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Soluble redox mediators (RMs) with favorable contact interface are considered to be an effective approach for high efficient lithium-oxygen (Li-O2) batteries. However, the shuttling effect of oxidized RMs from the cathode would lead to the degradation of the RMs’ functionality and poor cycling stability. Herein, TEMPO was anchored into three-dimensional porous ZnO@C/NF conductive substrate (ZnO@C@PPy-TEMPO/NF) and directly utilized as a self-supporting cathode for Li-O2 battery. This novel cathode serves multiple functions as redox mediator, abundant reaction center for lithium ion, as well as electron conduction matrix. The battery perform with a high discharge specific capacity of 6.9 mAh cm−2 and a low overpotential of 0.6 V similar with 4-OH-TEMPO in the electrolyte. The detailed catalysis mechanism of the immobilized TEMPO in improving the electrochemical performance has also been studied. During discharging, the cation-π effect between the conductive polypyrrole and lithium ions helps to realize the "isomorphic growth" of Li2O2. During charging, the TEMPO-immobilized electrochemical oxidation to TEMPO+ provides more direct contact with the discharge products, resulting in rapid chemical oxidation of Li2O2. The ingenious design and in-depth mechanism study provide a new avenue to address the shuttle effect of RMs and design an advanced cathode for Li-O2 batteries.

Lithium–oxygen (Li-O2) batteries have the potential needed for portable electronic devices and electric vehicles, but the sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) processes hinder the practical implementation. Here, we propose that the localized surface plasmon resonance (LSPR) of silver nanoparticles (Ag NPs) induced the plasmonic thermal and hot electron effects can simultaneously enhance reaction kinetics of ORR, OER, reduce the reaction activation energy and promote the discharge product selectivity to mitigate unfavourable side reactions, which greatly improves the catalytic performance of Ag NPs. Furthermore, we also calculated the photochemical conversion coefficient and the quantitative contribution of the ratio of two effects towards the catalytic activity. Notably, by accelerating both oxygen reduction and evolution reactions, the discharge voltage is significantly increased to 3.2174 V, which is surpass the thermodynamic limit of 2.96 V, and the charge voltage is reduced to 3.2487 V (overpotential of 0.0331 V), resulting in a high round-trip efficiency of 99%. The concept can be extended to other types of batteries, such as Zn-air battery, thus contributing to the development of advanced energy storage systems.

Lithium–oxygen (Li–O2) batteries have attracted considerable attention due to their high theoretical energy density. However nonrenewable and high-cost electrode materials have limited their progre...

Solid-state lithium (Li)–air batteries are recognized as a next-generation solution for energy storage to address the safety and electrochemical stability issues that are encountered in liquid battery systems1–4. However, conventional solid electrolytes are unsuitable for use in solid-state Li–air systems owing to their instability towards lithium metal and/or air, as well as the difficulty in constructing low-resistance interfaces5. Here we present an integrated solid-state Li–air battery that contains an ultrathin, high-ion-conductive lithium-ion-exchanged zeolite X (LiX) membrane as the sole solid electrolyte. This electrolyte is integrated with cast lithium as the anode and carbon nanotubes as the cathode using an in situ assembly strategy. Owing to the intrinsic chemical stability of the zeolite, degeneration of the electrolyte from the effects of lithium or air is effectively suppressed. The battery has a capacity of 12,020 milliamp hours per gram of carbon nanotubes, and has a cycle life of 149 cycles at a current density of 500 milliamps per gram and at a capacity of 1,000 milliamp hours per gram. This cycle life is greater than those of batteries based on lithium aluminium germanium phosphate (12 cycles) and organic electrolytes (102 cycles) under the same conditions. The electrochemical performance, flexibility and stability of zeolite-based Li–air batteries confer practical applicability that could extend to other energy-storage systems, such as Li–ion, Na–air and Na–ion batteries. Flexible, stable and energy-dense solid-state Li–air batteries are realised using ultrathin, chemically inert ion-conductive zeolite membranes as a solid electrolyte.

