Metallicity Research Articles

Interface Engineering and Modulation of Nickel Oxide for High Air-Stable p-Type Crystalline Silicon Solar Cells.

Dopant-free passivating contact crystalline silicon solar cells hold the potential of higher efficiency and cost down. In the hole-transport terminal, one still faces the challenge of trade-off between efficiency and stability. In this work, a H-Al2O3/NiOx/Ni stacked hole-transport layer is proposed, where the H-Al2O3 standing for H-rich Al2O3 film can effectively reduce the interfacial defects and the high work function Ni metal results in a low contact resistance of 47.12mΩcm2. Consequently, the solar cell achieves an efficiency of 20.51%, with a fill factor of 84.83%, demonstrating satisfactory stability. This work provides a strategy for reducing interfacial defects and highlights the potential of stacked structure design for enhancing passivated contact solar cell performance.

Degradation of Methylene Blue by Ozone Oxidation Catalyzed by the Magnetic MnFe2O4@Co3S4 Nanocomposite.

In this study, the MnFe2O4@Co3S4 magnetic nanocomposite was prepared by a two-step hydrothermal method and used to catalyze the ozone oxidation degradation of methylene blue. It was characterized by XRD, EDS, SEM, FT-IR, and XPS. The results showed that the introduction of Co3S4 made MnFe2O4 grow uniformly on Co3S4 nanosheets, which effectively prevented the agglomeration of MnFe2O4. Moreover, MnFe2O4 provided active sites and Mn3+/Mn2+ and Fe3+/Fe2+ cycles for the ozone oxidation process. Not only did Co3S4 provide the active site (Co2+/Co3+) for the ozone oxidation process but also its derived S2-/S22- accelerated the electron transfer rate on the surface of the material, thus improving the efficiency of catalytic ozone oxidation degradation of methylene blue. When the molar ratio of MnFe2O4 to Co3S4 was 6:3 (MnFe2O4@Co3S4-3), the catalytic ozone degradation efficiency of methylene blue was the best, which reached 93.55% in 12 min. The reactive oxygen species in catalytic ozonation degradation of MB were 1O2, O2.-, and ·OH. The MnFe2O4@Co3S4 magnetic nanocomposite is an efficient and stable O3 activator, which maintains high catalytic activity and low metal ion leaching after five cycles, indicating that it has a good application prospect in catalyzing ozone oxidation to degrade organic pollutants.

Environmental monitoring of La Concordia mine (Salta province, Argentina): assessing heavy metal bioaccumulation and physiological responses of Parastrephia quadrangularis.

The Puna region is distinguished by its extreme environmental conditions and highly valuable mining resources. However, the unregulated management of mine tailings poses a significant threat to the ecological integrity of this region. This study assesses the environmental impacts of mine tailings at La Concordia mine (Salta province, Argentina) and examines the physiological and biochemical adaptations of Parastrephia quadrangularis (Meyen) Cabrera that enable its survival under this extreme conditions. Our findings reveal that prolonged weathering of mine tailings results in the generation of acid mine drainage characterized by low pH levels (< 3.5) and elevated concentrations of As, Fe, Cu, Pb, and Zn. These levels exceed drinking water standards by 5-10 times for As, 6-13 times for Zn, 80-120 times for Pb, 20-380 times for Fe, and 4-10 times for Cu. Soil analyses highlight low pH, high salinity, and elevated concentrations of Zn (310mgkg-1), Pb (153mgkg-1), and Cu (128mgkg-1). Despite these harsh environmental conditions, 7 plant species where identified, with Parastrephia quadrangularis being the only species present at the most polluted site. This species exhibits high heavy metal bioaccumulation and robust tolerance mechanisms against heavy metal-induced oxidative damage, as evidenced by stable total chlorophylls and malondialdehyde content, and increased levels of carotenoids, proline, and phenolic compounds. These findings emphasize Parastrephia quadrangularis as a promising candidate for revegetation and phytostabilization for sustainable mine closure programs in La Puna region.

