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The development of modern information technology has recently put forward higher requirements for the ingenious design of electromagnetic wave absorbing (EMA) materials with a broad bandwidth at a low filling ratio. Herein, three-dimensional (3D) S-doped Co3O4 microflowers@reduced graphene oxide (S-Co3O4@RGO) aerogels are successfully prepared by interface and defect engineering with superior EMA capability. The 3D structure with a high surface-to-volume ratio can effectively avoid the agglomeration of Co3O4 and enhance the RGO–Co3O4 heterointerfaces to implement multiple reflection mechanisms. The synergistic effect of atom and phase cross-hybridization can improve defect-induced polarization centres and coherent interface-induced interface polarization. Meanwhile, the defects located at the interface have more charge transfer to enhance interface polarization than that at the interior, which is first proposed and demonstrated by density functional theory (DFT) calculations. Thus, the minimal reflection loss value can reach −56.7 dB (3.6 mm, 5.44 GHz) and the maximum effective absorption bandwidth is 8.48 GHz (ranging from 9.28 to 17.76 GHz) at a matching thickness of 2.3 mm with a filling ratio of 5 wt%. This work opens a new pathway to synthesize electromagnetic wave absorbents with synergistic defect and interface induced polarization loss, and has tremendous potential for EMA applications. [ABSTRACT FROM AUTHOR]

Bismuth (Bi) has been regarded as a promising anode material for potassium-ion batteries (PIBs) due to its high theoretical capacity (386 mA h g−1). However, the accompanying drastic volume change during charge/discharge processes has seriously hindered its practical application in PIBs. Herein, a multi-core–shell heterostructured Bi@Void@TiO2 embedded in one-dimensional carbon nanofibers (CNF) is synthesized to solve this problem. Specifically, the chamber between the Bi core and TiO2 shell can buffer the volume change of Bi, and the TiO2 shell not only effectively prevents carbon skeleton collapse during carbonization, but also inhibits the agglomeration of Bi during alloying/dealloying. Importantly, theoretical calculations confirm that the heterostructures between the TiO2 shell and Bi/carbon facilitate the reaction kinetics of K+. As a PIB anode, the Bi@Void@TiO2⊂CNF electrode presents a high capacity of 388.8 mA h g−1 at 0.05 A g−1, and a remarkable capacity of 171.6 mA h g−1 at 2 A g−1 after 3000 cycles with a capacity retention of 85.4%. Moreover, a K-ion full cell based on a Bi@Void@TiO2⊂CNF anode can afford stable capacity retention over 1500 cycles at 1 A g−1. This work offers a promising strategy to design long-lived PIB anodes that show potential for practical applications. [ABSTRACT FROM AUTHOR]

The Ag–Cu2O/PANI composite material was synthesized using a simple, fast, and low-cost process, which is attractive for its many applications in the fields of photocatalysis, surface enhanced Raman scattering (SERS), and characterization. SEM, TEM, XRD, FT-IR, TG, UV-Vis and XPS measurements confirmed the successful synthesis of the Ag–Cu2O/PANI composite material. First-principles calculations on the basis of density functional theory (DFT) were used to analyze regulation of the work function of Cu2O. The results showed that Ag–Cu2O/PANI had an extremely high stability when exposed to oxygen, water, and light for a long period of time, which was attributed to the physical coating of Ag nanoparticles (Ag NPs) transferring the electrons (e−) and holes (h+) inside the Cu2O to the surface through the Schottky barrier to prevent photocorrosion. The deposition of Ag NPs also increased the intensity and time of the oxidative stress reaction of Cu2O, as evidenced by the reactive oxygen species (ROS) test. Ag NPs distributed on the surface of Cu2O particles formed many ion release channels, resulting in an excellent sustained release of Cu2+ ions. PANI as a protective barrier prevented Cu2O from directly contacting the external solution and releasing Cu2+ ions. PANI had an excellent e− transfer ability as a conductive polymer, which improved the efficiency of photogenerated e− and h+ separation of Cu2O. Our results showed that the Ag–Cu2O/PANI exhibited a high long-term antibacterial activity against S. aureus and P. aeruginosa, bacterial inhibition rates of which were maintained around 78% and 80% after being stored in phosphate buffer saline solution for 30 days. In this paper, Ag–Cu2O/PANI is proposed which can enhance the photocatalytic performance of Cu2O and long-term antibacterial activity. [ABSTRACT FROM AUTHOR]

