Hierarchical PANI/NiCo-LDH Core-Shell Composite Networks on Carbon Cloth for High Performance Asymmetric Supercapacitor

In-Sb Covalent Bonds over Sb2Se3/In2Se3 Heterojunction for Enhanced Photoelectrochemical Water Splitting

Antimony selenide is a promising P-type photocatalyst, but it has a large number of deep energy level defects, leading to severe carrier recombination. The construction of a heterojunction is a common way to resolve this problem. However, the conventional heterojunction system inevitably introduces interface defects. Herein, we employ in situ synthesis to epitaxially grow In2Se3 nanosheets on Sb2Se3 nanorods and form In-Sb covalent interfacial bonds. This petal-shaped heterostructure reduced interface defects and enhanced the efficiency of carrier separation and transport. In this work, the photocurrent density in the proposed Sb2Se3/In2Se3 photocathode is 0.485 mA cm-2 at 0 VRHE, which is 30 times higher than that of pristine Sb2Se3 and it has prominent long-term stability for 24 h without obvious decay. The results reveal that the synergy of the bidirectional built-in electric field constructed between In2Se3 and Sb2Se3 and the solid In-Sb interfacial bonds together build a high-efficiency transport channel for the photogenerated carriers that display enhanced photoelectrochemical (PEC) water-splitting performance. This work provides efficient guidance for reducing interface defects via the in situ synthesis and construction of interfacial bonds.

One-Step Cooperative Growth of High Reaction Kinetics Composite Homogeneous Core-Shell Heterostructure

Reaction kinetics can be improved by the enhanced electrical contact between different components growing symbiotically. But so far, due to the necessity for material synthesis conditions match, the component structures of cooperative growth are similar, and the materials are of the same type. The collaborative growth of high-reaction kinetics composite homogeneous core-shell heterostructure between various materials is innovatively proposed with different structures in one step. The NiCo-LDH and PPy successfully symbiotically grow on activated carbon fiber fabric in one step. The open channel structure of the NiCo-LDH nanosheets is preserved while PPy effectively wrapped around the NiCo-LDH. The well-defined nanostructure with abundant active sites and convenient ion diffusion paths is favorable for electrolyte entry into the entire nanoarrays. In addition, owing to the enhanced electronic interaction between different components through XPS analysis, the NiCo-LDH@PPy electrode shows outstanding reaction kinetics and structural stability. The as-synthesized NiCo-LDH@PPy exhibited excellent super-capacitive storage capabilities, robust capacitive activity, and good rate survival. Furthermore, an asymmetric supercapacitor (ASC) device made of NiCo-LDH@PPy and activated carbon (AC) is able to maintain a long cycle life while achieving high power and energy densities.

Multifunctional Ni3S2@NF-based electrocatalysts for efficient and durable electrocatalytic water splitting

Transition-metal sulfides (TMSs) have indeed drawn dramatic interest as a potential species of electrocatalysts by virtue of their unique structural features. However, their poor stability and inherent activity have impeded their use in electrocatalytic water splitting. Here, we provide a rational design of a hierarchical nanostructured electrocatalyst containing CeOx-decorated NiCo-layered double hydroxide (LDH) coupled with Ni3S2 protrusions formed on a Ni foam (NF). Specifically, the as-prepared electrocatalyst, denoted as Ni2Co1 LDH-CeOx/Ni3S2@NF, presents only 250 and 300 mV overpotential at ±100 mA cm-2, respectively, along with the Tafel slope values of 92 and 52 mV dec-1, as well remarkable long-term life for water splitting in an alkaline electrolyte. Based on systematic experiments and theoretical analysis, the superior electrocatalytic property in terms of Ni2Co1 LDH-CeOx/Ni3S2@NF can be imputed to the following reasons: the porous framework of Ni3S2@NF provides a largely surface area and high conductivity; the NiCo LDH nanosheets provide enriched active sites and favorable adsorption ability; the oxygen-vacancy-rich CeOx optimizes the electronic configuration. Overall, these factors work synergistically to expedite the catalytic kinetics of splitting water. Our work concentrates on a rational interface to devise efficient, multifunctional, and serviceable electrocatalysts for future applications.

