Ion pair sites for efficient electrochemical extraction of uranium in real nuclear wastewater.

Electrochemical uranium extraction from nuclear wastewater represents an emerging strategy for recycling uranium resources. However, in nuclear fuel production which generates the majority of uranium-containing nuclear wastewater, fluoride ion (F-) co-exists with uranyl (UO22+), resulting in the complex species of UO2Fx and thus decreasing extraction efficiency. Herein, we construct Tiδ+-PO43- ion pair extraction sites in Ti(OH)PO4 for efficient electrochemical uranium extraction in wastewater from nuclear fuel production. These sites selectively bind with UO2Fx through the combined Ti-F and multiple O-U-O bonds. In the uranium extraction, the uranium species undergo a crystalline transition from U3O7 to K3UO2F5. In real nuclear wastewater, the uranium is electrochemically extracted with a high efficiency of 99.6% and finally purified as uranium oxide powder, corresponding to an extraction capacity of 6829 mg g-1 without saturation. This work paves an efficient way for electrochemical uranium recycling in real wastewater of nuclear production.

The efficient uptake of uranium by amine-functionalized ß-cyclodextrin supported fly ash composite from polluted water.

A novel polyethyleneimine/polydopamine-functionalized ß-cyclodextrin supported fly ash adsorbent (PEI/PDA/ß-CD/FA) had been synthesized to uptake uranium from polluted water. At pH = 5.0 and T = 298 K, the uranium uptake efficiency and capacity of PEI/PDA/ß-CD/FA reached to 98.7 % and 622.8 mg/g, respectively, which were much higher than those of FA (71.4 % and 206.7 mg/g).The excellent uranium uptake properties of PEI/PDA/ß-CD/FA could be explained by three points: (1) using ß-CD as a supporting material could effectively avoid the aggregation of FA and improve the hydrophily of FA; (2) the unique cavity structure of ß-CD could form chelates with uranyl ions; (3) the formation of PEI/PDA co-deposition coating on FA further enhanced the affinity of FA to UO22+. With the presence of interfering ions, the uptake efficiency of PEI/PDA/ß-CD/FA for uranium was still up to 94.5 % after five cycles, indicating the high selectively and recoverability of PEI/PDA/ß-CD/FA. In terms of the results of characterizations, uranium was captured by PEI/PDA/ß-CD/FA via electrostatic attraction, hydrogen bond, coordination and complexation. To sum up, PEI/PDA/ß-CD/FA was expected to be used for actual sewage treatment owing to its excellent uranium uptake efficiency/capacity, selectivity, cycle stability and feasibility of actual application.

Preliminary construction of a microecological evaluation model for uranium-contaminated soil.

With the extensive development of nuclear energy, soil uranium contamination has become an increasingly prominent problem. The development of evaluation systems for various uranium contamination levels and soil microhabitats is critical. In this study, the effects of uranium contamination on the carbon source metabolic capacity and microbial community structure of soil microbial communities were investigated using Biolog microplate technology and high-throughput sequencing, and the responses of soil biochemical properties to uranium were also analyzed. Then, ten key biological indicators as reliable input variables, including arylsulfatase, biomass nitrogen, metabolic entropy, microbial entropy, Simpson, Shannon, McIntosh, Nocardioides, Lysobacter, and Mycoleptodisus, were screened by random forest (RF), Boruta, and grey relational analysis (GRA). The optimal uranium-contaminated soil microbiological evaluation model was obtained by comparing the performance of three evaluation methods: partial least squares regression (PLS), support vector regression (SVR), and improved particle algorithm (IPSO-SVR). Consequently, partial least squares regression (PLS) has a higher R2 (0.932) and a lower RMSE value (0.214) compared to the other. This research provides a new evaluation method to describe the relationship between soil ecological effects and biological indicators under nuclear contamination.

Photosynthetic Responses of Racomitrium japonicum L. to Strontium Stress Evaluated through Chlorophyll a Fluorescence OJIP Transient Analysis.

