Designing novel acetic acid gas sensors is highly imperative for human health. Two-dimensional (2D) layered MXene Ti3C2Tx is becoming an emerging and promising material in gas sensing. In this manuscript, the hydrothermal method was used to synthesize MXenes Ti3C2Tx/Nb2CTx supported NiCo2O4-MnO2 composites and pure materials. The structure, chemical composition and morphology of the samples were studied by SEM, EDS, TEM, HRTEM, XRD, BET, FTIR, UV-visible, XPS and Raman, justifying the successful synthesis of products. The layered structure of Ti3C2Tx enhanced the BET surface area and provided sufficient sites, which assisted the gas sensing improvement. The gas sensors were fabricated from synthesized products and were tested for different kinds of VOCs deeply. The results exposed that the gas sensor of Ti3C2Tx-NiCo2O4-MnO2 (5% of Ti3C2Tx=NCO-Mn-Ti-5) was highly sensitive to 20 ppm acetic acid and very less responsive to all other VOCs (acetone, TMA, ethanol, methanol, formaldehyde, acetaldehyde, acetylene and xylene) at room temperature. The response (Rg/Ra) to 20 ppm acetic acid was 12.5 and the lowest detection limit was 0.05 ppm. Additionally, the sensor of NCO-Mn-Ti-5 revealed great stability/reproducibility, short response/recovery times and linearity between acetic acid concentration and response. The idea of the novel sensor (NCO-Mn-Ti-5) could be potentially useful in the field of sensors.

Hydrogen sulfide (H2S) gas sensors with high response and minimum limit of detection at room temperature are of great importance to ensure the safety of humans and the environment. A series of samples such as MXene Ti3C2, Ti3AlC2, WS2, MoSe2/Zn2SnO4 and spherical Zn2SnO4 nanoparticles were synthesized via hydrothermal method in this paper. Different characterizations were performed on these samples to check crystal structures, morphologies, chemical states, etc. And gas sensing properties were also performed and analyzed deeply. A series of sensor sheets were fabricated via the spin coating method based on synthesized samples for gas sensing properties. MXene Ti3C2/Zn2SnO4-5 based gas sensor detected the highest response (110) towards 8 ppm H2S with excellent selectivity, the minimum limit of detection (0.01 ppm), mediate long-term stability and good reproducibility compared with other fabricated sensors at room temperature. Also, the sensor response was increased with the increase of H2S concentration. Experimental results showed that the highest response of Ti3C2/Zn2SnO4-5 based gas sensor was accredited to heterojunction, higher BET surface area, and increased oxygen species. The simple way synthesized nanocomposite and fabricated sensors throw a novel idea for tracing H2S at the lowest concentration to prevent different diseases.

The “solvent-in-salt” electrolyte is considered as a technology of significance for rechargeable Zn metal batteries due to its non-flammable, moisture-tolerant and electrochemical stable merits. Particularly, the “co-solvent-in-salt” electrolyte with dual-solvent of water and acetonitrile is developed in this work. It possesses both the advantages of high-concentration and aqueous/organic hybrid solvent, such as, low cost, low water content, high concentration and impressive ion conductivity. The corresponding modulated solvation structure and chemical environmental in the optimized electrolyte system contribute to suppress the side reactions (hydrogen evolution reaction (HER), Zn corrosion, dendrites growth) significantly. And they further improve the homogeneous Zn deposition, the plating/stripping reversibility (∼99.8%) and the stability (∼2900 h) of Zn metal anode even in the Zn//NH4V4O10 full battery (500 cycles).

Molybdenum-based materials are regarded as promising candidates for aqueous zinc-ion batteries (AZIBs) because of their multi-valences and high specific capacity. However, the structural instability of MoS2 and sluggish reaction kinetics of MoO2 restrict their further development in AZIBs. Herein, the MoO2 with in situ inherited sulfur atoms (S-MoO2) is successfully prepared by heat treatment of MoS2 in static air. Benefiting from the synergistic effects of inherited S atoms and introduced O vacancies, the S-MoO2 exhibits higher specific/rate capacities (236 mAh g(-1) at 0.1 A g(-1) and 105 mAh g(-1) at 5.0 A g(-1)) and better cycling stability (81% capacity retention after 2000 cycles at 2.0 A g(-1)) than the perfect MoO2. More significantly, the in situ electrochemical quartz crystal microbalance (EQCM) and ex situ spectroscopic techniques comprehensively elucidate that zinc-ion and proton as joint charge carriers insert/extract into/from S-MoO2 through the (011) and (020) planes with high reversibility. This work provides a guideline for understanding the multi-ion storage mechanism of cathode materials for high-capacity AZIBs.