Waste Adsorbent-Derived Interconnected Hierarchical Attapulgite@Carbon/NiCo Layered Double Hydroxide Nanocomposites for Advanced Supercapacitors

The attapulgite@carbon/NiCo layered double hydroxide nanocomposites based on waste adsorbents are manufactured via simple and eco-friendly calcination and hydrothermal methods, by which they would be considerable electrode materials for advanced supercapacitors. To achieve sustainable development, the spent tetracycline-loaded attapulgite can act as a cost-effective available carbon source as well as a matrix material for carbon species and NiCo layered double hydroxide simultaneously. A controlled amount of attapulgite@carbon could be used to regulate the electrochemical properties of nanocomposites. The generated electrodes possess superior electrochemical properties with a specific capacitance of 2013.8 F g^-1 at 0.5 A g^-1, a retention rate of 87.7% at 5 A g^-1, and a cyclic stability of 64.9% for 4000 cycles at 5 A g^-1. Thus, the asymmetric supercapacitor device assembled with attapulgite@carbon/NiCo layered double hydroxide nanocomposites||active carbon shows a maximum capacitance of 231.3 F g^-1 at 0.5 A g^-1, with a preeminent energy density of 82.2 Wh kg^-1 when its power density is 4318 W kg^-1. This approach would contribute to the development of supercapacitors in an efficient and effective manner, as well as provide a feasible strategy for solving tetracycline pollution and recycling waste adsorbents to achieve sustainable development.

Nanoarchitectured two-dimensional layered double hydroxides-based nanocomposites for biomedical applications

Despite the exceptional physicochemical and morphological characteristics, the pristine layered double hydroxides (LDHs), or two-dimensional (2D) hydrotalcite clays, often suffer from various shortcomings in biomedicine, such as deprived thermal and chemical stabilities, acid-prone degradation, as well as lack of targeting ability, hampering their scale-up and subsequent clinical translation. Accordingly, diverse nanocomposites of LDHs have been fabricated by surface coating of organic species, impregnation of inorganic species, and generation of core-shell architectures, resulting in the complex state-of-the-art architectures. In this article, we initially emphasize various bothering limitations and the chemistry of these pristine LDHs, followed by discussions on the engineering strategies of different LDHs-based nanocomposites. Further, we give a detailed note on diverse LDH nanocomposites and their performance efficacy in various biomedical applications, such as drug delivery, bioimaging, biosensing, tissue engineering and cell patterning, deoxyribonucleic acid (DNA) extraction, as well as photoluminescence, highlighting the influence of various properties of installed supramolecular assemblies on their performance efficacy. In summary, we conclude with interesting perspectives concerning the lessons learned to date and the strategies to be followed to further advance their scale-up processing and applicability in medicine.

Polypyrrole Nanotunnels with Luminal and Abluminal Layered Double Hydroxide Nanosheets Grown on a Carbon Cloth for Energy Storage Applications

The structural design of transition metal-based electrode materials with gigantic energy storage capabilities is a crucial task. In this work, we report an assembly of thin layered double hydroxide (LDH) nanosheets arrayed throughout the luminal and abluminal parts of polypyrrole tunnels fastened onto both sides of a carbon cloth as a battery-type energy storage system. Electron microscopy images reveal that the resulting electrode (NiCo-LDH@H-PPy@CC, where H-PPy@CC represents carbon cloth-supported hollow polypyrrole fibers) is constructed by combining luminal and abluminal NiCo-LDH nanosheets onto a long polypyrrole tunnel on a carbon cloth. The primary sample shows an excellent specific capacity of 149.16 mAh g-1 at 1.0 mA cm-2, a remarkable rate capability of 80.45%, and comprehensive cyclic stability (93.4%). The improved performance is mainly attributed to the strategic organization of the electrode materials with superior Brunauer-Emmett-Teller (BET) surface area and conductivity. Moreover, an asymmetric supercapacitor device assembled with NiCo-LDH@H-PPy@CC and vanadium phosphate-incorporated carbon nanofiber (VPO@CNFs900) electrodes contributes a specific energy density of 32.42 Wh kg-1 at 3 mA cm-2 with a specific power density of 359.16 W kg-1. When the current density is increased by 6-fold, the specific power density reaches 1999.89 W kg-1 at a specific energy density of 20.06 Wh kg-1. This is a simple, cost-effective, and convenient synthetic strategy for the synthesis of porous nanosheet arrays assimilated into hollow fiber architectures, which can illuminate the ideal approach for the fabrication of novel materials with an immense potential for energy storage.

