Dual Porous 3D Zinc Anodes toward Dendrite-Free and Long Cycle Life Zinc-Ion Batteries.

Rechargeable aqueous zinc-ion batteries (ZIBs) have been proven to be an alternative energy storage system because of their high safety, low cost, and eco-friendliness. However, the poor stability of metallic Zn anodes suffering from uncontrolled dendrite formation and electrochemical corrosion has brought troublesome hindrances for their practical application. In this work, we report a dual porous Zn-3D@600 anode prepared by coating a Zn@C protective layer on a 3D zinc skeleton. The Zn-3D@600 anode exhibits a highly stable and low polarization voltage during the Zn plating/stripping process and possesses a smooth and dendrite-free interface after long-term cycling. Moreover, the assembled Zn-3D@600 cell shows excellent cycle stability and superlative rate performance, delivering a discharge capacity of 198.8 mAh g-1 after 1000 cycles at 1 A g-1. Such excellent electrochemical performance can be credited to the Zn@C protective layer regulating uniform Zn nucleation and the 3D zinc skeleton accommodating Zn deposition at a high current density.

Strategic Structure Tuning of Yolk-Shell Microcages for Efficient Nitrogen Fixation.

The electrocatalytic nitrogen reduction reaction (ENRR) under ambient conditions is considered as a promising process to produce ammonia. Towards highly efficient catalysts, here an optimized one-step pyrolysis strategy was tailored to design yolk-shell microcages (YS Co@C/BLCNTs), consisting of Co nanocrystals encapsulated in N-doped carbon framework and bridged by bamboo-like carbon nanotubes (BLCNTs). The cavity created between yolk and shell not only served as a "micro-bag" to store the reactant N2 and enhance its dissolution, but also induced a "cage effect" to confine the diffusion of reaction intermediate, hence making the reaction proceed in the direction of producing NH3 . This catalyst displayed excellent catalytic activities for ENRR: a high NH3 yield of 12.87 µg mgcat -1 h-1 at a high faradaic efficiency of 20.7 % at -0.45 V (vs. reversible hydrogen electrode, RHE). After 5 cycles of consecutive ENRR process, the NH3 yield rate was 11.29 µg mgcat -1 h-1 , indicating the excellent electrocatalytic stability. These results provide a structural engineering for ENRR catalyst with doped N, cooperating with non-precious metal to activate the inert triple bond of N2 and achieve NH3 fixation.

[Nitrous Oxide Emission and Denitrifying Bacterial Communities as Affected by Drip Irrigation with Saline Water in Cotton Fields].

A shortage of freshwater resources has become a fundamental and chronic problem for sustainable agriculture development in arid regions. Use of saline water irrigation has become an important means for alleviating freshwater scarcity. However, long-term irrigation with saline water may cause salt accumulation in the soil, and further affect nitrogen transformation and N2O emission. To investigate this, we conducted a ten-year field experiment to evaluate the effect of irrigation water salinity and N amount on N2O emission and denitrifying bacterial communities. The experimental design was a 2×2 factorial with two irrigation water salinity levels (salinity levels are expressed as electrical conductivity), 0.35 dS·m-1 and 8.04 dS·m-1, and two N amounts, 0 kg·hm-2 and 360 kg·hm-2, representing SFN0, SHN0, SFN360, and SHN360, respectively. The results indicated that long-term saline water irrigation significantly increased soil salinity, moisture, and NH4+-N content, whereas it decreased soil pH, NO3--N, organic matter, and total nitrogen content. Irrigation with saline water significantly inhibited N2O emission, being associated with a decreased in level of 45.19% (unfertilized plots) and 43.50% (fertilized plots) compared with irrigation with fresh water. N2O emission increased as the N amount increased; the N2O emission was 161% higher in the fertilized plots than in the unfertilized plots. In the unfertilized plots, saline water irrigation significantly reduced the activity of denitrifying enzymes, the abundance of nirK, nirS, and nosZ, and the diversity of denitrifying bacterial communities. In the fertilized plots, saline water irrigation did not significantly affect the abundance of nosZ, whereas it significantly reduced the abundance of nirK and nirS. Saline water irrigation and nitrogen application altered the community structures of denitrifying bacteria with nirK, nirS, and nosZ; the irrigation water salinity seemed to have a greater impact on the denitrifying bacterial community in comparison with fertilization. Linear discriminant analysis (LDA) effect size (LEfSe) analysis demonstrated that denitrifying bacterial potential biomarkers increased as the water salinity increased, meaning that saline water irrigation could alter the community structures of denitrifying bacteria, and promote the growth of dominant species. Our findings indicate that increased abundance of nosZ, nirK, and nirS promoted N2O emission, and although long-term saline water reduced soil N2O emission, it resulted in a continuous increase of soil salinity. The emission of N2O had extremely positive correlation with soil NO3--N, organic matter, total nitrogen, denitrifying bacteria abundance, and denitrifying enzyme activities, and was negatively correlated with soil moisture. The soil physiochemical properties and the community structure of denitrifying bacteria had a significant influence on soil N2O emission in cotton fields, and nirS bacteria showed the highest association with N2O emission, thus it might be a dominant microflora in the process of denitrification. This information will aid in reducing atmospheric N2O emissions in agriculturally productive alluvial grey desert soils.

