Performance Deterioration Research Articles

Mastering Proton Activities in Aqueous Batteries.

Advanced aqueous batteries are promising solutions for grid energy storage. Compared with their organic counterparts, water-based electrolytes enable fast transport kinetics, high safety, low cost, and enhanced environmental sustainability. However, the presence of protons in the electrolyte, generated by the spontaneous ionization of water, may compete with the main charge-storage mechanism, trigger unwanted side reactions, and accelerate the deterioration of the cell performance. Therefore, it is of pivotal importance to understand and master the proton activities in aqueous batteries. This Perspective commentson the following scientific questions: Why are proton activities relevant? What are proton activities? What doweknow about proton activities in aqueous batteries? How dowebetter understand, control, and utilize proton activities?

Effects of Diethoxymethylsilane/Helium Flow Rate Ratio on Low-k Films Deposited by Plasma-Enhanced Chemical Vapor Deposition

As the semiconductor industry has continuously reduced the integrated circuit (IC) chip size, a resistance-capacitance (RC) delay emerged, causing deterioration of the chip performance. To reduce the RC delay, low dielectric constant (low-k) films with suitable mechanical strengths have been adopted as intermetal dielectrics (IMDs). In this study, low-k plasma-polymerized diethoxymethylsilane (ppDEMS) films were fabricated by plasma-enhanced chemical vapor deposition of the DEMS precursor with a flow rate ratio of the DEMS precursor to helium (He) carrier gas (DEMS/He FRR) as a key parameter. As the DEMS/He FRR increased, the refractive index was reduced from 1.401 to 1.386, and the k value decreased from 2.77 to 2.10. From high-resolution scans of C1s, O1s, and Si2p peaks of X-ray photoelectron spectroscopy, the carbon contents increased, and the oxygen contents decreased, along with a decrease in the film density. With the increased DEMS/He FRR, hardness decreased from 2.5 to 1.8 GPa, and elastic modulus decreased from 17.08 to 11.50 GPa. Leakage current densities for all the ppDEMS films were less than 10−7 A cm−2 at 1 MV cm−1. The ppDEMS films could be suggested as the IMDs according to their electrical and mechanical performance.

Frictional properties and environmental adaptability of Ti-MoS2/WC multilayer films

Magnetron-sputtered molybdenum disulfide films are extensively utilized as solid lubricating coatings in space applications as a result of their low friction coefficient and minimal contamination. However, MoS2-based films are sensitive to hygrothermal and oxidation environment, and are easily oxidized to form MoO3, which results in high friction and wear of the films, significantly reducing their operational lifespan. Especially when the spacecraft adopts the launching mode of coastal launch or ocean platform, the performance deterioration caused by oxidation of MoS2 films during transportation, storage and launch is more serious. Therefore, to enhance the frictional performance and oxidation resistance of the films in humid and salt spray environments, the Ti-MoS2/WC multilayer films with preferred (002) crystal plane orientation were prepared, achieving a friction coefficient of 0.009 in a vacuum environment and a wear rate of 1.1×10-7 mm3/N∗m. In particular, the film can maintain this extremely low coefficient of friction even after exposure to moisture or salt spray. These findings demonstrate that the dual doping of Ti and WC and the design of multilayer structures enable MoS2 films to achieve outstanding frictional performance and oxidation resistance. This is crucial for designing MoS2 films with excellent environmental adaptability.

Review of early and accurate detection of Parkinson’s disease

Parkinson’s disease (PD) is a central sensory system-based progressive illness with no cure. The origin of this illness is unknown. According to various research, it has been found that it is caused due to genetics or environmental factors. It is usually found in older people. However, there is no accurate treatment for this disease. So, the patient must be monitored periodically. It usually starts with deterioration in speech performance. The major problem with this disease is that it’s very costly to treat. The paper aims to report details of numerous aspects of detection of PD published in recent years based on the focus and benefits of the study, the methodology being used, accuracy of the system, and future research suggested for the study. A systematic study was done based on a search of the literature. A total of 50 articles were discovered.

