Deposition Behavior Research Articles

Pulse Charge Suppressing Dendrite Growth at Low Temperature by Rapidly Replenishing Lithium Ion on Anode Surface.

Dendrite growth of lithium (Li) metal anodes is considered as one of the most tough issues for Li metal batteries with a theoretically high energy density. This is attributed to the rapid exhaustion of Li ions at the electrode/electrolyte interface, which is even worse at low temperatures with poor diffusion kinetics of Li ions. Here, pulse charge with intermittent rest time during battery charging is proposed to handle the dendrite growth issue of Li metal anodes at low temperatures. The depleted Li ions near the interfaces can be rapidly replenished during the rest time, thus effectively suppressing the dendrites growth. Further investigation found that the large dendrites can be suppressed at the Li ion nucleation stage. The equivalent lifespan considering the rest time is proposed. At -10 °C, the lifespan of Li||Li batteries cycled under 3 mA cm-2 and 1 mAh cm-2 is increased from 24 h to equivalent 64 h. Li||LiNi0.5Co0.2Mn0.3O2 batteries with 80% capacity retention can be stably operated from 39 cycles to 56 cycles. This design presents an efficient and convenient strategy to regulate the deposition behaviors of Li metal anodes with a dendrite-free morphology.

Ion‐sieving MXene flakes with quantum dots enable high plating capacity for dendrite‐free Zn anodes

AbstractThe commercial utilization of Zn metal anodes with high plating capacity is significantly hindered by the uncontrolled growth of dendrites and associated side reactions. Herein, a robust artificial ion‐sieving MXene flake (MXF)‐coating layer, with abundant polar terminated groups, is constructed to regulate the interfacial Zn2+ deposition behavior. In particular, the fragmented MXF coupled with in situ generated quantum dots not only has strong Zn affinity to homogenize electric fields but also generates numerous zincophilic sites to reduce nucleation energy, thus securing a uniform dendrite‐free surface. Additionally, the porous coating layer with polar groups allows the downward diffusion of Zn2+ to achieve bottom‐up deposition and repels the excessive free water and anions to prevent parasitic reactions. The ion‐sieving effect of MXF is firmly verified in symmetric cells with high areal capacity of 10–40 mAh cm−2 (1.0 mA cm−2) and depth of discharge of 15%–60%. Therefore, the functional MXF‐coated anode manifests long‐term cycling with 2700 h of stable plating/stripping in Zn||Zn cell. Such rational design of MXF protective layer breaks new ground in developing high plating capacity zinc anodes for practical applications.

A multi-step discharge/charge model of Li[sbnd]O2 batteries coupled with electrolyte decomposition and carbon electrode corrosion reactions

Electrolyte decomposition and electrode corrosion stand as two primary side reactions in lithium‑oxygen (LiO2) batteries during their discharge/charge cycles. In this work, a comprehensive LiO2 battery model combining multi-step lithium peroxide (Li2O2) formation, electrolyte decomposition, and electrode corrosion is proposed. Based on this model, the deposition behaviors and cycling performance of the LiO2 battery under deep discharge/charge cycles are investigated. The stop of discharge is mainly ascribed to the loss of active surface area for the battery using tetraethylene glycol dimethyl ether (TEGDME) electrolyte, while both O2 transport limitation and active surface area loss lead to the discharge termination for battery using dimethyl sulfoxide (DMSO) electrolyte. The incomplete decomposition of Li2O2 and lithium carbonate (Li2CO3) clogs electrode pores, leading to a continuous decline in the discharge capacity of the LiO2 battery. For the TEGDME-based battery, the undecomposed Li2CO3 gradually dominates the deposition with cycles, wherein electrode corrosion becomes the primary source of the undecomposed Li2CO3 after 3 cycles. For the DMSO-based battery, undecomposed Li2O2 is always a dominant trigger for battery discharge capacity degradation, although electrode corrosion remains a key contributor to Li2CO3 generation. Despite the DMSO-based battery exhibiting lower rates of electrolyte decomposition and electrode corrosion, it demonstrates poorer cyclic performance than the TEGDME-based battery due to the generation of more toroidal Li2O2. Moreover, when the charging cut-off voltage is reduced to 4.2 V, discharge capacity diminishes more rapidly due to the increased accumulation of undecomposed Li2O2, despite suppressed Li2CO3 deposition. Finally, the results confirm that thick electrodes lead to deteriorating cycling performance, stemming from increased discharge/charge overpotential and extended discharge/charge times, thus intensifying the side reactions.