Stellar population and metal production in AGN disks

Stellar population and metal production in AGN disks

Strategies of physiological, morpho-anatomical and biochemical adaptation in seedlings of native species exposed to mining waste.

Seeds of four native species of trees and shrubs (Larrea cuneifolia, Bulnesia retama, Plectrocarpa tetracantha and Prosopis flexuosa) were exposed to soil contaminated with As, Cu, Cd, and Zn from an abandoned gold mine to identify adaptation strategies. Several physiological, morpho-anatomical, and biochemical parameters were determined. The seed germination of L. cuneifolia, B. retama, and P. tetracantha was fully inhibited in 100 % contaminated soil. Toxicological endpoints as NOEC, LOEC and IC50 ranged from 10 % to 25 % of soil contaminated with mining waste. Radicle elongation was the most sensitive variable to high metal(loid) concentrations, except for L. cuneifolia that hypocotyl elongation was the most affected parameter. P. flexuosa was selected to evaluate biochemical biomarkers and morpho-anatomical parameters. It showed an increase in radicle diameter and central radicle cylinder. A concentration-dependent increase in the O2·- production was observed in radicle and cotyledon. A peak of the enzymatic activity of guaiacol peroxidase, ascorbate peroxidase and catalase enzymes in P. flexuosa seedlings showed a negative relationship between metal(loid) concentration and exposure time. After a drop in the enzymatic activity, an increase in the malondialdehyde content (lipid peroxidation) was observed. The tested native species could be useful for phytoremediation of soils with a very high degree of metal contamination. A further investigation should focus on strategies to improve soil physicochemical characteristics for plant survival at highest contamination levels.

Physical properties of circumnuclear ionising clusters II. NGC 7469

Circumnuclear star-forming regions (CNSFRs) found close to galactic nuclei are ionised by massive clusters. These entities give us an excellent opportunity to study star formation in environments with high metallicity, and to relate it with active galactic nuclei. Our principal aim is to derive the physical properties and dynamical masses of the CNSFRs in the two rings of the spiral NGC 7469, categorised as a luminous infrared galaxy (LIRG) and hosting a Seyfert 1 nucleus. We used archival data obtained with the MUSE spectrograph. The galaxy shows two prominent star-forming rings, one of them very close to their active galactic nucleus, within 1.5 arcsec from the galaxy centre. We constructed 2D flux maps of the different emission lines and two continuum bands. A map of the EW(Hα) emission shows the circumnuclear regions within the rings having EW(Hα) &gt; 50 Å, consistent with the presence of recent star formation. All emission lines appear to have at least two kinematical components. We ascribe the most intense and narrow component to the emission lines originated by the ionising star-forming complexes (SFC) since they follow the radial velocity of the galaxy disc. For each HII region, we derived the number rate of Lyman continuum photons; the gas electron density; the ionisation parameter; the filling factor; and the mass of ionised hydrogen. We used sulphur as a tracer for chemical abundances with the temperature-sensitive SIII λ 6312 Å emission line having been measured in ∼ 50 % of the total, allowing the derivation of abundances by the direct method. The evolutionary state of the SFC was inferred with the help of population synthesis models yielding mean ages of 5.7 Ma, agreeing with the presence of the broad Wolf--Rayet (WR) carbon feature at λ 5800 Å detected in all the regions. Ionising (lower limits) and photometric SFC masses were estimated from the number of Lyman continuum photons and absolute r-magnitudes using stellar population synthesis techniques, and give median values of 2.3 times 10^6 and 6.9 times 10^6, respectively. The dynamical masses (upper limit) were derived from the measured absorption CaT velocity dispersion and the sizes of each cluster were measured on continuum light, assuming virialisation, and yield a median value of 6.7 times 10^8. Regions in the studied galaxy show sizes larger than implied by simple photo-ionisation models, which can be explained by the stellar winds produced by WR stars. The inner ring regions seem to be more compact than the outer ones. The young stellar population of the clusters has contributions of ionising populations with ages around 5 Ma, and its masses constitute less than 1% of the total dynamical mass of each SFC. Finally, the comparison between the characteristics of the inner and outer ring ionising clusters, together with their derived dynamical masses, point to circumnuclear regions close to the active galactic nucleus being more compact and having higher gas density.

