detection of formaldehyde in food samples with satisfactory results.

Synergistic CuCoS-PANI materials for binder-free electrodes in asymmetric supercapacitors and oxygen evolution

In advanced electronics, supercapacitors (SCs) have received a lot of attention. Nevertheless, it has been shown that different electrode designs that are based on metal sulfides are prone to oxidation, instability, and poor conductance, which severely limits their practical application. We present a very stable, free-standing copper-cobalt sulfide doped with polyaniline as an electrode coated on nickel foam (CuCoS/PANI). The lightweight nickel foam encourages current collection as well as serving as a flexible support. The CuCoS-PANI electrode had a substantially greater 1659 C g-1 capacity at 1.0 A g-1. The asymmetric supercapacitor (ASC) can provide an impressive 54 W h kg-1 energy density while maintaining 1150 W kg-1 power. Additionally, when employed as an electrocatalyst in the oxygen evolution reaction, CuCoS/PANI exhibited a 200 mV overpotential and 55 mV dec-1 Tafel slope, demonstrating its effectiveness in facilitating the reaction.

In situ selective selenization of ZIF-derived CoSe2 nanoparticles on NiMn-layered double hydroxide@CuBr2 heterostructures for high performance supercapacitors

As an emerging energy storage device, the practical application of supercapacitors (SCs) is currently constrained by their low energy density. Enhancing the capacitance of supercapacitors by leveraging the synergistic effect of multiple components in composite electrodes with well-designed structures can effectively increase their energy density. Here, a wire-sheet-particle hierarchical heterostructured CoSe2@NiMn-layered double hydroxide (NiMn-LDH) @Cu1.8Se/Copper foam (CF) electrode is synthesized via phase pseudomorphic transformation process achieved by selective selenization for Cu and Co elements. Benefiting from the stable support structure of CuBr2, the large specific surface area of NiMn-LDH, and the excellent conductivity of CoSe2, the prepared binder-free electrode shows excellent electrochemical properties. The CoSe2@NiMn-LDH@Cu1.8Se hybrid electrode exhibits a superior specific areal capacitance of 7064 mF cm-2 at 2 mA cm-2 and a stable cyclic performance with 80.11 % capacitance retention after 10,000 cycles. Furthermore, the assembled CoSe2@NiMn-LDH@Cu1.8Se/CF//AC (activated carbon) asymmetric supercapacitor (ASC) achieves an energy density of 36.6 Wh kg-1 when the power density is 760.6 W Kg-1 and retains 87.35 % of the initial capacitance after 5000 cycles. Overall, this pioneering research provided new insight for preparing supercapacitor electrode materials by selective selenization and ration design of the structures.

Regulating the Oxygen Vacancy and Electronic Structure of NiCo Layered Double Hydroxides by Molybdenum Doping for High-Power Hybrid Supercapacitors

Amelioration of nickel-cobalt layered double hydroxides (NiCo-LDH) with a high specific theoretical capacitance is of great desire for high-power supercapacitors. Herein, a molybdenum (Mo) doping strategy is proposed to improve the charge-storage performance of NiCo-LDH nanosheets growing on carbon cloth (CC) via a rapid microwave process. The regulation of the electronic structure and oxygen vacancy of the LDH is consolidated by the density functional theory (DFT) calculation, which demonstrates that Mo doping narrows the band gap, reduces the formation energy of hydroxyl vacancies, and promotes ionic and charge transfer as well as electrolyte adsorption on the electrode surface. The optimal Mo-doped NiCo-LDH electrode (MoNiCo-LDH-0.05/CC) has an amazing specific capacity of 471.1 mA h g-1 at 1 A g-1 , and excellent capacity retention of 84.8% at 32 A g-1 , far superior to NiCo-LDH/CC (258.3 mA h g-1 and 76.4%). The constructed hybrid supercapacitor delivers an energy density of 103.3 W h kg-1 at a power density of 750 W kg-1 and retains the cycle retention of 85.2% after 5000 cycles. Two assembled devices in series can drive thirty LED lamps, revealing a potential application prospect of the rationally synthesized MoNiCo-LDH/CC as an energy-storage electrode material.

