Improving performance of flat plate solar collector using nanofluid water/zinc oxide

In this article,the effect of using water/zinc oxide nanofluid as a working fluid on the performance of solar collector is investigated experimentally.The volumetric concentration of nanoparticles is 0.4%,and the particle size is 40 nm,and the mass flow rate of the fluid varies from 1 to 3 kg/min.For this experiment,a device has been prepared with appropriate measuring instruments whose energy source is solar radiation.The solar energy absorbed by the flat plate collector is absorbed by the nanofluid of water/zinc oxide.The nanofluid is pumped to the consumer,a heat exchanger,where it heats the water.The temperature,radiation level,flow rate,and pressure in different parts of the device were measured.The pressure drop and the heat transferred are the most important results of this experimental work.The ASHRAE standard is used to calculate efficiency.The results showed that the use of water/zinc oxide nanofluid increases the collector performance compared to water.For 1 kg/min of mass flow rate,the nanofluids have a 16% increase in efficiency compared to water.From the results,it can be concluded that the choice of optimum mass flow rate in both water and nanofluid cases increases efficiency.

Quantitative trait loci identification reveals zinc finger protein CONSTANS-LIKE 4 as the key candidate gene of stigma color in watermelon(Citrullus lanatus)

Stigma color is a critical agronomic trait in watermelon that plays an important role in pollination.However,there are few reports on the regulation of stigma color in watermelon.In this study,a genetic analysis of the F2 population derived from ZXG1553(P1,with orange stigma)and W1-17(P2,with yellow stigma)indicated that stigma color is a quantitative trait and the orange stigma is recessive compared with the yellow stigma.Bulk segregant analysis sequencing(BSA-seq)revealed a 3.75 Mb segment on chromosome 6 that is related to stigma color.Also,a major stable effective QTL Clqsc6.1(QTL stigma color)was detected in two years between cleaved amplified polymorphic sequencing(CAPS)markers Chr06_8338913 and Chr06_9344593 spanning a~1.01 Mb interval that harbors 51 annotated genes.Cla97C06G117020(annotated as zinc finger protein CONSTANS-LIKE 4)was identified as the best candidate gene for the stigma color trait through RNA-seq,quantitative real-time PCR(qRT-PCR),and gene structure alignment analysis among the natural watermelon panel.The expression level of Cla97C06G117020 in the orange stigma accession was lower than in the yellow stigma accessions with a significant difference.A nonsynonymous SNP site of the Cla97C06G117020 coding region that causes amino acid variation was related to the stigma color variation among nine watermelon accessions according to their re-sequencing data.Stigma color formation is often related to carotenoids,and we also found that the expression trend of ClCHYB(annotated asβ-carotene hydroxylase)in the carotenoid metabolic pathway was consistent with Cla97C06G117020,and it was expressed in low amounts in the orange stigma accession.These data indicated that Cla97C06G117020 and ClCHYB may interact to form the stigma color.This study provides a theoretical basis for gene fine mapping and mechanisms for the regulation of stigma color in watermelon.

Vacancies and interfaces engineering of core-shell heterostuctured NiCoP/NiO as trifunctional electrocatalysts for overall water splitting and zinc-air batteries

The electronic structures and properties of electrocatalysts,which depend on the physicochemical structure and metallic element components,could significantly affect their electrocatalytic performance and their future applications in Zn-air battery(ZAB)and overall water splitting(OWS).Here,by combining vacancies and heterogeneous interfacial engineering,three-dimensional(3D)core-shell NiCoP/NiO heterostructures with dominated oxygen vacancies have been controllably in-situ grown on carbon cloth for using as highly efficient electrocatalysts toward hydrogen and oxygen electrochemical reactions.Theoretical calculation and electrochemical results manifest that the hybridization of NiCoP core with NiO shell produces a strong synergistic electronic coupling effect.The oxygen vacancy can enable the emergence of new electronic states within the band gap,crossing the Fermi levels of the two spin components and optimizing the local electronic structure.Besides,the hierarchical core-shell NiCoP/NiO nanoarrays also endow the catalysts with multiple exposed active sites,faster mass transfer behavior,optimized electronic strutures and improved electrochemical performance during ZAB and OWS applications.