Highly reversible Zn anode by guiding uniform Zn deposition through LiF protective layer

Deep-seated issues such as ineluctable dendrite deposition and parasitic reaction of Zn anode pose a major obstacle to the commercialization of aqueous zinc ion batteries (AZIBs). Herein, we proposed LiF as a solid-electrolyte interphase for highly reversible Zn anode. Combining experimental analyses and theoretical simulation calculations, the electronegative fluorine atoms could provide uniform zincophilic nucleation sites to regulate Zn deposition behavior. Additionally, a ZnF2 layer with outstanding Zn2+ conductive can be formed insitu thus further shielding bulk water molecules and expediting the Zn2+ transfer kinetics. Therefore, the LiF@Zn symmetric cells manifest long-cycling stability with 650 h at 1.0 mA/cm2 and 1.0 mAh/cm2 and 1000 h at 2.0 mA/cm2 and 1.0 mAh/cm2. Meanwhile, the rate performance of Zn//MnO2 and Zn//NH4V4O10 full cells are also enhanced by the LiF coating. This work provides a horizon for the design of artificial protective layer and promotes the large-scale practical development of AZIBs.

Effect of scanning strategy and laser peening on microstructure and fatigue properties of laser-directed energy deposition-built 15-5 PH stainless steel

PurposeThe aim of this paper is to study the effect of laser shock peening (LSP) on mechanical behaviour of the laser-directed energy deposition (LDED)-based printed 15-5 PH stainless steel with U and V notches. The study specifically concentrates on the evaluation of effect of scan strategy, machining and LSP processing on microstructural, texture evolution and fatigue behaviour of LDED-printed 15-5 PH steel.Design/methodology/approachFor LSP treatment, 15-5 PH steel was printed using LDED process with bidirectional scanning strategy (XX [θ = 0°) and XY [θ = 90°]) at optimised laser power of 600 W with a scanning speed of 300 mm/min and a powder feed rate of 3 g/min. Furthermore, LSP treatment was conducted on the V- and U-notched fatigue specimens extracted from LDED-built samples at laser energy of 3.5 J with a pulse width of 10 ns using laser spot diameter of 3 mm. Post to the LSP treatment, the surface roughness, fatigue life assessment and microstructural evolution analysis is performed. For this, different advanced characterisation techniques are used, such as scanning electron microscopy attached with electron backscatter diffraction for microstructure and texture, X-ray diffraction for residual stress (RS) and structure information, Vicker’s hardness tester for microhardness and universal testing machine for low-cycle fatigue.FindingsIt is observed that both scanning strategies during the LDED printing of 15-5 PH steel and laser peening have played significant role in fatigue life. Specimens with the XY printing strategy shows higher fatigue life as compared to XX with both U- and V-notched conditions. Furthermore, machining and LSP treatment led to a significant improvement of fatigue life for both scanning strategies with U and V notches. The extent of increase in fatigue life for both XX and XY scanning strategy with V notch is found to be higher than U notch after LSP treatment, though without LSP samples with U notch have a higher fatigue life. As fabricated sample is found to have the lowest fatigue life as compared to machines and laser peened with both scan strategies.Originality/valueThis study presents an innovative method to improve the fatigue life of 15-5 PH stainless steel by changing the microstructure, texture and RS with the adoption of a suitable scanning strategy, machining and LSP treatment as post-processing. The combination of preferred microstructure and compressive RS in LDED-printed 15-5 PH stainless steel achieved with a synergy between microstructure and RS, which is responsible to improve the fatigue life. This can be adopted for the futuristic application of LDED-printed 15-5 PH stainless steel for different applications in aerospace and other industries.Graphical abstract

The Dependence of Solid Electrolyte Interphase on the Crystal Facet of Current Collector in Li Metal Battery.