Regulation of Extra Li Inventory in Anode-Free Lithium Metal Batteries by Li-Rich Layered Oxide Cathode Materials.

Li-rich layered oxide (LRO) cathode material is utilized in anode-free Li metal batteries to provide extra Li inventory, compensating for the constant Li loss during cycling. The Li compensation mechanism of LRO in the anode-free system is elucidated by exploring the reversible/irreversible Li consumption behaviors. Moreover, the relationship between cathode areal capacity, Li inventory, and the cycling performance of the Cu||LRO cell is quantitatively analyzed. The well-designed Cu||LRO anode-free cell demonstrates 51% capacity retention after 60 cycles at a practical areal capacity of 5.0 mAh cm-2, overwhelming the 0.6% capacity retention for Cu||NCM523. Further optimization with an artificial anode protection layer and a fully fluorinated electrolyte enhances the capacity retention of Cu||LRO to 61.4% and 71.5% after 60 cycles, respectively. Combining its low initial Coulombic efficiency and high specific energy, the LRO cathode shows great prospects in the future development of high energy and long lifespan anode-free Li metal batteries.

The SRG/eROSITA All-Sky Survey: Large-scale view of the Centaurus cluster

The Centaurus cluster is one of the brightest and closest clusters. Previous comprehensive studies were done only in its brightest part (r&lt;30'), where the centers of the main substructures (Cen 30 and Cen 45) are located, and only a small fraction of the outskirts has been studied. Through this work, we aim to characterize the intracluster medium (ICM) morphology and properties of the Centaurus cluster out to the radius within which the density is 200 times the critical density of the Universe at the redshift of the cluster, R_ We utilized the combined five SRG/eROSITA All-Sky Survey data (eRASS:5) to perform X-ray imaging and spectral analyses in various directions out to large radii. We employed some image manipulation methods to enhance small- and large-scale features. Surface brightness profiles out to 2R_200 were constructed to quantify the features. We acquired the gas temperature, metallicity, and normalization per area profiles out to R_200. We compared our results with previous Centaurus studies, cluster outskirts measurements, and simulations. Comprehensive sky background analysis was done across the field of view in particular to assess the variation of the eROSITA Bubble emission that partially contaminates the field. The processed X-ray images show the known sloshing-induced structures in the core, such as the cool plume, cold fronts, and ram pressure-stripped gas. The spectra in the core (r≤11 kpc ) are better described with a two-temperature (2T) model than an isothermal model. With this 2T analysis, we measured a lower temperature from the cooler component (∼!1.0 keV ) and a higher metallicity (∼!1.6Z_⊙), signifying an iron bias. In the intermediate radial range, the temperature peaks at ∼!3.6 keV and we observed prominent surface brightness and normalization per area excesses in the eastern sector (Cen 45 location). Temperature enhancements near the location of Cen 45 imply that the gas is shock-heated due to the interaction with Cen 30. We reveal that the eastern excess emission extends even further out, reaching R_500. The peak excess of normalization is located at ∼!23' from the center ($8'$ behind the center of Cen 45) with a $45%$ and $7.7σ$ above the full azimuthal value. This might be the tail or ram pressure-stripped gas from Cen 45. There is a temperature decrease of a factor of about two to three from the peak to the outermost bin at -R_ . We find good agreement between the outer temperatures (r&gt;R_2500) with the temperature profile from simulations and the temperature fit from cluster outskirts measurements. We detect significant surface brightness emission to the sky background level out to R_200 with a $3.5σ$, followed by $2.9σ$ at 1.1R_200. The metallicity at -R_ is low but within the ranges of other outskirts studies. We present the first whole azimuth beyond ∼!30' measurement of the ICM morphology and properties of the Centaurus cluster, and increasing the probed volume by a factor of almost 30. While the cluster core is rich in features as a result of active galactic nucleus feedback and sloshing, the cluster outskirts temperature of Centaurus follows the temperature profile of clusters in simulations as well as the temperature fit from other cluster outskirts measurements.

