AgNWs/Fe3O4@NC Conductive Network Hierarchical Assembly to Prepare Flexible EMI Shielding Textile.

With the rapid development of high-power electronic instruments and communication technology, efficient electromagnetic shielding materials with strong absorption of electromagnetic waves and low reflection characteristics have become the focus of the world's attention. This study designs and synthesizes N-doped carbon-coated hollow Fe3O4 nanospheres (Fe3O4@NC) by spraying Ag nanowires (AgNWs) on textiles as conductive networks. Because of the high permeability and hollow structure Fe3O4@NC, electromagnetic wave goes through a unique process of "absorption, reflection, and reabsorption" when it passes through the surface of the composite textile. In X-band (≈8.2-12.4 GHz), the average electromagnetic interference shielding effectiveness (EMI SE) reaches 50.1 dB, while the reflectance shielding efficiency (SER) is only 2.6 dB, and the average reflectance power coefficient (R) is as low as 0.45. The composite fabric has excellent properties and provides an effective strategy for electromagnetic interference shielding based on absorption.

Optimizing the Electronic Structure of Atomically Dispersed Ru Sites with CoP for Highly Efficient Hydrogen Evolution in both Alkaline and Acidic Media.

Developing efficient and stable electrocatalysts for hydrogen evolution reaction (HER) over a wide pH range and industrial large-scale hydrogen production is critical and challenging. Here, a tailoring strategy is developed to fabricate an outstanding HER catalyst in both acidic and alkaline electrolytes containing high-density atomically dispersed Ru sites anchored in the CoP nanoparticles supported on carbon spheres (NC@RuSA -CoP). The obtained NC@RuSA -CoP catalyst exhibits excellent HER performance with overpotentials of only 15 and 13 mV at 10 mA cm-2 in 1 m KOH and 0.5 m H2 SO4 , respectively. The experimental results and theoretical calculations indicate that the strong interaction between the Ru site and the CoP can effectively optimize the electronic structure of Ru sites to reduce the hydrogen binding energy and the water dissociation energy barrier. The constructed alkaline anion exchange membrane water electrolyze (AAEMWE) demonstrates remarkable durability and an industrial-level current density of 1560 mA cm-2 at 1.8 V. This strategy provides a new perspective on the design of Ru-based electrocatalysts with suitable intermediate adsorption strengths and paves the way for the development of highly active electrocatalysts for industrial-scale hydrogen production.

Solid-State Thin-Film Supercapacitors with Ultrafast Charge/Discharge Based on N-Doped-Carbon-Tubes/Au-Nanoparticles-Doped-MnO2 Nanocomposites.

Although carbonaceous materials possess long cycle stability and high power density, their low-energy density greatly limits their applications. On the contrary, metal oxides are promising pseudocapacitive electrode materials for supercapacitors due to their high-energy density. Nevertheless, poor electrical conductivity of metal oxides constitutes a primary challenge that significantly limits their energy storage capacity. Here, an advanced integrated electrode for high-performance pseudocapacitors has been designed by growing N-doped-carbon-tubes/Au-nanoparticles-doped-MnO2 (NCTs/ANPDM) nanocomposite on carbon fabric. The excellent electrical conductivity and well-ordered tunnels of NCTs together with Au nanoparticles of the electrode cause low internal resistance, good ionic contact, and thus enhance redox reactions for high specific capacitance of pure MnO2 in aqueous electrolyte, even at high scan rates. A prototype solid-state thin-film symmetric supercapacitor (SSC) device based on NCTs/ANPDM exhibits large energy density (51 Wh/kg) and superior cycling performance (93% after 5000 cycles). In addition, the asymmetric supercapacitor (ASC) device assembled from NCTs/ANPDM and Fe2O3 nanorods demonstrates ultrafast charge/discharge (10 V/s), which is among the best reported for solid-state thin-film supercapacitors with both electrodes made of metal oxide electroactive materials. Moreover, its superior charge/discharge behavior is comparable to electrical double layer type supercapacitors. The ASC device also shows superior cycling performance (97% after 5000 cycles). The NCTs/ANPDM nanomaterial demonstrates great potential as a power source for energy storage devices.

Design hierarchical electrodes with highly conductive NiCo2S4 nanotube arrays grown on carbon fiber paper for high-performance pseudocapacitors.

