Surface Passivation Layer Research Articles

Research progress in passivation layer technology for crystalline silicon solar cells

Under the background of rapid advancements in photovoltaic technology, crystalline silicon (c-Si) solar cells, as the mainstream photovoltaic devices, have gained significant research attention for their excellent performances. In particular, silicon heterojunction (SHJ) solar cells, TOPCon (Tunnel Oxide Passivated Contact), and PERC (Passivated Emitter and Rear Cell) represent the cutting-edge technologies in c-Si solar cells. The surface passivation layer of crystalline silicon solar cells, as one of the key factors to improve cell performances, has been closely linked to the development of crystalline silicon solar cells. Due to the complex mechanism of passivation layer and the high demand of experimental research, it is challenging to achieve high quality surface passivation. This paper comprehensively reviews the key issues and research progress in interface passivation technologies for SHJ, TOPCon, and PERC solar cells. Firstly, the research progress of key technology breakthrough of SHJ solar cell is reviewed systematically, and the influences of growth conditions and doping layer on the passivation performances of SHJ solar cell are discussed in detail. Secondly, the important strategies and research achievements for improving the passivation performances of TOPCon and PERC solar cells in the past five years are systematically described. Finally, the development trend of passivation layer technology is prospected. This review offers valuable insights for future technological improvements and performance enhancements in c-Si solar cells.

Spatially-Resolved EELS Analysis of Surface Species on Metallic Lithium for the Development of Next Generation Li-Batteries.

Metallic Li is considered one of the most attractive anode candidates for solid-state battery technology as well as for the next generation Li-ions batteries [1,2] due to its ultrahigh theoretical specific capacity (3860 mAhg−1)[3]. However, several technical issues hinder its application as anode material. The widespread commercial usage of Li metallic sheet will necessitate a much better understanding of its microstructure and chemical nature.Metallic lithium is highly sensitive to hydrogen, oxygen, nitrogen, and carbon dioxide, which are the major components of wet air, and are likely to form rapidly LiOH, Li2O, Li2O2, Li3N, and Li2CO3 species [4] when exposed to air and/or moisture. It has been shown that this surface passivation layer has a direct impact on the anode interface resistance in solid state batteries [5]. Because of the nature of Li, very few works have looked directly at the surface chemical structure [6]. XPS and SIMS are normally used to study the nature and thickness of this passivation layer. However, these techniques do not allow to directly observe the nature and thickness of this layer. Direct observation, using TEM, would thus be much better.Because of the very high surface reactivity and the low hardness of Li, it is very difficult to prepare thin sample from a precise Li sheet for direct TEM observations and chemical analysis of the material structure and surface chemical nature. In this presentation we will show the direct HRTEM study of the surface chemical nature of metallic Li sheets. We have used a Hitachi air-protection cryogenic FIB holder to prepare thin Li samples and study the surface chemistry using Spatially-Resolved EELS (SR-EELS). The thin samples were prepared from different Li sheets using FIB (NB5000 from Hitachi) with the sample temperature at ~ -90 °C. The samples were transferred under vacuum using the same holder into a Hitachi HF-3300 cold FEG E-TEM for EELS analysis at low temperature without air contact.SR-EELS was done using a high-resolution GIF system (Gatan Quantum ER) for the rapid acquisition of the Li-K-edge, O-K-edge and C-K-edge respectively. Using this technique, it is possible to directly observe the different chemical variation in the passivation layer and its variation from sample to sample.[1] R. May, K. J. Fritzsching, D. Livitz, S. R. Denny, and L. E. Marbella ACS Energy Letters 6 (4), 1162-1169 (2021)[2] Y. Zhang, T.-T. Zuo, J. Popovic, K. Lim, Y.-X. Yin, J. Maier, Y.-G. Guo, Materials Today 33 , 56-74 (2020)[3] X.-B. Cheng, C.-Z. Zhao, Y.-X. Yao, H. Liu, Q. Zhang, Chem 5, 74-96 (2019)[4] D. Jeppson, J. Ballif, W. Yuan and B. Chou, 1978. Lithium literature review: Lithium’s properties and interactions. Richland, Washington: Hanford Engineering Development Lab[5] S.-K. Otto, T. Fuchs, Y. Moryson, C. Lerch, B. Mogwitz, J. Sann, J. Janek and A. Henss, ACS Appl. Energy Mater. 4, 12798−12807 (2021).[6] N. Brodusch, K. Zaghib and R. Gauvin, Micros. Res. & Tech. 78, 30-39 (2015)