Aqueous rechargeable Zn metal batteries (ARZBs) are extensively studied recently because of their low-cost, high-safety, long lifespan, and other unique merits. However, the terrible ion conductivity and insufficient interfacial redox dynamics at low temperatures restrict their extended applications under harsh environments such as polar inspections, deep sea exploration, and daily use in cold regions. Electrolyte modulation is considered to be an effective way to achieve low-temperature operation for ARZBs. In this review, first, the fundamentals of the liquid-solid transition of water at low temperatures are revealed, and an in-depth understanding of the critical factors for inferior performance at low temperatures is given. Furthermore, the electrolyte modulation strategies are categorized into anion/concentration regulation, organic co-solvent/additive introduction, anti-freezing hydrogels construction, and eutectic mixture design strategies, and emphasize the recent progress of these strategies in low-temperature Zn batteries. Finally, promising design principles for better electrolytes are recommended and future research directions about high-performance ARZBs at low temperatures are provided.

The static aqueous rechargeable Zn-Iodine batteries (ARZiBs) have been studied extensively because of their low-cost, high-safety, moderate voltage output, and other unique merits. Nonetheless, the poor electrical conductivity and thermodynamic instability of the iodine cathode, the complicated conversion mechanism, and the severe interfacial reactions at the Zn anode side induce their low operability and unsatisfactory cycling stability. This review first clarifies the typical configuration of ARZiBs with a focus on the energy storage mechanism and uncovers the issues of the ARZiBs from a fundamental point of view. After that, it categorizes the recent optimization strategies into cathode fabrication, electrolyte modulation, and separator/anode modification; and summarizes and highlights the achieved progress of these strategies in advanced ARZiBs. Given that the ARZiBs are still at an early stage, the future research outlook is provided, which hopefully may guide the rational design of advanced ARZiBs. Understanding the fundamentals and key issues of the ARZiBs is important toward the potent applications. The timely and objective strategies for the realistic high-performance ARZiBs are summarized. The conclusion and outlook are ultimately introduced to provide guidance for the future research.image

Aqueous rechargeable Zn//MnO2 batteries have been considered as the promising candidate for future energy storage system due to their economic and environmental merits. However, the high-performance Zn//MnO2 batteries are plagued by poor sluggish reaction kinetics and capacity degradation due to the strong electrostatic interactions and complicated reaction process. Herein, the synergistic effect of atom defects engineering and phase transformation mechanism is confirmed as the effective strategy to enhance ion/charge transfer kinetics and structural stability. Defects gradient controlling and electrochemically induced phase transformation from spinel to layered structure render the aqueous Zn//λ-MnO2 system delivers a high discharge capacity of 285 mAh/g and capacity retention of 81% after 500 cycles.

With high safety and low-cost features, aqueous zinc batteries have become the promising rechargeable battery technology for future. Recent research works reached a deep understanding on the underlying electrolyte chemistry in Zn batteries. This review aims to put forward the challenges that the aqueous electrolyte is facing, which include low voltage window, multifarious irreversible reactions, and low energy density. The innovative electrolyte modulation strategies, such as hybrid/concentrated solution, gel polymer electrolyte (hydrogel electrolyte), eutectic mixture, electrolyte additives, towards better zinc batteries performance are summarized. The conclusion and outlook are introduced to provide guidance for smart design of electrolyte for advanced Zn batteries.

Breakthroughs in super-concentrated electrolytes have pushed the aqueous solution to the forefront of the high-safety battery devices. An ideal electrolyte system should be cost-effective and stable in a wide electrochemical window. In recent years, eutectic mixtures have emerged as a green, safe, low-cost, and electrochemically stable electrolyte system for rechargeable metal-ion batteries (MIBs). Here, the fundamental understanding of the formation mecha-nisms, physio-chemical properties, and composition-structure-property rela-tionships of eutectic mixtures are summarized. Our focus is their advanced function and applications in MIBs. Considering that eutectic mixtures in MIBs are still at an early stage, we provide the challenges and perspectives which hopefully may guide the rational design of advanced eutectic mixtures for differ-ent electrochemical energy storage and conversion systems.

Despite the substantial progress in cathode materials in the past few years, rechargeable zinc batteries (RZBs) are plagued by rapid performance degradation due to dendrite formation and notorious side reactions at the Zn anode side. Here, an optimized hydrated eutectic electrolyte (HEE) system containing methylsulfonylmethane, zinc perchlorate, and water, in which an organic ligand coordinated the solvation shell of Zn ions with water molecules constituting the eutectic network, is proposed. Compared to common aqueous solutions, this HEE system is proven effective in promoting the smooth Zn deposition and plating/stripping reversibility as well as suppressing side reactions. The vanadium‐based zinc batteries based on this new HEE exhibit exceptionally high‐capacity retention (≈100% retention even after 1600 cycles at a relatively small current density of 1000 mA g −1 ). This study offers a new type of electrolyte for RZBs and a deep understanding of the effect of Zn 2+ solvent sheath structure on the cycle reversibility.