Water molecules and oxygen-vacancy modulation of vanadium pentoxide with fast kinetics toward ultrahigh power density and durable flexible all-solid-state zinc ion battery

Aqueous zinc ion battery(ZIB)with many virtues such as high safety,cost-effective,and good environmental compatibility is a large-scale energy storage technology with great application potential.Nevertheless,its application is severely hindered by the slow diffusion of zinc ions in desirable cathode materials.Herein,a technique of water-incorporation coupled with oxygen-vacancy modulation is exploited to improve the zinc ions diffusion kinetics in vanadium pentoxide(V_(2)O_5)cathode for ZIB.The incorporated water molecules replace lattice oxygen in V_(2)O_5,and function as pillars to expand interlayer distance.So the structural stability can be enhanced,and the zinc ions diffusion kinetics might also be promoted during the repeated intercalation/deintercalation.Meanwhile,the lattice water molecules can effectively enhance conductivity due to the electronic density modulation effect.Consequently,the modulated V_(2)O_5(H-V_(2)O_5)cathode behaves with superior rate capacity and stable durability,achieving 234 mA h g^(-1)over 9000 cycles even at 20 A g^(-1).Furthermore,a flexible all-solid-state(ASS)ZIB has been constructed,exhibiting an admirable energy density of 196.6 Wh kg^(-1)and impressive power density of 20.4 kW kg^(-1)as well as excellent long-term lifespan.Importantly,the assembled flexible ASS ZIB would be able to work in a large temperature span(from-20 to 70℃).Additionally,we also uncover the energy storage mechanism of the H-V_(2)O_5 electrode,offering a novel approach for creating high-kinetics cathodes for multivalent ion storage.

An Electrochemical Perspective of Aqueous Zinc Metal Anode

Based on the attributes of nonflammability,environmental benignity,and cost-effectiveness of aqueous electrolytes,as well as the favorable compatibility of zinc metal with them,aqueous zinc ions batteries(AZIBs)become the leading energy storage candidate to meet the requirements of safety and low cost.Yet,aqueous electrolytes,acting as a double-edged sword,also play a negative role by directly or indirectly causing various parasitic reactions at the zinc anode side.These reactions include hydrogen evolution reaction,passivation,and dendrites,resulting in poor Coulombic efficiency and short lifespan of AZIBs.A comprehensive review of aqueous electrolytes chemistry,zinc chemistry,mechanism and chemistry of parasitic reactions,and their relationship is lacking.Moreover,the understanding of strategies for suppressing parasitic reactions from an electrochemical perspective is not profound enough.In this review,firstly,the chemistry of electrolytes,zinc anodes,and parasitic reactions and their relationship in AZIBs are deeply disclosed.Subsequently,the strategies for suppressing parasitic reactions from the perspective of enhancing the inherent thermodynamic stability of electrolytes and anodes,and lowering the dynamics of parasitic reactions at Zn/electrolyte interfaces are reviewed.Lastly,the perspectives on the future development direction of aqueous electrolytes,zinc anodes,and Zn/electrolyte interfaces are presented.