Controlled preparation of cobalt carbonate hydroxide@nickel aluminum layered double hydroxide core-shell heterostructure for advanced supercapacitors

Herein, we report the rational fabrication of unique core-shell nanoclusters composed of cobalt carbonate hydroxide (Co-CH) @ nickel aluminum layered double hydroxide (NiAl-LDH) on a carbon cloth (CC) substrate using a two-step hydrothermal strategy. The one-dimensional (1D) Co-CH nanowires core-shell functions as a framework for the growth of two-dimensional (2D) NiAl-LDH nanosheets, leading to the formation of a hierarchically porous core-shell heterostructure. The presence of abundant heterointerfaces enhances electrical conductivity, reduces charge transfer resistance, and facilitates ion/electron transfer. Taking full advantage of its unique nanostructure and synergistic effect of two components, the as-prepared Co-CH@NiAl-LDH hybrid material illustrates a specific capacity of 1029.4 C/g (2058.9 mC cm-2) at 1 A g-1 and good rate capability with a capacity retention of 68.5% at 20 A g-1. Additionally, the assembled Co-CH@NiAl-LDH//pine pollen-derived porous carbon (PPC) hybrid supercapacitor (HSC) delivers impressive energy and power densities of 66.2 Wh kg-1 (0.27 Wh cm-2) and 17529.7 Wh kg-1 (0.11 Wh cm-2), respectively. This device also achieves a superior capacity retention of 80.3% over 20,000 cycles. These findings prove the importance of engineering heterointerfaces in heterostructure for the promotion of energy storage performance.

Laser-induced transient conversion of rhodochrosite/polyimide into multifunctional MnO2/graphene electrodes for energy storage applications

Laser-induced graphene (LIG) has been extensively investigated for electrochemical energy storage due to its easy synthesis and highly conductive nature. However, the limited charge accumulation in LIG usually leads to significantly low energy densities. In this work, we report a novel strategy to directly transform natural rhodochrosite into ultrafine manganese dioxide (MnO2) nanoparticles (NPs) in the polyimide (PI) substrate for high-performance micro-supercapacitors (MSCs) and lithium-ion batteries (LIBs) through a scalable and cost-effective laser processing method. Specifically, laser treatment on rhodochrosite/polyimide precursors induces the thermal explosion, which splits rhodochrosite (10 μm) into MnO2 NPs (12-16 nm) on the carbon matrix of LIG due to the sputtering effect. Benefiting from largely exposed active sites from the ultrafine MnO2 and the synergetic effect from highly conductive LIG, the MnO2/LIG MSCs show a high specific capacitance of 544.0 F g-1 (154.3 mF cm-2; 14.16 F cm-3) at 3 A/g and 82.1% capacitance retention after 10,000 cycles at 5A/g, in contrast to pure LIG (<100 F g-1). Moreover, the MnO2/LIG-based LIBs show the highest reversible discharge capacity of ∼1097 mAh g-1 at 0.2 A/g and ∼ 866.4 mAh g-1 at 1.0 A/g. This study opens a new route for synthesizing novel LIG-based composites from natural minerals.

Cationic and anionic defect decoration of CoO through Cu dopants and oxygen vacancy for a High‑Performance supercapacitor

CoO has attracted increasing attention as an electrochemical energy storage owing to its excellent redox activity and high theoretical specific capacitance. However, its low inherent electrical conductivity results in sluggish reaction kinetics, and the poor rate capability of CoO limits its widespread applications. Herein, a multiple-defect strategy of engineering oxygen vacancies and Cu-ion dopants into the low-crystalline CoO nanowires (Ov-Cu-CoO) is successfully applied. Because of the advantage of the dual defect synergetic effect, the electronic structure and charge distribution are effectively modulated, thus enhancing the electrical conductivity and enriched redox chemistry. The obtained Ov-Cu-CoO electrode exhibits a high specific capacity of 1388.6 F⋅g-1 at a current density of 1 A⋅g-1, an ultrahigh rate performance (81.2% of the capacitance retained at 20 A⋅g-1) and excellent cycling stability (101.1% after 10,000 cycles). Moreover, an asymmetric supercapacitor device with Ov-Cu-CoO as the positive electrode having a high energy density of 44.1 W⋅h⋅kg-1 at a power density of 800 W⋅kg-1, and can still remain 27.2 W⋅h⋅kg-1 at a power density of 16 kW⋅kg-1. This study demonstrates an effective strategy to enhance electrochemical performance of CoO that can be easy applied to other transition metal oxides.

