Elaborating the Crystal Water of Prussian Blue for Outstanding Performance of Sodium Ion Batteries.

Prussian blue (PB) is one of the main cathode materials with industrial prospects for the sodium ion battery. The structural stability of PB materials is directly associated with the presence of crystal water within the open 3D framework. However, there remains a lack of consensus regarding whether all forms of crystal water have detrimental effects on the structural stability of the PB materials. Currently, it is widely accepted that interstitial water is the stability troublemaker, whereas the role of coordination water remains elusive. In this work, the dynamic evolution of PB structures is investigated during the crystal water (in all forms) removal process through a variety of online monitoring techniques. It can be inferred that the PB-130 °C retains trace coordination water (1.3%) and original structural integrity, whereas PB-180 °C eliminates almost all of crystal water (∼12.1%, including both interstitial and coordinated water), but inevitably suffers from structural collapse. This is mainly because the coordinated water within the PB material plays a crucial role in maintaining structural stability via forming the -N≡C-FeLS-C≡N- conjugate bridge. Consequently, PB-130 °C with trace coordination water delivers superior reversible capacity (113.6 mAh g-1), high rate capability (charge to >80% capacity in 3 min), and long cycling stability (only 0.012% fading per cycle), demonstrating its promising prospect in practical applications.

Self-Powered and Broadband Photodetectors Based on High-performance Mixed Dimensional Sb2O3/PdTe2/Si Heterojunction for Multiplex Environmental Monitoring.

Solar-blind ultraviolet (SBUV) to near-infrared (NIR) broadband photodetectors (BB-PD) have important applications in environmental monitoring and other applications. However, it is challenging to prepare SBUV-IR photosensitive materials via simple steps and to construct SBUV-IR broadband devices for multiplex detection with high sensitivity at different wavelengths. Here, self-powered and broadband photodetectors using a high-performance mixed dimensional Sb2O3 nanorod 1-dimension (1D)/monodisperse microdiamond-like PdTe2 3-dimension (3D)/Si (3D) heterojunction for multiplex detection of environmental pollutants with high sensitivity at broadband wavelength are developed. The 1D/3D mixed dimensional Sb2O3/PdTe2/Si structure combines the advantages of strong light absorption, high carrier transport efficiency of 1D Sb2O3 nanorods, and expansion of interface barrier caused by 3D microdiamond-like PdTe2 interlayer to improve the photocurrent density and self-powered ability. The efficient photogenerated charge separation enables anon/off ratio of more than 5 × 106. The device exhibits excellent photoelectric properties from 255 to 980 nm with the responsivity from 4.56 × 10-2 to 6.55 × 10-1 AW-1, the detectivity from 2.36 × 1012 to 3.39 × 1013 Jones, and the sensitivity from 3.90 × 107 to 1.10 × 1010 cm2 W-1 without external bias. Finally, the proposed device is applied for the multiplex monitoring of environmental pollution gases NO2 with the detection limit of 200 ppb and PM2.5 particles at mild pollution at broadband wavelength. The proposed BB-PD has great potential for multiplex detection of environmental pollutants and other analytes at broadband wavelength.

Embedding oxophilic rare-earth single atom in platinum nanoclusters for efficient hydrogen electro-oxidation.

Designing Pt-based electrocatalysts with high catalytic activity and CO tolerance is challenging but extremely desirable for alkaline hydrogen oxidation reaction. Herein we report the design of a series of single-atom lanthanide (La, Ce, Pr, Nd, and Lu)-embedded ultrasmall Pt nanoclusters for efficient alkaline hydrogen electro-oxidation catalysis based on vapor filling and spatially confined reduction/growth of metal species. Mechanism studies reveal that oxophilic single-atom lanthanide species in Pt nanoclusters can serve as the Lewis acid site for selective OH- adsorption and regulate the binding strength of intermediates on Pt sites, which promotes the kinetics of hydrogen oxidation and CO oxidation by accelerating the combination of OH- and *H/*CO in kinetics and thermodynamics, endowing the electrocatalyst with up to 14.3-times higher mass activity than commercial Pt/C and enhanced CO tolerance. This work may shed light on the design of metal nanocluster-based electrocatalysts for energy conversion.