The instabilities of the battery including cathode corrosion/passivation, shuttling effect of the redox mediators, Li anode corrosion, and electrolyte decomposition are major barriers toward the practical implementation of lithium-oxygen(Li-O2) batteries. Functional materials offer great potential in high performance Li-O2 batteries owing to their functional tailorability of chemical modification for alleviating side reactions and improving catalysis activity, well-defined properties for discharge products storage, and fast mass and electron transfer paths. In this review, instability problems of non-aqueous Li-O2 batteries and recent studies related to the functional materials in tackling the instability issues from rational cathode construction, inhibition of redox mediators(RMs) shuttling, anode protection and novel electrolyte design are illustrated. Future research directions to overcome the critical issues are also proposed for this promising battery technology. The instability issues and the related strategies with functional materials based on the comprehensive consideration of all battery components proposed in this review provide the systematic, deep understanding and rational design of functional materials for Li-O2 batteries, which is beneficial to achieving the practical Li-O2 batteries.

With the rapid development of the internet of things, light-excited gas sensors have aroused great attention to meet the increasing demand for room-temperature devices with high portability and low power consumption. However, there are still many issues that need to be addressed, especially the lack of tailored structures specifically designed for light-excited gas sensors. In this work, ∼2600 PIC micron-scaled gas sensors and LED UVC light sources were integrated on a 2-inch sapphire wafer. The integrated microchip exhibited an excellent gas-sensing response to NO2 under in situ light excitation. The response of the device to 500 ppb NO2 was S = 1.12 and its response to an ultra-low concentration of 10 ppb NO2 was S = 1.01. The device exhibited a low resistance at the kΩ-level and fast response and recovery time of 30 s and 88 s, respectively, to 500 ppb NO2, making it ideal for portable applications at room temperature. Moreover, its sensing properties could be tuned by adjusting the wavelength and irradiance of the LED layer. This work lays the foundation for the fabrication of integrated multi-functional devices.

A photoinduced flexible Li-CO2 battery with well-designed, hierarchical porous, and free-standing In2 S3 @CNT/SS (ICS) as a bifunctional photoelectrode to accelerate both the CO2 reduction and evolution reactions (CDRR and CDER) is presented. The photoinduced Li-CO2 battery achieved a record-high discharge voltage of 3.14 V, surpassing the thermodynamic limit of 2.80 V, and an ultra-low charge voltage of 3.20 V, achieving a round trip efficiency of 98.1 %, which is the highest value ever reported (

Lithium-oxygen batteries with ultrahigh energy density have received considerable attention as of the future energy storage technologies. The development of effective electrocatalysts and a corresponding working mechanism during cycling are critically important for lithium-oxygen batteries. Here, a single cobalt atom electrocatalyst is synthesized for lithium-oxygen batteries by a polymer encapsulation strategy. The isolated moieties of single atom catalysts can effectively regulate the distribution of active sites to form micrometre-sized flower-like lithium peroxide and promote the decomposition of lithium peroxide by a one-electron pathway. The battery with single cobalt atoms can operate with high round-trip efficiency (86.2%) and long-term stability (218 days), which is superior to a commercial 5 wt% platinum/carbon catalyst. We reveal that the synergy between a single atom and the support endows the catalyst with excellent stability and durability. The promising results provide insights into the design of highly efficient catalysts for lithium-oxygen batteries and greatly expand the scope of future investigation., Li–O2 batteries represent one of the promising paths toward high energy density battery systems. Here the authors synthesize single atom Co electrocatalysts to regulate the formation and decomposition of the major discharge product Li2O2, realizing high round-trip efficiency and stability in a Li–O2 cell.

Severe polarization triggered by the limited electrochemical activity of carbon dioxide as well as the insulating and insoluble discharge product Li2CO3 significantly impedes the practical application of Li–CO2 batteries. Herein, a light-assisted Li–CO2 system employing SiC/RGO as the photo-electro-catalytic hybrid cathode is presented to overcome the obstacle of polarization in conventional Li–CO2 cells. RGO is capable of transferring high-energy electrons generated on SiC after absorbing photons, inhibiting the recombination of photogenerated electrons. During the discharge process, the kinetics of CO2 reduction reaction is promoted by the photogenerated electrons. Thus, the discharge voltage of the battery is increased to 2.77 V, which is very close to the theoretical potential for 4Li + 3CO2 → 2Li2CO3 + C (2.80 V). Besides, the holes generated on the photoelectrode upon charging promote the decomposition of Li2CO3, effectively alleviating the overpotential of the Li–CO2 battery. Consequently, the system exhibits an excellent energy efficiency of 84.4%. These findings demonstrate the promising potential of the photo-assisted electrochemical process in addressing the overpotential issue of Li–CO2 batteries.

