Passivation Layer Research Articles

Influence of Process Conditions During Aqueous and Direct Recycling of NMC811 Cathodes.

This study investigated the impact of various process conditions on the aqueous, direct recycling of LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes. Three model systems were used. The first system assumes that the current collector delamination is performed in a dry environment without the use of water as a process medium. Consequently, the NMC811 is only exposed to water during classification, where no aluminum foil is present. The second model system assumes that the current collector delamination occurs in water. Therefore, the NMC811 is exposed to water in the presence of aluminum foil. Due to the pH increase caused by the Li+/H+ exchange reaction, the pH value surpasses the stability window of the aluminum-oxide passivation layer (pH 4.5-8.5), resulting in the deposition of aluminum-containing species on the NMC811 surface. The third model system is identical to the second, with the exception that H3PO4 is added. This causes the pH to decrease and prevents corrosion of the aluminum foil. The findings reveal that process conditions significantly affect the surface chemistry on NMC811, influencing electrochemical performance. Notably, aluminum-containing species increase polarization. Heat treatment simulating regeneration led to cation mixing as surface species diffused into the NMC811 bulk structure, highlighting the need to control recycling process conditions.

Solution-Processed Fabrication of Ni3S2-Based Nanoheterostructure on Silicon Heterojunction Photocathode for Boosting Solar Hydrogen Generation.

Silicon heterojunction (SHJ) solar cell is an advanced and mature photovoltaic cell. Development of photoelectrochemical (PEC) water splitting devices for hydrogen fuel production using SHJ solar cells is considered as a promising approach to address energy crisis. To achieve this goal, it is necessary to deposit passivation layer and cocatalyst layer on the photoelectrode. However, the development of low-cost and scalable preparation methods for high-quality passivation and cocatalyst layer continues to be a significant challenge. Herein, an efficient passivation layer and hydrogen evolution reaction (HER) catalyst are successfully fabricated via solution processed methods. To improve the HER activity of Ni3S2, a Ni3S2-based nanoheterostructure of crystalline Ni3S2, Ni, and amorphous Y(OH)3 is constructed. The optimized photocathode exhibits excellent PEC-HER performance, which achieves a saturated photocurrent of -35.5mA cm-2 and an applied bias photon-to-current efficiency (ABPE) of 8.4 ±0.1% under simulated AM1.5G one-sun illumination and more than 120h of continuous water splitting. This study paves a way for the design and large-scale manufacturing of cost-efficient SHJ photocathode devices.

Atypical Attack of the Dissimilar Metal Welds of a Water–Water Energetic Reactor Nuclear Power Plant Secondary Circuit: Possible Mechanisms of Failure

ABSTRACTDissimilar metal welds are utilized in the energy industry to connect two materials with different material characteristics. In the case of nuclear power plants, the connected materials tend to be low‐alloyed steel and high‐alloyed material. Despite different material and corrosion properties, under the proper environmental conditions, the used construction materials and weld metals are protected either by a passive layer or by a high‐temperature oxide. Although dissimilar metal welds are used in both primary and secondary circuits, the most frequently documented damage is in the secondary circuit, where, in addition to material heterogeneities, local environmental heterogeneities may form. For dissimilar metal welds in WWER nuclear power plants, a water–water energetic reactor, a subtype of pressure water reactor, we note two main types of attack near the dissimilar fusion boundary: on the carbon steel side or on the high‐alloyed weld metal side (X10CrNiMoN16‐25‐6). The possible causes of the latter “atypical” corrosion attack are debated and can be generalized as a consequence of change of the grain boundary condition.

