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Iron-based superconductors (FeSCs), particularly the air-stable (Li,Fe)OHFeSe, have drawn considerable attention due to their complex crystalline structures and intriguing superconducting properties. This study focuses on the synthesis of (Li,Fe)OHFeSe, using hydrothermal ion exchange technology with a nearly vacancy-free (PY) x FeSe precursor. We successfully synthesized samples in both iron-poor and iron-rich reaction systems, with the iron-rich samples exhibiting superconductivity at a transition temperature ( T c ) of 40 K, while iron-poor samples did not. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) results showed an obvious difference in Se content between the original solutions of iron-poor and iron-rich systems after the hydrothermal reaction. We propose that in iron-rich system, Fe 2+ ions migration into the (Li,Fe)OH layer from the reaction solution directly maintains the stability of the FeSe layer in the precursor, facilitating superconductivity. Conversely, in iron-poor system, Fe 2+ ions migrate into the (Li,Fe)OH layer partly from the reaction solution and partly from the FeSe layer, creating Fe vacancies in the FeSe layer, which inhibit the occurrence of superconductivity. Our findings provide valuable insights into the synthesis of intercalated FeSe-based superconducting materials and the realization of superconductivity in FeSe based superconducting materials.

As pioneering Fe 3 O 4 nanozymes, their explicit peroxidase (POD)-like catalytic mechanism remains elusive. Although many studies have proposed surface Fe 2+ -induced Fenton-like reactions accounting for their POD-like activity, few have focused on the internal atomic changes and their contribution to the catalytic reaction. Here we report that Fe 2+ within Fe 3 O 4 can transfer electrons to the surface via the Fe 2+ -O-Fe 3+ chain, regenerating the surface Fe 2+ and enabling a sustained POD-like catalytic reaction. This process usually occurs with the outward migration of excess oxidized Fe 3+ from the lattice, which is a rate-limiting step. After prolonged catalysis, Fe 3 O 4 nanozymes suffer the phase transformation to γ-Fe 2 O 3 with depletable POD-like activity. This self-depleting characteristic of nanozymes with internal atoms involved in electron transfer and ion migration is well validated on lithium iron phosphate nanoparticles. We reveal a neglected issue concerning the necessity of considering both surface and internal atoms when designing, modulating, and applying nanozymes. The mechanism of peroxidase-like Fe 3 O 4 nanozymes remains elusive. Here, the authors show the electron transfer mechanism of Fe(II) ions to regenerate surface Fe(II) and the related phase transformation and depletion of activity.

To reveal the influencing process and mechanism of seawater intrusion on groundwater Fe in coastal zones, the local groundwater in Buzhuang Town, together with those in the neighboring area where no seawater intruded, was sampled and comparatively analyzed, and the static simulation experiments were also performed in laboratory. The local groundwater has Fe levels of 6.09–196.96 μg/L, with an average of 73.38 μg/L, but groundwater Fe levels from the neighboring area are 1.3–17.7 times of those in local groundwater. Such facts indicate the groundwater Fe levels decreased due to seawater intrusion. The groundwater Fe levels are significantly negatively correlated with pH, significantly positively correlated with Ca2+, Mg2+, and positively correlated with SO42−. The simulation experiments indicate leached Fe increases with a greater mixture of seawater, increasing concentrations of NaCl and CaCl2, but decreases with increasing NaHCO3 concentrations. Fe(OH)2 and Fe(OH)3 minerals are super-saturated because of the high pH and high OH− concentration resulting from seawater intrusion. By this way, the dissolving ability of groundwater Fe is restricted. Therefore, pH is the key factor determining groundwater Fe levels in coastal zones. Another, the decreasing of Ca2+, Mg2+ in groundwater decreases Fe levels because of the co-precipitation and deactivation of groundwater Fe. Salt effect and NaHCO3 contribute less to groundwater Fe levels because of the restriction of maximum Fe solubility by high OH− and super-saturation of Fe-bearing minerals. The influencing model of groundwater Fe levels under the effect of seawater intrusion is forwarded.

