Energy Barrier For Nucleation Research Articles

Experimental and computational investigation on synergistic enhancement spray cooling using micropillars and capillary-driven wicking hybrid structures

Spray cooling, which has a fast thermal response and low flow rate consumption, is a common and effective thermal management approach for high power electronic systems. Typically, to improve the heat transfer coefficient (HTC) for spray cooling, the target surface wettability is decreased, promoting nucleation boiling by reducing the surface energy barrier for bubble nucleation. However, the merging of bubbles and the formation of a vapor film have limitations in further increasing the critical heat flux (CHF). Hence, maximizing both the HTC and CHF of spray cooling can be mutually exclusive on the same heated surface. This paper presented a novel design for a vapor-liquid separation structure surface. It consisted of lower micropillars that serve as the vapor separation channel. On top of that, there was an upper multi-layer copper micromesh that wicks and spreads the coolant. Additionally, nano-grass attached to the micromesh to enhance capillary force and increase the nucleation sites simultaneously. Subsequently, we calculated the forward velocity and pressure drop of the droplets passing through the copper mesh to study the effects of droplet velocity and capillary force on heat transfer performance. The results show that the forward velocity of the droplets decreases rapidly as the increase of copper mesh layers and it drops to zero when passing through the third mesh. Therefore, the capillary force generated by the copper mesh is another important factor for the atomized droplets to pass through the copper mesh and reach the target surface. We have proven that all the vapor-liquid separation structure surfaces satisfy the condition ΔPcap>ΔPpore+ΔPlocal. Hence, the synergistic effects of the micropillar, copper micromesh, and nano-grass enable a circulation process of wicking-rewetting-vapor evacuation, which improves the onset of nucleate boiling (ONB), enhances the HTC, and increases the maximum heat flux dissipated by the system. Enhanced HTC (7.94 W/cm2/K) and maximum heat flux (817 W/cm2) were achieved at 1.50 ml/s on the vapor-liquid separation structure surfaces (#200 2-layer), representing an enhancement of 79.6% and 80.0% compared with that for the flat surface and the temperature of the heated surface at the ONB maximum decreased by approximately 30.8 °C.

Significantly enhanced high-temperature mechanical properties of Cu-Cr-Zn-Zr-Si alloy with stable second phases and grain boundaries

Improving high-temperature strength and resistance to high-temperature softening is an important method to promote the application of high-performance Cu-Cr-Zr alloy in fields such as resistance welding electrodes and high-speed railway contact wires. A Cu-1.0Cr-0.4Zn-0.1Zr-0.05Si alloy was designed and the combining effects of Zn and Si elements on the microstructure and high-temperature mechanical properties of the alloy were studied. The tensile strength of the alloy at room temperature was 556 MPa, and it was 349 MPa at 500℃ with a softening temperature of 620℃. The main strengthening phases of the alloy were submicron Cr3Si and nano-scaled Cr-rich precipitates. The Zn elements were uniformly solid-solved in the Cu matrix, and the addition of Zn and Si elements significantly retarded the phase transformation of the Cr-rich precipitates. Thermodynamics and kinetics analysis showed that Zn and Si elements promoted the dispersive precipitation of the nano-scaled FCC coherent Cr-rich precipitates by reducing the nucleation energy barrier, while the Si and Zr elements inhibited the coarsening of the Cr-rich precipitates by enriching at the phase boundaries, effectively impeding dislocation motion and grain boundary migration, which mainly contributed to good high-temperature strength and resistance to softening of the Cu-Cr-Zn-Zr-Si alloy.