Metal oxide based gas sensors should mostly work at high temperatures; the high working temperature is associated with safety concerns and high energy consumption, which makes portable and wearable devices almost impossible, and the inhomogeneous temperature distribution over a sensor also has a detrimental effect on the device performance. However, all the above problems can be effectively resolved by using visible light-excited sensors working at room temperature. By depositing an array of well-aligned In2O3 nanowires on polyimide (PI) substrates, we fabricate flexible and transparent sensors that achieve room temperature gas sensing using visible light as the excitation source. The detection limit to NO2 is as low as 10 ppb under illumination using both monochromatic (blue) and polychromatic (white) light sources. The sensing performance remains consistent after repetitive bending and long-term operation. Remarkably, the sensor exhibits recoverable response to 500 ppb NO2 even under the illumination of an iPhone screen with a low irradiance of 0.56 W m−2. Through a systematic study of the interaction between the photoelectric and gas sensing properties of the materials, we also explore the mechanism of photo-induced gas sensing reactions at room temperature. This work will lay the foundation for gas sensors that can be used in portable and wearable devices.

Although the lithium-oxygen (Li-O2) battery brings hope for the improvement of high-energy rechargeable batteries, the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics become the major stumbling block. Herein, the incorporation of a plasmonic silver cathode as an advanced strategy to promote ORR and OER kinetics due to strong local surface plasmon resonance (LSPR) is introduced. Chronoamperometry results revealed that the highly energetic electrons and holes excited by LSPR of silver nanostructure facilitated ORR and OER kinetics ascribe to the emission of hot carriers in femtosecond time scale. Furthermore, a relatively rare discharge voltage 3.1 V is obtained, correspondingly, the charge plateau also decline to 3.3 V, the energy efficiency of Li-O2 battery by a 23% increase in comparison with a commercial 5% Pt/C catalyst (discharge and charge plateau of 2.75 and 3.61 V). Additionally, the improvement in the efficient charge transfer manner result in a reversible spherical Li2O2 which further improve the ORR and OER kinetics. The LSPR strategy represents a critical step toward developing fast kinetics and high energy efficiency Li-O2 batteries.

Explorations of new second harmonic generation materials in Ag+-Hg2+/Bi3+-selenites systems afforded three new silver selenium oxides, namely, Ag4Hg(SeO3)2(SeO4) (1), Ag2Bi2(SeO3)3(SeO4) (2) and Ag5Bi(SeO3)4 (3). They exhibit flexible crystal chemistry. Compounds 1 and 2 are mixed valence selenium oxides containing Se(IV) and Se(VI) cations simultaneously. Compounds 1 and 3 exhibit a 3D open framework with 4-, 6- and 8-member polyhedral ring tunnels along a, b and c axes. Compound 1 crystallized in a polar space group and could display a subtle frequency doubling efficiency about 35% of the commercial KH2PO4 (KDP). UV-vis-NIR spectra reveal that compounds 1–3 are wide-band semiconductors with the optical bandgaps of 3.11, 3.65, 3.58 eV respectively. Theoretical calculations disclose that compounds 2 and 3 are indirect band gap structures and their bandgaps are determined by Ag, Bi, Se and O atoms together.

Summary: The rapid and effective formation and decomposition of Li2O2 during cycling is crucial to solve the problems associated with the practical limitation of lithium-oxygen (Li-O2) batteries. In this work, a highly dispersed electrocatalyst with Ru nanoclusters inside the special organic molecular cage (RuNCs@RCC3) through a reverse double-solvent method for Li-O2 batteries has been proposed for the first time. This RuNCs@RCC3 shows an effective catalyst enabling reversible formation and decomposition of the Li2O2 at the interface between the Li2O2 and the liquid electrolyte, rather than the sluggish solid-solid interface reactions on commonly used solid catalysts. As a result, the Li-O2 cells with RuNCs@RCC3 show enhanced electrochemical performance, including low overpotential (310 mV at a current density of 100 mA g−1), high specific capacity (15,068 mAh g−1), good rate capability (1,800 mAh g−1 at a current density of 2.8 A g−1), and especially superior cycle stability up to 470 cycles. : Electrochemistry; Energy Storage; Energy Materials Subject Areas: Electrochemistry, Energy Storage, Energy Materials