DFT insights into the selective NH3sensing mechanism of two dimensional ZnTe monolayer.

Exploring novel NH3sensing materials is crucial in chemical industries, fertilizing plants and medical fields. Herein, for the first time, the NH3sensing behaviors and sensing mechanisms of two dimensional (2D) ZnTe monolayer are systematically investigated by density functional theory calculations. It is shown that 2D ZnTe monolayer exhibits excellent selective NH3sensing properties. (220) crystal facet of ZnTe possesses a higher NH3adsorption energy (-1.59 eV) and a larger charge transfer (0.195e) than (111) and (311) crystal facets. The positive charges could enhance NH3sensing while the negative charges could reduce NH3sensing. The NH3adsorption strengths are significantly improved in O2atmosphere while it is negligibly affected by N2atmosphere and H2O atmosphere. Moreover, the presence of Zn vacancy and Fe, Co, Ni doping could improve the NH3sensing of ZnTe. Additionally, the experimental results confirms that ZnTe possesses a low detection limit of 0.1 ppm NH3. These theoretical predictions and experimental results present a wide range of possibilities for the further development of ZnTe monolayer in NH3sensing fields.

Atomic-precision Pt6 nanoclusters for enhanced hydrogen electro-oxidation.

The discord between the insufficient abundance and the excellent electrocatalytic activity of Pt urgently requires its atomic-level engineering for minimal Pt dosage yet maximized electrocatalytic performance. Here we report the design of ultrasmall triphenylphosphine-stabilized Pt6 nanoclusters for electrocatalytic hydrogen oxidation reaction in alkaline solution. Benefiting from the self-optimized ligand effect and atomic-precision structure, the nanocluster electrocatalyst demonstrates a high mass activity, a high stability, and outperforms both Pt single atoms and Pt nanoparticle analogues, uncovering an unexpected size optimization principle for designing Pt electrocatalysts. Moreover, the nanocluster electrocatalyst delivers a high CO-tolerant ability that conventional Pt/C catalyst lacks. Theoretical calculations confirm that the enhanced electrocatalytic performance is attributable to the bifold effects of the triphenylphosphine ligand, which can not only tune the formation of atomically precise platinum nanoclusters, but also shift the d-band center of Pt atoms for favorable adsorption kinetics of *H, *OH, and CO.

Polycyclic Aromatic Hydrocarbons as a New Class of Promising Cathode Materials for Aluminum-Ion Batteries.

As an emerging post-lithium battery technology, aluminum ion batteries (AIBs) have the advantages of large Al reserves and high safety, and have great potential to be applied to power grid energy storage. But current graphite cathode materials are limited in charge storage capacity due to the formation of stage-4 graphite-intercalated compounds (GICs) in the fully charged state. Herein, we propose a new type of cathode materials for AIBs, namely polycyclic aromatic hydrocarbons (PAHs), which resemble graphite in terms of the large conjugated π bond, but do not form GICs in the charge process. Quantum chemistry calculations show that PAHs can bind AlCl4 - through the interaction between the conjugated π bond in the PAHs and AlCl4 - , forming on-plane interactions. The theoretical specific capacity of PAHs is negatively correlated with the number of benzene rings in the PAHs. Then, under the guidance of theoretical calculations, anthracene, a three-ring PAH, was evaluated as a cathode material for AIBs. Electrochemical measurements show that anthracene has a high specific capacity of 157 mAh g-1 (at 100 mA g-1 ) and still maintains a specific capacity of 130 mAh g-1 after 800 cycles. This work provides a feasible "theory guides practice" research model for the development of energy storage materials, and also provides a new class of promising cathode materials for AIBs.

End Group Modification for Black Phosphorus: Simultaneous Improvement of Chemical Stability and Gas Sensing Performance.