An efficient hydrogen evolution reaction (HER) depends essentially on high-performing electrocatalysts. The aggregation of catalysts normally deteriorates their activity and stability. In this study, a two-step route was used to synthesize surface intercalated well-dispersed spherical MoS2xSe2(1−x) nanocatalysts. The resulting catalysts present a highly active and stable performance towards the HER with an overpotential of −143 mV at 10 mA cm−2, and a Tafel slope of 53.8 mV dec−1. The mechanism for the enhanced HER was analyzed and was attributed to three factors: (i) large numbers of defects and edge active sites arising from the coexistence of S and Se elements; (ii) enhanced electric conductivity arising from the phase transition from the semiconducting 2H-phase to metallic 1T-phase during the intercalation process; and (iii) enlarged contact areas between active sites and electrolyte caused by the increased surface roughness due to the surface intercalation. This work not only deepens our understanding of the improved HER performance of surface intercalated catalysts, but also provides novel strategies for preparing durable electrocatalysts through surface engineering. [ABSTRACT FROM AUTHOR]

As a promising electrocatalyst, MoS2 has attracted significant attention for application in the hydrogen evolution reaction (HER). However, the shortcomings such as limited active sites and the inherently low electroconductivity of the 2H-phase MoS2 restrain its application. Tuning of the phase composition (from 2H to 1T phase) and the microstructure of MoS2 have been proposed as effective strategies to improve the catalytic activity of MoS2. However, complicated chemical exfoliation and morphology regulation are generally involved in these process. Herein, we developed a facile hydrothermal method to in situ synthesize hierarchical MoS2 nanorods with mixed 1T and 2H phases. The coexisting 1T phase can provide more active sites and improve the electronic conductivity of the nanorods. In addition, the Schottky barriers formed at the boundaries of the 1T and 2H phases can improve the conductivity. Moreover, the hierarchical structure can improve the contact area between the MoS2 catalyst and the electrolyte, and the rod-like one-dimensional structure of the catalyst favors fast charge transfer and ion diffusion. Due to these unique properties, the as-synthesized MoS2 nanocatalyst exhibits excellent HER performance with a small overpotential of 156 mV at 10 mA cm−2, a small Tafel slope of 47.9 mV per decade, and robust stability. This study provides a guideline for the design of an electrocatalyst with high HER performance in multiscale principles. [ABSTRACT FROM AUTHOR]

In this study, a new carbon quantum dot (CQD) sensitized TiO2 nanorod (NR) electrode with a branch structure was fabricated for photoelectrochemical (PEC) water splitting by simple hydrothermal and impregnation methods. To enhance the adhesion between CQDs and TiO2 NRs and to accelerate the separation of electrons and holes by improving the interface properties, a thin Al2O3 passivation layer was introduced using an atomic layer deposition (ALD) technique to coat the outer surface of CQDs/TiO2 NRs. With the Al2O3 deposition thickness of 5 nm, a high photocurrent density of 3.20 mA cm−2 at 1.23 V vs. the reversible hydrogen electrode (RHE) and an incident-photon-to-current efficiency (IPCE) value of 77.41% at the wavelength of 385 nm were achieved under air mass 1.5 global (AM 1.5 G) illumination, which were nearly 5.35 times and 6.94 times higher than those of pure TiO2 NRs, respectively. In addition, the IPCE value increased from 3.19% to 5.16% at 440 nm, owing to the sensitization effect of CQDs which has obvious visible light absorption. More importantly, the photocurrent had nearly no decay during the PEC testing after coating the thin Al2O3 layer, greatly solving the falling off and instability problems of CQDs on the TiO2 NR surface, which makes it possible to be used in practical PEC water splitting, solar cells and other photocatalysis devices. [ABSTRACT FROM AUTHOR]