Pre-Treatment of Li-Metal Anode with Hydrohalic-Acid for Stable Cycling of Li-Metal Batteries Under Practical Conditions

Lithium (Li) metal anodes (LMAs) are considered as an ultimate choice for beyond Li-ion batteries because of their high capacity (3860 mAh g–1) and low working potential (–3.04 V vs. SHE). However, due to extremely high surface reactivity, uncontrollable dendritic plating, and infinite volume expansion, making Li-metal batteries (LMBs) has long encountered fatal challenges. Heterogeneous solid-electrolyte interphase (SEI) can be the main reason for Li dendrite growth, stemming from the electrolyte byproducts and native LMA surface. In this regard, uniform passivation of LMAs and homogenous SEI at the initial stage is necessary which can occur uniform Li+ ion flux. Furthermore, halogenated SEI is considered as promising component for achieving superior mechanical strength, insulating properties and thermodynamic stability.In this study, we present a simple LMA treatment using hydrohalic acids (HXs, X = F, Cl, Br, and I) to regenerate native passivation layer (NPL) of as-manufactured LMAs and evenly nourish halogenated compounds. The water molecules of aqueous HXs can dissolve the existing inorganic Li-compounds in the NPL, e.g., Li2O, LiOH, and Li2CO3, rendering the chemical reactions of HXs with pure Li, enriching the LiX compounds within the NPL. A comparative study was done to reveal which LiX compounds is beneficial to stabilize the LMA surface and to enhance the cycling stability of LMBs. Furthermore, it is elucidated that the pivotal role of LiX compounds was proved in the interfacial reaction when using localized high concentration electrolyte (LHCE) as an advanced electrolyte in LMBs. Through comparative study, building LiCl-rich SEI at the initial stage effectively reduces the energy barrier of Li nucleation and interfacial resistances, thereby enhancing the cycling performances in LMBs even under practical conditions.

High Capacity Sn Metal Anode for Aqueous Proton-Based Batteries

Aqueous proton-based batteries (APBs) as a good choice to respond battery diversity, delivering safety, cost, environmental friendliness and high-power necessary for renewable energy storage.1 However, most promising conventional aqueous battery anodes have relatively poor compatibility in acid. The limited existing anode options like Pb and MoO3 can hardly match the high-performance of advanced cathodes, leading low-voltage and unsatisfactory energy density of APBs.2-4 Therefore, the exploration of high-performance anode materials is thus of critical issue for the APB assembling.Sn metal should be one of the most suitable APB anode choices due to its relatively high hydrogen evolution reaction (HER) overpotential, large theoretical capacity (451.6 mAh g−1) and negative redox potential (−0.14 V vs. SHE). With a body-centered tetragonal crystal structure and similar facet surface energy, Sn metal deposit in polyhedral morphology isotropically. This may cause serious “dead Sn” issue when deposition capacity increases because large Sn particle has limited contact with the substrate and easily to shed from the electrode, resulting in low Coulombic efficiency and short lifespan.We will present our efforts of developing Sn anode with high capacity and long lifespan by an interfacial alloying regulation approach. Smaller grain size and more uniform Sn deposition can be achieved by higher propensity for nucleation and Sn migration energy barrier. Extra interfacial interaction suppresses shedding of Sn polyhedron particles, thus prohibiting the formation of “dead” Sn. Based on the optimized Sn metal anode, we propose several promising designs for APBs, with high performance such as high output voltages, good specific energy densities, fast kinetics, and long life. References X. Wu, J. J. Hong, W. Shin, L. Ma, T. Liu, X. Bi, Y. Yuan, Y. Qi, T. W. Surta, W. Huang, J. Neuefeind, T. Wu, P. A. Greaney, J. Lu, X. Ji. Nat. Energy 2019, 4, 123-130.W. Chen, G. Li, A. Pei, Y. Li, L. Liao, H. Wang, J. Wan, Z. Liang, G. Chen, H. Zhang, J. Wang, Y. Cui. Nat. Energy 2018, 3, 428-435.Y. Liang, Y. Jing, S. Gheytani, K. Y. Lee, P. Liu, A. Facchetti, Y. Yao. Nat. Mater. 2017, 16, 841-848.X. Wang, Y. Xie, K. Tang, C. Wang, C. Yan. Angew. Chem. Int. Ed. 2018, 57, 11569-11573.

Multifunctional Catalytic Hierarchical Interfaces of Ni12 P5 -Ni2 P Porous Nanosheets Enabled Both Sulfides Reaction Promotion and Li-Dendrite Suppression for High-Performance Li-S Full Batteries.