Nuclides pollution and its biological effects are of great concern, especially for bryophytes during their terrestrial adaptation. Understanding PSII activity and electron transport response is vital for comprehending moss abiotic stress reactions. However, little is known about the photosynthetic performance of moss under nuclide treatment. Therefore, this study aimed to evaluate the chlorophyll fluorescence of Racomitrium japonicum L. The moss was subjected to Sr2+ solutions at concentrations of 5, 50, and 500 mg/L to evaluate chlorophyll a fluorescence using the OJIP test. Moderate and high Sr2+ stress led to inner cell membrane dissolution and reduced chlorophyll content, indicating impaired light energy absorption. At 5 mg/L Sr2+, fluorescence kinetics showed increased light energy capture, energy dissipation, and total photosynthetic driving force, thus stimulating transient photosynthetic activity of PSII and improving PSI reduction. Linear electron transfer and PSII stability significantly decreased under moderate and high Sr2+ stress, indicating potential photosynthetic center damage. Cyclic electron transfer (CEF) alleviated photosynthetic stress at 5 mg/L Sr2+. Thus, low Sr2+ levels stimulated CEF, adjusting energy flux and partitioning to protect the photosynthetic apparatus. Nevertheless, significant damage occurred due to inefficient protection under high Sr2+ stress.

Enhancing Commercially Iron Powder Electron Transport by Surface Biosulfuration to Achieve Uranium Extraction from Uranium Ore Wastewater.

The zero-valent iron (ZVI) has attracted increasing attention due to the enhanced reactivity of ZVI to uranium wastewater. However, ZVI practical application is hampered due to its susceptibility to oxidation and the formation of passivation layers during storage and in situ restoration. To address these issues, we used a biosulfuration approach to modify ZVI for application in uranium ore wastewater treatment. A series of physicochemical characterization tools and photoelectronic analyses showed that BS-ZVI considerably increased carrier separation efficiency and visible light absorption capacity, resulting in a significant photoassisted enhancement effect on uranium extraction. Accordingly, the uranium removal efficiency of BS-ZVI reached 91% within 60 min, and its maximum adsorption capacity was 336.3 mg/g. By analyzing the mechanism, the improved U(VI) removal performance was mostly responsible on the dissolution of the passivation layer on the surface of ZVI, the generation of Fe(II) and FeS, and the important role of Shewanella putrefaciens extracellular polymers (EPS). Overall, the BS-ZVI biohybrid merges with the high activity of ZVI, bio-FeS, and self-regeneration ability of bacteria, expanding a promising new approach for sustainable treatment of uranium mine wastewater.

Effects of biochar pyrolysis temperature on uranium immobilization in soil remediation: Revealed by 16S rDNA and metabolomic analyses.

Uranium-stressed soil caused by nuclear industry development and energy acquisition have attracted extensive attentions for a long time. This study investigated the effects of biochar application with different pyrolysis temperatures (300 â„ƒ, 500 â„ƒ and 700 â„ƒ) on remediation of uranium-stressed soil. The results showed that higher pyrolysis temperature (700 â„ƒ) was benefit for ryegrass growing and caused a lower uranium accumulation in plants. At the same time, uranium immobilization was more effective at higher biochar pyrolysis temperature. Careful investigations indicated that activities of soil urease and sucrase were promoted, and bacterial diversity was strengthened in C700 group, which may contribute to uranium immobilization. The biochar application could activate metabolic of lipids and amino acids, organic acids and derivatives, and organic oxygen compounds. Nicotinate and nicotinamide metabolism, and Benzoxazinoid biosynthesis were unique metabolic pathways in the C700 group, which could enhance the uranium tolerance from different perspectives. Based on these results, we recommend to use biochar with 700 °C pyrolysis temperature when processing remediation of uranium-stressed soil. This study will facilitate the implementation of biochar screening and provide theoretical helps for remediation of uranium-stressed soil.

In Situ Metal-Oxygen-Hydrogen Modified B-Tio2 @Co2 P-X S-Scheme Heterojunction Effectively Enhanced Charge Separation for Photo-assisted Uranium Reduction.

Photo-assisted uranium reduction from uranium mine wastewater is expected to overcome the competition between impurity ions and U(VI) in the traditional process. Here, B-TiO2 @Co2 P-X S-scheme heterojunction with metal-oxygen-hydrogen (M-O-H) is developed insitu modification for photo-assisted U(VI) (hexavalent uranium) reduction. Relying on the DFT calculation and Hard-Soft-Acid-Base (HSAB) theory, the introduction of metal-oxygen-hydrogen (M-O-H, hard base) metallic bonds in the B-TiO2 @Co2 P-X is found to enhance the hydrophilicity and the capture capability for uranyl ion (hard acid). Accordingly, B-TiO2 @Co2 P-500 hybrid nanosheets exhibit excellent U(VI) reduction ability (>98%) in the presence of competing ions. By self-consistent energy band calculations and in-situ KPFM spectral analysis, the formation of the internal electric field between B-TiO2 and Co2 P at the heterojunction is proven, offering a strong driving force and atomic transportation highway for accelerating the S-scheme charge carriers directed migration and promoting the photocatalytic reduction of uranium. This work provides a valuable route to explore the functionally modified photocatalyst with high-efficiency photoelectron separation for U(VI) reduction.