The continuous electrolyte decomposition and uncontrolled dendrite growth caused by the unstable solid electrolyte interphase (SEI) have largely hindered the development of Li metal batteries. Here, we demonstrate that tuning the facet of current collector can regulate the composition of SEI and the subsequent Li deposition behavior using single-crystal Cu foils as an ideal platform. The theoretical and experimental studies reveal that the (100) facet of Cu possesses strong adsorption to anions, guiding more anions to participate preferentially in the inner Helmholtz plane and further promoting the formation of the stable inorganic-rich SEI. Consequently, the single-crystal Cu foils with a single [100] orientation (s-Cu(100)) achieve the dendrite-free Li deposition with enhanced Li plating/stripping reversibility. Moreover, the Li anode deposited on s-Cu(100) can stabilize the operation of an Ah-level pouch cell (350 Wh kg-1) with a low negative/positive capacity ratio (~2) and lean electrolyte (2.4 g Ah-1) for 150 cycles. Impressively, this strategy demonstrates universality in a series of electrolytes employed different anions. This work provides new insights into the correlation between the SEI and current collector, opening a universal avenue towards high-performance Li metal batteries.

The Dependence of Solid Electrolyte Interphase on the Crystal Facet of Current Collector in Li Metal Battery

AbstractThe continuous electrolyte decomposition and uncontrolled dendrite growth caused by the unstable solid electrolyte interphase (SEI) have largely hindered the development of Li metal batteries. Here, we demonstrate that tuning the facet of current collector can regulate the composition of SEI and the subsequent Li deposition behavior using single‐crystal Cu foils as an ideal platform. The theoretical and experimental studies reveal that the (100) facet of Cu possesses strong adsorption to anions, guiding more anions to participate preferentially in the inner Helmholtz plane and further promoting the formation of the stable inorganic‐rich SEI. Consequently, the single‐crystal Cu foils with a single [100] orientation (s‐Cu(100)) achieve the dendrite‐free Li deposition with enhanced Li plating/stripping reversibility. Moreover, the Li anode deposited on s‐Cu(100) can stabilize the operation of an Ah‐level pouch cell (350 Wh kg−1) with a low negative/positive capacity ratio (~2) and lean electrolyte (2.4 g Ah−1) for 150 cycles. Impressively, this strategy demonstrates universality in a series of electrolytes employed different anions. This work provides new insights into the correlation between the SEI and current collector, opening a universal avenue towards high‐performance Li metal batteries.

Sonochemical deposition of gold nano-shells on suspended polymeric spheres

Metal nanoparticles have drawn great interest due to their unique properties for applications in the fields of catalysis, biomedicine and environmental science depending on the architecture of the metal nanoparticle composites. Amongst different designing routes, the chemical template deposition offers great flexibility in terms of the template selection and interfacial interactions, giving rise to controllable designs. In order to control over nanoparticle size distribution and deposition efficiency, a sonochemical approach has been systematically followed in this study. Key parameters of the ultrasound-assisted deposition procedures during the seeding step to synthesise gold nanoparticle-coated poly(styrene) beads were investigated. The impact of the solution pH and the ultrasonic frequency on the template deposition was examined at 139, 300, 500 and 1000 kHz. The results, monitored by transmission electron spectroscopic imaging, show that the highest gold deposition was achieved at 300 kHz, revealing the mechanistic details of the nucleation-crystal growth behaviour as a function of ultrasonic frequency and reaction time. In addition, the concentration ratio between gold ions and poly(styrene) beads was varied. The highest deposition coverage and smallest particle size were reached at 0.05 mM and 2.5 mg, respectively. The proposed mechanism of the MNPs formation and deposition behaviour were then discussed based on the tested parameters.