CT imaging‐enhanced numerical simulation of microscopic structure and resilient safety of asphalt concrete

AbstractAsphalt concrete is a foundational material in water conservancy projects, serving a critical function in the construction of impermeable structures such as dams. The seismic response characteristics and resilient safety of concrete dams are heavily influenced by the arrangement and evolution of the microscopic structure of the dam material. In this study, a high‐precision computed tomography (CT) scanning technique, in conjunction with advanced numerical simulations, was employed to analyze the internal damage and crack extension mechanism of asphalt concrete. Microstructural images of the asphalt concrete specimen were accurately captured by CT scanning, followed by the construction of corresponding numerical models. Presented simulation results show that the displacement deformation of asphalt concrete reaches its maximum value in the top region of the model and subsequently decreases with depth. Material damage was first observed at the interface between aggregate and asphalt matrix, where microcracks emerge and extend to the entire asphalt matrix, resulting in a gradual deterioration of the model performance. The simulation results indicate that the overall strength of asphalt concrete is primarily influenced by the strength characteristics of its aggregates. The stress–strain curves obtained from the numerical simulations exhibit a hyperbolic relationship, which is in high agreement with the physical test results. This study not only enhances our comprehension of the mechanical behavior of concrete but also contributes to the analysis of seismic response and risk assessment in dam engineering through dynamic experimental testing and numerical simulation.

Microstructural analysis on the compatibility of various dilution oils on magnetorheological grease performance

This research explores the effects of dilution oils on the storage stability of magnetorheological grease (MRG) by studying the effect of dilution oil viscosity on the microstructure of carrier fluids medium for MRG, which can help address practical challenges encountered in the development and deployment of MRG. Three samples of MRG with 70 wt% CIP are prepared; a control, and 2 samples diluted until 10 wt% hydraulic fluid and kerosene respectively. The resulting samples were analysed using a modular compact rheometer (MCR) for oscillatory strain sweep and rotational current sweep. Rheological analyses were repeated after one year in storage. Fourier-Transform Infrared (FTIR) spectroscopy and Atomic Force Microscopy (AFM) results show significant microstructural and performance deterioration of grease thickener in the sample with kerosene, which concludes that kerosene had a very significant effect on the degradation of the grease thickener. From this study, it was revealed that low viscosity oils disrupt the reconstruction of the thickener of lithium grease, which in turn causes deteriorating shear rheological performance of MRG at off-state conditions. This comprehensive analysis explains the relationships between MRG composition, microstructural characteristics, and performance parameters, offering a foundational framework for further exploration and advancement in this scientific field.

Sustainable hydrogen production by integrating solar PV electrolyser and solar evacuated tube collector with hybrid nanoparticles enhanced PCM

The investigation is motivated to analyze the influence of Phase change material (PCM), nano PCMs, and hybrid Nano PCM in sustainable hydrogen production systems. An emerging and highly effective method for hydrogen production involves the use of proton exchange membrane (PEM) technology, which separates water into its constituent parts through electrolysis. Its susceptibility to performance deterioration over time, however, demandsroutine maintenance and component replacement, which negatively impacts operational effectiveness and cost-effectiveness. In this study, the PEM system for electricity and water heating was integrated with the evacuated tube collector and photovoltaic panel to produce hydrogen. Additionally, hybrid Al2O3 and SiO2 nanoparticles with a combined concentration of 0.1 % in equal shares improved the thermal characteristics of PCM in heat exchangers. The research result shows that the heat exchanger of the ETSC circuit with the hybrid nanoparticles enhanced PCM demonstrated improved thermal performance as well as increased hydrogen production. With hybrid nanoparticles enhanced PCM in the heat exchanger, the maximum energy and electrical energy were observed as246.5 kWh and 44.7 kWh, respectively. The ETSC efficiency, electrical efficiency, and PEM electrolyser efficiency reached their highest points at 93.1 %, 15.5 %, and 39.2 %, respectively. Furthermore, hybrid nanoparticle-enhanced PCM produces an average of 25.9 g of hydrogen.

Compatibility study of recycled Polypropylene (PP)/Poly(ethylene terephthalate) (PET) blends nanocomposites with PP‐g‐MAH: Modeling of twin screw extrusion

AbstractAlthough the utilization of recycled polymers is essential to sustain the environment, conventional recycled polymers face limitations in application due to the degradation of their properties caused by impurities. To solve the problem the performance deterioration of these recycled polymers, this study aimed to enhance their compatibility by chemically adding polypropylene‐graft‐maleic anhydride (PP‐g‐MAH) and physically manipulate a screw profile by using an extrusion simulation program. As a result of applying the optimized extrusion process set by the simulation program, significant improvements in the compatibility and dispersion of fillers within the polymer were observed through scanning electron microscopy image analysis. In addition, through detailed analysis of rheological data, the positive impact of adding compatibilizer and changing screw profile on rheological properties was demonstrated. As the compatibility of recycled polymer blends improved, tensile strength increased by approximately two‐fold and thermal conductivity was significantly improved, which were decisive factors in dramatically enhancing the performance of recycled polymers. These improved polymer properties provide an opportunity for recycled polymers to be applied more broadly and will expand the potential for new applications in various industrial fields.