Black phosphorus (BP) nanosheets have been receiving attention for gas sensing showing superior sensitivity and selectivity among various two-dimensional materials. However, the instability of BP nanosheets due to chemical degradation, especially in humid environments, has severely limited their potential applications. Here, we propose to control the chemical stability of BP nanosheets through modifying their end groups via silanization treatment. Compared with other chemical passivation methods, the end group modification strategy proposed here can be well-controlled and results in little variation in the electronic structure of the puckered phosphorus plane. The results show that modification with fluoroalkylsilane leads the hydrophilic BP to become hydrophobic and exhibits extended chemical stability in oxidizing, humid environments. The sensitivity of fluoroalkylsilane-modified BP (F-BP) to NO2 improved by 3.9-fold in comparison with that of pristine BP nanosheets. More importantly, the NO2 sensing response could remain stable under changing relative humidity ranging from 5% to 95%. Such excellent sensing performance is ascribed to the strong interaction between NO2 and BP decorated with fluoroalkylsilane, as confirmed by density functional theory calculations. This work offers an effective means for preventing degradation of BP in ambient environments and provides a promising solution to solve the issue regarding humidity dependence in gas sensors.

Reusable membrane with multifunctional skin layer for effective removal of insoluble emulsified oils and soluble dyes.

The organic pollutants, typical of emulsified oils and soluble organic dyes, is commonly found in wastewater, however simultaneous removal of them remains challenging because of their difference in surface charge, molecule size, and solubility in water. Inspired by the water purification of the earth's multilayer strata, a fibrous membrane with multifunctional skin is fabricated by coupling sub-micrometer pores layer of polyaniline (PANI) and nano molecular brush of polyacrylic acid (PAA)/polyethyleneimine (PEI) on polyacrylonitrile membrane, for cross-scale organic pollution/water separation. This ultrathin skin of PANI/PAA/PEI is endowed with sub-micrometer pores and strong hydration, which can effectively prevent tiny oil droplets from entering or adhering the membrane pores. Furthermore, this skin with double electric layer can selectively adsorb and even filtrate anionic/cationic dyes by protonation and deprotonation effect in different pH solutions. The synergy of these features enables this membrane with ultra-high water flux (>3000 L m-2 h-1 bar-1), oil rejection rates (>99.6%), and anionic/cationic dyes adsorbability (>49.1 mg/g). Besides, the membrane also exhibits desirable reusability, excellent mechanical durability and outstanding acid/alkali resistance, promising for removal of insoluble emulsified oils and soluble organic dyes in wastewater.

CH4 and CO2 Adsorption Mechanism in Kaolinite Slit Nanopores as Studied by the Grand Canonical Monte Carlo Method.

To confirm the rules and transformation conditions of shale gas adsorption and establish a model for evaluating the adsorption capacity of shale gas quantitatively, it is necessary to reveal the shale gas adsorption mechanism. The adsorption mechanism of CH4 and CO2 in Kaolinite slit nanopores has been studied under the simulated conditions of 90 °C and 30 or 50 MPa by the grand canonical Monte Carlo (GCMC) method. The results indicate that CH4 is controlled only by the Van der Waals forces on the mineral surface because CH4 is nonpolar, while CO2 is controlled by both Van der Waals forces and Coulomb forces due to a certain electric quadrupole moment, which makes the adsorption capacity of CO2 on kaolinite greater than that of CH4. Due to the overlapping adsorption potential on the kaolinite surface of micropores (1 nm), the peak of the density profile is higher in the micropores than the peak in the mesopores (4 nm), resulting in the filling effect in the micropores. On the surface of the silicon-oxygen octahedron, the adsorption site for CH4 and CO2 is in the center of the silicone hexagon-ring, and CO2 with a quadrupole moment shifts near the polar oxygen atoms. In contrast, the adsorption sites of CH4 are relatively dispersed on the surface of the aluminum-oxygen octahedron with a hydroxyl group, while the adsorption sites of CO2 are concentrated in the location of the aggregated oxygen atoms. When CH4 and CO2 coexist, CO2 tends to be adsorbed prior to CH4. With the proportion of CO2 increasing, the competitive adsorption effect is gradually aggravated, which suggests the rationality of injecting CO2 to improve the recovery efficiency of shale gas. These findings can provide theoretical support for shale gas exploration and development.

Dual-functional membrane decorated with flower-like metal-organic frameworks for highly efficient removal of insoluble emulsified oils and soluble dyes.