Large-scale electrical energy storage (EES) technology with high safety, low cost, and high stability determines the future energy structure adjustment and smart grid construction. Rechargeable Zn batteries (RZBs) would be an ideal candidate for EES devices because of their intrinsic environment-friendly and cost-effective properties. Although substantial progress has been achieved in RZBs in the past several years, the state-of-art RZBs are plagued by severe side-reactions like cathode materials dissolution, dendrites growth, Zn corrosion, and hydrogen evolution, which are associated with the active free water and hydrated Zn(OH)(6)(2+) ion in common aqueous solution. In this review, the electrolyte strategies including concentration, additives, and solvation structure modulation for improving Zn cycling performance are discussed in detail. This paper combines reviews and perspectives on electrolyte strategies, which would shed light on the development of high-performance RZBs.

Aqueous rechargeable batteries have been considered as promising candidates to achieve the requirements for the stationary energy storage system. In recent years, numerous studies have focused on aqueous rechargeable zinc batteries (ARZBs) due to their merits of low-cost, material abundance, acceptable energy density, and environmental friendliness. The fundamental advances in energy storage of batteries are largely dependent on the electrode materials. Focusing on the recent advances of ARZBs, in this review, the reaction mechanisms, electrochemical performances, and challenges about Mn-based materials for ARZBs are systematically introduced. Meanwhile, the optimization strategies for high-performance Mn-based materials with different nanostructures, morphologies, and compositions for ARZBs are discussed as well. This paper combining reviews and perspectives of Mn-based electrodes may shed light on the development of advanced aqueous zinc batteries.

Aqueous zinc-ion batteries have been regarded as a promising alternative to large-scale energy storage, due to associated low-cost, improved safety and environmental friendliness. However, a high-performance cathode material for both rate capability and specific capacity is still a challenge. One kind of the more promising candidates are sodium manganese oxide(NMO) materials, although they suffer from individual issues and need to be further improved. Herein, we present a novel mixed phase NMO material composed of nearly equal amounts of Na 0.55 Mn 2 O 4 and Na 0.7 MnO 2.05 . The structured configuration with particle size of 200–500 nm is found to be beneficial towards improving the ion diffusion rate during the charge/discharge process. Compared with Na 0.7 MnO 2.05 and Na 0.55 Mn 2 O 4 , the mixed phase NMO demonstrates an enhanced rate capability and excellent long-term cycling stability with a capacity retention of 83% after 800 cycles. More importantly, the system also delivers an impressive energy density and power density, as 378 W·h·kg -1 at 68.7 W·kg -1 , or 172 W·h·kg -1 at 1705 W·kg -1 . The superior electrochemical performance is ascribed to the fast Zn 2+ diffusion rate because of a large ratio of capacitive contribution(63.9% at 0.9 m V·s -1 ). Thus, the mixed phase route provides a novel strategy to enhance electrochemical performance, enabling mixed phase NMO as very promising material towards large-scale energy-storage applications.

Neotame is an artificial sweetener with increasing consumption in recent years, excessive intake of it may bring potential health risk. In this work, a rapid method was developed to detect neotame in instant grain beverages, which was based on surface-enhanced Raman scattering (SERS) technique and filter paper-based silver nanoparticles (AgNPs@FP) substrates. The designed substrate exhibits good SERS activity with an enhancement factor of 10(5) because of the synergistic effect of the concentrated silver nanoparticles and filter paper. Meanwhile, the stability and repeatability of this fabricated substrate have been investigated with the relative standard deviation of 6.1%. In addition, it shows an excellent linear relationship (R-2 = 0.997) between the SERS signal and the logarithm concentration of neotame with a wide concentration range (0.05-5 g/kg) in the quantitative analysis. The limit of detection of neotame can be as low as 0.01 g/kg in instant grain beverages, which is below the maximum allowable addition level for neotame in instant grain beverages set in China (GB2760-2014, 0.16 g/kg). The proposed method has great potential for the identification and quantification of neotame in food safety applications with high sensitivity.