Self-cleaned surface of vanadium boride for long-lasting and boosted Fenton oxidation

Coupling extra electron supply with iron-mediated advanced oxidation processes (AOPs) is an efficient strategy for long-lasting oxidation of organic contaminants in environmental remediation. Many subsequent attempts have been made, such as homogeneous catalysts and metal catalysts, of which secondary organic pollution and surface passivation layers limit their application. In this work, metal borides as co-catalysts can efficiently accelerate the Fenton reaction by firmly sacrificing electrons to Fe(III) reduction. Among multiple metallic borides, vanadium boride (VB2) performs superiorly as dual active sites to solve the Fe(III) cycle dilemma and quickly generate hydroxyl radicals via Fenton reaction for almost completely eliminating almost carbamazepine (CBZ) in VB2/Fe(III)/H2O2. Characterization analysis and the density functional theory (DFT) calculation unveil that the synergistic effect of V and B on the surface of VB2 makes Fe-O bonds of FeOH2+ weaker (from 173.8 pm to 178.4 pm) to produce more active Fe(III) species. And meanwhile, active Fe(III) can be rapidly reduced into Fe(II) on the surface of VB2 and then be completely released into solution for subsequent Fenton reaction and hydroxyl radical generation. More importantly, VB2 performs steadily and efficiently for 7th consecutive test in VB2/Fe(III)/H2O2 to degrade more than 95% CBZ, resulting from the self-cleaning surface of VB2 to expose reactive regions for persistent electron sacrifice and sustainably stimulative Fenton oxidation. Therefore, this research offers the detailed fundamental perception into the genesis of VB2 as well as a novel electron donor for boosting Fenton oxidation towards water remediation.

Improving thermal shock and oxidation resistance of Cr3C2/WC-NiCr cermet coating by embedding large NiCrAlY superalloy particles

Cr3C2/WC-based cermet coating is widely used on the surface of mechanical equipment to strengthen its wear and corrosion resistance. Improving the high-temperature performance of cermet coating is the key to its industrial application. In this study, a novel type of bimodal microstructure cermet coating with the design of functional sites was fabricated via high-velocity air fuel (HVAF) spray technology. The toughness NiCrAlY superalloy particles are introduced into the traditional Cr3C2/WC-NiCr cermet structure to construct the thermal stress release site, which significantly improved the thermal shock resistance and thermal oxidation properties of the coating. The addition of NiCrAlY superalloy particle reduces the porosity of Cr3C2/WC-NiCr coating to 0.29 % and creates high-quality interface bonding and surface passivation layer. The newly structured cermet coating exhibits outstanding high-temperature performance. In a 1000 °C oxidation environment, the new coating remained intact after 120 h of exposure, while the traditional Cr3C2/WC-NiCr cermet coating exfoliated completely after 48 h of exposure. Further, in the thermal shock condition at 1000 °C, the lifetime of the new coating is 50 times greater than that of the traditional cermet coating, displaying excellent ability to relieve thermal stress. Additionally, the new coating shows good wear resistance and stability during high-temperature thermal exposure. After thermal exposure for 24 h and 72 h, the wear rates of the coating are 5.28 and 5.83 × 10−5 mm3 N−1 m−1, respectively, which is slightly lower than that of the as-sprayed coating. This study provides guidance for the improvement of high temperature resistance of thermally sprayed Cr3C2/WC-based cermet coatings.

The effect of Al2O3 surface passivation layer prepared by ALD method on the performance of CdZnTe thick film detectors

In this work, cadmium zinc telluride (CdZnTe) thick films were grown using close-spaced sublimation (CSS), while Al2O3 films of varying thicknesses were deposited by atomic layer deposition (ALD) as surface passivation layers. The influence of the Al2O3 surface passivation layer on the structure, surface morphology, chemical composition and electrical performance of the CdZnTe thick films was analyzed using XRD, EDS, SEM, AFM, XPS and current–voltage (I-V) characterization systems. The results demonstrate that the surface passivation layer could significantly improves surface defects and reduces the surface leakage current (SLC) of CdZnTe thick films. The CdZnTe thick film radiation detector exhibited an improved energy resolution, decreasing from 18.6 % to 15.1 % with a 40 nm Al2O3, as measured using a 60 KeV 241Am γ-ray source.