High-performance membranes for simultaneously removing insoluble emulsified oils and soluble organic dyes are in urgently demand for industrial wastewater treatment, but are strictly limited by the single-function and serious fouling problem. Herein, a dual-functional membrane with excellent antifouling ability for efficiently dye/oil/water emulsion separation has been fabricated by growing flower-like metal-organic frameworks (MIL-53-OH) on polyacrylonitrile/polyethyleneimine membrane for the first time. The synergistic effect of the hierarchical flower-like structure and superhydrophilic compositions with high hydration ability endows the obtained membrane with a stable and ultra-strong oil-repelling hydration layer, thus imparting the membrane formidable oil resistance and exceptional oil/water emulsion separation performance (permeate flux>4000 L m-2 h-1). What's more, the superhydrophilic compositions render the membrane an excellent dye remove capacity by electrostatic forces and hydrogen bonding. The membrane rejections for dyes and emulsified oils are above 99%, and the dyes and oils on the used membrane can be easily washed away with methanol and water, respectively, confirming that the membrane has desirable recyclability. Besides, the membrane possesses excellent mechanical performance and outstanding acid and alkali resistance, indicating that the membrane is a promising candidate for removing insoluble emulsified oils and soluble dyes.

Bioinspired Anti-Oil-Fouling Hierarchical Structured Membranes Decorated with Urchin-Like α-FeOOH Particles for Efficient Oil/Water Mixture and Crude Oil-in-Water Emulsion Separation.

Designing and constructing a stable water-retention layer acting as the isolation between the oil and membrane surface holds great significance for solving the membrane fouling problems in oil/water separation, including common layered oil/water mixtures, immiscible oil-in-water emulsions, and even high-viscosity crude oil-in-water emulsions. Inspired by the self-cleaning property of sea urchin thorns, a bioinspired anti-oil-fouling hierarchically structured membranes decorated with urchin-like α-FeOOH particles was successfully prepared via the layer-by-layer (LBL) self-assembly method, maintaining numerous effective micro-nanopores. The hierarchical structured membrane exhibited superior superhydrophilicity/underwater superoleophobicity, high water-retention ability, and preferable anti-oil-fouling properties. Furthermore, the biomimetic membrane with controllable pore sizes could not only separate common layered oil/water mixtures but also effectively separate immiscible surfactant-stabilized oil-in-water emulsions of both low-viscosity crude oil and high-viscosity crude oil with an ultrahigh water flux up to 2598.4 L m-2 h-1 and an outstanding separation efficiency of 98.5%, revealing its promising prospect in oily wastewater treatment.

ß-Hydrogen of Polythiophene Induced Aluminum Ion Storage for High-Performance Al-Polythiophene Batteries.

The urgent need for large-scale, low-cost energy storage has driven a new wave of research focusing on innovative batteries. Due to the high capacity and the low-cost of elemental Al, aluminum-ion batteries (AIBs) are expected as promising candidates for future energy storage. However, further development of AIBs is restricted by the performance of existing carbon-based cathodes and metal chalcogenide cathode materials. In this work, we deposited polythiophene (Pth) on a graphene oxide (Pth@GO) composite and used it as an AIB cathode material. This Pth@GO composite possesses high exposure of Pth active sites, high conductivity, and high structure stability while providing a very high discharge capacity (up to 130 mAh g-1) and outstanding cyclic stability (maintaining above 100 mAh g-1 after 4000 cycles). First principles calculations and experimental results show that the charge is stored on Pth@GO through an electrostatic attraction between AlCl4- and ß-hydrogen (Cß-H) sites in polythiophene.

Flexible SnSe Photodetectors with Ultrabroad Spectral Response up to 10.6 µm Enabled by Photobolometric Effect.