The development of lithium-sulfur (Li-S) batteries is very promising and yet faces the issues of hindered polysulfides conversion and Li dendrite growth. Different from using different materials strategies to overcome these two types of problems, here multifunctional catalytic hierarchical interfaces of Ni12 P5 -Ni2 P porous nanosheets formed by Ni2 P partially in situ converted from Ni12 P5 are proposed. The unique electronic structure in the interface endows Ni12 P5 -Ni2 P effective electrocatalysis effect toward both sulfides' reduction and oxidation through reducing Gibbs free energies, indicating a bidirectional conversion acceleration. Importantly, Ni12 P5 -Ni2 P porous nanosheets with hierarchical interfaces also reduced the Li nucleation energy barrier, and a dendrite-free Li deposition is realized during the overall Li deposition and stripping steps. To this end, Ni12 P5 -Ni2 P decorated carbon nanotube/S cathode showing a high capacity of over 1500 mAh g-1 , and a high rate capability of 8 C. Moreover, the coin full cell delivered a high capacity of 1345 mAh g-1 at 0.2 C and the pouch full cell delivered a high capacity of 1114 mAh g-1 at 0.2 C with high electrochemical stability during 180° bending. This work inspires the exploration of hierarchical structures of 2D materials with catalytically active interfaces to improve the electrochemistry of Li-S full battery.

Anion receptor and heavy metal-free redox mediator decorated separator for lithium-sulfur batteries

The adsorption-catalysis synergy for accelerated conversion of polysulfides is critical toward the electrochemical stability of lithium-sulfur battery (LSB). Herein, a non-metallic polymer network with anion receptor units, trifluoromethanesulfonyl (CF3SO2-) substituted aza-ether, was in-situ integrated on PE separator, working as an efficient host for anchoring lithium thiophosphates (LPS) as redox mediators and polysulfides through Lewis acid-base interaction. The anchored LPS on the modified PE separator displayed a robust chemical adsorption ability towards polysulfides through the formation of SS bond. Meanwhile, LPS decreased the energy barrier of Li2S nucleation and promoted redox reaction kinetics. The battery with LPS decorated separator revealed a long cycling lifespan with a per cycle decay of 0.056 % after 600 cycles, and a competitive initial capacity of 889.1 mAh/g when the of sulfur cathode increased to 3 mg cm−2. This work developed a new design strategy to promote the utilization of lithium phosphorus sulfide compounds in LSB.

Regulated Zn Plating and Stripping by a Multifunctional Polymer-Alloy Interphase Layer for Stable Zn Metal Anode.

Metallic zinc electrode with a high theoretical capacity of 820mAhg-1 is highly considered as a promising candidate for next-generation rechargeable batteries. However, the unavoidable hydrogen evolution, uncontrolled dendrite growth, and severe passivation reaction badly hinder its practical implementations. Herein, a robust polymer-alloy artificial protective layer is designed to realize dendrite-free Zn metal anode by the integration of zincophilic SnSb nanoparticles with Nafion. In comparison to the bare Zn electrode, the Nafion-SnSb coated Zn (NFSS@Zn) electrode exhibits lower nucleation energy barrier, more uniform electric field distribution and stronger anti-corrosion capability, thus availably suppressing the Zn dendrite growth and interfacial side reactions. As a consequence, the NFSS@Zn electrode exhibits a long cycle life over 1500h at 1mAcm-2 with an ultra-low voltage hysteresis (25mV). Meanwhile, when paired with a MnO2 cathode, the as-prepared full cell also demonstrates stable performance for 1000cycles at 3Ag-1 . This work provides an inspired approach to boost the performance of Zn anodes.