In-situ electrodeposited Co0.85Se@Ni3S2 heterojunction with enhanced performance for supercapacitors

Rational design of porous heterostructured electrode materials for high-performance supercapacitors remains a big challenge. Herein, we report the in situ synthesis of Co0.85Se@Ni3S2 hybrid nanosheet arrays supported on carbon cloth (CC) substrate though an efficient two-step electrodeposition method. Compared with pure Co0.85Se and Ni3S2, the well-defined Co0.85Se@Ni3S2 heterojunction possesses enriched active sites, improved electrical conductivity, and reduced ion diffusion resistance. Benefiting from its hierarchically porous nanostructure and the synergistic effect of Co0.85Se and Ni3S2, the as-synthesized Co0.85Se@Ni3S2 electrode delivers a gravimetric capacitance (Cg)/volumetric capacitance (Cv) of 1644.1F g-1/3161.7F cm-3 at 1 A g-1, outstanding rate capability of 60.7% capacitance retention at 20 A g-1, as well as good cycling performance of 87.8% capacitance retention after 5000 cycles. Additionally, a hybrid supercapacitor (HSC) device presents a maximum energy density (E) of 65.7 Wh kg-1 at 696.2 W kg-1 with 93.3% cyclic durability after 15,000 cycles. Thus, this work proposes a simple and effective strategy to fabricate porous heterojunctions as high-performance electrode materials for energy storage devices.

Nitrogen-doped graphene quantum dots embedding CuCo-LDH hierarchical hollow structure for boosted charge storage capability in supercapacitor

The nanostructure optimization of layered double hydroxide (LDH) can effectively alleviate fragile agglomerated problems. Herein, nitrogen-doped graphene quantum dots (NGQDs) embedded in CuCo-LDH hierarchical hollow structure is synthesized by hydrothermal and impregnation methods. The electrochemical results show that the ordered multi-component structure could effectively inhibit the aggregation and layer stacking. At the same time, the hierarchical structure establishes new electron and ion transfer channels, greatly reducing the resistance of interlayer transport and accelerating the diffusion rate of electrolyte ions. Besides, NGQDs have both good electrical conductivity and abundant active sites, which can further improve the electron transmission rate and effectively strengthen the energy storage capacity of the material. Therefore, the large specific capacity of 1009 F g-1 can be displayed at 1 A g-1. The energy density of the assembled carbon cloth (CC)@CuCo-LDH/NGQDs//activated carbon (AC) device can reach 58.6 Wh kg-1 at 850 W kg-1. Above test results indicate that CC@CuCo-LDH/NGQDs//AC devices exhibit stable multi-component hierarchical structure and excellent electrical conductivity, which provides an effective strategy for enhancing the electrochemical characteristics of asymmetric supercapacitors.

Engineering Interfacial Built-in Electric Field in Polymetallic Phosphide Heterostructures for Superior Supercapacitors and Electrocatalytic Hydrogen Evolution

Herein, a patterned rod-like CoP@NiCoP core-shell heterostructure is designed to consist of CoP nanowires cross-linked with NiCoP nanosheets in tight strings. The interfacial interaction within the heterojunction between the two components generates a built-in electric field that adjusts the interfacial charge state and create more active sites, accelerating the charge transfer and improving supercapacitor and electrocatalytic performance. The unique core-shell structure suppresses the volume expansion during charging and discharging, achieving excellent stability. As a result, CoP@NiCoP exhibits a high specific capacitance of 2.9 F cm-2 at a current density of 3 mA cm-2 and a high ion diffusion rate (Dion is 2.95 × 10-14  cm2  s-1 ) during charging/discharging. The assembled asymmetric supercapacitor CoP@NiCoP//AC exhibits a high energy density of 42.2 Wh kg-1 at a power density of 126.5 W kg-1 and excellent stability with a capacitance retention rate of 83.8% after 10 000 cycles. Furthermore, the modulated effect induced by the interfacial interaction also endows the self-supported electrode with excellent electrocatalytic HER performance with an overpotential of 71 mV at 10 mA cm-2 . This research may provide a new perspective on the generation of built-in electric field through the rational design of heterogeneous structures for improving the electrochemical and electrocatalytical performance.

Waste jean derived self N-containing activated carbon as a potential electrode material for supercapacitors

The rapid rise of the world population increases the annual amount of waste textile products. Textile products create a significant amount of CO2, water, and chemical footprints during production. Therefore, the reusability of textile products has an important environmental and economic impact. Waste denim was used in this study to produce activated carbon (AC) samples as the alternative substance for supercapacitor electrodes. Characterisation studies showed that AC samples contain nitrogen originating from the elastane in the denim structure. Electrochemical characterisation tests proved the pseudocapacitive behaviour of the denim-derived AC due to the nitrogen content. Specific capacitance values observed for the three-electrode and two-electrode cell configurations were 95.93 F/g and 54.64 F/g at 1 A/g, respectively. Good capacitive retention (83.01%) of the cell after 3000 galvanostatic charge-discharge cycles at 1 A/g shows that waste denim can be considered as raw material for energy storage systems.