Numerical investigation on the polarization-dependent light extraction of 275-nm AlGaN based nanowire with bowtie antenna array or passivation layer

Abstract The low light extraction efficiency (LEE) is one of the major factors hindering the application of AlGaN based deep ultraviolet (DUV) light-emitting diodes (LEDs). Here we investigate the LEE of AlGaN based nanowire (NW) DUV LEDs emitting at 275 nm for bare NW, NW integrated with aluminum (Al) bowtie antenna array, and NW with passivation layer under transverse-electric (TE) and transverse-magnetic (TM) polarization. It is observed that by integrating plasmonic Al bowtie antenna array with AlGaN based NW, the LEE up to 83% and 74% can be achieved under TE and TM polarization. In addition, the effect of the three different passivation layer SiO2, SiNx and AlN on the LEE of AlGaN based NW is also analysed, the results suggests that SiO2, which has smaller refractive index than NW core, could extract more photons from the NW and lead to large enhancement of LEE. For SiNx and AlN passivation layer, which has refractive index similar to the NW core, have strong coupling with the NW core, when the thickness of passivation layer satisfy resonance coupling conditions, the LEE could be achieved more than 80% for both TE and TM polarization. These integrated NW/antenna array and NW with passivation layer system can provide guidelines for designing other nano-photonic devices.

Influence of Chloride and Electrolyte Stability on Passivation Layer Evolution at the Negative Electrode of Mg Batteries Revealed byoperandoEQCM-D.

Rechargeable magnesium batteries are promising for future energy storage. However, among other challenges, their practical application is hindered by low coulombic efficiencies of magnesium plating and stripping. Fundamental processes such as the formation, structure, and stability of passivation layers and the influence of different electrolyte components on them are still not fully understood. In this work, we gain unique insights into the initial Mg plating and stripping cycles by comparing Mg bis(trifluoromethanesulfonyl)imide (Mg(TFSI)2)- and Mg tetrakis(hexafluoroisopropyloxy)borate (Mg[B(hfip)4]2)-based electrolytes, each with and without MgCl2, on gold electrodes by highly sensitive operando electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D) applying hydrodynamic spectroscopy. With the stable Mg[B(hfip)4]2-based electrolytes, highly efficient and interphase-free cycling is possible and passivation layers are attributed to electrolyte contaminants. These are forming and degrading during the so-called initial conditioning process. With the more reactive Mg(TFSI)2-based electrolyte, thick passivation layers with small pores are growing during cycling. We demonstrate that the addition of chloride lowers the amount of passivated Mg deposits in these electrolytes and accelerates the currentless dissolution of the passivation layer. This has a positive effect since we observe the most efficient cycling and uniform deposition when no interphase is present on the electrode.

Influence of Chloride and Electrolyte Stability on Passivation Layer Evolution at the Negative Electrode of Mg Batteries Revealed by operando EQCM‐D

Rechargeable magnesium batteries are promising for future energy storage. However, among other challenges, their practical application is hindered by low coulombic efficiencies of magnesium plating and stripping. Fundamental processes such as the formation, structure, and stability of passivation layers and the influence of different electrolyte components on them are still not fully understood. In this work, we gain unique insights into the initial Mg plating and stripping cycles by comparing Mg bis(trifluoromethanesulfonyl)imide (Mg(TFSI)2)‐ and Mg tetrakis(hexafluoroisopropyloxy)borate (Mg[B(hfip)4]2)‐based electrolytes, each with and without MgCl2, on gold electrodes by highly sensitive operando electrochemical quartz crystal microbalance with dissipation monitoring (EQCM‐D) applying hydrodynamic spectroscopy. With the stable Mg[B(hfip)4]2‐based electrolytes, highly efficient and interphase‐free cycling is possible and passivation layers are attributed to electrolyte contaminants. These are forming and degrading during the so‐called initial conditioning process. With the more reactive Mg(TFSI)2‐based electrolyte, thick passivation layers with small pores are growing during cycling. We demonstrate that the addition of chloride lowers the amount of passivated Mg deposits in these electrolytes and accelerates the currentless dissolution of the passivation layer. This has a positive effect since we observe the most efficient cycling and uniform deposition when no interphase is present on the electrode.