By employing metal oxides as oxygen carriers, chemical looping demonstrates its effectiveness in transferring oxygen between reduction and oxidation environments to partially oxidize fuels into syngas and convert CO2 into CO. Generally, NiFe2O4 oxygen carriers have demonstrated remarkable efficiency in chemical looping CO2 conversion. Nevertheless, the intricate process of atomic migration and evolution within the internal structure of bimetallic oxygen carriers during continuous high‐temperature redox cycling remains unclear. Consequently, the lack of a fundamental understanding of the complex ionic migration and oxygen transfer associated with energy conversion processes hampers the design of high‐performance oxygen carriers. Thus, in this study, we employed in situ characterization techniques and theoretical calculations to investigate the ion migration behavior and structural evolution in the bulk of NiFe2O4 oxygen carriers during H2 reduction and CO2/lab air oxidation cycles. We discovered that during the H2 reduction step, lattice oxygen rapidly migrates to vacancy layers to replenish consumed active oxygen species, while Ni leaches from the material and migrates to the surface. During the CO2 splitting step, Ni migrates toward the core of the bimetallic oxygen carrier, forming Fe–Ni alloys. During the air oxidation step, Fe–Ni migrates outward, creating a hollow structure owing to the Kirkendall effect triggered by the swift transfer of lattice oxygen. The metal atom migration paths depend on the oxygen transfer rates. These discoveries highlight the significance of regulating the release–recovery rate of lattice oxygen to uphold the structures and reactivity of oxygen carriers. This work offers a comprehensive understanding of the oxidation/reduction‐driven atomic interdiffusion behavior of bimetallic oxygen carriers. During chemical looping CO2 conversion, in situ environmental transmission electron microscopy–electron energy loss spectroscopy combined with quasi in situ X‐ray photoelectron spectroscopy, and theoretical calculations have been utilized to reveal the migration and diffusion processes of lattice oxygen and metal atoms inside oxygen carriers. It is highlighted that the structure of the oxygen carrier depends on the migration rate of lattice oxygen.

Metal sulfide oxidation in abandoned exposed stone coal mines leads to the generation of Acid Mine Drainage (AMD), characterized with high uranium concentration, which is a major concern for local public health. This work employed approaches of geochemical analysis and modeling to determined the mode of occurrence of uranium. Additionally, potential environmental risks were evaluated. The results revealed that the primary source of uranium pollutants in the surrounding environmental media was attributed to the weathering of mine wastes. The acidity and concentrations of harmful metals (e.g., U, Fe) and sulfate in water rapidly decreased to background level with increasing distance from the mine. The geochemical distribution characteristics of sediments and water exhibited notable similarities. The species of uranium underwent a transformation as uranium in mine waste rocks migrated to environmental media. In acidic pit water, uranium primarily existed as uranyl sulfate, gradually transitioning downstream to complexes dominated by hydrophosphate and carbonate. This transition was accompanied by the coprecipitation of significant amounts of uranium with phosphate and iron hydroxides. Results from the geoaccumulation index (I geo ) and risk assessment codes (RAC) indicated that uranium in unweathered waste rocks and newly formed pit sediments posed a high environmental risk, with a bioavailable fraction reaching up to 26.44% and 48.0%, respectively. This research holds significant importance in devising remediation and management strategies for abandoned coal mines to mitigate the impact of uranium release and mobility on the surrounding ecological environment. Highlights The weathering of stone coal waste is the main source of uranium pollution. Newly formed pit poses strong acid generation capacity and high environmental risk. The mode of occurrence and environmental conditions determine the mobility of uranium.

The behavior of iron (Fe) in clayey aquitards has a significant effect on the groundwater environment. However, the release processes and impact of Fe within clayey sediments during compaction remain unknown. Two groups of simulation experiments were carried out to demonstrate the migration and transformation mechanisms of Fe during clayey sediment compaction. Experiment A, which simulated a natural deposition condition, revealed that pressurization changed the reaction environment from oxidative to reductive by isolating oxygen. Oxidation of ferrous ions was followed by reduction dissolution of poorly crystalline Fe (III) and crystalline Fe (III) oxides. Under the microbial utilization of organic matter, the main transformation process of sediment Fe was the dissimilatory reduction of poorly crystalline Fe (III) oxides. The total Fe concentration in pore water was 0.09–11.61 mg/L, with ferrous ions predominating among the Fe species. The lower moisture content (<~36%) in the later stage of compaction inhibited the dissimilatory reduction of Fe (III), and the formation of Fe (II) minerals resulted in a decrease in Fe concentration. Experiment B, which simulated an artificial compaction state, revealed that the sediment Fe was primarily released by physical dissolution because of changes in pore structure and solubility. The concentration of total Fe in pore water was 0.02–1.96 mg/L, with a significant increase in response to a rapid increase in pressure. According to the estimates in the Chen Lake wetland (eastern China), the contribution of clay pore water release accounted for 19.9–31.9% of the average Fe concentration in groundwater during natural deposition.