(Invited) Insights into the Electrocatalytic Behavior of Mxenes

The continued rise in global energy consumption, along with the associated environmental hazards, pose a significant risk to our society’s infrastructure unless the main source is changed. Electrocatalysis involving hydrogen evolution reaction (HER), nitrogen reduction reaction (NRR), and oxygen reduction reaction (ORR), provide a pathway for energy storage and conversion due to their enhanced environmental friendliness and efficient energy input compared to their thermocatalytic counterparts. Currently, the state-of-the-art electrocatalysts suffer from scarcity and high cost. MXenes, a novel family of two-dimensional (2D) transition metal carbide and nitride materials, show potential as cost-efficient and highly abundant electrocatalysts with limited knowledge on their electrocatalytic mechanisms. This is especially true when considering the often-overlooked nitride family of MXenes. Herein, we investigate the electrocatalytic performance of a Ti2N nitride MXene under different electrocatalytic conditions. The effect of surface phenomena is investigated through manipulation of the surface passivation layer, as evidenced by Raman and Fourier-transform infrared (FTIR) spectroscopies, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Successful decoupling of the bulk and surface phenomena is achieved through Raman laser power attenuation. Under acidic medium, the surface reactivity towards HER is poor but the bulk reactivity for NRR is favored, making it an optimal NRR catalyst. Under alkaline medium, the surface reactivity of the pristine Ti2N MXene for ORR is high, but also leads to surface passivation and thus hinders the electrocatalytic activity. Overall, these results provide fundamental insights into future optimization strategies of the Ti2N nitride MXene, along with other MXene electrocatalysts, towards electrocatalytic applications.

Columnar self-assembled heteroatom bay-annulated perylene bisimide as passivating layer for high performance perovskite solar cells

The interfaces within Perovskite solar cells (PSCs) are imperative for regulating defects, managing carrier dynamics, preventing ion migration, optimizing energy band alignment, and controlling morphology. The interfaces amidst the absorber layer and the hole transport layer (HTL) pose challenges related to ineffective charge extraction and charge recombination, necessitating enhancement. Spiro-OMeTAD is commonly utilized as p-type material in the HTL of planar architecture, entailing the inclusion of diverse additives to enhance solar cell efficiency, which can restrict device performance and stability. Herein, we explore the influence of a discotic liquid crystalline (DLCs) based semiconductor, a heteroatom bay-annulated perylene bisimide (PBI-SeO10), which is derived from tri-n-alkoxy anilines. Our study examines the function of PBI-SeO10 as an interfacial passivation layer within the perovskite/Spiro-OMeTAD interface, assessing its effects on both device performance and stability. Our results indicate that integrating PBI-SeO10 as a surface passivation layer not only aids in effective hole extraction from the perovskite layer but also substantially diminishes defects, leading to an improvement in overall device performance by approximately 7 %. Furthermore, PBI-SeO10 passivation also reduces ionic/molecular species diffusion into the device and provides good moisture resistivity leading to improved device stability.

SiC and Si detectors comparison for high carbon energy spectrometry

An innovative SiC Schottky junction and a traditional p-n Si surface barrier detector have been compared to detect carbon ions with MeVs kinetic energy. To this, a comparison was performed during Rutherford backscattering spectrometry (RBS) using 2–10 MeV carbon ion beams. The energy resolution and detection efficiency for RBS analysis using the two detectors and their detection electronics are presented.The detector parameters dependencies on the surface passivating layers, ion energy and current dependence, ion penetration depth, detection efficiency, energy resolution, and others are discussed.The comparison of RBS analysis with SiC and Si is investigated highlighting the advantages and disadvantages of using SiC with respect to the traditional Si surface barrier detectors. The two detectors employed for proton, helium and carbon RBS spectrometry of different targets have been also compared on the base of the literature data.