Leadership in Platform Engineering: Best Practices for High-Traffic E-Commerce Retail Applications

High-traffic retail applications need great platform engineering leadership to assure operational excellence and scalability in the continually changing e-commerce industry. This study examines how leadership matters in platform engineering for high-traffic e-commerce retail systems. It covers best practices, methods, and frameworks for managing and optimizing platforms with high traffic and flawless user experiences. The report defines platform engineering executives' key duties as connecting technology strategy with business objectives. Platform engineering leaders must be technical, innovative, manage cross-functional teams, and respond to market changes. Leaders must promote continual development and adaptability to maintain high performance in dynamic e-commerce settings. it focuses on the architectural design concepts that support high-traffic e-commerce systems. Leaders must ensure platform design is durable, scalable, and can handle peak traffic without performance deterioration. The article explores microservices architectures, containerization, and cloud-native solutions for scalability and flexibility. Effective data management and caching are also investigated to improve platform performance and user experience. Security is another important paper topic. E-commerce sites are obvious targets for cyberattacks, therefore executives must employ robust security measures. Proactive security, strict access limits, and vulnerability monitoring are best practices. The article emphasizes the need of data protection rules and industry standards to secure consumer data and build confidence.

Higher striatal dopamine is related with lower physical performance fatigability in community-dwelling older adults.

Fatigability in community-dwelling older adults is highly prevalent and disabling, but lacks a treatment. Greater nigrostriatal dopaminergic signaling can ameliorate performance fatigability in healthy young adults, but its role in community-dwelling older adults is not known. We hypothesized that higher nigrostriatal dopaminergic integrity would be associated with lower performance fatigability, independent of cardiopulmonary and musculoskeletal energetics and other health conditions. In 125 older adults participating in the Study of Muscle, Mobility and Aging, performance fatigability was measured as performance deterioration during a fast 400 meter walk (% slowing down from the 2nd to the 9th lap). Nigrostriatal DA integrity was measured using (+)-[11C] dihydrotetrabenazine (DTBZ) PET imaging. The binding signal was obtained separately for the subregions regulating sensorimotor (posterior putamen), reward (ventral striatum) and executive control processes (dorsal striatum). Multivariable linear regression models of performance fatigability (dependent variable) estimated the coefficients of dopamine integrity in striatal subregions, adjusted for demographics, comorbidities, and cognition. Models were further adjusted for skeletal muscle energetics (via biopsy) and cardiopulmonary fitness (via cardiopulmonary exercise testing). Higher [11C]-DTBZ binding in the posterior putamen was significantly associated with lower performance fatigability (demographic-adjusted standardized Beta = -1.08, 95% CI: -1.96, -0.20); results remained independent of adjustment for other covariates, including cardiopulmonary and musculoskeletal energetics. Associations with other striatal subregions were not significant. Dopaminergic integrity in the sensorimotor striatum may influence performance fatigability in older adults without clinically overt diseases, independent of other aging systems.

Collaborative forecasting management model for multi‐energy microgrid considering load response characterization

AbstractMulti‐energy microgrids (MEMG) have become an effective means of integrated energy management due to their unique advantages, including area independence, diverse supply, flexibility, and efficiency. However, the uncertain deviation of the renewable energy generators (REGs) output and the uncertain deviation of the multiple energy load response cumulatively lead to the deterioration of the MEMG model performance. To address these issues, this article proposes a cooperative forecasting management model for MEMG that considers multiple uncertainties and load response knowledge characterization. The model combines a multi‐energy load prediction model with a management model based on deep reinforcement learning. It proposes multiple iterations of data, fits the dynamic environment of MEMG by continuously improving the long short‐term memory (LSTM) neural network based on knowledge distillation (KD) architecture, and then optimizes the MEMG state space by considering the knowledge of load response characteristics, Furthermore, it combines multi‐agent deep deterministic policy gradient (MADDPG) with horizontal federated (hF) learning to co‐train multi‐MEMG, addressing the issues of training efficiency during co‐training. Finally, the validity of the proposed model is demonstrated by an arithmetic example.