Unveiling the Critical Role of Surface Hydroxyl Groups for Electro-Assisted Uranium Extraction from Wastewater.

The electro-driven extraction of uranium from fluorine-containing uranium wastewater is anticipated to address the challenge of separating fluoro-uranium complexes in conventional technologies. Herein, we developed hydroxy-rich cobalt-based oxides (CoOx) for electro-assisted uranium extraction from fluorine-containing wastewater. Relying on theoretical calculations and other spectral measurements, the hydroxy-rich CoOx nanosheets can enhance the affinity for uranium due to the existence of a substantial quantity of hydroxyl groups. Accordingly, the CoOx nanosheets exhibit outstanding U(VI) removal efficiency in the presence of fluorine ions. Through the utilization of X-ray absorption fine structure (XAFS), we confirm that hydroxy-rich CoOx nanosheets capture free uranyl ions to form a sturdy 2Oax-1U-3Oeq configuration, which can be achieved through electro-driven fluorine-uranium separation. Notably, for the first time, the whole reaction process of uranium species on the CoOx surface from the initial uranium single atom growth to uranium oxide nanosheets is monitored by aberration-corrected transmission electron microscopes (AC-TEM). This work provides a paradigm for the advancement of novel functional materials as electrocatalysts for uranium extraction, as well as a new approach for studying the evolution mechanism of uranium species.

In-situ constructing amidoxime groups on metal-free g-C3N4 to enhance chemisorption, light absorption, and carrier separation for efficient photo-assisted uranium(VI) extraction.

The development of inexpensive and efficient semiconductor catalysts for photo-assisted uranium extraction from seawater remains a huge challenge. Herein, we have successfully synthesized amidoxime-rich g-C3N4 (AO-C3N4) by simply amidoximing a cyano-rich precursor for photo-assisted uranium extraction from seawater. The amidoxime groups not only served as the U(VI) binding sites for efficient uranium adsorption, but also significantly improved the visible light absorption capacity and carrier separation efficiency via introducing defect energy level, resulting in the excellent photocatalytic activity for AO-C3N4 towards photo-assisted uranium extraction. In the process of photo-assisted uranium extraction, U(VI) was first adsorbed by the amidoxime groups on the AO-C3N4 and then reduced to U(IV), while (UO2)O2·2H2O and (UO2)O2·4H2O were further formed by the oxidation of U(IV) by superoxide radicals (·O2-). Moreover, the generated reactive oxygen species (ROS) under light endowed AO-C3N4 with outstanding antibacterial properties, preventing the limitation of uranium extraction capacity from marine biofouling.

Thermal Air Oxidation-Mediated Synchronous Coordination and Carbonation of Lanthanum on Biochar toward Phosphorus Adsorption from Wastewater.

Biochar has attracted increasing attention as the sustainable and structure-tunable carrier for lanthanum (La) species for diverse applications. Carbonated La species possesses a higher biocompatibility and a lower leaching potential than other commonly used La species, while less attention is paid on the application of carbonated La in phosphorus (P) adsorption. Herein, thermal air oxidation (TAO) was applied as a novel strategy for synchronously tuning the coordination environment and chemical species of La on biochar surface. The results demonstrated that TAO induced the coordination of La with oxidation-generated oxygenated functional groups (OFGs) and carbonation of La species by the oxidation-generated CO2 on the biochar surface. The batch adsorption results showed that the Qm of resultant biochar remarkably increased from 68.92 to 132.49 mg/g at 1 g/L dosage. It also showed a robust adsorption stability in pH 2-6, a strong resistance to the co-existing Cl-, SO42-, NO3-, CO32-, or HCO3-, a stable adsorption recyclability, and an ultralow La leaching potential. The P adsorption was dominated by ligand exchange-induced inner-sphere complexation. In practical swine wastewater, the resultant biochar composite (1 g/L) removed 99.87% of P from 92.3 to 0.12 mg/L at a practical pH of 7.12. The density functional theory calculation further revealed the significant role of the binding of carbonated La by the biochar surface OFGs in reducing the P adsorption energies, indicating the synergism between the oxygenated biochar carrier and the carbonated La in P adsorption. Finally, this study provided a novel route to synchronously tune the coordination environment and chemical species of La on biochar via a facile TAO process for high-efficient P adsorption from wastewater.