Nuclear level density and γ -ray strength function of Ni67 and the impact on the i process

Proton-γ coincidences from (d,p) reactions between a Ni66 beam and a deuterated polyethylene target have been analyzed with the inverse-Oslo method to find the nuclear level density (NLD) and γ-ray strength function (γSF) of Ni67. The Ni66(n,γ) capture cross section has been calculated using the Hauser-Feshbach model in using the measured NLD and γSF as constraints. The results confirm that the Ni66(n,γ) reaction acts as a bottleneck when relying on one-zone nucleosynthesis calculations. However, the impact of this reaction is strongly dampened in multizone models of low-metallicity AGB stars experiencing i-process nucleosynthesis. Published by the American Physical Society 2025

Dry-Solid-Electrochemical Synthesis: A General Method for Large Scale Synthesis of Single-Atom Catalysts with High Metal loadings.

Single-atom catalysts (SACs) with high metal loadings are highly desirable but still challenging for large scale synthesis. Here we report a new technique named as dry-solid-electrochemical synthesis (DSES) for a general large-scale synthesis of SACs with high metal loadings in an energy-conservation and environment-friendly way. With it, a series of pure carbon-supported metal SACs (Platinum up to 35.0 wt%, Iridium 21.2 wt%, Ruthenium 20.4 wt% and Iron 17.6 wt%) with high metal loadings were obtained. Particularly, a Pt SAC with Pt 23.9 wt% and remarkable oxygen reduction reaction (ORR) performance in fuel cells is synthesized on kilogram scale. Based on multiple control experiments, a unique redox mechanism for DSES process is proposed: metal precursors on conductive supports are reduced to metals via a homolytic cleavage of metal-halogen bonds by the attacking of electrons flowing through the dry solid phase. Such versatile technique paves a new economical and environment-friendly pathway for fabricating high-metal-loading SACs or atomic dispersion catalysts.

High-resolution imaging of the radio source associated with Project Hephaistos Dyson Sphere Candidate G

Abstract We present high-resolution e-MERLIN and EVN (e-VLBI) observations of a radio source associated with Dyson Sphere candidate G, identified as part of Project Hephaistos. The radio source, VLASS J233532.86-000424.9, is resolved into 3 compact components and shows the typical characteristics of a radio-loud AGN. In particular, the EVN observations show that it has a brightness temperature in excess of 108 K. No radio emission is detected at the position of the M-dwarf star. This result confirms our earlier hypothesis, that at least some of the Dyson Sphere candidates of project Hephaistos are contaminated by obscured, background AGN, lying close to the line of sight of otherwise normal galactic stars. High-resolution radio observations of other Dyson Sphere candidates can be useful in distinguishing truly promising candidates from those contaminated by background sources.

What Is the Mechanism by which the Introduction of Amorphous SeOx Effectively Promotes Urea-Assisted Water Electrolysis Performance of Ni(OH)2?