Regulation of surface oxygen vacancy of Cu-CeO2/TiO2 heterostructures via fast Joule heating method for enhanced CO2 electrochemical reduction

Strict control of carbon emissions is crucial for expediting the achievement of carbon neutrality. However, the current CO2RR electrocatalytic exhibits numerous shortcomings that impede the enhancement of catalytic activity. Issues such as lengthy catalyst preparation times, and high levels of precious metal content. Additionally, the aggregation of ultrafine nanoparticles contributes to a rapid deterioration in catalytic performance. Herein, a Joule-heating method is efficiently utilized to synthesize heterostructures nano-catalysts for CO2 electroreduction on carbon cloth substrates. This method takes advantage of the thermoelectric coupling of the carbon cloth to achieve carbothermal reduction, while also regulating phase composition and introduction of oxygen vacancies. The Cu-CeO2/TiO2/CC catalyst synthesized in this method showed a current density in CO2 of −32 mA·cm−2 at −1.0 V (vs. RHE). Notably, this catalyst demonstrated high CO selectivity and Faraday efficiency (FECO) of up to 82.5 % at a low potential of −0.3 V (vs. RHE). Optimal electrochemical performance is achieved at a power of 40 W. The ultra-fast temperature change process prevented the agglomeration of catalyst particles and facilitated the construction of a stable heterogeneous interface with a high oxygen vacancy concentration. In conclusion, this study presents a promising approach, particularly for the rapid preparation of low-cost, highly selective non-precious metal electrocatalysts.

Triggering aqueous electrolyte molecular association via solvent eutectic strategy to enable zinc metal battery operation at −60℃

It is a great challenge to circumvent the performance deterioration of aqueous zinc metal batteries (AZMBs) at low temperatures, which root from solvent solidification of water. Herein, via triggering aqueous electrolyte molecular association by solvent eutectic strategy, an aqueous solvent eutectic electrolyte of DMF-H2O solvent (SE-electrolyte) is prepared for adapting to the application of zinc metal battery at low temperature. The SE-electrolyte reduces the content of free water molecules, lowers the freezing point of the electrolyte, thus avoiding side reactions and broadening the operating temperature range of zinc batteries to −60℃. At room temperature, Zn||PANI full battery can cycle stably more than 10,000 times at 2 A/g high discharge current, the capacity retention rate is about 50%, and the average Coulomb efficiency is 99.79%. Under the harsh conditions of −45℃ and −60℃, the Zn||PANI whole battery can be stably cycled more than 1000 cycles with the current density of 0.2 A/g, and the Coulomb efficiency is close to 100%. The excellent low temperature electrochemical performance of SE-electrolyte indicates a bright prospect for the use of aqua zinc batteries in low temperature, and is a key step for the comprehensive and extensive application of aqueous zinc metal batteries.

Synergistic performance enhancement of lead-acid battery packs at low- and high-temperature conditions using flexible phase change material sheets

Thermal management of lead-acid batteries includes heat dissipation at high-temperature conditions (similar to other batteries) and thermal insulation at low-temperature conditions due to significant performance deterioration. To address this trader-off, this work proposes a thermal management solution based on flexible phase change materials (PCMs) with moderate thermal conductivity and other favourable properties including high specific heat capacity and high latent heat. A novel type of flexible PCM sheets is prepared with paraffin, olefin block copolymers (OBC) and expanded graphite using the co-melting method. The flexible PCM sheets are attached to a common type of lead-acid battery packs (12 Ah, dimensions of 151 × 98 × 97 mm) and thermal management performance is experimentally investigated at –10 °C and 40 °C as low- and high-temperature conditions, respectively, along with 25 °C as a baseline case for comparison purposes. Thermal properties of the battery packs such as temperature regulation and electric properties including charge/discharge capacities and rates are studied synchronously based on a standard high-performance battery detection facility. The results indicate that at –10 °C condition, the PCM sheet enhances thermal insulation of the battery pack and significantly promotes the service temperature during the charging processes. Compared with a benchmark pack attached with an encapsulated sheet, the charge and discharge capacities of the PCM-attached pack are improved by 3.7% and 5.9%, respectively. At 40 °C condition, phase transition of the PCM sheet restrains the temperature rise of the battery pack, with a maximum temperature decrease of 4.2 °C during the charging processes relative to the benchmark pack, and the temperature of the PCM-attached pack is maintained below 45 °C across 60% of the overall charge period. The overcharge and overdischarge have also been alleviated by 3.2% and 2.8%, respectively, and thus the running stability and service lifespan can be improved. The proposed PCM sheets with preferable thermal properties demonstrate potential to promote performance of lead-acid battery packs and such components are also expected to improve heat dissipation and thermal insulation in similar applications including building energy saving, thermal management of electronic chips and thermal regulation of electronic devices.