Effect of Ag, Sn, and SiCN Surface Coating Layers on the Reliability of Nanotwinned Cu Redistribution Lines Under Temperature Cycling Tests

Nanotwinned Cu (NT-Cu) is a promising candidate for Cu redistribution lines (RDLs). However, oxidation in NT-Cu lines is of concern because it increases electrical resistance and endangers the reliabilities of semiconductor devices such as temperature cycling tests (TCTs). In order to enhance the reliabilities, the passivation of NT-Cu lines is needed. In this study, immersion Ag/Sn and plasma-enhanced chemical vapor deposition (PECVD) SiCN were used to passivate the surfaces of NT-Cu RDLs at low operating temperatures (60 °C for immersion and 150 °C for PECVD). We found that Ag- and SiCN-capped NT-Cu lines showed negligible changes in microstructures and resistance after TCTs. As for Sn-coated NT-Cu lines, the resistance remained stable after 250 cycles of TCTs, with low oxygen signals detected. These three coating layers can block oxygen and moisture, effectively preventing oxidation and maintaining the resistance of NT-Cu RDLs during the TCT. The findings demonstrate the effectiveness of Ag, Sn, and SiCN coatings in enhancing reliability, providing options for passivation layers of NT-Cu RDLs.

Linked variations of bioleaching performance, extracellular polymeric substances (EPS) and passivation layer in the uranium bacterial-leaching system

Linked variations of bioleaching performance, extracellular polymeric substances (EPS) and passivation layer in the uranium bacterial-leaching system

Indium Oxide Layer Dual Functional Modified Bismuth Vanadate Photoanode Promotes Photoelectrochemical Oxidation of Water to Hydrogen Peroxide.

The photoelectrochemical (PEC) dual-electron pathway for water oxidation to produce hydrogen peroxide (H2O2) shows promising prospects. However, the dominance of the four-electron pathway leading to O2 evolution competes with this reaction, severely limiting the efficiency of H2O2 production. Here, we report a In2O3 passivator-coated BiVO4 (BVO) photoanode, which effectively enhances the selectivity and yield of H2O2 production via PEC water oxidation. Based on XPS spectra and DFT calculations, a heterojunction is formed between In2O3 and BVO, promoting the effective separation of interface and surface charges. More importantly, Mott-Schottky analysis and open-circuit potential measurements demonstrate that the In2O3 passivation layer on the BVO photoanode shifts the hole quasi-Fermi level towards the anodic direction, enhancing the oxidation level of holes. Additionally, the widening of the depletion layer and the flattening of the band bending on the In2O3-coated BVO photoanode favor the generation of H2O2 while suppressing the competitive O2 evolution reaction. In addition, the coating of In2O3 can also inhibit the decomposition of H2O2 and improve the stability of the photoanode. This work provides new perspectives on regulating PEC two/four-electron transfer for selective H2O2 production via water oxidation.

Synergistic effect of FeOOH cocatalyst and Al2O3 passivation layer on BiVO4 photoanode for enhanced photoelectrochemical water oxidation

BiVO4 is one of the most attractive photoanodes for water oxidation due to its 2.4 eV narrow band gap, suitable band edge position, good stability in aqueous solution, low cost and non-toxicity. However, due to some inherent disadvantages such as low carrier mobility, severe charge recombination and slow water oxidation kinetics, the actual BiVO4 photocurrent density is often lower than the theoretical value of 7.5 mA cm−2. In this paper, BiVO4 was modified by alkali-treated Al2O3 passivation layer and FeOOH, and the photocurrent density of BiVO4 reached an astonishing 3.8 mA cm−2 at 1.23 VRHE, and the ABPE (applied bias photon-to-current efficiency) was close to 1 %. The detailed structural characterization and electrochemical test show that Al2O3 prepared by ALD (atomic layer deposition) can play a role in passivation of BiVO4 surface state after alkali treatment, inhibit electron hole recombination on BiVO4 surface, and accelerate hole transfer. As a hole storage layer and catalyst layer, FeOOH promoted the interfacial hole transfer, increased the active sites at the electrode electrolyte interface, and significantly increased the water oxidation activity. This work provides a novel method to enhance the performance of water electrolysis by using ALD to assist passivation of bismuth vanadate photoanode surface states.