We report on the development of highly conductive NiCo2S4 single crystalline nanotube arrays grown on a flexible carbon fiber paper (CFP), which can serve not only as a good pseudocapacitive material but also as a three-dimensional (3D) conductive scaffold for loading additional electroactive materials. The resulting pseudocapacitive electrode is found to be superior to that based on the sibling NiCo2O4 nanorod arrays, which are currently used in supercapacitor research due to the much higher electrical conductivity of NiCo2S4. A series of electroactive metal oxide materials, including CoxNi1-x(OH)2, MnO2, and FeOOH, were deposited on the NiCo2S4 nanotube arrays by facile electrodeposition and their pseudocapacitive properties were explored. Remarkably, the as-formed CoxNi1-x(OH)2/NiCo2S4 nanotube array electrodes showed the highest discharge areal capacitance (2.86 F cm(-2) at 4 mA cm(-2)), good rate capability (still 2.41 F cm(-2) at 20 mA cm(-2)), and excellent cycling stability (∼ 4% loss after the repetitive 2000 cycles at a charge-discharge current density of 10 mA cm(-2)).

Coaxial nickel cobalt selenide/nitrogen-doped carbon nanotube array as a three-dimensional self-supported electrode for electrochemical energy storage.

Herein, we propose a one-step urea pyrolysis method for preparing a nitrogen-doped carbon nanotube array grown on carbon fiber paper, which is demonstrated as a three-dimensional scaffold for constructing a nickel cobalt selenide-based coaxial array structure. Thanks to the large surface area, interconnected porous structure, high mass loading, as well as fast electron/ion transport pathway of the coaxial array structure, the nickel cobalt selenide/nitrogen-doped carbon nanotube electrode exhibits over 7 times higher areal capacity than that directly grown on carbon fiber paper, and better rate capability. The cell assembled by a nickel cobalt selenide/nitrogen-doped carbon nanotube positive electrode and an iron oxyhydroxide/nitrogen-doped carbon nanotube negative electrode delivers a volumetric capacity of up to 22.5 C cm-3 (6.2 mA h cm-3) at 4 mA cm-2 and retains around 86% of the initial capacity even after 10 000 cycles at 10 mA cm-2. A volumetric energy density of up to 4.9 mW h cm-3 and a maximum power density of 208.1 mW cm-3 are achieved, and is comparable to, if not better than, those of similar energy storage devices reported previously.

General and Facile Synthesis of Co/CoO Nanoparticals Supported by Nitrogen-Doped Graphenic Networks as Efficient Oxygen Electrocatalyst for Zn-Air Batteries.

Reasonable design of low-cost, high-efficiency and stable bifunctional oxygen electrocatalysts is of great significance to improve the reaction efficiency of Zn-air batteries, which is still a huge challenge. Here, we report a highly efficient bifunctional oxygen electrocatalyst with three-dimensional (3D) N-doped graphene network-supported cobalt and cobalt oxide nanoparticles (Co/CoO-NG), which can be in situ synthesized by inducing metal ions on metal plates via graphene oxide as an inducer. This 3D network structure and open active center show excellent bifunctional oxygen electrocatalytic activity under alkaline conditions, and can be used as an air electrode in rechargeable Zn-air batteries, with significantly better power density (244.28 mW cm-2) and stability (over 340 h) than commercial Pt/C+RuO2 mixtures. This work is conducive to advancing the practical application of graphene-based materials as air electrodes for rechargeable zinc-air batteries.

Continuous On-Site H2O2 Electrosynthesis via Two-Electron Oxygen Reduction Enabled by an Oxygen-Doped Single-Cobalt Atom Catalyst with Nitrogen Coordination.

Single-Co atom catalysts are suggested as an efficient platinum metal group-free catalyst for promoting the oxygen reduction into water or hydrogen peroxide, while the relevance of the catalyst structure and selectivity is still ambiguous. Here, we propose a thermal evaporation method for modulating the chemical environment of single-Co atom catalysts and unveil the effect on the selectivity and activity. It discloses that nitrogen functional groups prefer to proceed the oxygen reduction via a 4e- pathway and notably improve the intrinsic activity, especially when being coordinated with the Co center, while oxygen doping tempts the electron delocalization around cobalt sites and decreases the binding force toward HOO* intermediates, thereby increasing the 2e- selectivity. Consequently, the well-designed oxygen-doped single-Co atom catalysts with nitrogen coordination deliver an impressive 2e- oxygen reduction performance, approaching the onset potential of 0.78 V vs RHE and selectivity of >90%. As an impressive cathode catalyst of an electrochemical flow cell, it generates H2O2 at a rate of 880 mmol gcat-1 h-1 and faradaic efficiency of 95.2%, in combination with an efficient nickel-iron oxygen evolution anode.

Exploring the degradation mechanism of nickel-copper-molybdenum hydrogen evolution catalysts during intermittent operation.