Understanding the hydrogen and halogen bonds of ionic liquids in regulating ion solvation and dynamic behaviors of aqueous zinc electrolytes

Despite their low cost and intrinsic safety, aqueous rechargeable zinc-ion batteries suffer from rapid performance deterioration originating from parasitic reactions and inhomogeneous deposition on the Zn anode. Halogen bonds share similarities with hydrogen bonds, yet their unique directionality, strength tunability, and hydrophobicity provide a promising approach for enhancing the reversibility of Zn anodes. Herein, a systematic comparison of ionic liquids with different anions, acetate (Ac−) and chloride (Cl−), is performed to explore the non-covalent interactions in regulating ion solvation and dynamic behaviors of electrolytes. Different from the Ac− possessing a strong capacity to form hydrogen bonds with water, the Cl−-water halogen bonds not only enable the structural diffusion of Zn2+ with better diffusion efficiency but also reduce the Zn2+ de-solvation energy barrier to promote uniform Zn nucleation. Consequently, the accelerated ions diffusion and homogeneous Zn deposition work in synergy to ensure high reversibility of Zn anode. These fundamental insights highlight the importance of hydrogen and halogen bonds in determining the dynamics and electrochemical behavior of electrolytes, providing theoretical guidance for the rational design of high-performance electrolytes.

Investigation of the mechanism of carrier recombination in GaN-based blue laser diodes before lasing

Abstract The carrier recombination behavior of GaN-based blue laser diodes (LDs) is studied and analyzed by experiments and simulation calculations before lasing, with a particular focus on the role of Auger recombination. It is found that Auger recombination plays a crucial role in the decrease in differential efficiency and threshold current of GaN-based blue LDs. The theoretical calculation results show that a large Auger recombination rate may lead to a dominant recombination channel before lasing, which could exceed the radiation recombination and result in an obvious decrease in the differential efficiency. Such a high Auger recombination will dissipate a large number of carriers in the quantum well, resulting in deterioration of device performance, a higher threshold current and a lower efficiency. This work presents a method to evaluate Auger recombination through differential efficiency and also provides evidence that suppressing the Auger recombination rate is beneficial to improve the performance of blue LDs.

Effects of attentional focus strategies in drop landing biomechanics of individuals with unilateral functional ankle instability.

Functional Ankle Instability (FAI) is a pervasive condition that can emerge following inadequate management of lateral ankle sprains. It is hallmarked by chronic joint instability and a subsequent deterioration in physical performance. The modulation of motor patterns through attentional focus is a well-established concept in the realm of motor learning and performance optimization. However, the precise manner in which attentional focus can rehabilitate or refine movement patterns in individuals with FAI remains to be fully elucidated. The primary aim of this study was to evaluate the impact of attentional focus strategies on the biomechanics of single-leg drop landing movements among individuals with FAI. Eighteen males with unilateral FAI were recruited. Kinematic and kinetic data were collected using an infrared three-dimensional motion capture system and force plates. Participants performed single-leg drop landing tasks under no focus (baseline), internal focus (IF), and external focus (EF) conditions. Biomechanical characteristics, including joint angles, ground reaction forces, and leg stiffness, were assessed. A 2 × 3 [side (unstable and stable) × focus (baseline, IF, and EF)] Repeated Measures Analysis of Variance (RM-ANOVA) analyzed the effects of attentional focus on biomechanical variables in individuals with FAI. No significant interaction effects were observed in this study. At peak vertical ground reaction force (vGRF), the knee flexion angle was significantly influenced by attentional focus, with a markedly greater angle under EF compared to IF (p < 0.001). Additionally, at peak vGRF, the ankle joint plantarflexion angle was significantly smaller with EF than with IF (p < 0.001). Significant main effects of focus were found for peak vGRF and the time to reach peak vGRF, with higher peak vGRF values observed under baseline and IF conditions compared to EF (p < 0.001). Participants reached peak vGRF more quickly under IF (p < 0.001). Leg Stiffness (kleg) was significantly higher under IF compared to EF (p = 0.001). IF enhances joint stability in FAI, whereas EF promotes a conservative landing strategy with increased knee flexion, dispersing impact and minimizing joint stress. Integrating these strategies into FAI rehabilitation programs can optimize lower limb biomechanics and reduce the risk of reinjury.