Experimental study on the ash deposition and NO emission of high-alkali coal under the staged O2/CO2 and O2/RFG conditions

The oxy-fuel combustion contributes to carbon capture, while the recirculation of flue gas brings about high concentrations of SO2 and H2O, which can affect the transformation of minerals in high-alkali coal. The staged oxy-fuel combustion, as an effective method for NOx reduction, can also change the ash deposition behavior of high-alkali coal. Two kinds of diluting agents, including pure CO2 for O2/CO2 combustion and simulated “recycled flue gas” (CO2, SO2, and H2O) for O2/RFG combustion, were employed in the present work. The ash deposition and NO emission of high-alkali coal during the staged oxy-fuel combustion were simultaneously studied under O2/CO2 and O2/RFG conditions. The conversion ratios of fuel-nitrogen to NO (CNO) and ash deposition efficiencies (Ed) at different stoichiometric ratios in primary combustion zone (SR1) and different oxygen concentrations were obtained. Afterwards, a series of tests were performed to further analyze the ash deposits. The experimental results show that as SR1 increases from 0.6 to 1.2, CNO jumps from 2.0 % to 23.5 % (O2/CO2 combustion) and from 1.9 % to 19.9 % (O2/RFG combustion). The additions of SO2 and H2O can reduce the NO emission. With the rising SR1, Ed under the O2/CO2 and O2/RFG conditions decreases from 4.0 % to 2.6 % and from 4.8 % to 2.1 %, respectively. At high SR1, the CaSO4 amount declines and the iron contributes less to the ash deposition. In O2/RFG combustion, the small sticky particles of sodium aluminosilicates on large particle surfaces reduce, and the large particles of calcium aluminosilicates shrink because some calcium produces CaSO4. Moreover, the exposure of ferrous iron to H2O helps its oxidization so iron is harder to cause severe adhesion. As O2 concentration rises from 21 % to 40 %, CNO shows an upward trend. Meanwhile, Ed under the O2/CO2 and O2/RFG conditions increases from 2.6 % to 3.7 % and from 2.3 % to 2.7 %, respectively. The present work is expected to provide some conducive information for the clean utilization of high-alkali coal and secure operation of boiler, as well as large-scale CO2 capture.

The Strategy to Tune Li Stripping/Plating Behavior in Li Alloy Anode

Li metal anode is the most promising anode for high-energy-density batteries due to its high specific capacity (3860 mAh/g) and highest oxidation potential. However, the high reactivity of Li metal with electrolytes and the resultant formation of Li dendrites restrict its practical applications. To tune the reactivity and Li deposition behavior, Li alloys were widely studied and demonstrated to perform better than Li in Li metal batteries.1-4 Here, we studied the electrochemical behavior of one solid-solution phase Li alloy. In this work, the phase transition in the Li stripping process and phase separation after Li plating were observed, which can be attributed to the sluggish Li diffusion in the solid-solution phase of the alloy. To unlock the Li stripping capacity without phase transition, we designed a bi-phase Li composite anode by introducing Li+ conductive materials. Due to the reduced diffusion length, Li can diffuse into the Li solid-solution phase after plating back on the bi-phase Li composite anode, resulting in uniform Li deposition morphology. Accordingly, the bi-phase Li composite anodes showed much better rate performance than the Li alloy or pristine Li. With these findings, it is expected that the new bi-phase Li composite anodes are a promising direction for long-life, high-power, and high-energy Li metal batteries, including Li-S batteries.