Effect of calcium pimelate on crystallization kinetics of polyphenylene sulfide

AbstractThe use of nucleating agents (NAs) to accelerate semicrystalline polymers crystallization is a widely recognized technique during processing. However, the commercially available NA for poly(phenylene sulfide) (PPS) has been rather limited. In this work, it is found that calcium pimelate (CaPim), a commercial nucleating agent for isotactic polypropylene, could also accelerate the crystallization process of PPS. The influence of CaPim addition on the crystallization behaviors of PPS was investigated under non‐isothermal and isothermal condition. Upon the addition of 0.3 wt% CaPim, the crystallization peak temperature and the onset crystallization temperature increases by 5.3 and 8.4°C at 10°C/min cooling rate, and the half‐time of crystallization reduces 51% at crystallization temperature of 272°C. Polarized optical observation revealed a substantial enhancement in nucleation due to the presence of CaPim. Avrami equation analysis suggested that the nucleating agent significantly increased the crystallization rate constant without affecting the growth dimension. Moreover, Lauritzen–Hoffman theory analysis indicateed that the addition of CaPim lowers the nucleation energy barrier, contributing to its high‐nucleation efficiency. These findings demonstrate that calcium pimelate holds promise as an effective nucleating agent for PPS.

Lithiophilic composite solid electrolyte interphase layer modified Li foils: Li metal battery failure analysis

Li metal battery with higher energy density becomes increasing important to reach a carbon neutrality society. However, the usage of Li metal is usually failed due to the side-reactions, dendrite formations, and volume expansion. To tackle these difficulties, artificial solid electrolyte interphase with multiple functions is proposed. In our work, a magnesium-based inorganic-organic film is coated on Li metal with tape-casting. LixMg alloy and nano-LiF particles produced after activation process can lower the nucleation energy barriers and increase the Li ion transportation. Polymer layers with high flexibility are adopted to control the volume change caused by repeatly lithium plating/stripping. As a result, the Li symmetrical cell runs stable for 1300 h with a lower over-potential of 3 mV under limited carbonate electrolyte. Li metal batteries degradation mechanism with different N/P ratio and C rates are discussed in details. The full cell with LiFePO4 and 30 μm Li foil delivers a capacity of 132 mA h g−1 after 300 cycles, the bare Li is dead after 75 cycles due to the loss of active lithium. LiNi0.6Co0.2Mn0.2O2 coupled with modified Li foil with mass loading of 1.44 mA h cm−2 is superior than bare Li at 1 C, the latter quickly die due to the dry-out of electrolyte.

Surfaces with modified morphology and wettability arrangement: a potential medium for water harvesting in desertification areas

Abstract The cost of water transport for irrigating drought-endurable plants in desertification areas makes it important to develop other water sources. Research shows that freshwater produced by dewing could satisfy the water requirement during germination of desert plants, therefore, functional materials that promote dew formation provide solutions for reduction of plant irrigation costs in desertification regions. In this review, feasibility of utilizing trace irrigation for ensuring survival of desert plants has been demonstrated. The technologies of preparing water harvesting materials with modified microstructure and wettability arrangement have been introduced, it has been shown that surface embedded with a bump array which has counter wettability compared with its plane section is a common morphology adopted by current works. After comparing climates in desertification regions with those in dewing chambers, it has been found that currently, the expected values of dew productivities of most water harvesting materials in deserted areas will not be as efficient as they performed in experiments due to low relative humidity. However, hydrophobic surface with submicron scale hydrophilic spherical cavity array produced by nanosphere lithography has shown reliable prospects in reducing the energy barrier of heterogeneous nucleation and thus become a more potential medium in dew water production.

Spatially Confined Silver Nanoparticles in Mercapto Metal-Organic Frameworks to Compartmentalize Li Deposition Towards Anode-Free Lithium Metal Batteries.

As the promising next-generation energy storage solution lithium metal battery (LMB) has gained great attention but still suffers from troubles associated with the highly active metallic lithium. Herein, weaim to develop anode-free LMB engaging no Li disk or foil by modifying the Cu current collector with mercapto metal organic frameworks (MOFs) impregnating Ag nanoparticles (NPs). While the polar mercapto groups facilitate and guide Li+ transport, the highly lithiophilic Ag NPs help to enhance the electric conductivity and lower the energy barrier of Li nucleation. Furthermore, the MOF pores allow compartmentalizing bulk Li into a 3D matric Li storage so that not only the local current density is reduced, but also is the plating/stripping reversibility greatly enhanced. As a result, full cells pairing the prelithiated Ag@Zr-DMBD/Cu anodes with LiFePO4 cathodes demonstrate a high initial specific capacity of 159.8 mAh g-1 , first-cycle Coulombic efficiency of 96.6%, and long-term cycling stability over 1000 cycles with 99.3% capacity retention at 1C. This study underlines the multi-aspect functionalization of MOFs to impart lithiophilicity, polarity, and porosity to achieve reversible Li plating/stripping, and paves the way for realizing high-performance anode-free LMBs through exquisite modification of the Cu current collector. This article is protected by copyright. All rights reserved.