We investigate the dynamic degradation behaviors of a nickel-copper-molybdenum hydrogen evolution catalyst in a liquid and solid polymer electrolyte to figure out its endurance in a renewable energy-driven electrolyzer. A cathode current protection approach is proposed to achieve a durable electrolyzer during intermittent operation.

Rational Design of Trimetallic Sulfide Electrodes for Alkaline Water Electrolysis with Ampere-Level Current Density.

Electrochemical water splitting is considered an environmentally friendly approach to hydrogen generation. However, it is difficult to achieve high current density and stability. Herein, we design an amorphous/crystalline heterostructure electrode based on trimetallic sulfide over nickel mesh substrate (NiFeMoS/NM), which only needs low overpotentials of 352 mV, 249 mV, and 360 mV to achieve an anodic oxygen evolution reaction (OER) current density of 1 A cm-2 in 1 M KOH, strong alkaline electrolyte (7.6 M KOH), and alkaline-simulated seawater, respectively. More importantly, it also shows superior stability with negligible decay after continuous work for 120 h at 1 A cm-2 in the strong alkaline electrolyte. The excellent OER performance of the as-obtained electrode can be attributed to the strong electronic interactions between different metal atoms, abundant amorphous/crystalline hetero-interfaces, and 3D porous nickel mesh structure. Finally, we coupled NiFeMoS/NM as both the anode and cathode in the anion exchange membrane electrolyzer, which can achieve low cell voltage and high stability at ampere-level current density, demonstrating the great potential of practicability.

Two-Dimensional Cobalt Sulfide/Iron-Nitrogen-Carbon Holey Sheets with Improved Durability for Oxygen Electrocatalysis.

Transition-metal sulfide as a promising bifunctional oxygen electrocatalyst alternative to scarce platinum-group metals has attracted much attention, but it suffers activity loss over time owing to poor structural/compositional stability during catalysis. Herein, we report a self-template method for preparing a two-dimensional cobalt sulfide holey sheet superstructure with hierarchical porosity followed by the encapsulation of thin iron-nitrogen-carbon as a protective layer. The iron-nitrogen-carbon layer to some degree precludes the phase transition of cobalt sulfide underneath and preserves the structural integrity during catalysis, therefore rendering an exceptional durability in terms of no obvious activity loss after 10,000 cycles of the accelerated durability test. It also noticeably enhances the intrinsic activity of cobalt sulfide and does not influence its exposure into the electrolyte, resulting in showing an extraordinary electrochemical performance in terms of a potential difference of 0.69 V for the overall oxygen redox. A rechargeable zinc-air battery assembled by a cobalt sulfide/iron-nitrogen-carbon air cathode delivers approximately 4.2 times higher power density than that without an iron-nitrogen-carbon layer and stably operates for 300 h with a high voltaic efficiency. This work gives a facile and effective strategy for improving the long-term durability of transition-metal sulfide electrocatalysts.

Cation Modulation of Cobalt Sulfide Supported by Mesopore-Rich Hydrangea-Like Carbon Nanoflower for Oxygen Electrocatalysis.

Transition-metal sulfide is pursued for replacing scare platinum-group metals for oxygen electrocatalysis and is of great importance in developing low-cost, high-performance rechargeable metal-air batteries. We report herein a facile cationic-doping strategy for preparing nickel-doped cobalt sulfide embedded into a mesopore-rich hydrangea-like carbon nanoflower. Nickel cations are introduced to induce the formation of Co3+-active species and more oxygen vacancies due to higher electronegativity and smaller ionic radius, thereby strengthening the intrinsic activity for oxygen electrocatalysis. Moreover, hydrangea-like superstructure composed of interconnected carbon cages provides abundant accessible active sites and hierarchical porosity. As a result, it shows excellent catalytic performance with a superior mass activity for the oxygen reduction reaction to the state-of-the-art Pt/C catalyst and a low overpotential of 314 mV at 10 mA cm-2 for the oxygen evolution reaction. When used as an air cathode for the rechargeable Zn-air battery, it delivers a peak power density of 96.3 mW cm-2 and stably operates over 214 h. This work highlights the importance of cationic doping in strengthening the electrocatalytic performance of 3d-transition-metal chalcogenides.

Biomimetic mineralization of CaCO3 on a phospholipid monolayer: from an amorphous calcium carbonate precursor to calcite via vaterite.