Small-scale supercapacitors or microsupercapacitors (MSCs) can be integrated with miniaturized electronics to work as stand-alone power sources, or as efficient energy storage units coupling with energy harvesters to realize self-powered microdevices. Despite many advances, research and development of MSCs are still in their infancy. In this work, in-plane flexible solid-state MSCs based on interdigital electrodes are developed through a facile, cost-effective, universal and industrially applicable protocol, i.e. screen printing technique. To verify the generality of such method, activated carbon (AC) nanospheres and molybdenum oxide (MoO3-x) nanorods as representative electrical double-layer capacitive material and intercalation pseudocapacitive material are used as the electrode active material, respectively. Using a highly viscous AC nanosphere or MoO3-x nanorod paste, shape-designable microelectrodes with an effective area of 0.415 cm2, and a spacing of 250 μm between the two electrode fingers are printed on flexible substrate in several seconds. The MSCs can deliver high areal capacitances and energy densities (5.04 mF cm−2 and 0.7 μWh cm−2 for the MSC with AC nanosphere electrodes, 41.7 mF cm−2 and 5.8 μWh cm−2 for the MSC with MoO3-x nanorod electrodes), own excellent rate capability and long cycle life for both the electric double-layer capacitive material and pseudocapacitive material. This work demonstrates the opportunity and practicability for developing MSCs for flexible on-chip electronic devices.

Nanocrystalline Tb3+-doped Na5Lu9F32 powders were prepared by a facile and environmentally-friendly hydrothermal process for the first time. Upon excitation at 368 nm, the Na5Lu9F32:Tb3+ nanocrystals show the characteristic f-f emissions and gives strong green emission. Furthermore, the optimum doping concentration of the Tb3+ is 7 mol% and its lifetime value is 10.227 ms. Compared with the strong absorbed exciting radiation (at 368 nm), the weak absorbed exciting radiation (at 317 nm) can be used to explore the mechanism of concentration quenching and the concentration quenching was demonstrated to occur among nearest-neighbor ions. The temperature-dependent PL spectra suggested that the products possessed good thermal stability and the activation energy was found to be 0.14 eV. These results show this green-emitting phosphors material may have potential applications in w-LEDs.

In this work, we synthesized highly uniform and well-dispersed hexagonal phase GdPO4 nanorods by hydrothermal method at 180 °C, which were transformed to GdPO4 nanocrystals with the monoclinic phase upon heating above 800 °C. The phase transformation process and photoluminescence properties of as-prepared samples were investigated via XRD, FE-SEM, and PL spectroscopy. The integrated emission intensity of GdPO4:0.07 Tb3+ (monoclinic) is almost 2.62 times stronger than that of GdPO4·H2O:0.07 Tb3+ (hexagonal). By codoping the Tb3+ and Eu3+ ions into the GdPO4 host, the emitting colors could be adjusted from the green to warm white due to the efficient energy transfer from Tb3+ to Eu3+ at 368 nm excitation. Moreover, the energy transfer from Tb3+ to Eu3+ was revealed to be resonant type by quadrupole-quadrupole mechanism, and the energy transfer efficiency of GdPO4:Tb3+, y Eu3+ reached about 96.1% when the concentration unit of Eu3+ was 12 mol%. These merits demonstrate that this material may find potential application in warm-white display fields.

The photo-assisted lithium-oxygen (Li-O2) system emerged as an important direction for future development by effectively reducing the large overpotential in Li-O2 batteries. However, the advancement is greatly hindered by the rapidly recombined photoexcited electrons and holes upon the discharging and charging processes. Herein, we make a breakthrough in overcoming these challenges by developing a new magnetic and optical field multi-assisted Li-O2 battery with 3D porous NiO nanosheets on the Ni foam (NiO/FNi) as a photoelectrode. Under illumination, the photogenerated electrons and holes of the NiO/FNi photoelectrode play a key role in reducing the overpotential during discharging and charging, respectively. By introducing the external magnetic field, the Lorentz force acts oppositely on the photogenerated electrons and holes, suppressing the recombination of charge carriers. The magnetic and optical field multi-assisted Li-O2 battery achieves an ultra-low charge potential of 2.73 V, a high energy efficiency of 96.7%, as well as a good cycling stability of 200 h. This external magnetic and optical field multi-assisted technology paves a new way of developing high-performance Li-O2 batteries and other energy storage systems.