In-situ confined growth of defective MIL-100(Fe) in macroporous polyacrylate spherical substrate at room temperature for high-efficient toluene removal

The hazard caused by toluene has attracted worldwide attention, and it is of practical significance to study the efficient adsorption of toluene for environmental governance. In this work, a hierarchical metal–organic framework (MOF), MIL-100(Fe), was crystallized on the surface of a macroporous polyacrylate (PAA) spherical substrate at room temperature through an in-situ confinement growth strategy to form MIL-100(Fe)@PAA composite. By decreasing the nucleation energy barrier, the average size of MIL-100(Fe) crystals was reduced from 400 nm to 55 nm and defects as adsorption sites for toluene were able to install in the crystal lattices. Therefore, the composite provided excellent static and dynamic adsorption properties for toluene, much better than the pristine MIL-100(Fe). The potential mechanism for crystal defects to significantly improve the adsorption performance was subsequently explored through kinetic fitting and density functional theory (DFT) calculation. All results indicated that the innovative MIL-100(Fe)@PAA prepared using defect engineering and effective molding technology was potent in both toluene removal and regeneration, which was expected to provide a new avenue for the facile synthesis of molded MOF composites.

Nucleation kinetics of reactive crystallization of ammonium di-uranate

ABSTRACT The reactive crystallisation of ammonium di-uranate (NH4U2O7) from uranyl nitrate (UO2 (NO3)2) and ammonia (NH3) is a key process in the nuclear fuel cycle towards uranium-bearing fuel preparation. However, the process kinetics and mechanism remain poorly understood and the modelling of the reactive crystallisation of NH4U2O7(ADU) is not available. Hence, this work aims to determine the kinetics and mechanisms of the nucleation and growth of ADU through induction time measurements by comparing sonochemical and conventional precipitation methods. Induction was measured as functions of initial supersaturation starting from S = 1.07 to S = 1.875 and in a temperature range of 30 °C to 80 °C. The solubility data of ADU were also found experimentally. The trends in the experimental data suggest that two nucleation mechanisms co-exist: heterogeneous and homogeneous nucleation at low and high supersaturations respectively. Due to acoustic cavitation of the ultrasound prompting micromixing, the induction time is markedly reduced in the sonochemical route owing to the reduction of the energy barrier for nucleation. The induction time data were also analysed to calculate the interfacial energy (γ) and other parameters including the radius of the critical nucleus (r*), critical free energy of the nucleus (ΔG*) and nucleation rate (J). Determination of nucleation kinetics gives us insights into the fundamentals of the ADU crystallisation process for control and optimisation. Highlights: Nucleation kinetics of the reactive crystallisation of ADU was studied through classical nucleation theory Induction time data with supersaturation are interpreted by classical nucleation theory and different crystallisation kinetic parameters were determined Homogeneous and heterogeneous nucleation was determined from the correlation A comparison of sonochemical and conventional precipitation shows that in the sonochemical route, the nucleation happens at lower supersaturation with lower induction time because of much lower activation energy requirement All the model data gives us an insight into the crystallisation kinetics to optimise and control the crystallisation process of ADU

Surface Overpotential as a Key Metric for the Discharge-Charge Reversibility of Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries (AZIBs) are receiving increasing attention for power-grid energy storage systems. Nevertheless, warranting long-term reversible operation is not trivial owing to uncontrolled interfacial phenomena related to zinc dendritic growth and parasitic reactions. Herein, the addition of hexamethylphosphoramide (HMPA) to the electrolyte revealed the surface overpotential (|ηs|) to be a key metric of the reversibility. HMPA adsorbs onto active sites on the zinc metal surface, raising the surface overpotential toward lowering the nucleation energy barrier and decreasing the critical size (rcrit) of nuclei. We also correlated the observed interface-to-bulk properties by the Wagner (Wa) dimensionless number. The controlled interface enables a Zn|V6O13 full cell to retain 75.97% capacity for 2000 cycles, with a capacity loss of only 1.5% after 72 h resting. Our study not only delivers AZIBs with unparalleled cycling and storage performance but also proposes surface overpotential as a key descriptor regarding the sustainability of AZIB cycling and storage.