Influence of Sulfonates on the Interfacial Ion Transfer Kinetics of Cu at Au(111) Surfaces

Corrosion reactions profoundly impact the operational stability of various electrochemical components, such as electrocatalysts, conductive supports, and semiconducting light absorbers. Understanding the kinetics of ion transfer at electrode/electrolyte interfaces is crucial for deciphering the durability of copper-containing electrochemical devices. This study investigates the corrosion and deposition behavior of copper adlayers on gold(111) surfaces in sulfate and sulfonate electrolytes, with a focus on adsorption kinetics influenced by anion structure and Lewis acidity. At low scan rates, the adsorption and desorption capacitance of the broad adsorption region previously assigned to random adsorption of Cu on Au(111) surface in sulfuric acid, were nearly symmetric in E and invariant with ν, indicating reversible kinetics across all four electrolytes. At faster scan rates, the experiments reveal distinct adsorption/desorption responses for different anions, shedding light on the interplay between ion transfer kinetics, corrosion rates, and the microenvironment of electrocatalysts. The results provide valuable insights into the fundamental processes governing interfacial ion transfer and offer implications for the design and optimization of electrochemical systems. Figure 1

A dual-functional electrolyte additive displaying hydrogen bond fusion enables highly reversible aqueous zinc ion batteries

In recent years, aqueous zinc-ion batteries (AZIBs) have attracted significant attention in energy storage due to their notable advantages, including high safety, low cost, high capacity, and environmental friendliness. However, side reactions like hydrogen evolution and zinc (Zn) dendrites can significantly impact their Coulombic efficiency (CE) and lifespan. Effectively addressing these issues has become a focus of research in this field. In our study, dimethyl sulfoxide (DMSO) and nanodiamonds (NDs) were used to optimize the electrolyte of AZIBs. Benefiting from the hydrogen bond fusion of DMSO and NDs, which regulates the Zn deposition behavior, effectively inhibiting the growth of Zn dendrites, hydrogen evolution, and corrosion. The Zn | |Zn symmetric cells using NDs-DMSO-ZS demonstrate exceptional cycling stability for over 1500 h at 1 mA cm−2, while the Zn//Cu asymmetric cells achieve up to 99.8% CE at 2 mA cm−2. This study not only shows the application prospects of electrolyte optimization in enhancing AZIBs performance, but also provides a reference for the advancement of electrolyte technology in advanced AZIBs technology.

Electrochemical quartz crystal microbalance study of underpotential deposition of mercury on iridium metal and iridium oxide

AbstractTo evaluate the properties of an Ir‐based catalyst (IrOx), which is the anode in polymer electrolyte membrane‐type water electrolysis, a new method for estimating the electrochemical surface area (ECSA) is required. ECSA evaluation using the underpotential deposition of mercury (Hg‐UPD) can be applied to metals and oxides. However, research regarding Hg‐UPD is needed because several Hg(II)/Hg(I) redox reactions occur simultaneously, and direct evidence of Hg‐UPD on IrOx has not been reported. We previously confirmed the Hg‐UPD phenomenon on Ir polycrystalline films using the electrochemical quartz crystal microbalance (EQCM) method. However, measurements on IrOx electrodes were not performed. In this study, Ir and IrOx electrodes are prepared by the sputtering method, and their Hg deposition behavior observed by EQCM. We quantitatively confirm Hg‐UPD on Ir metal surfaces and provide new evidence of Hg‐UPD on the IrOx surface. These results contribute to establishing the ECSA evaluation of various Ir‐based catalysts.

A two-dimensional cellular automaton-finite difference (CA-FD) model for lithium dendrite simulation

The non-uniform lithium deposition behavior on the negative electrode during the charging process in lithium metal batteries leads to serious safety hazards in practical applications. The phase field (PF) method is the most commonly used to simulate the evolution of the microscopic morphology of lithium dendrite, which is computationally expensive due to the coupled partial differential equations (PDEs). Compared to PF, cellular automaton (CA) can efficiently process the evolution of solid-liquid interface with the neighbor configuration and interaction rules. In this paper, a two-dimensional cellular automaton-finite difference (CA-FD) model based on the decentered square algorithm (DSCA) is established. In this model, the growth of the moving solid-phase interface is described by CA, and the distribution of concentration and electric potential is solved by FD, therefore achieving a higher computation efficiency. During the modeling process, it has been verified that DSCA is more favorable to simulate the preferential growth of lithium dendrite tips than Neumann neighbors and Moore neighbors. Based on this model, the effect of different operating conditions of the lithium metal battery on the growth of lithium dendrites is investigated. The simulation results indicate that an increase in either the interfacial overpotential or the exchange current density accelerates the growth of lithium dendrites, in addition, more side branches are generated under higher overpotential. Therefore, low-rate charging mode is recommended in lithium metal battery to inhibit the growth of lithium dendrite.