In this study, monodisperse and uniform β-NaYF4 hexagonal microtubes were successfully synthesized via a simple hydrothermal method without any organic surfactants, employing Y(OH)CO3 colloid spheres as precursors. The possible formation mechanism was studied on the basis of a series of time-dependent control experiments and its intrinsic crystal structure. The integrated emission intensity of β-NaYF4:0.05Tb3+ is almost 1.78 times stronger than that of α-NaYF4:0.05Tb3+. In addition, the photoluminescence properties of β-NaYF4:Ln3+ (Ln = Eu, Tb, Tm, Sm, Ho) were studied in detail, and it was found that the photoluminescence color of β-NaYF4:0.03Tm3+ phosphor was close to the standard blue light (0.14, 0.08). Moreover, by co-doping the Tb3+ and Eu3+ ions into the β-NaYF4 host, multicolor tunable emissions were obtained due to the efficient energy transfer from Tb3+ to Eu3+ at 368 nm excitation. These merits demonstrate that this material may find potential application in color display fields.

Highly uniform and monodisperse β-NaLuF4:Ln3+ (Ln = Eu, Tb, Dy, Sm, Tm, Ho) hexagonal prisms have been synthesized via a facile two-step hydrothermal method without any organic surfactants. The structures, morphologies and luminescence properties of the samples were investigated through XRD, SEM, and PL spectra. Furthermore, the shapes and sizes of the products can be further manipulated through adjusting the pH values of initial solutions. Upon excitation at 368 nm, the β-NaLuF4:Tb3+ phosphors exhibit the strongest green emission at pH = 9.0. Moreover, the photoluminescence properties of β-NaLuF4:Ln3+ were studied in detail, and it was found that the photoluminescence color of the β-NaLuF4:0.03Tm3+ phosphor was close to standard blue light (0.14, 0.08). Under 356 nm irradiation, multicolour emission from blue to sapphire and then to pale green has been achieved from the Tm3+/Dy3+ co-doped β-NaLuF4 samples. The energy transfer process from Tm3+ to Dy3+ was studied and was demonstrated to be an electric dipole–dipole interaction mechanism. It is obvious that the β-NaLuF4 phosphors may have potential applications in the field of full-color displays.

A two-step synthetic route using RE(OH)CO3 colloid spheres as the sacrificial template was designed to prepare monodisperse, pure bastnasite (RECO3F: RE = Ce, La, Pr, Nd) with a hole structure for the first time. A variety of morphologies, including jujube core-like, stacked nanoblocks, and stacked nanosheets were obtained through changing the ratio of reactants. The phase, structure, shapes, and photoluminescence properties of samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. The CeCO3F:Ln3+ (Ln = Tb, Eu, Dy) phosphors give green, yellow and blue emission, respectively, due to the f-f transitions of Ln3+ ions. Furthermore, the energy transfer from Ce3+ to Dy3+ and Tb3+ was described in detail.

The hysteresis kinetics of carbon dioxide reduction reaction (CDRR) and evolution reaction (CDER) reaction are major barriers toward the practical implementation of lithium-carbon dioxide (Li-CO2) batteries. Herein, a free-standing and binder-free cathode composed of rutile TiO2 nanorod arrays (TiO2 NAs) and carbonized natural sponge was designed and realized by a simple seeds-assisted construction. The novel air cathode was found to exhibits a high specific capacity of 4.38 mAh cm−2 and long cycle life of more than 1600 h, as well as the discharge products, which would deposit at the surface of the TiO2 NAs rather than carbon substrate during the discharge process. The improved performance can be ascribed to the interconnected conductive sponge framework with macropore and mesoporous channels that can house more discharge products, and the reactant molecules can unrestricted contact with the active sites. Furthermore, the good adhesion to the carbon substrate and the numerous available catalytic sites of the TiO2 NAs contribute intimate contact of the discharge products with the TiO2 NAs, improving CDRR and CDER kinetics effectively and boosting the electrochemical reactions. This TiO2/Sponge represents a promising design in the development of a nature-inspired, self-standing, and binder-free electrode for high-performance Li-CO2 batteries.