A broad spectral response is highly desirable for radiation detection in modern optoelectronics; however, it still remains a great challenge. Herein, we report a novel ultrabroadband photodetector based on a high-quality tin monoselenide (SnSe) thin film, which is even capable of detecting photons with energies far below its optical band gap. The wafer-size SnSe ultrathin films are epitaxially grown on sodium chloride via the 45° in-plane rotation by employing a sputtering method. The photodetector delivers sensitive detection to ultraviolet-visible-near infrared (UV-Vis-NIR) lights in the photoconductive mode and shows an anomalous response to long-wavelength infrared at room temperature. Under the mid-infrared light of 10.6 µm, the fabricated photodetector exhibits a large photoresponsivity of 0.16 A W-1 with a fast response rate, which is ∼3 orders of magnitude higher than other results. The thermally induced carriers from the photobolometric effect are responsible for the sub-bandgap response. This mechanism is confirmed by a temperature coefficient of resistance of -2.3 to 4.4% K-1 in the film, which is comparable to that of the commercial bolometric detectors. Additionally, the flexible device transferred onto polymer templates further displays high mechanical durability and stability over 200 bending cycles, indicating great potential toward developing wearable optoelectronic devices.

Wafer-size growth of 2D layered SnSe films for UV-Visible-NIR photodetector arrays with high responsitivity.

Due to its excellent electrical and optical properties, tin selenide (SnSe), a typical candidate of two-dimensional (2D) semiconductors, has attracted great attention in the field of novel optoelectronics. However, the large-area growth of high-quality SnSe films still remains a great challenge, which limits their practical applications. Here, wafer-size SnSe ultrathin films with high uniformity and crystallization were deposited via a scalable magnetron sputtering method. The results showed that the SnSe photodetector was highly sensitive to a broad range of wavelengths in the UV-visible-NIR range, especially showing an extremely high responsivity of 277.3 A W-1 with the corresponding external quantum efficiency of 8.5 × 104% and detectivity of 7.6 × 1011 Jones. These figures of merits are among the best performances for the sputter-fabricated 2D photodetector devices. The photodetecting mechanisms based on a photogating effect induced by the trapping effect of localized defects are discussed in detail. The results indicate that the few-layered SnSe films obtained from sputtering growth have great potential in the design of high-performance photodetector arrays.

Small graphite nanoflakes as an advanced cathode material for aluminum ion batteries.

Here, we prepared small graphite nanoflakes (SGN) by a new strategy of pulverization as the cathode of aluminum ion batteries (AIBs). Electrochemical measurements show that SGN has a very high discharge capacity, excellent rate performance and good cycling stability mainly due to its enlarged edge plane, reduced thickness and high crystallinity. This work provides a new route for preparing high performance graphite-based materials for AIBs.

High-performance aqueous sodium-ion battery using a hybrid electrolyte with a wide electrochemical stability window.

The practical application of aqueous sodium-ion batteries (ASIBs) is limited by the electrolysis of water, which results in a low working voltage and energy density of ASIBs. Here, a NaClO4-based acetonitrile/water hybrid electrolyte (NaClO4(H2O)2AN2.4) is applied to ASIBs for the first time, which effectively extends the electrochemical stability window (ESW) to 3.0 V and reduces the internal resistance of the battery. Based on this hybrid electrolyte, an ASIB full cell using carbon coated Na2.85K0.15V2(PO4)3 and NaTi2(PO4)3 as the cathode and anode materials, respectively, can afford a discharge capacity and energy density of 52 mA h g-1 and 51 W h kg-1, respectively, at a current density of 1 A g-1. The energy density of this battery exceeds almost all reported traditional ASIBs.

TiO2@TiO2-xHx core-shell nanoparticle film/Si heterojunction for ultrahigh detectivity and sensitivity broadband photodetector.