Pore-scale behaviors of CO2 hydrate formation and dissociation in the presence of swelling clay: Implication for geologic carbon sequestration

Hydrate-based CO2 sequestration (HBCS) under seafloor with huge storage capacity and long-term mechanical stability is attractive for large-scale carbon reduction. However, as representative geochemical constituents of marine sediments, swelling clay minerals still play ambiguous roles in hydrate phase transition and sedimentary structure stability. In this study, pore-scale behaviors of hydrate deposition and reservoir structure evolution in the presence of montmorillonite (MMT), a representative swelling clay, was investigated using low-field nuclear magnetic resonance (LNMR) technique. Total inter-particle interaction energy of 195.4 KbT ensured the dispersion of clay in 0.5 wt% MMT system, which facilitated homogeneous hydrate formation by providing nucleation sites and surface electric fields, improving hydrate conversion from 78.2 % to 89.6 %. Weak water activity caused by strong water absorption of swelling clay resulted in a 14.4 % reduction in CO2 storage capacity of high-concentration (10.0 wt%) MMT reservoir. Hydrate phase transition accompanied by the migration of MMT particles and liquid water synergistically contributed to sedimentary structure evolution. Migration of MMT-rich fluid with high viscosity could cause irreversible geologic damages by exacerbating sedimentary skeleton deformation. This work reveals the interaction between swelling clay and CO2 hydrate at microscopic scale, providing new perspectives for effective implementation of CO2 geologic sequestration in marine sediments.

Regulating the horizontal confined deposition of lithium metal by Co-Nx modified honeycomb-like carbon nanosheets

The uncontrollable Li dendrite growth as well as the severe volume expansion of Li metal anodes during cycling significantly impedes the practical applications of high-energy-density Li metal batteries. In this work, an innovative modulation strategy has been developed by constructing honeycomb-like nitrogen-doped carbon nanosheets with uniformly anchored cobalt nanoparticles (denoted as Co@HNC) for regulating the Li deposition behavior and meanwhile alleviating volume change during cycling. On one hand, the lithiophilic Co-Nx sites can largely reduce the energy barrier of Li nucleation and subsequently guide horizontal confined Li deposition in the honeycomb-like holes of Co@HNC, which is verified by the density functional theory calculations and in-situ optical microscopy observations. On the other hand, the honeycomb-like carbon framework with good structural integrity can endure the huge volume change during repeated Li plating/stripping processes. Consequently, the optimized Co@HNC electrode delivered a promoted cycling life for over 600 times with high Coulombic efficiency of 98.5 % at 1 mA cm−2. When matched with the high-mass-loading LiFePO4 (20 mg cm−2) or high-voltage LiNi0.8Mn0.1Co0.1O2 cathode, the Li@Co@HNC anode exhibited outstanding cycling stability and rate capability under low negative/positive capacity ratio, demonstrating its great potential in practical applications of high-energy-density lithium metal batteries.