Anti-Icing Mechanism for a Novel Slippery Aluminum Stranded Conductor.

The icing of transmission conductor seriously threatens the safe operation of power grids. Slippery lubricant-infused porous surface (SLIPS) has shown great potential for anti-icing applications. However, aluminum stranded conductors have complex surfaces, and the current SLIPSs are almost prepared and studied on small flat plates. Herein, the construction of SLIPS on the conductor was realized through anodic oxidation and the anti-icing mechanism of the slippery conductor was studied. Compared to the untreated conductor, the SLIPS-conductor reduces the icing weight by 77% in the glaze icing test and shows very low ice-adhesion strength (7.0 kPa). The excellent anti-icing performance of the slippery conductor is attributed to the droplet impact dynamics, icing delay, and lubricant stability. The dynamic behavior of water droplets is most affected by the complex shape of the conductor surface. Specifically, the impact of the droplet on the conductor surface is asymmetric and the droplet can slide along the depression in low-temperature and high-humidity environments. The stable lubricant of SLIPS increases both the nucleation energy barriers and the heat transfer resistance, which greatly delays the freezing time of droplets. Besides, the nanoporous substrate, the compatibility of the substrate with the lubricant, and the lubricant characteristics contribute to the lubricant stability. This work provides theoretical and experimental guidance on anti-icing strategies for transmission lines.

Influence of Guest Molecular Mass on Gas Hydrate Nucleation via Molecular Simulation

Hydrates are ice-like crystals. Its nucleation event has important significance for many industrial fields, such as seawater desalination, gas separation, and gas storage. Therefore, researchers are looking for a kind of highly effective promoters to accelerate hydrate nucleation and stabilize hydrate crystals so that hydrate-based technology can be sustainable and economical. Herein, we use the molecular simulation method and construct ideal guest molecules to study the influence of guest molecular mass on the hydrate nucleation process. Our results show that lighter guest molecules nucleate more easily. However, when the light and heavy guest molecules coexist, the light guest molecules can only enhance the formation of the nucleation precursor but cannot effectively reduce the free energy barrier of hydrate nucleation because of the competition between the light and heavy guest molecules around the critical nuclear state. Overall, our work provides a theoretical basis for the development of hydrate promoters, which is expected to be helpful for their efficient design.

Anomalously enhanced subcooled flow boiling in superhydrophobic graphene-nanoplatelets-coated microchannels

In boiling heat transfer, superhydrophobic surface is deemed to reduce the critical heat flux (CHF) due to the immediate formation of an insulating vapor film that inhibits effective heat transfer despite its smaller energy barrier for bubble nucleation than that of a superhydrophilic surface. Here, a subcooled flow boiling investigation is carried out in a microchannel heat sink at a low mass flux condition using the superhydrophilic and superhydrophobic graphene nanoplatelets (GNPs) composite coatings. Interestingly, the flow boiling performance of the superhydrophobic GNPs-coated microchannel significantly transcends that of its superhydrophilic counterpart. By benchmarking with the performance of an uncoated microchannel, the CHF and heat transfer coefficient of the superhydrophobic GNPs-coated microchannel are enhanced up to 134% and 135%, respectively. This anomaly is ascribed to the Cassie Baxter-to-Wenzel transition on the superhydrophobic GNPs-coated surface, which is infiltrated with liquid, restricting the nucleating bubbles from expanding into a vapor film and sustaining an efficient boiling. The initial Wenzel state of the superhydrophobic GNPs surface is primarily ascribed to the rapid intercalation of water molecules via the unique graphene nanostructure. This study sheds new light on the unique wetting behavior of graphene-nanostructured surfaces in the context of microscale flow boiling heat transfer.