Effects of Torrefaction Pretreatment on the Structural Features and Combustion Characteristics of Biomass-Based Fuel.

Wheat straw, a typical agricultural solid waste, was employed to clarify the effects of torrefaction on the structural features and combustion reactivity of biomass. Two typical torrefaction temperatures (543 K and 573 K), four atmospheres (argon, 6 vol.% O2, dry flue gas and raw flue gas) were selected. The elemental distribution, compositional variation, surface physicochemical structure and combustion reactivity of each sample were identified using elemental analysis, XPS, N2 adsorption, TGA and FOW methods. Oxidative torrefaction tended to optimize the fuel quality of biomass effectively, and the enhancement of torrefaction severity improved the fuel quality of wheat straw. The O2, CO2 and H2O in flue gas could synergistically enhance the desorption of hydrophilic structures during oxidative torrefaction process, especially at high temperatures. Meanwhile, the variations in microstructure of wheat straw promoted the conversion of N-A into edge nitrogen structures (N-5 and N-6), especially N-5, which is a precursor of HCN. Additionally, mild surface oxidation tended to promote the generation of some new oxygen-containing functionalities with high reactivity on the surface of wheat straw particles after undergoing oxidative torrefaction pretreatment. Due to the removal of hemicellulose and cellulose from wheat straw particles and the generation of new functional groups on the particle surfaces, the ignition temperature of each torrefied sample expressed an increasing tendency, while the Ea clearly decreased. According to the results obtained from this research, it could be concluded that torrefaction conducted in a raw flue gas atmosphere at 573 K would improve the fuel quality and reactivity of wheat straw most significantly.

Enhanced soft magnetic properties and high-frequency stability of FeNiMo powder cores by coating SiO2 insulation layer.

FeNiMo/SiO2 powder cores were prepared using the sol-gel method. Tetraethyl orthosilicate (TEOS) was added to produce an amorphous SiO2 coating outside the FeNiMo particles to form a core-shell structure. The thickness of the SiO2 layer was designed by varying the concentration of TEOS, and the optimized permeability and magnetic loss of the powder core could achieve 78.15 and 633.44 kW m-3 at 100 kHz and 100 mT, respectively. Compared with other soft magnetic composites, these FeNiMo/SiO2 powder cores have a significantly higher effective permeability and a lower core loss. Surprisingly, the high-frequency stability of permeability could be substantially enhanced through the insulation coating process in which µf/µ100 kHz could reach 98.7% at 1 MHz. In comparison with 60µ commercial products, the comprehensive soft magnetic properties of the FeNiMo/SiO2 cores were superior to most manufacturers, which would be potentially applied to high-performance inductance devices in high-frequency ranges.

Amplified Single-Atom U-O Interfacial Effect Originated from U 5f-O 2p Hybridization over UOx/GO for Enhanced Nitrogen Reduction Reaction.

Uranium-based catalysts have been regarded as promising candidates for N2 fixation owing to the low-valent uranium metal active sites possessing the ability to enhance the electron back-donating to the π* antibonding orbitals of N2 for N≡N dissociation. Herein, we report a directional half-wave rectified alternating current electrochemical method to confine oxygen-rich uranium precursors over ultrathin 2D GO nanosheets. The as-prepared uranium catalysts exhibit a considerable Faradaic efficiency of 12.7% for NH3 and the NH3 yield rate of 18.7 µg h-1 mg-1 for N2 electroreduction. Operando XAS and isotope-labeling FTIR further unravel the preferred nitrogen adsorption reaction intermediate N-(2Oax-1 U-4Oeq) and confirm the key *N2Hy intermediate species derived from the fed N2 gas. Theoretical simulations demonstrate that the U-O atomic interface originated from U 5f-O 2p orbital hybridization can accumulate partial charge from GO, which can facilitate the N≡N dissociation and lower the thermodynamic energy barrier of the first hydrogenation step.

Preparation of biochar@chitosan-polyethyleneimine for the efficient removal of uranium from water environment.