Towards advanced zinc anodes by interfacial modification strategies for efficient aqueous zinc metal batteries

Developing sustainable and clean energy sources(e.g.,solar,wind,and tide energy)is essential to achieve the goal of carbon neutrality.Due to the discontinuous and inco nsistent nature of common clean energy sources,high-performance energy storage technologies are a critical part of achieving this target.Aqueous zinc metal batteries(AZMBs)with inherent safety,low cost,and competitive performance are regarded as one of the promising candidates for grid-scale energy storage.However,zinc metal anodes(ZMAs)with irreversible problems of dendrite growth,hydrogen evolution reaction,self-corrosio n,and other side reactions have seriously hindered the development and commercialization of AZMBs.An increasing number of researchers are focusing on the stability of ZMAs,so assessing the effectiveness of existing research strategies is critical to the development of AZMBs.This review aims to provide a comprehensive overview of the fundamentals and challenges of AZMBs.Resea rch strategies for interfacial modification of ZMAs are systematically presented.The features of artificial interfacial coating and in-situ interfacial coating of ZMAs are compared and discussed in detail,as well as the effect of modified interfacial ZMA on the full-battery performance.Finally,perspectives are provided on the problems and challenges of ZMAs.This review is expected to offer a constructive reference for the further development and commercialization of AZMBs.

Mechanical reliable,NIR light-induced rapid self-healing hydrogel electrolyte towards flexible zinc-ion hybrid supercapacitors with low-temperature adaptability and long service life

Hydrogel electrolytes hold great potential in flexible zinc ion supercapacitors(ZICs)due to their high conductivity,good safety,and flexibility.However,freezing of electrolytes at low temperature(subzero)leads to drastic reduction in ionic conductivity and mechanical properties that deteriorates the performance of flexible ZICs.Besides,the mechanical fracture during arbitrary deformations significantly prunes out the lifespan of the flexible device.Herein,a Zn^(2+)and Li^(+)co-doped,polypyrrole-dopamine decorated Sb_(2)S_(3)incorporated,and polyvinyl alcohol/poly(N-(2-hydroxyethyl)acrylamide)double-network hydrogel electrolyte is constructed with favorable mechanical reliability,anti-freezing,and self-healing ability.In addition,it delivers ultra-high ionic conductivity of 8.6 and 3.7 S m^(-1)at 20 and−30°C,respectively,and displays excellent mechanical properties to withstand tensile stress of 1.85 MPa with tensile elongation of 760%,together with fracture energy of 5.14 MJ m^(-3).Notably,the fractured hydrogel electrolyte can recover itself after only 90 s of infrared illumination,while regaining 83%of its tensile strain and almost 100%of its ionic conductivity during−30–60°C.Moreover,ZICs coupled with this hydrogel electrolyte not only show a wide voltage window(up to 2 V),but also provide high energy density of 230 Wh kg^(-1)at power density of 500 W kg^(-1)with a capacity retention of 86.7%after 20,000 cycles under 20°C.Furthermore,the ZICs are able to retain excellent capacity even under various mechanical deformation at−30°C.This contribution will open up new insights into design of advanced wearable flexible electronics with environmental adaptability and long-life span.

Insights on advanced substrates for controllable fabrication of photoanodes toward efficient and stable photoelectrochemical water splitting

Conversion of solar energy into H_(2) by photoelectrochemical(PEC)water splitting is recognized as an ideal way to address the growing energy crisis and environmental issues.In a typical PEC cell,the construction of photoanodes is crucial to guarantee the high efficiency and stability of PEC reactions,which fundamentally rely on rationally designed semiconductors(as the active materials)and substrates(as the current collectors).In this review work,we start with a brief introduction of the roles of substrates in the PEC process.Then,we provide a systematic overview of representative strategies for the controlled fabrication of photoanodes on rationally designed substrates,including conductive glass,metal,sapphire,silicon,silicon carbide,and flexible substrates.Finally,some prospects concerning the challenges and research directions in this area are proposed.