Preparation and Performance Evaluation of Microporous Transport Layers for Proton Exchange Membrane (PEM) Water Electrolyzer Anodes

In this work, ≈25 μm thin titanium microporous layers (MPLs) with ≈2 μm small pores and low surface roughness were coated and sintered on top of ≈260 μm thick commercial titanium-powder-sinter sheets with ≈16 μm pores, maintaining a porosity of ≈40% in both layers. Serving as porous transport layers (PTLs) on the anode side in proton exchange membrane water electrolyzers (PEMWEs), these pore-graded, two-layer sheets (“PTL/MPL”) are compared to single-layer PTLs in single-cell PEMWEs. The PTL/MPL samples prepared here give a 3–6 mΩ cm2 lower high-frequency resistance (HFR) compared to the as-received single-layer PTL, which is attributed to a partial reduction of the TiO2 surface passivation layer during the MPL sintering process. For ≈1 μm thin anodes with an iridium loading of ≈0.2 mgIr cm−2, the use of an MPL leads to a ≈24 mV improvement in HFR-free cell voltage at 6 A cm−2. As no such benefit is observed for ≈9 μm thick anodes with ≈2.0 mgIr cm−2, mass transport resistances within the PTL/MPL play a minor role. Possible reasons for the higher catalyst utilization in ultra-thin electrodes when using an MPL are discussed. Furthermore, an MPL provides superior mechanical membrane support, which is particularly relevant for thin membranes.

Local and quantitative measurement of mechanical properties by electrical-nanoindentation in situ SEM: Application to a multi-phase AgCuPd alloy

Nanoindentation has now become the key technique for measuring the mechanical properties of materials at small scales. However, the quantitative and accurate processing of nanoindentation data relies on a physical quantity that is not directly available: the contact area (Ac) between the indenter tip and the sample under test. In complex systems, determining Ac is challenging due to the limitations of standard methods: analytical models have restricted validity domains (sample homogeneity and rheology), and post-mortem observations of residual imprints are time-consuming, do not appraise property gradients and cannot be applied to materials with significant elastic recovery.In this paper, a comprehensive methodology is proposed to continuously measure contact area during indentation. The proposed methodology, referred to as electrical-nanoindentation (ENI), is based on real-time monitoring of the electrical contact resistance (ECR). The protocol only requires mechanical and electrical calibrations of the indenter tip on reference materials, leading to one-to-one relationship between ECR and contact area. An original approach is also proposed to deal with the presence of surface passivating layers that generally disturb ECR measurements. As an illustration, the methodology is applied to the characterization of a multi-phase alloy (MPA) composed of silver, copper and palladium. This alloy raises the same challenges as those usually faced by nanoindentation in advanced metallurgy: heterogenous distribution of individual phases at the micro-scale, composite response of a complex mixture of hard/stiff and ductile/soft phases, … In addition, the ohmicity of contact is disturbed by surface passivating layers. Despite these numerous hindrances, the proposed methodology is successfully applied to this material. The evolution of contact area is compared with standard methods: an impressive accuracy of <2% standard-deviation is achieved when compared to post-mortem observations. The elastic moduli and hardnesses of individual phases are then accurately extracted. In addition, in order to gain in spatial definition, the ENI set-up is integrated into a scanning electron microscope (SEM), enabling indent positioning with a precision close to 100 nm.Two challenges are successfully met with the ENI methodology. On a mechanical point of view, the response of individual phases can be identified despite the complex rheology of heterogeneous materials, proving the approach applies to all mechanical behaviors (sink-in or pile-up rheologies, homogeneous or heterogeneous materials, with or without elastic recovery, …). On an electrical point of view, even if contact ohmicity is the only requirement of the methodology, it is possible to identify and overcome deviations from contact ohmicity induced by surface passivation. In particular, the non-linear resistive contribution of insulating layers fades during indentation thanks to its dependence as the reciprocal of the square of contact radius. The present work provides the keys to monitoring the contact area on any metallic sample, whether oxide-free or oxidized, making this methodology a promising alternative to standard methods.