Thermal management of lithium-ion battery modules optimized based on the design of cold plate with convex pack structure

To address the issue of temperature increase in battery modules using liquid cooling plates, a convex pack structure within the flow channel is proposed to enhance flow efficiency. High temperatures can lead to battery performance deterioration, increased safety risks, and reduced service life. The optimal parameters for the convex structure (radius, transverse spacing, and longitudinal spacing) were determined through simulation analysis and orthogonal experiments. The effects of discharge rate, ambient temperature, coolant inlet temperature, and inlet speed on the heat dissipation of the battery module were also studied. The results show that the convex pack structure enhances heat transfer by increasing the contact area and fluid velocity while inducing eddy currents to achieve lateral mixing. The optimal parameters were found to be: radius (r) = 0.75 mm, horizontal spacing (x) = 3.50 mm, and vertical spacing (y) = 4.50 mm. At low discharge rates, the battery performs well, but high discharge rates negatively affect temperature uniformity. An increase in ambient temperature raises the temperature difference and maximum battery temperature. Lower coolant inlet temperatures reduce the maximum temperature but may result in uneven temperature distribution. Achieving a balanced coolant flow rate is essential to minimize temperature variations and control pressure buildup. This research introduces an innovative heat transfer structure, the convex pack, which significantly improves cooling efficiency. Further research on enhanced heat transfer structures is necessary to continue advancing cooling technologies for battery modules.

Optimized removal of silica during manure treatment by electrocoagulation-flotation (EC-F) in view of fouling prevention of reverse osmosis membranes

Reverse osmosis (RO) membrane fouling threatens the performance of manure treatment. In this regard, silica is considered one of the most challenging inorganic foulants. Removing silica fouling from RO membranes is difficult, ultimately leading to performance deterioration, including reduced permeability and premature membrane failure. This study examines the removal of silica during manure treatment using a novel tubular electrocoagulation-flotation (EC-F) reactor with an Al electrode. The EC-F was positioned between an ultrafiltration and a RO membrane filtration system. The operational parameters—current density, electrolysis residence time, and initial pH—were optimized for maximum silica removal efficiency and minimum operational cost. At the optimum conditions (pH of 8.2, current density of 160 A/m2 and electrolysis residence time of 23 s), 88 % of silica (initial concentration of 104 mg/L) was removed. Subsequent membrane fouling assessment revealed that EC-F pretreatment decreased the fouling potential by 28 % (from 7.11 × 1016 to 5.10 × 1016 Pa·s/m2·t), indicating efficient foulant removal. SEM-EDX analysis of the membrane confirmed the lack of scale formation when using EC-F pretreated manure as a feed stream. This study demonstrates that the use of innovative EC-F pretreatment significantly reduces the operational expenditure (1.75 €/m3) compared to prior EC-F research for silica removal from manure, thereby reducing the fouling of RO membranes.

Effects of surface hydrophobization on the phase evolution behavior of iron-based catalyst during Fischer–Tropsch synthesis

Iron-based Fischer–Tropsch synthesis (FTS) catalyst is widely used for syngas conversion, but its iron carbide active phase is easily oxidized into Fe3O4 by the water produced during reaction, leading to the deterioration of catalytic performance. Here, we show an efficient strategy for protecting the iron carbide active phase of FTS catalyst by surface hydrophobization. The hydrophobic surface can reduce the water concentration in the core vicinity of catalyst during syngas conversion, and thus inhibit the oxidation of iron species by water, which enhances the C − C coupling ability of catalyst and promotes the formation of long-chain olefins. More significantly, it is unraveled that appropriate shell thickness plays a crucial role in stabilizing the iron carbide active phase without Fe3O4 formation and achieving good catalytic performance.