Water-Mediated Surface Engineering Enhances High-Voltage Stability of Fast-Charge LiCoO2 Cathodes.

Maintaining the surface structure stability of LiCoO2 (LCO) during rapid charge-discharge processes (>5C) and under high-voltage conditions (>4.2 V) is challenging due to interfacial side reactions, cobalt dissolution, and oxygen redox activity at deeply delithiated states, all of which contribute to performance degradation. Herein, different from traditional surface coating methods, we report a water-mediated strategy that modifies the surface architecture of LCO, creating a passivating layer to inhibit surface degradation and enhance cycling stability under fast charging conditions. The surface etching of LCO by H2O is accompanied by a concurrent Li+/H+ cation exchange, which passivates surface oxygen with H+ ions, thereby enhancing both the hydrophobicity and structural stability. Consequently, the modified LCO exhibits superior capacity retention, which is 2.5 times that of the pristine LCO, after 100 cycles at a current density of 1000 mA g-1 (∼6C at 4.5 V). Even at an elevated temperature of 45 °C, it maintains impressive cycling stability at a current density of 500 mA g-1 (∼3C), as demonstrated in practical full-cell configurations. Investigation with multiple samples confirmed that the water-mediated strategy demonstrated broad applicability. We emphasize that the water-mediated modification of the surface architecture on cathode materials offers significant insights into enhancing the stability of high-energy-density lithium-ion batteries (LIBs).

Passivation Effect of Rock-Salt Nitride Materials on a Planar p-Si Photocathode for Solar Water Reduction.

Photoelectrochemical water splitting, which uses sunlight to produce clean hydrogen fuel, is gaining traction with rising concerns about fossil fuels and pollution. Silicon (Si) photocathodes are promising for this process due to their light absorption and favorable band alignment for hydrogen production. However, limitations such as reflectance, low photovoltage, and rapid photocorrosion hinder their overall performance and stability. An interfacial insulating layer such as SiOx ensures superior durability to p-Si photocathodes. However, the inherent heterogeneity and intrinsic defects pose challenges to effective surface passivation. This study investigates the challenges of photocorrosion and utilization of a thin titanium nitride (TiN) passivation layer deposited using direct-current magnetron sputtering to protect the native silicon oxide (SiOx) layer. Additionally, a molybdenum oxynitride (Mo(O,N)x) bifunctional layer is employed to enhance both the electrocatalytic activity and durability of the photocathode. The presence of oxygen and nitrogen within this cocatalyst layer modifies the surface chemistry of the p-Si photocathode, promoting favorable interfacial interactions with electrolyte species during PEC reactions. This modification facilitates efficient charge transfer processes and accelerates reaction kinetics, ultimately optimizing the performance and operational lifetime of the photocathode. The resulting Mo(O,N)x/TiN/p-Si photocathode exhibited a remarkable onset potential of +0.46 VRHE in harsh acidic conditions under simulated sunlight (AM 1.5G illumination, 100 mW·cm-2). Notably, the photocathode demonstrated exceptional long-term stability exceeding 140 h, highlighting the combined TiN passivation and Mo(O,N)x cocatalyst as a protection strategy.