A novel chitosan-based composite with rich active sites was synthesized by uniformly dispersing biochar into the cross-linked network structure formed by chitosan and polyethyleneimine. Due to the synergistic effect of biochar (minerals) and chitosan-polyethyleneimine interpenetrating network (amino and hydroxyl), the chitosan-based composite possessed an excellent adsorption performance for uranium(VI). It could rapidly (<60 min) achieve a high adsorption efficiency (96.7 %) for uranium(VI) from water and a high static saturated adsorption capacity (633.4 mg/g), which was far superior to other chitosan-based adsorbents. Moreover, the separation for uranium(VI) on the chitosan-based composite was suitable for a variety of actual water environments and the adsorption efficiencies all exceeded 70 % in different water bodies. The soluble uranium(VI) could be completely removed by the chitosan-based composite in the continuous adsorption process, which could meet the permissible limits of the World Health Organization. In sum, the novel chitosan-based composite could overcome the bottleneck of current chitosan-based adsorption materials and become a potential adsorbent for the remediation of actual uranium(VI) contaminated wastewater.

Construction of dopamine supported Mg(Ca)Al layered double hydroxides with enhanced adsorption properties for uranium.

A novel dopamine-supported Mg(Ca)Al layered double hydroxide composite was synthesized by co-precipitation method. The existence of Ca2+ and dopamine could promote the capture of uranium on the layered double hydroxides. In batch experiments, the composite exhibited good uranium removal performance, including high adsorption capacity (687.3 mg/g), strong anti-interference and good reusability (the removal percentage was still higher than 90 % after five cycles). At low initial uranium concentration, the uranium removal percentage on the composite exceeded 99.7 % and the residual concentration of uranium in the solution was <0.03 mg/L, reaching the limited standard of the World Health Organization. The studies of adsorption kinetics and isotherm indicated that the uranium adsorption behavior on the composite conformed to the pseudo-second-order kinetic and Langmuir isotherm models, suggesting that the process was a monolayer adsorption dominated by chemical adsorption. Furthermore, the high-efficiency uranium adsorption on the Mg(Ca)Al layered double hydroxide was mainly attributed to the strong complexation between the active sites (-OH and -NH2) and uranium, the precipitation of interlayer intercalation ions (CO32- and OH-) to uranium and the ion exchange of Ca2+ to uranium. Due to these advantages, the dopamine-supported Mg(Ca)Al layered double hydroxide composite is expected to be used as fine adsorbent to remove uranium from wastewater.

Mussel inspired synthesis of polydopamine/polyethyleneimine-grafted fly ash composite adsorbent for the effective separation of U(VI).

Polydopamine/polyethyleneimine-grafted fly ash composite (PDA/PEI/FA), an efficient multifunctional adsorbent for U(VI) with excellent separation efficiency (94.5 %) and capacity (422.5 mg/g), was synthesized by grafting PDA and PEI on FA via Mussel inspiration and Michael addition reaction. The introduction of PDA and PEI had brought numerous functional groups with fine affinities to uranium, like catechol, amino and imino, causing good U(VI) separation performances. Langmuir and Pseudo-second-order models were well matched with experimental data, illustrating the U(VI) separation on PDA/PEI/FA was a homogeneous chemical adsorption process. After five cycles, the U(VI) adsorption efficiency for PDA/PEI/FA was still up to 90.2 %, implying that PDA/PEI/FA possessed good stability and reusability. Besides, the good dynamic adsorption performances of PDA/PEI/FA further demonstrated that PDA/PEI/FA was an ideal adsorbent for the practical wastewater treatment. According to the characterization results, U(VI) was absorbed by PAD/PEI/FA through complexation, redox reaction, electrostatic attraction and hydrogen bonding. Given the above, PDA/PEI/FA showed good practical application prospect in U(VI) separation.

A critical review on the development of lanthanum-engineered biochar for environmental applications.

Biochar and lanthanum (La) have been widely used in environment. However, there is a lack of knowledge and perspective on the development of La-engineered biochar (LEB) for environmental applications. This review shows that LEBs with a variety of La species via pre-/post-doping routes are developed for environmental applications. Specifically, precipitation, gelation, and calcination are the common sub-processes involved in the pre-/post-doping of La on the resultant LEB. The dominant La species for LEBs is La(OH)3, which is formed through precipitation of La ions with various bases. Various La carbonates, e.g., LaOHCO3, La2(CO3)3, La2CO5, and NaLa(CO3)2, are also involved in the preparation of LEBs. The LEBs are high-efficient in the adsorption of phosphate, arsenic, antimonate and fluoride ions, attributed to the strong affinity of La to oxyanions and Lewis hard base. Lanthanum is also favorable for co-doping with transition metal species to further enhance the performances in adsorption or catalysis. This review also analyzes the prospects and future challenges for the preparation and application of LEBs in environment. Finally, this review is beneficial to inspire new breakthroughs on the preparation and environmental application of LEBs.