Nickel hydroxide (Ni(OH)2) is considered to be one of the most promising electrocatalysts for urea oxidation reaction (UOR) under alkaline conditions due to its flexible structure, wide composition and abundant 3D electrons. However, its slow electrochemical reaction rate, high affinity for the reaction intermediate *COOH, easy exposure to low exponential crystal faces and limited metal active sites that seriously hinder the further improvement of UOR activities. Herein it is reported electrocatalyst composed of rich oxygen-vacancy (Ov) defects with amorphous SeOx-covered Ni(OH)2 (Ov-SeOx/Ni(OH)2). Surprisingly, at 100 mA cm-2, compared with Ni(OH)2 (1.46 V (vs RHE)), Ov-SeOx/Ni(OH)2 has a potential of 1.35 V. Meanwhile, Ov-SeOx/Ni(OH)2 catalyst also showed good hydrogen evolution reaction (HER) performance, so it is used as the electrolytic cell assembled by UOR and HER bifunctional catalysts and only 1.57 V could reach 100 mA cm-2. Density functional theory (DFT) study revealed that introduce of amorphous SeOx optimizes the electronic structure of the central active metal, amorphous/crystalline interfaces promote charge-carrier transfer, shift d-band center and entail numerous spin-polarized electrons during the reaction, which speeds up the UOR reaction kinetics.

An Indication of Gas Inflow in Clumpy Star-forming Galaxies near z ∼ 1: Lower Gas-phase Metallicities in Clumpy Galaxies Compared to Nonclumpy Galaxies

Abstract Despite the ubiquity of clumpy star-forming galaxies at high-redshift, the origin of clumps are still largely unconstrained due to the limited observations that can validate the mechanisms for clump formation. We postulate that if clumps form due to the accretion of metal-poor gas that leads to violent disk instability, clumpy galaxies should have lower gas-phase metallicities compared to nonclumpy galaxies. In this work, we obtain the near-infrared spectrum for 42 clumpy and nonclumpy star-forming galaxies of similar masses, star formation rates, and colors at z ≈ 0.7 using the Gemini Near-Infrared Spectrograph (GNIRS) and infer their gas-phase metallicity from the [N ii]λ6584 and Hα line ratio. We find that clumpy galaxies have lower metallicities compared to nonclumpy galaxies, with an offset in the weighted average metallicity of 0.07 ± 0.02 dex. We also find an offset of 0.06 ± 0.02 dex between clumpy and nonclumpy galaxies in a comparable sample of 23 star-forming galaxies at z ≈ 1.5 using existing data from the FMOS-COSMOS survey. Similarly, lower [N ii]λ6584/Hα ratios are typically found in galaxies that have more of their UVrest luminosity originating from clumps, suggesting that clumpier galaxies are more metal-poor. We also derive the intrinsic velocity dispersion and line-of-sight rotational velocity for galaxies from the GNIRS sample. The majority of galaxies have σ 0/v c ≈ 0.2, with no significant difference between clumpy and nonclumpy galaxies. Our result indicates that clump formation may be related to the inflow of metal-poor gas; however, the process that forms them does not necessarily require significant, long-term kinematic instability in the disk.

A Possible Metal-dominated Atmosphere below the Thick Aerosols of GJ 1214 b Suggested by Its JWST Panchromatic Transmission Spectrum

Abstract GJ 1214b is the archetype sub-Neptune for which thick aerosols have prevented us from constraining its atmospheric properties for over a decade. In this study, we leverage the panchromatic transmission spectrum of GJ 1214b established by the Hubble Space Telescope (HST) and JWST to investigate its atmospheric properties using a suite of atmospheric radiative transfer, photochemistry, and aerosol microphysical models. We find that the combined HST, JWST/NIRSpec, and JWST/MIRI spectrum can be well explained by atmospheric models with an extremely high metallicity of [M/H] ∼ 3.5 and an extremely high haze production rate of F haze ∼ 10−8 to 10−7 g cm−2 s−1. Such high atmospheric metallicity is suggested by the relatively strong CO2 feature compared to the haze absorption feature or the CH4 feature in the NIRSpec-G395H bandpass of 2.5–5 μm. The flat 5–12 μm MIRI spectrum also suggests a small scale height with a high atmospheric metallicity that is needed to suppress a prominent ∼6 μm haze feature. We tested the sensitivity of our interpretation to various assumptions for uncertain haze properties, such as optical constants and production rate, and all models tested here consistently suggest extremely high metallicity. Thus, we conclude that GJ 1214b likely has a metal-dominated atmosphere where hydrogen is no longer the main atmospheric constituent. We also find that different assumptions for the haze production rate lead to distinct inferences for the atmospheric C/O ratio. We stress the importance of high-precision follow-up observations to confirm the metal-dominated atmosphere, as it challenges the conventional understanding of interior structure and evolution of sub-Neptunes.