Cysteine desulfurase (NFS1) is highly expressed in a variety of tumors, which is closely related to ferroptosis of tumor cells and affects prognosis. The relationship between NFS1 and the development of gastric cancer (GC) remains unknown. Here we showed that NFS1 expression was significantly higher in GC tissues compared to adjacent normal tissues. Patients with high expression of NFS1 in GC tissues had a lower overall survival rate than those with low expression. NFS1 was highly expressed in cultured GC cells compared to normal gastric cells. Knockdown of NFS1 expression reduced the viability, migration and invasion of GC cells. In cultured GC cells, NFS1 deficiency promoted ferroptosis. Mechanistically, NFS1 inhibited ferroptosis by upregulating the signal transduction and activator of transcription 3 (STAT3) signaling pathway in cultured GC cells. NFS1 knockdown using siRNA inhibited the STAT3 pathway, reduced the expression of glutathione peroxidase 4 (GPX4) and solute carrier family 7 member 11 (SLC7A11), and elevated intracellular levels of reactive oxygen species (ROS), ferrous ion (Fe2+), and malondialdehyde (MDA) in cultured GC cells. A specific STAT3 activator significantly reversed the inhibitory effect of NFS1 deficiency on ferroptosis in cultured GC cells. These in vitro results were further confirmed by experiments in vivo using a mouse xenograft tumor model. Collectively, these results indicate that NFS1 is overexpressed in human GC tissues and correlated with prognosis. NFS1 inhibits ferroptosis by activating the STAT3 pathway in GC cells. These results suggest that NFS1 may be a potential prognostic biomarker and therapeutic target to treat GC.

Considering the complex coupling of steel corrosion in partially saturated concrete filled with water, the quantitative description of control mechanisms is still under debate. This work provides new experimental evidence supporting that diffusion control (relative diffusion coefficient) is the dominant mechanism in controlling corrosion rate by limiting the ferrous ion migration in unsaturated concrete. Furthermore, a new mechanism-based kinetic model is developed to predict the corrosion rate in different cementitious materials and corrosion conditions. In addition, the proposed kinetic model can quantify the variation of critical [Cl − ]/[OH − ] with degree of saturation, classify corrosive conditions, and predict the electrical resistivity and corrosion rate relationships.

Arsenic (As) migration and transformation in the supergene environment and eucalyptus planting have essential effects on ecology or even human health, respectively. However, the combined environmental impact of As migration and transformation and eucalyptus planting has not been studied. Here we report a case of soil As contamination caused by eucalyptus planting and address the fate of As in Longmen county, Guangdong Province, China. We found high As content in weathered arsenopyrite bearing granite or granite-derived soil, where a large area of eucalyptus is planted. The release of organic acids from eucalyptus roots promoted the electrochemical reaction of arsenopyrite to produce AsO33−. In the subsequent supergene migration process, As species change from arsenite to arsenate with the addition of oxygen and the effect of clay minerals, last with As infiltration, precipitation, and enrichment, forming the As contamination in soil. The whole process reveals the activation process of eucalyptus to the As source (arsenopyrite), the migration and transformation process of As in the supergene environment, and the formation mechanism of soil As contamination. This finding provides a new perspective of soil As contamination around arsenopyrite bearing granite of the Nanling area with eucalyptus planting and proposes that the negative effects of Nanling eucalyptus planting may be greater than expected.

High-temperature structural materials face severe degradation challenges due to oxidation and corrosion, leading to reduced long-term stability and performance. This review comprehensively examines the interfacial migration mechanisms of reactive elements (REs) such as Ti, Al, and Cr in Ni/Fe-based alloys, emphasizing their role in forming and stabilizing protective oxide layers. We discuss how these oxide layers impede ion migration and mitigate environmental degradation. Key findings highlight the importance of selective oxidation, oxide layer healing, and the integration of novel alloying elements to enhance resistance under ultra-supercritical conditions. Advanced insights into grain boundary engineering, alloy design strategies, and quantum approaches to understanding charge transport at passive interfaces are also presented. These findings provide a foundation for developing next-generation high-temperature alloys with improved degradation resistance tailored to withstand extreme environmental conditions.