Suppression of crack formation in wafer-scale amorphous SiNx films by residual hydrogen-ligands manipulation

Plasma-Enhanced Chemical Vapor Deposition (PECVD) of amorphous silicon nitride (SiNx) thin films is a critical procedure in microelectronics serving as a surface passivation layer and dielectric barrier. However, intrinsic film stress continuously builds up along with PECVD growth, leading to film cracking. How to achieve crack-free PECVD amorphous SiNx film within a large thickness range remains a critical unresolved challenge in semiconductor industry. In this study, we revealed that high residual NH ligands from the NH3 precursor could induce excessive tensile strain at the SiNx/Si wafer interface and consequently aggravate SiNx film crack formation. With a heating pretreatment on the wafer, residual H ligands were effectively reduced to achieve homogenous chemical composition in SiNx film. As a result, the crack number declined ∼42% and the remaining crack length was substantially shorter in contrast to the original SiNx film. This work demonstrates the crucial role of residual ligands on internal strain regulation and points out a pathway to achieve crack-free PECVD SiNx films in industrial manufacturing.

Effect of Secondary Phase on Passivation Layer of Super Duplex Stainless Steel UNS S 32750: Advanced Safety of Li-Ion Battery Case Materials.

Aluminum, traditionally the primary material for battery casings, is increasingly being replaced by UNS S 30400 for enhanced safety. UNS S 30400 offers superior strength and corrosion resistance compared to aluminum; however, it undergoes a phase transformation owing to stress during processing and a lower high-temperature strength. Duplex stainless steel UNS S 32750, consisting of both austenite and ferrite phases, exhibits excellent strength and corrosion resistance. However, it also precipitates secondary phases at high temperatures, which are known to form through the segregation of Cr and Mo. Various studies have investigated the corrosion resistance of UNS S 32750; however, discrepancies exist regarding the formation and thickness of the passivation layer. This study analyzed the oxygen layer on the surface of UNS S 32750 after secondary-phase precipitation. The microstructure, volume fraction, chemical composition, and depth of O after the precipitation of the secondary phases in UNS S 32750 was examined using FE-SEM, EDS, EPMA and XRD, and the surface chemical composition and passivation layer thickness were analyzed using electron probe microanalysis and glow-discharge spectroscopy. This study demonstrated the segregation of alloy elements and a reduction in the passivation-layer thickness after precipitation from 25 μm to 20 μm. The findings of the analysis aid in elucidating the impact of secondary-phase precipitation on the passivation layer.

Engineering an organic electron-rich surface passivation layer for efficient and stable perovskite solar cells

Engineering an organic electron-rich surface passivation layer for efficient and stable perovskite solar cells

Experimental investigation on synergistic slow oxidation and rapid combustion of micron-sized iron and aluminum powders for energy storage application

The investigation into the individual application of iron and aluminum as carbon-free fuel sources has been extensively explored and holds significant promise. However, there remains a gap in understanding synergistic effects achievable through the blending of these two fuels, as well as a need for comparative analyses between the slow oxidation and rapid combustion processes of these fuels to complement each other. This research proposes blending micron aluminum and iron powders to analyze their slow oxidation and rapid combustion features under diverse atmospheric conditions and heating rates, using thermogravimetric methods, kinetic calculations, and in-flow experiments. The research blending micron iron and aluminum powders to analyze their slow oxidation and rapid combustion features under diverse atmospheric conditions and heating rates, using thermogravimetric methods, kinetic calculations, and in-flow experiments. The findings reveal that the combination of aluminum and iron powders promotes oxidation, resulting in increased weight gain and heat flux rate compared to individual metals. Moreover, the triggering temperature rises from 545 to 652 °C with an increase in aluminum powder content. As heating rates increase, characteristic parameters T1, T2, and Hpeak2, rise for both fuels. However, aluminum powder tends to decrease Ti, while iron powder slightly increases it due to differences in oxide layers. The slow oxidation of aluminum and iron powders conforms to different models, yielding distinct oxidation patterns. The apparent activation energy of aluminum decreases from 258.4 to 238.7 kJ·mol−1 with rising heating rates, while that of iron exhibits a lower increase and remains lower than aluminum providing insights into combustion initiation conditions. Combustion initiation is contingent upon the concentration of metal powder and oxygen, with both aluminum and iron powders combustion being enhanced and subsequently attenuated with increasing excess air ratio. However, due to differing reactivity and surface passivation layers, the excess air ratio required for aluminum powder combustion (1.2–2.4) exceeds that of iron powder (1.3–1.7). The research elucidates the mechanisms underlying the slow oxidation of iron and aluminum fuels, delineates suitable combustion conditions, and furnishes new empirical and theoretical underpinnings for the oxidation characteristics of mixed iron-aluminum fuels, thereby advancing metal-fueled energy storage technologies.