A phospholipid monolayer, approximately half the bilayer structure of a biological membrane, can be regarded as an ideal model for investigating biomineralization on biological membranes. In this work on the biomimetic mineralization of CaCO(3) under a phospholipid monolayer, we show the initial heterogeneous nucleation of amorphous calcium carbonate precursor (ACC) nanoparticles at the air-water interface, their subsequent transformation into the metastable vaterite phase instead of the most thermodynamically stable calcite phase, and the ultimate phase transformation to calcite. Furthermore, the spontaneity of the transformation from vaterite to calcite was found to be closely related to the surface tension; high surface pressure could inhibit the process, highlighting the determinant of surface energy. To understand better the mechanisms for ACC formation and the transformation from ACC to vaterite and to calcite, in situ Brewster angle microscopy (BAM), ex situ scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray diffraction analysis were employed. This work has clarified the crystallization process of calcium carbonate under phospholipid monolayers and therefore may further our understanding of the biomineralization processes induced by cellular membranes.

Microstructure Engineering of Fe/Fe3C-Decorated Metal-Nitrogen-Carbon Mesoporous Nanospheres via a Self-Template Method for Enhancing Oxygen Reduction Activity.

We report a self-template and facile pyrolysis method to synthesize Fe/Fe3C-decorated metal-nitrogen-carbon mesoporous nanospheres, of which preserved plum-like and hollow structures can be simply engineered via controlling the thickness of the outermost polydopamine layer in the precursors. The preserved plum-like structure is demonstrated to show a large electrochemically active surface area and facilitate fast charge transfer, in comparison with the hollow one. The catalytic activities of metal-nitrogen-carbon and nitrogen-doped carbon active sites in the outer carbon layer toward oxygen reduction are improved under the activation of the encased Fe species. Hence, preserved plum-like structures exhibit excellent catalytic kinetics toward the oxygen reduction reaction in alkaline media. The mass activity of 21.0 mA mgcatalyst-1 at 0.9 V vs RHE is achieved and the half-wave potential is 50 mV more positive than that of the Pt/C catalyst with the same mass loading. Moreover, the outer carbon layer endows the tolerance of strong acidic and alkaline environments, resulting in good durability. Our study proposes a simple strategy for the rational design of novel transition metal carbide-based catalysts, making it a promising candidate for replacing platinum-group metal catalysts in low-temperature fuel cells.

Ultrasonic-irradiation-assisted oriented assembly of ordered monetite nanosheets stacking.

Bioactive monetite (anhydrous calcium hydrogen phosphate, CaHPO(4)) with orderly layered structure assembled by nanosheets has been successfully synthesized by a sonochemical-assisted method in the presence of cetyltrimethylammonium bromide (CTAB). The thicknesses of the nanosheets are 100-200 nm, and the lateral sizes are about 2 microm. Because of the strong affinity with the phosphate ions as well as the (200) faces of the crystals, CTAB molecules can make the formation and stabilization of monetite nanosheets with (200) exposed face. Ultrasonic irradiation makes the transition from disordered state to oriented state before the oriented assembly of monetite nanosheets. The ultrasonic irradiation provides enough external work to make the assemble process possible in thermodynamics. The drastic flow stirred by the supersonic jet in the solution accomplishes the transition and successive oriented assembly of nanosheets in dynamics. This study would offer a simple method to design and synthesize oriented-assembled materials.

An asymmetric coating composed of gelatin and hydroxyapatite for the delivery of water insoluble drug.

An asymmetric coating composed of gelatin and hydroxyapatite on Ti6Al4V alloy implant was prepared to control the release of water-insoluble drug ibuprofen and improve the surface properties of the implant. The asymmetric coating developed into a thin dense outer layer and a thick porous inner layer using a dip-coating method and a succedent phase-inversion process. The drug loading ranged from 10 to 30% (w/w), and depended on the immersion time and drug concentration in the quenching solution. The in vitro release from this system was always at an approximately zero-order rate and at least lasted for 30 days. The in vitro studies in SBF revealed that the coating could induce the formation of apatite, and was fully covered after 14 days soaking in SBF solution. This asymmetric coating had better bioactivity of inducing the formation of apatite in vitro, compared with pure gelatin coating and bare Ti6Al4V implant.

In situ growth of Fe(ii)-MOF-74 nanoarrays on nickel foam as an efficient electrocatalytic electrode for water oxidation: a mechanistic study on valence engineering.

In this work, our theoretical results first demonstrate that varying the metal valence in MOFs plays a significant role in tuning their stable intrinsic electronic structure. Different valence Fe(ii) and Fe(iii) based pristine MOF-74 nanoarrays on nickel foam are further synthesized as electrodes for highly efficient electrocatalytic water oxidation.