Hematite (α-Fe2O3) is a red material with a band gap of about 2.0 eV, which indicates that it can absorb more solar light. It is a promising photocatalyst applied in many fields. In this paper, α-Fe2O3 single crystal hollow hexagonal bipyramids were synthesized by a simple one-pot hydrothermal method. The morphology and structure of the prepared α-Fe2O3 hollow hexagonal bipyramids were studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The hollow single crystals show a good light absorption and performance in photodegradation of methylene blue (MB). Due to the strategy of depositing ultra-thin layers of Al2O3 by atomic layer deposition (ALD), the photoelectrochemical (PEC) performance of α-Fe2O3 under the simulated solar light irradiation is also improved. [ABSTRACT FROM AUTHOR]

Li-ion capacitors have been considered as next-generation advanced energy storage systems to meet the requirements of both high energy and high power due to the combination of rapid and long-term charge storage of supercapacitors and the high energy storage capacity of lithium ion batteries. Herein, we demonstrate the design of 2D nanostructured electrodes from low-cost biomass-kapok fiber for Li-ion capacitors: 2D carbon nanosheets with a high surface area and hierarchical porosity for the positive electrode, and 2D MnO/C nanocomposites with a large surface area and nanosized particles for the negative electrode. With the benefit of the structure of the Li-ion capacitor, the hybrid device can be operated at a high operating voltage of 4 V, exhibiting a high energy density of 100 W h kg−1 at 83 W kg−1, a high power density of 20 kW kg−1 at 30 W h kg−1 based on the active materials, and a capacity retention ratio of 70% after 5000 cycles. These results clearly demonstrate that biomass-derived electrodes are potential candidates for low-cost, fast and efficient energy storage systems in the future. [ABSTRACT FROM AUTHOR]

A strategy of utilizing biomass in energy applications has been highly sought after due to low cost, renewability and environmental friendliness. In this work, based on the unique multilayered structure of ginkgo leaves, an interconnected carbon nanosheet with rich micro/meso pores has been fabricated using hydrothermal treatment and a KOH activation process. Attractively, due to the intensive reactions between the rich organism components of the ginkgo leaves and sulfuric acid in the preparation process, the highest amount of sulfur doping (8.245 wt%) ever reported has been achieved in the as-obtained biomass derived carbons. Combined with the N doping derived from the proteins in ginkgo leaves, S,N dual-doping porous carbons with an interconnected sheet-like structure demonstrate excellent electrochemical performance in both EDLCs and NIBs. The application in EDLCs in aqueous electrolyte showed a high specific capacitance of 364 F g−1 at 0.5 A g−1 and only 2% capacitance loss after 30 000 cycles. In an ionic liquid electrolyte, the devices were able to deliver an energy density of 16 W h kg−1 at an extremely high power density of 50 kW kg−1. As a sodium-ion battery anode, it has the capacity of 200 mA h g−1 after 500 cycles (99% capacity retention) at 0.2 A g−1, which is superior or at least comparable to those of biomass derived carbons reported recently. Therefore, all these results exhibit the promising potential of the ginkgo leaves-derived carbon for wide applications in the field of energy storage devices. [ABSTRACT FROM AUTHOR]

Recently, much attention has been given to the synthesis and application of 3D hierarchical nanomaterials, which can have superior performance for supercapacitors compared with other nanostructured materials. Herein, unique hierarchical nanoribbon-based 3D fan-like nanostructures of α-MnMoO4 were controllably synthesized for the first time by using a simple method. We have assembled supercapacitors based on the hierarchical nanoribbon-based α-MnMoO4 3D fan-like nanostructures, which display a specific capacitance of 562 F g−1 at a current density of 1 A g−1, and good cycling stability with 99.8% specific capacitance retention after 1000 cycles. These results further implied that constructing unique 3D hierarchical structures can improve electrochemical properties. [ABSTRACT FROM AUTHOR]

3D NiO/Co3O4 p–p junction foam was fabricated and applied for electrochemical detection of biomarkers. The theoretical model of employing the interfacial potential barrier as an electrochemical tuning factor was explored in depth. The signals of different targets with similar redox properties could be controllably distinguished by depressing or strengthening the potential barrier. The absorbed positively charged molecules would induce negative charges, inciting a decrease of the potential barrier height Φ and resistance, which is an enhanced tuning factor of the electrochemical signal. However, the effects of the absorbed negatively charged molecules went completely in the inverse direction; the resistance increased following by the increased Φ, which is a weakened tuning factor. Furthermore, the optimum adjustive effects of the p–p junction were validated as both the p-type regions are fully exposed. It is a general strategy to solve the difficulty in selective electrochemical detection of an analyte with similar redox properties. The results build a bridge to connect the potential barrier and electrochemical detection. [ABSTRACT FROM AUTHOR]