Characteristics of zero-valent iron surface oxide films under the catalytic interface reactions by assisting ligands in nitrate-contaminated groundwater

The surface passivation layer coating on zero-valent iron (ZVI) particles impedes the electron transfer from ZVI to nitrate. To enhance the efficiency of nitrate reduction by Fe(0), we tested the chemical process and the thickness of the iron oxide film on the surface of Fe(0) particles, utilizing Fe2+aq in aqueous solution and wheat straw as ligands. A novel principal surface catalyzing reaction was formulated as follows: NO3−+0.67Fe2++2.2Fe0+2.33H2O→NH4++1.18Fe3O4+0.64OH−. When Fe2+aq concentration increased from 0 - 200 mg·L−1, the NO3- removal rate increased from 6.95% to 82.6% respectively during 12 h and it was 48%, 72%, 79% and 94% respectively in Fe0/WS ratio of 0, 0.25, 0.5 and 1 system. Uniform surface iron oxide films formed around the Fe(0) particles within 12 h after the adding Fe2+aq or wheat straw to the Fe(0) system. The composition and thickness of these films were dependent on the quantity of added materials. X-ray diffraction (XRD) analysis revealed that surface oxide iron mainly consisted of Fe2+ or Fe3+ oxides, with Fe3O4 being predominant. The X-ray photoelectron spectroscopy (XPS) etching indicated that the addition of Fe(0)/straw at mass ratios of 1 or system with 20 mg·L−1 Fe2+aq resulted in the thinnest surface iron oxide layer. The study demonstrated that reducing the oxide layer’s thickness was achieved through partial catalysis and enhanced complexation capacity. This reduction was facilitated by the introduction of Fe2+aq or wheat straw into the Fe(0) system, potentially improving proton dissociation and promoting the ligand-assisted dissolution of Fe3+ oxides.

Effect of LLZTO Tablet Pressing Process on Electrochemical Properties of Button Batteries

AbstractThe garnet‐type Li6.4La3Zr1.4Ta0.6O12 (LLZTO) is a widely studied solid‐state electrolytes (SSEs) due to its high ionic conductivity and electrochemical stability. However, the conventional preparation process of LLZTO electrolyte tablets has encountered several issues such as powder embedment in the mold gaps and inadequate bonding between powders, leading to fragile electrolyte tablets that are prone to cracking. In this study, the effects of LLZTO electrolyte tablet pressing process parameters, including mixed powder content, polyvinyl alcohol (PVA) content and cold pressing pressure, on the electrochemical properties of button cells were investigated. The results indicated that the produced solid‐state electrolyte tablets with high quality, low interfacial resistance and low surface passivation layer (Li2CO3) content was obtained by using 0.8 g of mixed powder content, 0.7 g of PVA content and 20Mpa pressure. The interface resistance decreased from 2927.1 Ω to 1069.7 Ω under these conditions. Additionally, the Li symmetric cell treated with adhesive exhibited stable cycling for over 400 hours at 25 °C under a current density of 0.1 mA ⋅ cm−2.

Comparison between conventional Si and new generation of SiC detector for high proton energy spectrometry

A SiC Schottky diode and a Si surface barrier detector have been compared during Rutherford backscattering spectrometry (RBS) using 2–3 MeV proton beams. Both detectors are suited to detect high energetic ions with high-energy resolution for spectroscopic analysis. The correlations between the detector parameters and the surface passivating layers, ion energy and current dependence, ion penetration depth, detection efficiency and energy resolution, are outlined. Comparative RBS analysis performed using SiC and Si detectors has been investigated to highlight the advantages and disadvantages of the use of SiC with respect to the traditional Si junction detector. RBS spectrometry has been carried out using projectiles of proton incident on different targets to analyse their composition and thickness by the detection of the backscattered ions revealed by Si and SiC detectors.