In-Situ Fabrication of Bone-Like CoSe2 Nano-Thorn Loaded on Porous Carbon Cloth as a Flexible Electrode for Na-Ion Storage.

Sodium-ion batteries (SIBs) based on flexible electrode materials are being investigated recently for improving sluggish kinetics and developing energy density. Transition metal selenides present excellent conductivity and high capacity; nevertheless, their low conductivity and serious volume expansion raise challenging issues of inferior lifespan and capacity fading. Herein, an in-situ construction method through carbonization and selenide synergistic effect is skillfully designed to synthesize a flexible electrode of bone-like CoSe2 nano-thorn coated on porous carbon cloth. The designed flexible CoSe2 electrode with stable structural feature displays enhanced Na-ion storage capabilities with good rate performance and outstanding cycling stability. As expected, the designed SIBs with flexible BL-CoSe2 /PCC electrode display excellent reversible capacity with 360.7 mAh g-1 after 180 cycles at a current density of 0.1 A g-1 .

The encapsulation of MnFe2O4 nanoparticles into the carbon framework with superior rate capability for lithium-ion batteries.

Binary transition metal oxides (BTMOs) have been regarded as one of the most hopeful anode materials for lithium-ion batteries (LIBs) owing to their high theoretical capacity, excellent electrochemical activity and abundant electrochemical reactions. However, BTMOs still suffer from two main problems, which are poor conductivity and large volume expansion during the charge/discharge processes. In order to address the above-mentioned problems, mesoporous MnFe2O4@C nanorods have been successfully synthesized in this work. The synergistic effect of the cross-linked carbon framework and mesoporous structure greatly improves the electrochemical performances. As expected, the mesoporous MnFe2O4@C electrode manifests discharge capacities of 987.5 and 816.6 mA h g-1 at the current densities of 100 and 2000 mA g-1, respectively, with the capacity retention ratio of 82.7%, exerting distinguished rate capabilities for LIBs.

A Calcium Organic Salt/rGO composite with Low Solubility and High Conductivity as a Sustainable Anode for Sodium-Ion Batteries.

Organic electrodes hold great promise for sustainable electrodes in sodium-ion batteries (SIBs) owing to their easy availability from biomass. However, traditional organic electrodes suffer from two inherent problems, high solubility in organic electrolytes and low electronic conductivity. Here, a calcium organic salt, Cabpdc (bpdc=4,4'-biphenyldicarboxylate) was designed and formed into a composite with reduced graphene oxide (rGO) to improve these two problems by a "two-in-one" approach. As expected, the Cabpdc/rGO composite displayed competitive cycle and rate performances as an anode for SIBs. Additionally, all-organic sodium-ion full cells were successfully fabricated combining this anode with a commercial organic cathode, promising applications for sustainable SIBs.