Directly converting and storing abundant solar energy in next-generation energy storage devices is of central importance to build a sustainable society. Herein, a new prototype of a light-promoted rechargeable and flexible Li-CO2 battery with a TiO2 /carbon cloth (CC) cathode is reported for the direct utilization of solar energy to promote the kinetics of the carbon dioxide reduction reaction and carbon dioxide evolution reaction (CO2 ER). Under illumination, photoelectrons are generated in the conduction band of TiO2 /CC, followed by the enhancing diffusion of electrons and lithium ions during the discharge process. The photoelectrons on the cathode surface can regulate the morphology of the discharge product Li2 CO3 , contributing to boosting the kinetics of the subsequent CO2 ER process. In the reverse charge process, photogenerated holes can favor the decomposition of Li2 CO3 , leading to a negative charge potential of 2.88 V without increased polarization over ≈60 h of cycling. Owing to an ultralow overpotential of 0.06 V between the discharge and charge process, an ultrahigh energy efficiency of 97.9% is attained under illumination. The introduction of a light-promoted flexible Li-CO2 battery can pave the way toward developing the use of solar energy to address the charging overpotential of conventional Li-CO2 batteries.

Hierarchical and hollow porous Fe2O3 nanoboxes (with an average edge length of ∼500 nm) were derived from metal–organic frameworks (MOFs) and the gas sensing characteristics were investigated. Sensors based on Fe2O3 nanoboxes exhibited a response (resistance ratio) of 1.23 to 0.25 ppm (ppm) hydrogen sulfide (H2S) at 200 °C, the response/recovery speed is fast and the selectivity to H2S is excellent. Remarkably, the sensor showed fully reversible response to 5 ppm of H2S at 50 °C, demonstrating its promise for operating at near room temperature, which is favorable for medical diagnosis and indoor/outdoor environment monitoring. The excellent performance of the Fe2O3 nanoboxes can be ascribed to the unique morphology with high specific surface area (SSA) and porous nanostructure.

LaCo1 − xFexO3 (x ranging from 0 to 1) nanoparticles were prepared using the co-precipitation method, and the CO gas sensing properties of LaCo1 − xFexO3 nanoparticles were investigated. The LaCo0.3Fe0.7O3 sensor shows the highest response at 250 °C (S = 40.9), and reliable dynamic response-and-recovery to different CO concentrations at a temperature as low as 50 °C. On the other hand, the LaCo0.2Fe0.8O3 sensor exhibits the fastest response and recovery in the entire temperature region of 250 to 450 °C. The excellent CO sensing properties could be ascribed to the intense oxidation of CO by adsorbed O2 on the LaCo1 − xFexO3 (x = 0.6, 0.7, 0.8) surface.

Red-blood-cell-shaped chitosan microparticles with acid-triggered dissolution and auto-fluorescence were successfully fabricated by a simple strategy combining electrospraying with a solvent diffusion process controlled by solvent evaporation. The sizes of the prepared chitosan microparticles were relatively uniform. Control of the solvent diffusion process was crucial for the formation of microparticles with concave morphology. A chitosan aqueous solution containing 20 vol% ethanol as the evaporable solvent and 30 vol% dimethyl sulfoxide as the diffusible solvent was optimal for preparation of chitosan microparticles with the desired red-blood-cell-like size and shape. These chitosan microparticles will be highly attractive for many biological and biomedical applications.

Ce-doped BaTiO 3 (Ba 0.99 Ce 0.01 TiO 3 ) nanoparticles with the sizes of 30–60 nm were prepared by the co-precipitation method, and sensors were fabricated by spin coating the nanoparticles on FTO substrates. To further enhance the sensing properties, α-Fe 2 O 3 was decorated to the Ba 0.99 Ce 0.01 TiO 3 sensor. The Fe 2 O 3 -Ba 0.99 Ce 0.01 TiO 3 sensor showed fascinating gas sensing performances towards H 2 S, including the ability to detect low concentrations of H 2 S (400 ppb or lower), fast response and recovery speed ( t res = 45 s and t rec = 124 s) and low working temperatures (150 °C). When exposed to H 2 S, the sensor resistance increased, due to the reduction of Ce 4+ to Ce 3+ and the chemical reactions of oxygen species.