Multiple Electron Transfers Enable High-Capacity Cathode Through Stable Anionic Redox.

Single-electron transfer, low alkali metal contents, and large-molecular masses limit the capacity of cathodes. This study uses a cost-effective and light-molecular-mass orthosilicate material, K2FeSiO4, with a high initial potassium content, as a cathode for potassium-ion batteries to enable the transfer of more than one electron. Despite the limited valence change of Fe ions during cycling, K2FeSiO4 can undergo multiple electron transfers via successive oxygen anionic redox reactions to generate a high reversible capacity. Although the formation of O‒O dimers in K2FeSiO4 occur upon removing large amounts of potassium, the strong binding effect of Si on O mitigates irreversible oxygen release and voltage degradation during cycling. K2FeSiO4 achieves 236 mAh g-1 at 50mA g-1, with an energy density of 520Wh kg-1, which can be comparable with commercial LiFePO4 materials. Moreover, it also exhibits 1400 stable cycles under high-current conditions. These findings enhance the potential commercialization prospects for potassium-ion batteries.

Visible-Light-Induced Glycosylation/Annulation of 2-Isocyanobiaryls and Glycosyl NHP Esters to Access Nonclassical Heteroaryl C-Glycosides

Visible-Light-Induced Glycosylation/Annulation of 2-Isocyanobiaryls and Glycosyl NHP Esters to Access Nonclassical Heteroaryl C-Glycosides

Trade-offs encountered in traditional mobility enhancement techniques applied to contact-controlled thin film transistors

Various mobility enhancement strategies are used at the material, process, and design geometry levels, to improve the performance of conventional thin film transistors (TFTs). These include the optimization of contact barrier height, semiconductor carrier concentration, post-annealing, and channel length optimization. In this study, the effects of these strategies on the performance metrics of contact-controlled amorphous Indium Gallium Zinc oxide (a-IGZO) TFTs are analyzed. Using a low barrier contact metal and a higher channel concentration can enhance the mobility of these TFTs by aiding the high field mode of operation with barrier lowering effect, but this leads to higher values of saturation coefficient, channel length sensitivity, and saturation voltage, with a lower value of output impedance. For a device working in the low-field mode, though the process of annealing improves the mobility characteristics, it deteriorates contact-controlled performance. Channel length upscaling also negatively affects all the contact-controlled performance metrics except output impedance. Thus, this study brings out the deteriorative effect of conventional mobility enhancement strategies on the performance metrics of a contact-controlled device, by unraveling the underlying semiconductor transport physics and the interplay between contact resistance and channel resistance.

Rising from the ashes: evidence of old stellar populations and rejuvenation events in the very early Universe