Metal oxide-based supercapacitors: progress and prospectives.

Distinguished by particular physical and chemical properties, metal oxide materials have been a focus of research and exploitation for applications in energy storage devices. Used as supercapacitor electrode materials, metal oxides have certified attractive performances for fabricating various supercapacitor devices in a broad voltage window. In comparison with single metal oxides, bimetallic oxide materials are highly desired for overcoming the constraint of the poor electric conductivity of single metal oxide materials, achieving a high capacitance and raising the energy density at this capacitor-level power. Herein, we investigate the principal elements affecting the properties of bimetallic oxide electrodes to reveal the relevant energy storage mechanisms. Thus, the influences of the chemical constitution, structural features, electroconductivity, oxygen vacancies and various electrolytes in the electrochemical behavior are discussed. Moreover, the progress, development and improvement of multifarious devices are emphasized systematically, covering from an asymmetric to hybrid configuration, and from aqueous to non-aqueous systems. Ultimately, some obstinate and unsettled issues are summarized as well as a prospective direction has been given on the future of metal oxide-based supercapacitors.

MOF based on a longer linear ligand: electrochemical performance, reaction kinetics, and use as a novel anode material for sodium-ion batteries.

A metal-organic framework based on a longer linear ligand was rationally designed and evaluated as a novel anode material for sodium-ion batteries. It delivered a high specific capacity of 269 mA h g-1 with a desired voltage plateau and demonstrated excellent capacity retention (79.0% after 1000 cycles). In addition, its reaction kinetics was also investigated in detail by performing cyclic voltammetry and a predominantly diffusion-controlled process was clearly revealed.

Facile Synthesis of A 3D Flower-Like Mesoporous Ni@C Composite Material for High-Energy Aqueous Asymmetric Supercapacitors.

A 3D flower-like mesoporous Ni@C composite material has been synthesized by using a facile and economical one-pot hydrothermal method. This unique 3D flower-like Ni@C composite, which exhibited a high surface area (522.4 m2 g-1 ), consisted of highly dispersed Ni nanoparticles on mesoporous carbon flakes. The effect of calcination temperature on the electrochemical performance of the Ni@C composite was systematically investigated. The optimized material (Ni@C 700) displayed high specific capacity (1306 F g-1 at 2 A g-1 ) and excellent cycling performance (96.7 % retention after 5000 cycles). Furthermore, an asymmetric supercapacitor (ASC) that contained Ni@C 700 as cathode and mesoporous carbon (MC) as anode demonstrated high energy density (60.4 W h kg-1 at a power density of 750 W kg-1 ).

In Situ Synthesis of 3D Flower-Like Nanocrystalline Ni/C and its Effect on Hydrogen Storage Properties of LiAlH4.

Lithium alanate (LiAlH4 ) is of particular interest as one of the most promising candidates for solid-state hydrogen storage. Unfortunately, high dehydrogenation temperatures and relatively slow kinetics limit its practical applications. Herein, 3D flower-like nanocrystalline Ni/C, composed of highly dispersed Ni nanoparticles and interlaced carbon flakes, was synthesized in situ. The as-synthesized nanocrystalline Ni/C significantly decreased the dehydrogenation temperature and dramatically improved the dehydrogenation kinetics of LiAlH4 . It was found that the LiAlH4 sample with 10 wt % Ni/C (LiAlH4 -10 wt %Ni/C) began hydrogen desorption at approximately 48 °C, which is very close to ambient temperature. Approximately 6.3 wt % H2 was released from LiAlH4 -10 wt %Ni/C within 60 min at 140 °C, whereas pristine LiAlH4 only released 0.52 wt % H2 under identical conditions. More importantly, the dehydrogenated products can partially rehydrogenate at 300 °C under 4 MPa H2 . The synergetic effect of the flower-like carbon substrate and Ni active species contributes to the significantly reduced dehydrogenation temperatures and improved kinetics.