High concentration LiBr is beneficial to enhance the Br− oxidation rate, displaying stable low voltage plateau during charging process for lithium–oxygen batteries. However, the sufficient cyclic performance is generally restricted by uncontrollable high level Br3−, resulting in the low energy efficiency and shuttle effect. Herein, a nanoreactor, red-ox mediators shuttling suppressor and lithium-metal protector with the combination of the high concentration and shuttle-free LiBr are successfully constructed by anchoring the Br3− to carbonized ZIF-8 supported on reduced graphene oxide substrate (ZC-rGO). ZnO-decorated/nitrogen-doped 3D carbon framework of ZC-rGO cathode can accurately capture Br3− by space confinement effects and/or chemisorption, which is beneficial to improve the oxidation of discharge products (Li2O2) and avoid the anode corrosion. The Li–O2 battery demonstrates enormous advantages of the RMs in comparation with the typical rGO-based batteries, such as better cycling performance (>90 cycles) and more stable overpotential (

The issue of cathode passivation during cycling resulting in rapid capacity fading and premature battery death is a major challenge that hinders the applications of lithium–oxygen (Li–O2) batteries. Here, a facile strategy of introducing a functional separator based on flexible amination SiO2/TiO2 inorganic woven film (STON WF) is proposed to suppress the cathode passivation problem. The by-products, i.e. HCOOLi, CH3COOLi and Li2CO3 can be selectively adsorbed on the STON WF separator preferably compared with the cathode and further proved by the density functional theory (DFT) calculations. Thus, benefiting from the separator, the Li–O2 cells with super P carbon and catalyst-free cathode show enhanced electrochemical performance (5645 mA h g−1 at a current density of 200 mA g−1), good rate capability (discharge voltage of 2.43 V at a current density of 1.5 A g−1) and especially superior cycle stability up to 268 cycles. These findings present a promising approach to prevent the premature battery death.

Mesoporous LaCoO3 nanowires with diameters of 200–800 nm and grain sizes of 30–60 nm were prepared by electrospinning, and functionalized with Pd nanodots. The Pd-functionalized LaCoO3 mesoporous nanowires demonstrate excellent CO sensing characteristics at low temperatures: the Pd-LaCoO3 nanowires show reliable dynamic response-and-recovery to different CO concentrations at a temperature as low as 60 °C, and at 250 °C the Pd-LaCoO3 nanowires achieve a high response of ∼113.6 to 100 ppm CO. The excellent CO sensing properties of the Pd-LaCoO3 nanowires at low temperatures can be ascribed to the mesoporous nanostructure and the catalytic sensitization by the Pd nanodots.

Porous materials possessing high surface area, large pore volume, tunable pore structure, superior tailorability, and dimensional effect have been widely applied as components of lithium-oxygen (Li-O2 ) batteries. Herein, the theoretical foundation of the porous materials applied in Li-O2 batteries is provided, based on the present understanding of the battery mechanism and the challenges and advantageous qualities of porous materials. Furthermore, recent progress in porous materials applied as the cathode, anode, separator, and electrolyte in Li-O2 batteries is summarized, together with corresponding approaches to address the critical issues that remain at present. Particular emphasis is placed on the importance of the correlation between the function-orientated design of porous materials and key challenges of Li-O2 batteries in accelerating oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) kinetics, improving the electrode stability, controlling lithium deposition, suppressing the shuttle effect of the dissolved redox mediators, and alleviating electrolyte decomposition. Finally, the rational design and innovative directions of porous materials are provided for their development and application in Li-O2 battery systems.

Photo-assisted charging is considered an effective approach to reducing the overpotential in lithium-oxygen (Li-O2 ) batteries. However, the utilization of photoenergy during the discharge process in a Li-O2 system has been rarely reported, and the functional mechanism of such a process remains unclear. Herein, a novel bifunctional photo-assisted Li-O2 system is established by employing a hierarchical TiO2 -Fe2 O3 heterojunction, in which the photo-generated electrons and holes play key roles in reducing the overpotential in the discharging and charging processes, respectively. Moreover, the morphology of the discharge product (Li2 O2 ) can be modified via the dense surface electrons of the cathode under illumination, resulting in promoted decomposition kinetics of Li2 O2 during the charging progress. Accordingly, the output and input energies of the battery can be tuned by illumination, giving an ultralow overpotential of 0.19 V between the charge and discharge plateaus with excellent cyclic stability (retaining a round-trip efficiency of ≈86% after 100 cycles). The investigation of the bifunctional photo-assisted process presented here provides significant insight into the mechanism of the photo-assisted Li-O2 battery and addresses the overpotential bottleneck in this system.