Abstract While JWST has observed galaxies assembling as early as $z\sim 14$, evidence of galaxies with significant old stellar populations in the Epoch of Reionization (EoR) – the descendants of these earliest galaxies – are few and far between. Bursty star-formation histories (SFHs) have been invoked to explain the detectability of the earliest UV-bright galaxies, but also to interpret galaxies showing Balmer breaks without nebular emission lines. We present the first spectroscopic evidence of a $z\sim 7.9$ galaxy, A2744-YD4, which shows a Balmer break and emission lines, indicating the presence of both a mature and young stellar population. The spectrum of A2744-YD4 shows peculiar emission line ratios suggesting a relatively low ionization parameter and high gas-phase metallicity. A median stack of galaxies with similar emission line ratios reveals a clear Balmer break in their stacked spectrum. This suggests that a mature stellar population (∼80 Myr old) has produced a chemically enriched, disrupted interstellar medium. Based on SED-fitting and comparison to simulations, we conclude that the observed young stellar population is in fact the result of a rejuvenation event following a lull in star formation lasting ∼20 Myr, making A2744-YD4 and our stack the first spectroscopic confirmation of galaxies that have rejuvenated following a mini-quenched phase. These rejuvenating galaxies appear to be in an exceptional evolutionary moment where they can be identified. Our analysis shows that a young stellar population of just ∼30 per cent of the total stellar mass would erase the Balmer break. Hence, ‘outshining’ through bursty SFHs in early galaxies is likely plaguing attempts to measure their stellar ages and masses accurately.

Producing Type Ia Supernovae from Hybrid CONe White Dwarfs with Main-sequence Binary Companions at Low Metallicity of Z = 0.0001

Abstract The nature of progenitors of Type Ia supernovae (SNe Ia) and their explosion mechanism remains unclear. It has been suggested that SNe Ia may have resulted from thermonuclear explosions of hybrid carbon–oxygen–neon white dwarfs (CONe WDs) when they grow in mass to approach the Chandrasekhar mass limit by accreting matter from a binary main-sequence (MS) companion. In this work, we combine the results of detailed binary evolution calculations with population synthesis models to investigate the rates and delay times of SNe Ia in the CONe WD + MS channel at a low metallicity environment of Z = 0.0001. For a constant star formation rate of 5 M ⊙ yr−1, our calculations predict that the SN Ia rates in the CONe WD + MS channel at low metallicity of Z = 0.0001 is about 0.11−3.89 × 10−4 yr−1. In addition, delay times in this channel cover a wide range of 0.05−2.5 Gyr. We further compare our results to those given by a previous study for the CONe WD + MS channel with a higher metallicity of Z = 0.02 to explore the influence of metallicity on the results. We find that these two metallicity environments give a slight difference in rates and delay times of SNe Ia from the CONe WD + MS channel, although SNe Ia produced at a low metallicity environment of Z = 0.0001 have relatively longer delay times.

Efficient activation of sodium percarbonate by hydroxylamine-enhanced zero-valent transition metals for the removal of AZO: performance, free radical generation and mechanism

Azoxystrobin (AZO) fungicides are novel organic pollutants which are stable in water environment. These pollutants can be degraded using low cost zero-valent metals (zero-valent iron (ZVI) and zero-valent copper (ZVC)) to activate sodium percarbonate (SPC), and the introduction of hydroxylamine (HA) can effectively improve the reaction efficiency of this system. According to the experimental results, HA significantly promoted the regeneration of Fe2+ and Cu+ in the decomposed solution of SPC, significantly accelerating the formation of hydroxyl radicals (•OH) and facilitating the degradation of AZO. Under optimal conditions, when pH = 3, the rate of AZO removal by the HA/ZVI/SPC system reached 99.0 % in 15 min, while the HA/ZVC/SPC system required 50 min to reach 99.1 % removal. Both of the tested HA/zero-valent metal/SPC processes produced •OH, carbonate radicals (CO3·-), superoxide radicals (O2·-) and singlet oxygen (1O2), among which, •OH appeared to be the main reactant responsible for AZO removal. Furthermore, it was found that •OH reacted with trace levels of carbonate ions to generate other reactive oxygen species and promote AZO degradation. The addition of HA not only slowed down the surface passivation of zero-valent metals, but also promoted the conversion of high-valent metal ions to low-valent metal ions, resulting in the generation of more reactive oxygen species within the system. In addition, the degradation intermediates were identified by LC-MS analysis and density-functional theory (DFT), allowing the possible AZO degradation pathways to be proposed.