Additive effect of Li on electrical property of ZnO passivation layer to control dendritic growth of Zn during recharge processes

This study investigates the effect of Li+ on the dendritic growth of Zn anodes in the presence of a ZnO passivation layer formed after discharge, with particular attention to the initial recharge process. 0.1 mol dm−3 Li+ effectively suppresses dendrites, while 2 mol dm−3 Li+ addition facilitates the same. The difference in Zn dendrite formation behavior is also indicated by the attenuation tendency of the potential oscillation accompanied by hydrogen evolution reaction during recharge. This is attributed to Li+ concentration dependence of the properties of the ZnO passivation layer formed during Zn anode discharge. Li+ modulates the carrier density of ZnO by altering its crystalline defect characteristics; the carrier density of ZnO with 0.1 mol dm−3 Li+ addition becomes approximately three times as high as that without additive owing to the oxygen vacancies and interstitial zinc that form additional donor level. By contrast, 2 mol dm−3 Li+ reduces the carrier density of ZnO by inducing zinc vacancies to form acceptor levels. The highly conductive ZnO produced by adding 0.1 mol dm−3 Li+ improves the reaction uniformity during recharge, which suppresses dendrite formation. This study provides valuable insight into the mechanisms and control strategies of Zn dendrite growth during the charge-discharge cycling of alkaline Zn rechargeable batteries.

Enhanced Stability of N‐Type Organic Electrochemical Transistors Via Small‐Molecule Passivation

AbstractOrganic electrochemical transistors (OECTs) are of great interest owing to their potential applications in bioelectronics and neuromorphic systems. However, n‐type OECTs suffer from poor stability and facile degradation, mainly due to the oxygen reduction reactions in organic mixed ionic‐electronic conductors during device operation. In this study, a small‐molecule passivation strategy is introduced to greatly improve the stability of poly(benzobisimidazobenzophenanthroline) (BBL)‐based n‐type OECTs. 6,6‐Phenyl‐C61‐butyric acid methyl ester (PCBM) is spin‐coated onto the BBL layer to form a smooth and hydrophobic passivation layer, which effectively inhibits the oxygen reduction reactions while enabling ion permeation in aqueous electrolytes. Consequently, the OECTs employing the PCBM/BBL bilayers with an optimized PCBM thickness exhibit significantly improved operational stability at various electrolyte conditions (0.1 m NaCl or NaOH) and over a wide gate‐voltage sweep range (from −0.7 to 0.7 V). Owing to the high electron mobility of PCBM, the carrier mobility and switching speed of the PCBM/BBL OECTs are also improved compared with those of the pristine BBL OECTs. This study demonstrates the beneficial effects of simple surface passivation in organic mixed ionic‐electronic conductors and provides valuable insights for the design of high‐performance and stable OECTs for more specialized and advanced applications.

Potential-Dependent ATR-SEIRAS and EQCM-D Analysis of Interphase Formation in Zinc Battery Electrolytes.

With the heightening interest in bivalent battery technology, there arises a necessity for a thorough investigation into zinc-ion battery (ZIB) electrolytes, accommodating their chemical attributes and potential-dependent structural dynamics. While the phenomenon of in situ solid electrolyte interphase formation is extensively documented in lithium-ion batteries, its analogous occurrences in ZIBs remain limited. Herein is a comparative study of three zinc electrolytes of interest: ZnSO4, ZnOTF, and Zn(TFSI)2/LiTFSI hybrid water-in-salt electrolyte. Additionally, the impact of an acetonitrile additive is scrutinized, with a comparative assessment of the interfacial behavior in aqueous solutions. Utilizing ATR-SEIRAS, potential-dependent alterations in the composition of the electrolyte/electrode interface were monitored, while EQCM-D facilitated a comprehensive understanding of variations in the mass and structural properties of the adsorbed layer. Aqueous ZnSO4 demonstrated the accumulation of porous Zn4SO4(OH)6·xH2O at negative potentials, leading to a mass of 1.47 μg cm-2 after five cycles. Bisulfate formation was observed at positive potentials. SEIRAS measurements for ZnOTF demonstrated reorientation and surface adsorption of CF3SO3- to favor CF3 at the surface for positive potentials, and acetonitrile showed increased stability for the electrode at negative potentials. The additive was also reported to lead to the accumulation of a substantial passivation layer with viscoelastic properties. The zinc water-in-salt showed exceptional surface stability at negative potentials and a widened potential window. A thin rigid zinc SEI layer is reported with a mass of 0.7 μg cm-2. The compositional intricacies of these surface structures are discussed in relation to their solvent conditions. This investigation not only sheds light on the initial charge/discharge cycles in ZIBs but also underscores their pivotal role in instigating enduring transformations that can significantly influence their long-term cycling performance.