Development of Fe0 biochar composites synergistically activated with MgFe2O4 and Fe2+ through one-step pyrolyzing Fe sludge and MgCl2 for enhanced aqueous Cr(VI) removal

The surface passivation layer on Fe0 severely restricts its reactivity during environmental decontamination. In this study, a new composite—an Fe0 biochar composite (Fe0/BC) coupled with MgFe2O4 and Fe2+—was first developed for enhanced Cr(VI) removal by simple co-pyrolysis of Fe sludge (FS) with MgCl2. The characterization results demonstrated that MgFe2O4 and Fe0 could be formed simultaneously at 700 ℃. However, MgFe2O4 disappeared at temperatures of 800 and 900 ℃. By varying the flow rate of N2 and holding time, Fe0/BC was further optimized based on the determined MgCl2 to FS mass ratio (1.9:10.0) and temperature (700 °C). The optimal Fe0/BC (MBC700120-400–30) achieved a Cr(VI) removal efficiency of 97.67%, which was 2.43 times higher than that of the unmodified Fe0/BC obtained at 700 ℃. This enhanced reactivity was directly related to the electron transfer of Fe0 stimulated by MgFe2O4 as well as the conversion of passive corrosion products into Fe3O4 facilitated by soluble Fe2+ components. The predicted maximum adsorption capacity of MBC700120-400–30 was 85.43 mg/g (pH = 5) and the removal of Cr(VI) was dominated by chemisorption. The reduction of Cr(VI) to Cr(Ⅲ) was identified as the principal removal mechanism. Overall, this study demonstrates a novel strategy for developing functional Fe0-based materials for water contamination treatment.

Realizing High Reversible Zinc Metal Anode by Modulating Surface Chemistry and Crystal Structure

AbstractThe uncontrollable dendrite growth on the Zn metal anode severely deteriorates the capacity and cycling stability of aqueous zinc–ion batteries (AZIBs), thereby retarding their practical application. In this work, through the combination of surface chemistry and crystal structure regulation, a duplex route of plasma sputtering and mechanical stretching is proposed to remove surface passivation layer and increase surface crystal defect (dislocations and textures) of Zn metal anode itself. Plasma sputtering can almost completely remove the surface passivation layer, ensuring a uniform Zn2+ flux at the interface, which is conducive to uniform nucleation. Mechanical stretching can increase the surface dislocation density and (002) texture, the former can reduce Zn2+ nucleation barrier, while the latter can guide Zn to grow parallel to the surface, inhibiting the growth of dendrites. Consequently, the as‐fabricated symmetrical cells exhibit stable and long lifespan (3560 h at 0.5 mA cm−2 for 0.5 mA h cm−2). The assembled full cells with α‐MnO2 cathode deliver a nearly 100% average coulombic efficiency even after 1000 cycles at 5 A g−1. Coupling a surface chemistry regulation with crystal structure control will be enlightening for solve the issues of metallic anodes in advanced metallic‐based batteries.

Mitigation of charge heterogeneity by uniform in situ coating enables stable cycling of LiCoO2 at 4.6V

LiCoO2 is a predominant cathode for lithium-ion batteries of portable electronics owing to its merit of high volumetric energy density. Nevertheless, it experiences rapid capacity deterioration under high voltages, concomitant with structural degradation and numerous intragranular cracks. Coating has been recognized as an efficacious strategy to ameliorate the decline in cycling performance of LiCoO2 at high voltages. Hence, a systematic elucidation of the precise mechanisms underlying the mitigation of structural degradation via coating layers assumes paramount importance in the context of advancing the next generation of high-voltage LiCoO2. In this work, the intricate interrelation among lithium-ion diffusion coefficients, charge heterogeneity, and crack distribution is explicated through techniques inclusive of galvanostatic intermittent titration technique (GITT), finite element analysis (FEA), and X-ray computed tomography (XCT). A robustly stable lithium-ion-conducting coating material serves the function of curtailing the occurrence of surface passivation layers, achieved by diminishing side reactions between the LiCoO2 and the electrolyte; while a uniform coating ensures a homogeneous lithium-ion flux, thereby mitigating charge heterogeneity and the resultant mechanical strain as well as intragranular cracks. Both are important elements that collectively allow the coating to effectively protect the surface from structural degradation, thus achieving superior performances upon high-voltage charging.