The pesticide residues in agri-foods are threatening people’s health. This study aims to establish a fast and low-cost surface-enhanced Raman scattering (SERS) method for the on-site detection of flumetsulam in wheat. The two-step modified concentrated gold nanoparticles (AuNPs) acted as the SERS substrate with the aid of NaCl and MgSO4. NaCl is served as the activator to modify AuNPs, while MgSO4 is served as the aggregating agent to form high-density hot spots. The activation and aggregation are two essential collaborative procedures to generate remarkable SERS enhancement and achieve the trace-level detection of flumetsulam. This method exhibits good enhancement effect with an enhancement factor of 106 and wide linear range (5–1000 μg/L). With simple pretreatment, the flumetsulam residue in real wheat samples can be successfully detected with the limit of detection (LOD) down to 0.01 μg/g, which is below the maximum residue limit of flumetsulam in wheat (0.05 μg/g) set in China. The recovery of flumetsulam residue in wheat ranges from 88.3% to 95.6%. These results demonstrate that the proposed SERS method is a powerful technique for the detection of flumetsulam in wheat, which implies the great application potential in the rapid detection of other pesticide residues in various agri-foods.

Aqueous zinc-ion batteries (ZIBs) are attractive energy storage technology due to merits of high safety, low-cost and environment-friendliness. However, the further development of aqueous ZIBs is plagued by severely uneven zinc deposition on the anode side, which leads to low Coulombic efficiency and formation of dendrites. In this work, novel anodes are prepared by electroplating zinc on different substrates (copper foam, copper foil and Ni foam), namely, Cu foam@Zn, Cu foil@Zn and Ni foam@Zn, respectively. As a result, Cu foam@Zn is screened as optimal anode, for Cu foam@Zn anode exhibits small voltage hysteresis, high Coulombic efficiency and negligible self-discharge. Moreover, the assembled Cu foam@Zn vertical bar beta-MnO2 cell shows good cycle stability (206.9 mA h g(-1) after 500 cycles at a current density of 1 A g(-1)) and excellent rate performance. This superior electrochemical performance could be attributed to the three-dimensional porous architecture, superb electrical conductivity and good corrosion resistance of Cu foam@Zn anode, guaranteeing its faster electrochemical kinetics, more uniform zinc deposition and stable cyclability.

The aqueous Zn-ion battery (ZIBs) is regarded as the most promising alternative energy storage system. However, the poor shelf life and restoration capacity caused by dendrite growth and the irreversible consumption of metal Zn anode, are remaining challenges for practical cell technologies. In this work, a hierarchically three-dimensional Zn2+-conductor gel electrolyte (Alg-Zn) is prepared based on ion-crosslinking to enable highly reversible dendritefree zinc metal anode. The Alg-Zn possesses a high ionic conductivity of 1.83 x 10(-2) S cm(-1) and superior mechanical performance for aqueous ZIBs applications. Given the ion-confinement capability in gel electrolyte and deliberated characterization of symmetric Zn/Zn over 270 h cycled testing, it can effectively suppress dendrite growth and reduce the generation of irreversible by-products. By coupling with this gel electrolyte, the Zn/MnO2 batteries exhibit good cycling stability and rate performance. Especially, after resting over 60 h, the capacity can rapidly recover and maintain similar to 320 mA h g(-1). This work demonstrates that the gel electrolyte can effectively suppress the notorious parasitic reactions for static states usually in the Newtonian liquid electrolytes, and thus endow the Zn-based battery with outstanding shelf life and restoration capacity.

We have observed the unique reduction displacement reaction mechanism in an aqueous ZIB system, on the basis of a Zn/Cu3(OH)2V2O7·2H2O cell. This cell is capable of exhibiting excellent electrochemical properties, including high capacity and long-term cycling stability.

Flexible electrodes of vertically oriented Sn3O4 nanoflakes grown on carbon fiber cloth were synthesized by a hydrothermal reaction, exhibiting superior electrochemical performance.

Rechargeable aqueous Zn/manganese dioxide (Zn/MnO2) batteries are attractive energy storage technology owing to their merits of low cost, high safety, and environmental friendliness. However, the beta-MnO2 cathode is still plagued by the sluggish ion insertion kinetics due to the relatively narrow tunneled pathway. Furthermore, the energy storage mechanism is under debate as well. Here, beta-MnO2 cathode with enhanced ion insertion kinetics is introduced by the efficient oxygen defect engineering strategy. Density functional theory computations show that the beta-MnO2 host structure is more likely for H+ insertion rather than Zn2+, and the introduction of oxygen defects will facilitate the insertion of H+ into beta-MnO2. This theoretical conjecture is confirmed by the capacity of 302 mA h g(-1) and capacity retention of 94% after 300 cydes in the assembled aqueous Zn/beta-MnO2 cell. These results highlight the potentials of defect engineering as a strategy of improving the electrochemical performance of beta-MnO2 in aqueous rechargeable batteries.