Chemical magnetic field-assisted batch polishing method of 316L stainless steel

316L stainless steel has been extensively employed in the manufacturing of medical equipment and biomedical implants because of its good ductility, corrosion resistance and biocompatibility, etc. However, there has always been a non-neglected problem of low polishing precision and efficiency in the whole machining chain for such parts, hence, it is difficult to meet the batch demand of the market for 316L stainless steel with high-precision surface. Based on the principle of magnetic field-assisted batch polishing (MABP) proposed by our research team previously, a novel chemical magnetic field-assisted batch polishing (CMABP) method here is developed by adding chemical reagents (i.e., the mixture of oxalic acid and hydrogen peroxide) in the preparation process of regular magnetic brush, desiring and expecting to further realize the polishing of 316L stainless steel with higher precision and efficiency simultaneously. The preliminary experimental results demonstrated that the value of surface roughness Sa after CMABP became smaller and the material removal rate increased comparing to that after MABP, which did verify the potential advantage of the established CMABP approach. In detail, CMABP experiments with pH value and H2O2 concentration as variables were carried out quantitatively. The results suggested that, within the set range of pH value (from 2 to 7) and H2O2 concentration (from 0.3 wt.% to 2.0 wt.%), when pH was chosen as 4 and H2O2 concentration was adjusted as 2.0 wt.%, the value of Sa after CMABP was the minimum, which could be 38% lower than that of MABP approximately. Nonetheless, material removal rate reached to the maximum, which could be around 168% more than that after MABP, when pH and H2O2 concentration were determined as 3.0 and 2.0 wt.%, respectively. Additionally, the discrepancy between the chemical and the regular magnetic brushes were detected and analyzed comparatively both at macro and micro scales. Also, the products on the surface of 316L stainless steel, such as the weak-binding layer and the passive layer, were discovered and taken to interpret the experimental phenomena of the surface roughness and material removal rate varying with the content of chemical reagents in CMABP, thereby revealing the material removal mechanisms correspondingly and interestingly. This work is capable of providing valuable reference undoubtedly for batch precision polishing of 316L stainless steel and other significant functional materials.

Effect of ultra-thin ZnS passivation using ALD technique on the performance of heterojunction solar cells

Hybrid solar cells (HSCs) using poly (3,4-ethylenedioxy-thiophene) polystyrene sulfonate (PEDOT:PSS) and n-silicon provide heterojunctions with the potential of light trapping, cost effectiveness, and high efficiency. However, charge recombination at rear interface hampers built-in potential and power conversion efficiency (PCE). Here, a superior, conformal, and uniform ultra-thin layer of Zinc sulfide (ZnS) is deposited on rear interface using atomic layer deposition (ALD) technique. The ALD-deposited ZnS thin layer serves as a passivation, electron conductive, and hole-blocking layer. The optimized HSCs exhibit a remarkable PCE of 12.37 % alongside a high open-circuit voltage of 0.625 V and a substantial fill factor of 71.5 %. These advancements stem from enhanced back junction quality between n-Si and electrode. The outcomes demonstrate an effective suppression of charge recombination and enhanced charge transfer facilitated by ALD-deposited ZnS thin layer, resulting an improved photovoltaic performance.