Engineering of Defective MOF-801 Nanostructures within Macroporous Spheres for Highly Efficient and Stable Water Harvesting.

Water harvesting using the metal-organic framework (MOF)-801 is restricted by limited working capacity, powder structuring, and finite stability. To overcome these issues, wecrystallized MOF-801 on the surface of macroporous poly(N-isopropylacrylamide-glycidyl methacrylate) spheres, called P(NIPAM-GMA), through an in situ confined growth strategy, forming spherical MOF-801@P(NIPAM-GMA) composite with temperature-responsive function. By lowering the nucleation energy barrier, the average size of the MOF-801 crystals decreased by 20 times. Thus, abundant defects as adsorption sites for water couldbe installed in the crystals lattices. As a consequence, the composite provides an unprecedented high water harvesting efficiency. The composite wasproduced in the kilogram-scale and can capture 1.60kg H2 O/kg composite/day from 20% RH between 25°C and 85°C. This work provides an effective methodology for improving the adsorption capacity through controlled defects formation as adsorption sites and to improve the kinetics through the design of a composite with macroporous transport channel network. This article is protected by copyright. All rights reserved.

Controllable Etching of Ti3SiC2 to Produce Fluorine‐Enriched, Hydrophobic 2D Titanium Carbide for Ultrastable Zinc Ion Batteries

AbstractMXenes are mainly produced via selectively etching MAX phases in aqueous F‐containing solutions, commonly showing a highly hydrophilic character due to their plentiful ‐O and ‐OH terminations. However, the hydrophilic nature of MXenes may deteriorate their durability and stability as employed in humid and aqueous environments. Here, this work demonstrates a new etching approach to produce fluorine‐enriched MXene Ti3C2Fx via selective etching of Si from Ti3SiC2 in sulfur hexafluoride (SF6) gas. During the etching process, SF6 enables the selective removal of Si species with the formation of volatile SiF4 and efficiently reacts with the exposed surface of Ti3C2 slabs, affording Ti3C2Fx MXene with a fraction of ‐F termination up to 87 at.% and good hydrophobicity. Such hydrophobic Ti3C2Fx MXene is beneficial to suppress water‐induced side reactions and decrease the Zn nucleation energy barrier, delivering a long cyclic lifespan of 1200 h and superior rate performance up to 6.4 mA cm−2 in Ti3C2Fx/Zn symmetric cells. Coupled with nickel hexacyanoferrate (NiHCF) as a cathode, the zinc full cell with Ti3C2Fx/Zn anode exhibits good rate capabilities (58 mAh g−1, 3.2 A g−1) and long cycling stability up to 1000 cycles at 3.2 A g−1.

Active Screen Plasma-Enabled Metal Alloying for Stable Zinc Metal Growth toward Aqueous Zinc-Ion Batteries.

Active-screen plasma (ASP) has attracted much attention as a versatile and powerful surface engineering method owing to its simple setup, low temperature, eco-friendliness, treatment uniformity, ability to deposit nano/microparticles with sputtering targets, and capability for controlling the chemical composition and morphology of the deposition layer. Recent investigations have shown that ASP technology has been used to treat various electrode materials for excellent electrochemical performance. This work demonstrates the feasibility of ASP technology to construct an artificial alloy layer on host materials and serve as promising Zn anode supports. We reveal the effect of some controllable or measurable variables on the formed alloy layer and discuss the core process of ASP-enabled metal alloying. Attractively, a stable and uniform Cu5Zn8 alloy layer with good zincophilic can effectively reduce the energy barrier of Zn nucleation and guide uniform Zn nucleation, which alleviates the dendritic growth during Zn deposition. Consequently, the Cu5Zn8-modified Cu host as the Zn anode support displays a high Coulombic efficiency of 99.5%, a lower overpotential of 45 mV, and a longer cycling life over 330 h. The assembled full cells deliver an exceptional capacity of 114 mA h g-1 after 500 cycles with a capacity retention of 68%. This work provides an idea for constructing a stable Zn deposition interface and promotes the development of ASP technology.