Nitrogen and oxygen codoped hierarchical porous carbons have been synthesized by using a direct carbonization/activation procedure of biomass algae – Enteromorpha. The proposed procedure allowed us to produce carbons with high surface area (up to 2073 m2 g−1), sponge-like 3D interconnected structure, combined macro/meso/micropores, and rich N (0.64–0.85 at%) and O (11.36–12.24 at%) doping. The application of the produced carbons in supercapacitors based on an ionic liquid electrolyte showed a high specific capacitance of 201 F g−1 (10.7 μF cm−2) at 1 A g−1 and 20 °C, a capacitance retention ratio of 61% at 100 A g−1 and a capacitance loss of 9% after 10 000 cycles. The devices were able to deliver an energy density of 24 or 35 W h kg−1 (on an active mass normalized basis) at an extremely high power density of 60 kW kg−1 at 20 or 60 °C. The application of the produced carbons in a lithium-ion battery anode based on the LiPF6 electrolyte exhibited a high specific capacity of 1347–1709 mA h g−1, a good initial coulombic efficiency of 61–64%, and a good cyclability up to 500 cycles. We believe that this simple precursor-synthesis route offers excellent potential for facile large-scale material production for supercapacitors and lithium ion batteries. [ABSTRACT FROM AUTHOR]

Determining the fatigue threshold of elastomers is particularly important to predict their durability and lifespan. However, there has been almost no effective approach to calculate this threshold fast and accurately so far. To realize rapid fatigue performance testing, in this paper, a new method is proposed to calculate the fatigue threshold through the elastic limit strain point of elastomers that can be obtained from the continuous Mullins test. Compared with the traditional binary method to predict fatigue threshold, this method significantly reduces the time required for fatigue testing of elastomers, which can save approximately 2-3 sampling points in the fatigue test, i.e. a time savings of around 40%. Our method also proved to be effective for the elastomers at 0 °C. Additionally, a dual-network elastomer was synthesized using the interpenetrating network method, exhibiting improved elasticity (2.1 MPa and 3.1 MPa), toughness (1423 J m -2 and 2100 J m -2 ), and higher fatigue threshold (125 J m -2 and 385 J m -2 ) at 0 °C and room temperature. This material presents great application potential in marine anti-fouling.

An efficient hydrogen evolution reaction (HER) depends essentially on high-performing electrocatalysts. The aggregation of catalysts normally deteriorates their activity and stability. In this study, a two-step route was used to synthesize surface intercalated well-dispersed spherical MoS 2x Se 2(1-x) nanocatalysts. The resulting catalysts present a highly active and stable performance towards the HER with an overpotential of -143 mV at 10 mA cm -2 , and a Tafel slope of 53.8 mV dec -1 . The mechanism for the enhanced HER was analyzed and was attributed to three factors: (i) large numbers of defects and edge active sites arising from the coexistence of S and Se elements; (ii) enhanced electric conductivity arising from the phase transition from the semiconducting 2H-phase to metallic 1T-phase during the intercalation process; and (iii) enlarged contact areas between active sites and electrolyte caused by the increased surface roughness due to the surface intercalation. This work not only deepens our understanding of the improved HER performance of surface intercalated catalysts, but also provides novel strategies for preparing durable electrocatalysts through surface engineering.

Hematite (α-Fe 2 O 3 ) is a red material with a band gap of about 2.0 eV, which indicates that it can absorb more solar light. It is a promising photocatalyst applied in many fields. In this paper, α-Fe 2 O 3 single crystal hollow hexagonal bipyramids were synthesized by a simple one-pot hydrothermal method. The morphology and structure of the prepared α-Fe 2 O 3 hollow hexagonal bipyramids were studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The hollow single crystals show a good light absorption and performance in photodegradation of methylene blue (MB). Due to the strategy of depositing ultra-thin layers of Al 2 O 3 by atomic layer deposition (ALD), the photoelectrochemical (PEC) performance of α-Fe 2 O 3 under the simulated solar light irradiation is also improved.