Experimental study on the effect of water absorption level on rockburst occurrence of sandstone

To investigate the mechanism of rockburst prevention by spraying water onto the surrounding rocks,15 experiments are performed considering different water absorption levels on a single face.High-speed photography and acoustic emission(AE)system are used to monitor the rockburst process.The effect of water on sandstone rockburst and the prevention mechanism of water on sandstone rockburst are analyzed from the perspective of energy and failure mode.The results show that the higher the ab-sorption degree,the lower the intensity of the rockburst after absorbing water on single side of sand-stone.This is reflected in the fact that with the increase in the water absorption level,the ejection velocity of rockburst fragments is smaller,the depth of the rockburst pit is shallower,and the AE energy is smaller.Under the water absorption level of 100%,the magnitude of rockburst intensity changes from medium to slight.The prevention mechanism of water on sandstone rockburst is that water reduces the capacity of sandstone to store strain energy and accelerates the expansion of shear cracks,which is not conducive to the occurrence of plate cracking before rockburst,and destroys the conditions for rockburst incubation.

Development of advanced anion exchange membrane from the view of the performance of water electrolysis cell

Green hydrogen produced by water electrolysis combined with renewable energy is a promising alternative to fossil fuels due to its high energy density with zero-carbon emissions.Among water electrolysis technologies,the anion exchange membrane(AEM) water electrolysis has gained intensive attention and is considered as the next-generation emerging technology due to its potential advantages,such as the use of low-cost non-noble metal catalysts,the relatively mature stack assembly process,etc.However,the AEM water electrolyzer is still in the early development stage of the kW-level stack,which is mainly attributed to severe performance decay caused by the core component,i.e.,AEM.Here,the review comprehensively presents the recent progress of advanced AEM from the view of the performance of water electrolysis cells.Herein,fundamental principles and critical components of AEM water electrolyzers are introduced,and work conditions of AEM water electrolyzers and AEM performance improvement strategies are discussed.The challenges and perspectives are also analyzed.

Influence of water coupling coefficient on the blasting effect of red sandstone specimens

This study investigates the impact of different water coupling coefficients on the blasting effect of red sandstone.The analysis is based on the theories of detonation wave and elastic wave,focusing on the variation in wall pressure of the blasting holes.Using DDNP explosive as the explosive load,blasting tests were conducted on red sandstone specimens with four different water coupling coefficients:1.20,1.33,1.50,and 2.00.The study examines the morphologies of the rock specimens after blasting under these different water coupling coefficients.Additionally,the fractal dimensions of the surface cracks resulting from the blasting were calculated to provide a quantitative evaluation of the extent of rock damage.CT scanning and 3D reconstruction were performed on the post-blasting specimens to visually depict the extent of damage and fractures within the rock.Additionally,the volume fractal dimension and damage degree of the post-blasting specimens are calculated.The findings are then combined with numerical simulation to facilitate auxiliary analysis.The results demonstrate that an increase in the water coupling coefficient leads to a reduction in the peak pressure on the hole wall and the crushing zone,enabling more of the explosion energy to be utilized for crack propagation following the explosion.The specimens exhibited distinct failure patterns,resulting in corresponding changes in fractal dimensions.The simulated pore wall pressure–time curve validated the derived theoretical results,whereas the stress cloud map and explosion energy-time curve demonstrated the buffering effect of the water medium.As the water coupling coefficient increases,the buffering effect of the water medium becomes increasingly prominent.

Efficient degradation of dye pollutants in wastewater via photocatalysis using a magnetic zinc oxide/graphene/iron oxide-based catalyst

In this paper, we present a proof-of-concept study of the enhancement of photocatalytic activity via a combined strategy of fabricating a visible-light responsive ternary heterostructure and improving overall photostability by incorporating magnetic zinc oxide/graphene/iron oxide (ZGF). A solvothermal approach was used to synthesize the catalyst. X-ray diffraction (XRD), scanning electron microscopic, energy dispersive X-ray, transmission electron microscopic, vibrating sample magnetometric, and ultraviolet–visible diffuse reflectance spectroscopic techniques were used to characterize the synthesized samples. The obtained optimal Zn(NO_(3))_(2) concentration, temperature, and heating duration were 0.10 mol/L, 600℃, and 1 h, respectively. The XRD pattern revealed the presence of peaks corresponding to zinc oxide, graphene, and iron oxide, indicating that the ZGF catalyst was effectively synthesized. Furthermore, when the developed ZGF was used for methylene blue dye degradation, the optimum irradiation time, dye concentration, catalyst dosage, irradiation intensity, and solution pH were 90 min, 10 mg/L, 0.03 g/L, 100 W, and 8.0, respectively. Therefore, the synthesized ZGF system could be used as a catalyst to degrade dyes in wastewater samples. This hybrid nanocomposite consisting of zinc oxide, graphene, and iron oxide could also be used as an effective photocatalytic degrader for various dye pollutants.