Dissolution behavior of steam generator deposit in oxalic acid

Dissolution behavior of steam generator deposit in oxalic acid

Interfacial coordination effects for uniform and reversible zinc anode deposition

The instability resulting from side reactions including zinc dendrites and hydrogen evolution observed at the interface between the anode and electrolyte has impeded the progress of aqueous zinc-ion batteries (AZIBs). In this study, 1,5-naphthalenedisulfonic acid (NA) is introduced to guide homogeneous and reversible deposition behavior of Zn2+ based on metal-coordination chemistry. Theoretical calculations combined with experiments demonstrate that the strong coordination effect between S and Zn results in the adsorption of a NA layer on the anode surface, suppressing side reactions while facilitating the uniform deposition of Zn2+. By and large, the inclusion of NA extends the cycling stability to nearly 3600 h at a current density of 0.5 mA cm−2 (0.5 mAh cm−2), and it enables durable cycling for 200 h even at a high current density of 20 mA cm−2 (10 mAh cm−2). The Zn||VNNC full battery can be cycled stably for 700 cycles at 5 A g−1 at a low N/P ratio (2.58). The consequence caters a new perspective on the coordination effect at the interface for zinc anodes to achieve high reversibility in AZIBs and ZICs.

Hydrophobic, zincophilic and conductive SEI protective layer stabilizes metallic Zn anode under high current densities

The uncontrollable growth of Zn dendrites and adverse side reactions significantly hinder the application of metallic Zn anodes in aqueous batteries. Herein, nitrogen-doped carbon skeleton/ZnO nanocrystalline are grown in-situ within carbon hollow dodecahedrons (denoted as CZCHD) through the controlled pyrolysis of zeolitic imidazole framework-8 dodecahedrons coated with polydopamine. The solid electrolyte interface layer constructed by CZCHD suppresses hydrogen evolution and corrosion reactions, reduces nucleation barrier, improves Zn deposition kinetics, accelerates desolvation and transport of Zn2+ ions, and regulates Zn deposition behavior. When tested in symmetric cells, CZCHD@Zn anodes afford exceptional plating/stripping stability at 5 mA cm−2/1 mAh cm−2 (2681 h), 10 mA cm−2/10 mAh cm−2 (780 h), and 20 mA cm−2/20 mAh cm−2 (240 h). In asymmetric cells, CZCHD@Cu exhibits average Coulombic efficiency of 99.5 % over 500 cycles. Morphological and structural evolution analyses demonstrate the preferential horizontal flaky Zn deposition beneath the CZCHD protective layer, with no Zn dendrites observed on the surface. Furthermore, when coupled with MnVO cathodes, the assembled full cells display stable cycling performance at 2 and 5 A/g. The stable, reversible, efficient, dendrite-free Zn deposition is attributed to the synergistic effects of high hydrophobicity, strong zincophilicity and high electrical conductivity of CZCHD, which is confirmed by contact angle measurements, theoretical calculations based on density functional theory, and electrochemical impedance spectroscopy.

Deactivation mechanism of NiWS/SAPO-11 catalyst in hydroisomerization of n-hexadecane: Insights into coke deposition behavior and active phase migration

The application of non-noble metal supported catalysts in the hydroisomerization of long-chain n-alkanes is a novel field, and there is currently not any research available on the deactivation process of these catalysts. We investigated into the deactivation mechanism of NiWS/SAPO-11 catalyst in the hydroisomerization of n-hexadecane in this work for the first time. Specifically, coke deposition behavior and active phase migration were investigated. The reduction of catalytic efficiency of the catalyst was partially aided by the decrease in specific surface area, pore volume, and acid density. From the perspective of the active phase, the clusters of NiWS active phase migrated as the reaction time increased, mostly resulting in an increase in both the stacking number and the length of active phase slabs. The migration of active phase increased the distance between active phase clusters and metal sites, and decreased the utilization ratio of active metal atoms. From the perspective of coke deposition, the coke formed on the catalyst includes soft coke and hard coke. The formation and evolution of coke on the catalyst were investigated. The soft coke (aliphatic compounds) progressively transformed into hard coke (polycyclic aromatic hydrocarbons and graphite-like), and the coke gradually migrated from the external surface of the catalyst to the pore channels as the reaction time increased. It is expected to provide theoretical basis and reference value for the deactivation research and design of non-noble metal supported hydroisomerization catalyst.