Efficient Strategy for U(VI) Photoreduction: Simultaneous Construction of U(VI) Confinement Sites and Water Oxidation Sites.

Reduction of hexavalent uranium [U(VI)] by the photocatalytic method opens up a novel way to promote the selectivity, kinetics, and capacity during uranium removal, where organic molecules act as the sacrificial agents. However, the addition of sacrificial agents can cause a secondary environmental pollution and increase the cost. Here, a UiO-66-based photocatalyst (denoted as MnOx/NH2-UiO-66) simultaneously with efficient U(VI) confinement sites and water oxidation sites was successfully developed, achieving excellent U(VI) removal without sacrificial agents. In MnOx/NH2-UiO-66, the amino groups served as efficient U(VI) confinement sites and further decreased the U(VI) reduction potential. Besides, MnOx nanoparticles separated the photogenerated electron-hole pairs and provided water oxidation sites. The U(VI) confinement sites and water oxidation sites jointly promoted the U(VI) photoreduction performance of MnOx/NH2-UiO-66, resulting in the removal ratio of MnOx/NH2-UiO-66 for U(VI) achieving 97.8% in 2 h without hole sacrifice agents. This work not only provides an effective UiO-66-based photocatalyst but also offers a strategy for effective U(VI) photoreduction.

Non-targeted metabolomics and 16s rDNA reveal the impact of uranium stress on rhizosphere and non-rhizosphere soil of ryegrass.

As a radioactive heavy metal element with a long half-life, uranium causes environmental pollution when it enters the surrounding soil. This study analyzed the changes about soil enzyme activity, non-targeted metabolomics, microbial community structure and function microbial community structure and function to assess the differences in the effects of uranium stress on rhizosphere and non-rhizosphere soil. Results showed that uranium stress significantly inhibited the activities of urease and sucrase in rhizosphere and non-rhizosphere, which had less effect on rhizosphere. Compare to the non-rhizosphere soil, the uranium stress induced the production of gibberellin A1, to promoted several metabolic pathways, such as nitrogen and PTS (Phosphotransferase system) metabolic in rhizosphere soil. The species and abundance of Aspergillus, Acidobacter, and Synechococcus in both rhizosphere and non-rhizosphere soil were decreased by uranium stress. However, the microorganisms in rhizosphere soil were less inhibited according to the soil metabolism and microbial network map analysis. Furthermore, the Chujaibacter in rhizosphere soil under uranium stress was found significantly positively correlated with lipid and organic oxygen compounds. Overall, the results indicated that ryegrass roots significantly alleviated the effects of uranium stress on soil microbial activity and population abundances, thus playing a protective role. The study also provided a theoretical basis for in-depth understanding of the biological effects, prevention and control mechanisms of uranium-contaminated soil.

Actinide-uranium single-atom catalysis for electrochemical nitrogen fixation.

Actinide-based catalysts have been regarded as promising candidates for N2 fixation owing to their unique 5f orbital with flexible oxidation states. Herein, we report for the first time the dispersion of uranium (U) single atoms on TiO2 nanosheets via oxygen vacancy confinement for N2 electroreduction. The single-atom U catalyst exhibited a high NH3 yield of 40.57 µg h-1 mg-1, with a reasonably high Faraday efficiency of 25.77%, ranking first among the reported nitrogen-free catalysts. Isotope-labeling operando synchrotron infrared spectroscopy verifies that the key *N2Hy intermediate species was derived from the N2 gas of the feed. By using operando X-ray absorption spectroscopy, we found enhanced metal-support interaction between U single atoms and TiO2 lattice with more U-Olatt coordination under working conditions. Theoretical simulations suggest that the evolved 1Oads-U-4Olatt moieties act as a critical electron-feedback center, lowering the thermodynamic energy barrier for the N2 dissociation and the first hydrogenation step. This work provides the possibility of tailoring the interaction between metal active sites and supports for designing high-performance actinide-based single-atom catalysts.