A simple hydrogenation treatment is used to synthesize unique oxygen-deficient TiO2 with a core/shell structure (TiO2@TiO2-xHx), superior to the high H2-pressure process (under 20 bar for five days). It is demonstrated that oxygen-deficient TiO2 nanoparticle film/Si heterojunction possesses improved photoresponse performance compared to the untreated TiO2 nanoparticle film/Si heterojunction. Particularly, under 900 nm of 0.5 µW cm-2, the oxygen-deficient TiO2 nanoparticle film (TiO2@TiO2-xHx core-shell nanoparticle film)/Si heterojunction shows high responsivity (R) of 336 A W-1, prominent sensitivity (S) of 1.3 × 107 cm2 W-1, accompanied with a fast rise and decay time of 6 and 5 ms, respectively. Significantly, the detectivity (D*) of the photodetector is up to 1.17 × 1014 cm Hz1/2 W-1, which is better than that reported in metal oxide nanomaterials/Si heterojunction photodetectors, and is 4-5 orders of magnitude higher than some 2D nanosheets/Si heterojunctions of 109-1010 cm Hz1/2 W-1, indicating the excellent ability to detect weak signals. The oxygen vacancies generated in amorphous shell TiO2-xHx make the Fermi level of TiO2-x shift near the conduction band minimum and can lead to reduced dark current. The high absorption and reduced dark current of the heterojunction ensure excellent photoresponse properties of oxygen-deficient TiO2 nanoparticle film/Si heterojunction. The H-reduced oxygen-deficient amorphous shell may be an excellent candidate to enhance the photoresponse performance of metal oxide/Si heterojunction.

A hierarchical structured steel mesh decorated with metal organic framework/graphene oxide for high-efficient oil/water separation.

A hierarchical structured steel mesh decorated with metal organic framework (UiO-66-NH2) nanoparticles/graphene oxide (GO) nanosheets was successfully prepared via a simple self-assemble method. Because water molecules tend to build hydrogen bonds with the amine, carboxyl and hydroxyl functional groups of UiO-66-NH2/GO hierarchical structure, the hierarchical structure can easily capture water and tightly lock the water to build a stable water layer on the steel mesh surface and block oil in contact with the steel mesh. Therefore, the obtained hierarchical structured steel mesh exhibits super-hydrophilicity, underwater super-oleophobicity, excellent oil resistance and outstanding oil/water separation performance with a superior high permeating flux (54,500 L m-2 h-1) and rejection (>99.9%) under gravity force, indicating the mesh possesses great potential for treating oily wastewater.

Layer-by-layer self-assembly of polyaniline nanofibers/TiO2 nanotubes heterojunction thin film for ammonia detection at room temperature.

In this paper, for the first time, polyaniline nanofibers/TiO2 nanotubes (PANI/TiO2) heterojunction thin film has been prepared on Pt interdigital electrodes by layer-by-layer self-assembly method and applied in room temperature NH3 detection. It is found that the optimal self-assembly layer number is three (PANI/TiO2-3) compared to one layer (PANI/TiO2-1) and five layers (PANI/TiO2-5). The PANI/TiO2-3 thin film sensor possesses superior response characteristics compared with our other PANI based sensors, including higher response value (336%@5 ppm NH3), acceptable response/recovery time (110 s/1 086 s@5 ppm NH3), low detection limit (0.5 ppm), and remarkable selectivity. The enhanced gas sensing performances could be ascribed to the tremendous variation of the carrier concentration caused by the p-n junctions as well as the increased specific surface area and pore volume. This work not only offers a superb strategy to fabricate heterojunction thin film but also accelerates the development of room-temperature operable NH3 sensors.

Synthesis of nanowire bundle-like WO3-W18O49 heterostructures for highly sensitive NH3 sensor application.

Heterojunctions are very promising structures due to their hybrid properties, which are usually obtained via a multistep growth process. However, in this paper, WO3-W18O49 heterostructures are synthesized via a novel one-step approach by using isopropanol as reaction media and are applied in NH3 gas detection for the first time. The obtained WO3-W18O49 heterostructures with loose nanowire bundle-like morphology show a response value of 23.3 toward 500 ppm NH3 at 250 °C, which is 5.63 times higher than that of pristine W18O49. In addition, the WO3-W18O49 sensor also exhibits great dynamic response/recovery characteristics (13 s/49 s @ 500 ppm NH3), superb selectivity and low detection limit of 460 ppb. The substantial improvement in the response of WO3-W18O49 heterostructures toward NH3 can be explained by the formation of n-WO3/n-W18O49 heterojunctions that facilitate the generation of a more extended depletion layer as well as the enhancement of specific surface area and pore volume. Our research results open an easy pathway for facile one-step preparation of heterojunctions with high response and low cost, which can be used for the development of other high-performance gas sensors.