Recent advances in cobalt phosphide-based materials for electrocatalytic water splitting:From catalytic mechanism and synthesis method to optimization design

Electrochemical water splitting has long been considered an effective energy conversion technology for trans-ferring intermittent renewable electricity into hydrogen fuel,and the exploration of cost-effective and high-performance electrocatalysts is crucial in making electrolyzed water technology commercially viable.Cobalt phosphide(Co-P)has emerged as a catalyst of high potential owing to its high catalytic activity and durability in water splitting.This paper systematically reviews the latest advances in the development of Co-P-based materials for use in water splitting.The essential effects of P in enhancing the catalytic performance of the hydrogen evolution reaction and oxygen evolution reaction are first outlined.Then,versatile synthesis techniques for Co-P electrocatalysts are summarized,followed by advanced strategies to enhance the electrocatalytic performance of Co-P materials,including heteroatom doping,composite construction,integration with well-conductive sub-strates,and structure control from the viewpoint of experiment.Along with these optimization strategies,the understanding of the inherent mechanism of enhanced catalytic performance is also discussed.Finally,some existing challenges in the development of highly active and stable Co-P-based materials are clarified,and pro-spective directions for prompting the wide commercialization of water electrolysis technology are proposed.

Investigation of hydroxyl-terminated polybutadiene propellant breaking characteristics and mechanism impacted by submerged cavitation water jet

A submerged cavitation water jet(SCWJ)is an effective method to recycle solid propellant from obsolete solid engines by the breaking method.Solid propellant's breaking modes and mechanical process under SCWJ impact are unclear.This study aims to understand those impact breaking mechanisms.The hydroxyl-terminated polybutadiene(HTPB)propellant was chosen as the research material,and a self-designed test system was used to conduct impact tests at four different working pressures.The high-speed camera characterized crack propagation,and the DIC method calculated strain change during the impact process.Besides,micro and macro fracture morphologies were characterized by scanning electron microscope(SEM)and computed tomography(CT)scanning.The results reveal that the compressive strain concentration region locates right below the nozzle,and the shear strain region distributes symmetrically with the jet axis,which increases to 4% at first 16th ms,the compressive strain rises to 2% and 6% in the axial and transverse direction,respectively.The two tensile cracks formed first at the compression strain concentrate region,and there generate many shear cracks around the tensile cracks,and those shear cracks that develop and aggregate cause the cracks to become wider and cut through the tensile cracks,forming the tensile-shear cracks and the impact parts eventually fail.The HTPB propellant forms a breaking hole shaped conical after impact 10 s.The mass loss increases by 17 times at maximum,with the working pressure increasing by three times.Meanwhile,the damage value of the breaking hole remaining on the surface increases by 7.8 times while 2.9 times in the depth of the breaking hole.The breaking efficiency is closely affected by working pressures.The failure modes of HTPB impacted by SCWJ are classified as tensile crack-dominated and tensile-shear crack-dominated damage mechanisms.