A CoNi telluride heterostructure supported on Ni foam as an efficient electrocatalyst for the oxygen evolution reaction

The excellent oxygen evolution reaction performance of a CoNi telluride heterostructure (0.4CoNi LDH@Te-180C) can be attributed to the inherent layered structure, interconnected nanoarray structures and the synergistic effect of Co and Ni species.

Nickel-Cobalt Hydroxides with Tunable Thin-Layer Nanosheets for High-Performance Supercapacitor Electrode

Layered double hydroxides as typical supercapacitor electrode materials can exhibit superior energy storage performance if their structures are well regulated. In this work, a simple one-step hydrothermal method is used to prepare diverse nickel-cobalt layered double hydroxides (NiCo-LDHs), in which the different contents of urea are used to regulate the different nanostructures of NiCo-LDHs. The results show that the decrease in urea content can effectively improve the dispersibility, adjust the thickness and optimize the internal pore structures of NiCo-LDHs, thereby enhancing their capacitance performance. When the content of urea is reduced from 0.03 to 0.0075 g under a fixed precursor materials mass ratio of nickel (0.06 g) to cobalt (0.02 g) of 3:1, the prepared sample NiCo-LDH-1 exhibits the thickness of 1.62 nm, and the clear thin-layer nanosheet structures and a large number of surface pores are formed, which is beneficial to the transmission of ions into the electrode material. After being prepared as a supercapacitor electrode, the NiCo-LDH-1 displays an ultra-high specific capacitance of 3982.5 F g^-1 under the current density of 1 A g^-1 and high capacitance retention above 93.6% after 1000 cycles of charging and discharging at a high current density of 10 A g^-1. The excellent electrochemical performance of NiCo-LDH-1 is proved by assembling two-electrode asymmetric supercapacitor with carbon spheres, displaying the specific capacitance of 95 F g^-1 at 1 A g^-1 with the capacitance retention of 78% over 1000 cycles. The current work offers a facile way to control the nanostructure of NiCo-LDHs, confirms the important affection of urea on enhancing capacitive performance for supercapacitor electrode and provides the high possibility for the development of high-performance supercapacitors.

Photocatalytic and Oxidative Synthetic Pathways for Highly Efficient PANI-TiO2 Nanocomposites as Organic and Inorganic Pollutant Sorbents

Polyaniline (PANI)-materials have recently been proposed for environmental remediation applications thanks to PANI stability and sorption properties. As an alternative to conventional PANI oxidative syntheses, which involve toxic carcinogenic compounds, an eco-friendly procedure was here adopted starting from benign reactants (aniline-dimer and H₂O₂) and initiated by ultraviolet (UV)-irradiated TiO₂. To unlock the full potential of this procedure, we investigated the roles of TiO₂ and H₂O₂ in the nanocomposites synthesis, with the aim of tailoring the properties of the final material to the desired application. The nanocomposites prepared by varying the TiO₂:H₂O₂:aniline-dimer molar ratios were characterized for their thermal, optical, morphological, structural and surface properties. The reaction mechanism was investigated via mass analyses and X-ray photoelectron spectroscopy. The nanocomposites were tested on both methyl orange and hexavalent chromium removal. A fast dye-sorption was achieved also in the presence of interferents and the recovery of the dye was obtained upon eco-friendly conditions. An efficient Cr(VI) abatement was obtained also after consecutive tests and without any regeneration treatment. The fine understanding of the reaction mechanism allowed us to interpret the pollutant-removal performances of the different materials, leading to tailored nanocomposites in terms of maximum sorption and reduction capability upon consecutive tests even in simulated drinking water.