Compared to phase-change fibers with hydrophilic polymer shell, those with hydrophobic polymer are more stable in water and moist environments. However, their fabrication processes are involved in some toxic organic solvents. Here, the nanofibers with phase-change material (PCM, i.e., octadecane) as core and hydrophobic shell (i.e., polyvinyl butyral) are fabricated via coaxial electrospinning using environmental friendly ethanol as solvent. Effects of the polyvinyl butyral concentration in ethanol solution as well as the flow rates of core and shell fluids on the morphology of octadecane/polyvinyl butyral (PCM/PVB) nanofibers are systematically investigated. The thermo-regulating capability of PCM/PVB nanofibers is demonstrated by observing the surface and inner temperatures of model houses covered with fibers. The higher the PVB concentration and the shell flow rate are, the better the morphology of core/shell PCM/PVB nanofibers becomes, leading to higher encapsulation efficiency. At a constant shell flow rate, the encapsulation ratio of PCM/PVB nanofibers increases with the core flow rate. The encapsulation ratio of the PCM/PVB nanofibers, which fabricated with PVB concentration of 20 % (w/v) and at the core flow rate of 0.60 ml h−1 and the shell flow rate of 3.0 ml h−1, respectively, reaches to the maximum of 46.4 %. The corresponding melting enthalpy (ΔH m) and the crystallization enthalpy (ΔH c) of these PCM/PVB nanofibers are 105.9 and 106.5 J g−1, respectively. The PCM/PVB nanofibers exhibit good thermo-regulating capability under the simulated solar irradiation, regulating the temperature at around 28 °C. The resultant PCM/PVB nanofibers exhibit satisfactory stability and repeatability in the thermo-regulating capability during repeated heating/cooling cycles. The results provide valuable guidance for environmental friendly preparation of phase-change nanofibers with satisfactory and stable thermal characteristics.

Lotus pollens were used as templates to prepare WO3 microspheres; the intriguing structural features of the pollens, e.g. hollow sphere with highly porous double shells, were perfectly inherited by the WO3 microspheres. The hierarchically porous structure of the WO3 microspheres was ideal for gas sensing. The WO3 microsphere-based sensor exhibited a high sensitivity (S = 46.2) to 100 ppm NO gas with a pretty fast response and recovery speed (62 s/223 s) at 200 °C. Compared with NO sensors reported in the literature so far, the WO3 microsphere-based sensor has among the highest sensitivity and fastest response/recovery.

Monodisperse erythrocyte-sized and acid-soluble chitosan microspheres are successfully prepared by an electrospraying method for the first time. Effects of the physical properties of the polymer solution and the condition parameters of the electrospraying process on the size and size distribution of the chitosan microspheres are systematically studied, to optimize the conditions for preparation of chitosan microspheres with our specific requirements. The microsphere size is mainly controlled by the viscosity of the spray liquid, and the microsphere monodispersity mainly depends on the electric conductivity of the spray liquid, the flow rate and the needle size. Under the optimized conditions, monodisperse chitosan microspheres with an average diameter of 6.4 μm, which is similar to the erythrocyte size, are prepared with a narrow size distribution (CV < 3%). Due to the use of terephthalaldehyde as cross-linker via formation of Schiff base bonds, the prepared chitosan microspheres can maintain structural integrity and show green fluorescence in a neutral medium, but display rapid acid-triggered decomposition. The prepared erythrocyte-sized and acid-soluble chitosan microspheres are highly attractive as promising substitutes of blood samples for calibration of hematology analyzers and flow cytometers.

The interference on the geo-electrical resistivity observation from DC power lines is a key issue puzzling seismic monitoring. According to the working principle of geoelectrical resistivity observation instrument,the reason of interference on geoelectrical resistivity observation is analyzed.The calculation formulas of potential in soil, which is represented as horizontal two-layer electrical model, are derived by equivalent complex image method which responding to the ground electrodes of DC power line with various models: one vertical ground electrode, horizontal double-ring ground electrode and four vertical ground electrodes.In this way, the values of interference on geoelectrical resistivity observation from DC power lines under various situations are calculated and researched.The results show that the value of interference could be reduced 50% for horizontal double-ring ground electrode, and four vertical ground electrodes could be reduced 75%.

By FEA method, the bending of the copper alloy thin-plates by continuous laser forming (CLF) and pulse laser forming (PLF) was studied. Based on the analysis of dynamic change and steady distribution for the fields of temperature, stress/strain and displacement, the forming mechanism and rule of copper alloy by different laser modes were revealed. The whole deformation of PLF was the additive effect of all impulse action, while CLF mainly was the result of thermal stress. To get the same deformation, laser pulse energy is about 6 times of the continuous laser，CLF is suitable for larger deformation demands, and PLF is more seemly for micro-forming.