Grain yield and N uptake of maize in response to increased plant density under reduced water and nitrogen supply conditions

The development of modern agriculture requires the reduction of water and chemical N fertilizer inputs.Increasing the planting density can maintain higher yields,but also consumes more of these restrictive resources.However,whether an increased maize density can compensate for the negative effects of reduced water and N supply on grain yield and N uptake in the arid irrigated areas remains unknown.This study is part of a long-term positioning trial that started in 2016.A split-split plot field experiment of maize was implemented in the arid irrigated area of northwestern China in 2020 to 2021.The treatments included two irrigation levels:local conventional irrigation reduced by 20%(W1,3,240 m^(3)ha^(-1))and local conventional irrigation(W2,4,050 m^(3)ha^(-1));two N application rates:local conventional N reduced by 25%(N1,270 kg ha^(-1))and local conventional N(360 kg ha^(-1));and three planting densities:local conventional density(D1,75,000 plants ha^(-1)),density increased by 30%(D2,97,500 plants ha-1),and density increased by 60%(D3,120,000 plants ha^(-1)).Our results showed that the grain yield and aboveground N accumulation of maize were lower under the reduced water and N inputs,but increasing the maize density by 30% can compensate for the reductions of grain yield and aboveground N accumulation caused by the reduced water and N supply.When water was reduced while the N application rate remained unchanged,increasing the planting density by 30% enhanced grain yield by 13.9% and aboveground N accumulation by 15.3%.Under reduced water and N inputs,increasing the maize density by 30% enhanced N uptake efficiency and N partial factor productivity,and it also compensated for the N harvest index and N metabolic related enzyme activities.Compared with W2N2D1,the N uptake efficiency and N partial factor productivity increased by 28.6 and 17.6%under W1N1D2.W1N2D2 had 8.4% higher N uptake efficiency and 13.9% higher N partial factor productivity than W2N2D1.W1N2D2 improved urease activity and nitrate reductase activity by 5.4% at the R2(blister)stage and 19.6% at the V6(6th leaf)stage,and increased net income and the benefit:cost ratio by 22.1 and 16.7%,respectively.W1N1D2 and W1N2D2 reduced the nitrate nitrogen and ammoniacal nitrogen contents at the R6 stage in the 40-100 cm soil layer,compared with W2N2D1.In summary,increasing the planting density by 30% can compensate for the loss of grain yield and aboveground N accumulation under reduced water and N inputs.Meanwhile,increasing the maize density by 30% improved grain yield and aboveground N accumulation when water was reduced by 20% while the N application rate remained constant in arid irrigation areas.

Recent advances and future prospects on Ni_(3)S_(2)-Based electrocatalysts for efficient alkaline water electrolysis

Green hydrogen(H_(2))produced by renewable energy powered alkaline water electrolysis is a promising alternative to fossil fuels due to its high energy density with zero-carbon emissions.However,efficient and economic H_(2) production by alkaline water electrolysis is hindered by the sluggish hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).Therefore,it is imperative to design and fabricate high-active and low-cost non-precious metal catalysts to improve the HER and OER performance,which affects the energy efficiency of alkaline water electrolysis.Ni_(3)S_(2) with the heazlewoodite structure is a potential electrocatalyst with near-metal conductivity due to the Ni–Ni metal network.Here,the review comprehensively presents the recent progress of Ni_(3)S_(2)-based electrocatalysts for alkaline water electrocatalysis.Herein,the HER and OER mechanisms,performance evaluation criteria,preparation methods,and strategies for performance improvement of Ni_(3)S_(2)-based electrocatalysts are discussed.The challenges and perspectives are also analyzed.

High donor-number and low content electrolyte additive for stabilizing zinc metal anode