A novel dual-tasking hollow cube NiFe2O4-NiCo-LDH@rGO hierarchical material for high preformance supercapacitor and glucose sensor

Binary transition metal oxides as electroactive materials have continuously aroused grumous attention due to their high theoretical specific capacitance, high valtage window, and multiple oxidation states. However, the tiny specific surface area, poor conductivity and unsatisfactory cycle stability limit their practical application. Hence, a synthetic strategy is designed to fabricate a dual-tasking hollow cube nickel ferrite (NiFe₂O₄) - based composite (NiFe₂O₄-NiCo-LDH@rGO) with hierarchical structure. The composite is constructed by firstly preparing hollow NiFe₂O₄ from cube-like Ni - Fe bimetallic organic framework (NiFe-MOF), and then integrating nickel cobalt layered double hydroxide (NiCo-LDH) nanowires, together with reduced graphene oxide (rGO) via pyrolysis in conjuction with hydrothermal method. The NiFe₂O₄ possessing cubic hollow structure contributes to a huge accessible surface area, meanwhile alleviates large volume expansion/contraction effect, which facilitates suffcient permeation of the electrolyte and rapid ion/charge transport, and results in high cycling stability. The introduction of layered NiCo-LDH results in hierarchical structure and thus offers maximum contact areas with electrolyte, which heightens the specific capacitance of obtained composite and enhances the electro-catlytic activity towards oxidation of glucose. Furthermore, rGO layer greatly improves the electrical conductivity and ion diffusion/transport capability of composite. Benefiting from the unique structure and individual components of NiFe₂O₄-NiCo-LDH@rGO composite, the electrode delivers a high specific capacitance (750 C g^-1) and superb durability. Simultaneously, the asymmetrical device based on NiFe₂O₄-NiCo-LDH@rGO as positive electrode delivers remarkable energy density (50 Wh kg^-1). Moreover, NiFe₂O₄-NiCo-LDH@rGO exhibits good sensing performance with a sensitivity of 111.86 µA/µM cm^-2, the wide linear range of 3.500 × 10^-5 - 4.525 × 10^-3 M, and the detection limit of 12.94 × 10^-6 M with a signal to noise ratio of 3. Consequently, the NiFe₂O₄-NiCo-LDH@rGO could provide a prospective notion constructing bifunctional materials with hollow-cube hierarchical structure in the field of supercapacitors and electrochemical sensors.

A facile synthesis of layered double hydroxide based core@shell hybrid materials

A simple and scalable co-precipitation method to obtain zeolite Z13X@Mg₂Al–CO₃-LDH and Mg-MOF-74@Mg₂Al–CO₃-LDH has been reported.

Homogeneous Core/Shell NiMoO4@NiMoO4 and Activated Carbon for High Performance Asymmetric Supercapacitor

Here, we report the extraordinary electrochemical energy storage capability of NiMoO₄@NiMoO₄ homogeneous hierarchical nanosheet-on-nanowire arrays (SOWAs), synthesized on nickel substrate by a two-stage hydrothermal process. Comparatively speaking, the SOWAs electrode displays superior electrochemical performances over the pure NiMoO₄ nanowire arrays. Such improvements can be ascribed to the characteristic homogeneous hierarchical structure, which not only effectively increases the active surface areas for fast charge transfer, but also reduces the electrode resistance significantly by eliminating the potential barrier at the nanowire/nanosheet junction, an issue usually seen in other reported heterogeneous architectures. We further evaluate the performances of the SOWAs by constructing an asymmetric hybrid supercapacitor (ASC) with the SOWAs and activated carbon (AC). The optimized ASC shows excellent electrochemical performances with 47.2 Wh/kg in energy density of 1.38 kW/kg at 0–1.2 V. Moreover, the specific capacity retention can be as high as 91.4% after 4000 cycles, illustrating the remarkable cycling stability of the NiMoO₄@NiMoO₄//AC ASC device. Our results show that this unique NiMoO₄@NiMoO₄ SOWA has great prospects for future energy storage applications.