Urchin-like non-precious-metal bifunctional oxygen electrocatalysts: Boosting the catalytic activity via the In-situ growth of heteroatom (N, S)-doped carbon nanotube on mesoporous cobalt sulfide/carbon spheres.

We successfully design and construct urchin-like non-precious-metal bifunctional oxygen electrocatalysts via a two-step pyrolysis process, where nitrogen, sulfur co-doped carbon nanotube frameworks are grafted onto mesoporous cobalt sulfide/nitrogen, sulfur co-doped carbon spheres. The urchin-like structure grants large electrochemically active area, good electron and mass transfer capability, as well as excellent structural stability. Nitrogen, sulfur co-doped carbon can synergistically enhance the catalytic activity of cobalt sulfide sites, and also contribute to the exposure of heteroatom-induced active sites, such as, pyridinic N, graphitic N, and C-S-C. Hence, benefiting from the unique architecture and efficient catalytic sites, the resulting catalysts demonstrate excellent bifunctional catalytic activities with a positive half-wave potential of 0.860 V vs. RHE for oxygen reduction reaction and low overpotential of ∼390 mV at the current density of 10 mA cm-2 for oxygen evolution reaction in alkaline medium, which can rank them among one of the most promising cobalt-based bifunctional oxygen electrocatalysts reported previously.

Coordination-Assisted Polymerization of Mesoporous Cobalt Sulfide/Heteroatom (N,S)-Doped Double-Layered Carbon Tubes as an Efficient Bifunctional Oxygen Electrocatalyst.

It is a critical challenge to construct efficient precious-metal-free bifunctional oxygen electrocatalysts for fuel cell and metal-air batteries via structural and component engineering. Herein, a one-dimensional mesoporous double-layered tubular structure, where Co9S8 nanocrystals are incorporated into nitrogen, sulfur codoped carbon, is successfully synthesized via the coordinated-assisted polymerization and sacrificial template methods. The double-layered tubular structure provides for a large electrochemically active surface area and promotes fast mass transfer. Cobalt oxides/oxyhydroxides, which are evolved from the sulfides during the catalytic processes, as the main active sites efficiently catalyze the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), in cooperation with the Co-N-C and heteroatom-induced active sites. Hence, it demonstrates excellent bifunctional electrocatalytic activity with the overvoltage between the OER potential at 10 mA cm-2 ( E10) and ORR half-wave potential ( E1/2) of 0.707 V, which is superior to most of precious-metal-free bifunctional oxygen electrocatalysts reported recently, as well as the state-of-art Pt/C and RuO2 catalysts.

Triple Acceptors in a Polymeric Architecture for Balanced Ambipolar Transistors and High-Gain Inverters.

The exploration of novel molecular architectures is crucial for the design of high-performance ambipolar polymer semiconductors. Here, a "triple-acceptors architecture" strategy to design the ambipolar polymer DPP-2T-DPP-TBT is introduced. The utilization of this architecture enables DPP-2T-DPP-TBT to achieve deep-lying highest occupied molecular orbital (HOMO)/lowest unoccupied molecular orbital (LUMO) levels of -5.38/-4.19 eV, and strong intermolecular interactions, which are favorable for hole/electron injection and intermolecular hopping through π-stacking. All these factors result in excellent ambipolar transport characteristics and promising applications in complementary-like circuits for DPP-2T-DPP-TBT under ambient conditions with high hole/electron mobilities and a gain value of up to 3.01/3.84 cm2 V-1 s-1 and 171, respectively, which are among the best performances in ambipolar polymer organic thin-film transistors and associated complementary-like circuits, especially in top-gate device configuration with low-cost glass as substrates. These results demonstrate that the "triple-acceptors architecture" strategy is an effective way for designing high-performance ambipolar polymer semiconductors.

Hollow Nitrogen-Doped Carbon Spheres with Fe3O4 Nanoparticles Encapsulated as a Highly Active Oxygen-Reduction Catalyst.

The development of nonprecious electrocatalyst with low cost and high efficiency for the oxygen reduction reaction (ORR) is a main challenge for electrochemical energy technology. In this work, a hierarchical hollow core-shell structured N-doped carbon spheres (N-HSCS), in which Fe3O4 nanoparticles are encapsulated (Fe3O4/N-HCSC) has been successfully prepared. The Fe3O4/N-HCSC electrocatalyst exhibits a remarkable catalytic performance toward ORR. The porous hollow core-shell structure and synergistic effect between Fe3O4 and protective nitrogen-doped graphitic layers are mainly responsible for such an excellent ORR catalytic property and stability. This work demonstrates a promising strategy of nanostructure-engineering to the future design and preparation of highly efficient non-noble metal electrocatalysts.