Density functional theory study on vanadium selective leaching separation from iron in stone coal via Fe2O3 (001) surface passivation

When vanadium is extracted from stone coal, iron impurities readily precipitate and reduce the purity of the vanadium product. Thus, separating vanadium from iron impurities at source is essential. The mechanism of surface passivation of Fe2O3 (001) for the selective leaching separation of vanadium from iron in stone coal was established in the present work. Analysis of mineral phase transformation and microscopic morphology indicates that Fe2O3 in stone coal can undergo a reaction with HF and F-. Subsequently, the hematite surface was covered with FeF3 passivation layer, resulting in the inhibition of hematite dissolving reaction. The results of density functional theory (DFT) computations demonstrate that the HF and F- can reform the Fe2O3 (001) surface via sedimentary behavior at mineral interface, and the adsorption energy can be down to -99.93kJ/mol for the F- adsorption configuration. During sulfuric acid leaching with CaF2 as an aiding agent, the transfer of electrons from Fe atoms to F atoms can weaken the stable Fe-F bonds and decrease the reactive activation of Fe atoms in Fe2O3. This study demonstrates the separation of vanadium from iron by means of hematite passivation in the attendance of fluoride at the atomic level of analysis.

The Corrosion-Inhibitory Influence of Graphene Oxide on Steel Reinforcement Embedded in Concrete Exposed to a 3.5M NaCl Solution

Steel reinforcement corrosion significantly reduces the durability and service life of concrete structures, particularly in chloride-rich environments such as marine and coastal areas. This study aims to reduce the corrosion rate using graphene oxide (GO) as a corrosion inhibitor. Two GO dosages (0.0005 and 0.005 wt.%) were evaluated for their effectiveness in mitigating corrosion in reinforced concrete exposed to a 3.5M NaCl solution. To assess the corrosion behavior of the steel reinforcement, Open Circuit Potential (OCP), Electrochemical Impedance Spectroscopy (EIS), and Linear Polarization Resistance (LPR) were evaluated to monitor corrosion over one year by of wetting/drying cycles. Oxygen permeability and electrical resistivity tests were also conducted to evaluate the concrete's susceptibility to corrosion. Both GO content demonstrated significant corrosion inhibition, with the 0.005 wt.% dosage providing the most effective protection. This was evidenced by the lowest icorr values recorded during the final cycle (52), larger capacitive loops, and higher impedance in EIS results, indicating enhanced corrosion resistance. Visual inspection of steel bars further confirmed these findings, showing no signs of deterioration or discoloration in GO-modified concrete compared to steel bars extracted from reference concrete. SEM-EDS analysis revealed higher carbon content on the steel surface, suggesting GO adsorption and the formation of a protective passive layer. These results suggest that GO is a promising nanomaterial for inhibiting corrosion in steel-reinforced concrete exposed to aggressive environmental conditions.

Directly Regenerating of Spent LiCoO2 with Gradient F-Doped Subsurface towards Ultra-Stable Storage Properties.

As great potential recycling strategy, the direct regeneration of spent LiCoO2 (LCO) is beneficial for lowering environmental pollutions and promoting global sustainability. However, owing to the using of binder and electrolyte, some fluorine impurities would be remained into spent materials. Considering the doping behaviors of F-elements, their suitable content introducing would facilitate the energy-storage abilities of regenerated LCO. Herein, through the tailored introduction of F-elements, spent LCO are successfully regenerated with physical-chemical evolutions. Benefitting from the existed oxygen vacancies, the diffusion energy-barrier of F-elements is reduced from 1.73 eV to 0.61 eV, facilitating the establishment of gradient F-doped subsurface, along with the formation of rigid CoO5F. Meanwhile, excess F-elements (1 wt %, as a threshold) lead to the formation of LiF passivation layer on the surface. Thus, the as-optimized sample displays a considerable capacity of 154.4 mAh g-1 even at 5.0 C, with retention rate (88.3 %) in 3.0-4.5 V. Supported by detailed electrochemical and kinetic analysis, the structural advantages are confirmed to boost the improved redox activity of Co-ions and the alleviating of irreversible oxygen-release. Give this, the work is anticipated to reveal the evolutions of regenerated LCO with the introduced F-elements, whilst providing the practical regeneration strategies toward excellent high-voltage properties.