The aqueous zinc ion batteries(AZIBs)are thought as promising competitors for electrochemical energy storage,though their wide application is curbed by the uncontrollable dendrite growth and gas evolution side reactions.Herein,to stabilize both zinc anodes and water molecules,we developed a modified electrolyte by adding a trace amount of N,N-diethylformanmide(DEF)into the ZnSO_(4)electrolyte for the first time in zinc ion batteries.The effectiveness of DEF is predicted by the comparison of donor number and its preferential adsorption behavior on the zinc anode is further demonstrated by several spectroscopy characterizations,electrochemical methods,and molecular dynamics simulation.The modified electrolyte with 5%v.t.DEF content can ensure a stable cycling life longer than 3400 h of Zn‖Zn symmetric cells and an ultra-reversible Zn stripping/plating process with a high coulombic efficiency of 99.7%.The Zn‖VO_(2)full cell maintains a capacity retention of 83.5%and a 104 mA h g^(-1)mass capacity after 1000cycles.This work provides insights into the role of interfacial adsorption behavior and the donor number of additive molecules in designing low-content and effective aqueous electrolytes.

Some Indicators of the Water Regime in Some Varieties Belonging to the Monarda didyma L. Genus in the Conditions of Tashkent (Uzbekistan)

In this article, the names of 3 varieties of Monarda didyma L., which are considered to be introduced species, some indicators of the water regime in the climatic conditions of Uzbekistan: the amount of water in the leaves, water deficit, water storage capacity were studied in spring and summer, and seasonal changes were determined. According to these indicators of the water regime, the studied varieties belong to the labile water regime, high green mass (centner), seed yield (how many grams), resistance to diseases and pests have been determined, which shows that it is promising for introduction in the conditions of our republic. Therefore, it is recommended to breed these varieties in the foothills and hilly regions of Uzbekistan, where the amount of precipitation is more than 400 - 500 mm.

Design Strategies for Aqueous Zinc Metal Batteries with High Zinc Utilization: From Metal Anodes to Anode-Free Structures

Aqueous zinc metal batteries(AZMBs)are promising candidates for next-generation energy storage due to the excellent safety, environmental friendliness, natural abundance, high theoretical specific capacity, and low redox potential of zinc(Zn) metal. However,several issues such as dendrite formation, hydrogen evolution, corrosion, and passivation of Zn metal anodes cause irreversible loss of the active materials. To solve these issues, researchers often use large amounts of excess Zn to ensure a continuous supply of active materials for Zn anodes. This leads to the ultralow utilization of Zn anodes and squanders the high energy density of AZMBs. Herein, the design strategies for AZMBs with high Zn utilization are discussed in depth, from utilizing thinner Zn foils to constructing anode-free structures with theoretical Zn utilization of 100%, which provides comprehensive guidelines for further research. Representative methods for calculating the depth of discharge of Zn anodes with different structures are first summarized. The reasonable modification strategies of Zn foil anodes, current collectors with pre-deposited Zn, and anode-free aqueous Zn metal batteries(AF-AZMBs) to improve Zn utilization are then detailed. In particular, the working mechanism of AF-AZMBs is systematically introduced. Finally, the challenges and perspectives for constructing high-utilization Zn anodes are presented.

Recent advances and perspectives of zinc metal-free anodes for zinc ion batteries

Zinc-ion batteries(ZIBs) are recognized as potential energy storage devices due to their advantages of low cost, high energy density, and environmental friendliness. However, zinc anodes are subject to unavoidable zinc dendrites, passivation, corrosion, and hydrogen evolution reactions during the charging and discharging of batteries, becoming obstacles to the practical application of ZIBs. Appropriate zinc metal-free anodes provide a higher working potential than metallic zinc anodes, effectively solving the problems of zinc dendrites, hydrogen evolution, and side reactions during the operation of metallic zinc anodes. The improvement in the safety and cycle life of batteries creates conditions for further commercialization of ZIBs. Therefore, this work systematically introduces the research progress of zinc metal-free anodes in “rocking chair” ZIBs. Zinc metal-free anodes are mainly discussed in four categories: transition metal oxides,transition metal sulfides, MXene(two dimensional transition metal carbide) composites, and organic compounds, with discussions on their properties and zinc storage mechanisms. Finally, the outlook for the development of zinc metal-free anodes is proposed. This paper is expected to provide a reference for the further promotion of commercial rechargeable ZIBs.