XANES Research Articles

Exploring the Depths of Corrosion: A Novel GE-XANES Technique for Investigating Compositionally Complex Alloys.

In this study, we propose the use of nondestructive, depth-resolved, element-specific characterization using grazing exit X-ray absorption near-edge structure spectroscopy (GE-XANES) to investigate the corrosion process in compositionally complex alloys (CCAs). By combining grazing exit X-ray fluorescence spectroscopy (GE-XRF) geometry and a pnCCD detector, we provide a scanning-free, nondestructive, depth-resolved analysis in a sub-micrometer depth range, which is especially relevant for layered materials, such as corroded CCAs. Our setup allows for spatial and energy-resolved measurements and directly extracts the desired fluorescence line, free from scattering events and other overlapping lines. We demonstrate the potential of our approach on a compositionally complex CrCoNi alloy and a layered reference sample with known composition and specific layer thickness. Our findings indicate that this new GE-XANES approach has exciting opportunities for studying surface catalysis and corrosion processes in real-world materials.

Anti-corrosion and erosion properties of multilayers with diamond-like carbon and silicon films deposited on low-carbon steel

A multilayer of diamond-like carbon (DLC) and silicon (Si) films were deposited on low-carbon steel (CS) using a combination of bipolar-pulsed magnetron sputtering (MS) and the radio frequency plasma enhanced chemical deposition (RF-PECVD) methods. Spectroscopic techniques such as Raman spectroscopy, synchrotron-based X-ray photoemission spectroscopy (XPS), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy were used to investigate the chemical and structural properties of the film. The mechanical properties were measured using nanoindentation and nano-scratch testers. The films' electrochemical performance and corrosion behavior were evaluated in the 3.5 wt% NaCl solution at room temperature. The erosion resistance of the films was studied under the sand jet impingement apparatus. The results indicate that the 2 Si-layers in the DLC film and CS substrate increase the C‒sp3 content at the DLC film surface resulting in high mechanical hardness. The adhesion of the DLC film on the CS substrate was also improved by adding the Si layer between the CS substrate and DLC film. Consequently, multilayer Si/DLC film resists the elastic deformation of films caused by graphitization.

Ray-tracing Simulations and Spectral Models of X-Ray Radiation in Dusty Media

Dust can play an important role in shaping the X-ray spectra and images of astrophysical sources. In this work we report on the implementation of dust in the ray-tracing platform RefleX. We illustrate the different effects associated with the interaction between X-ray photons and dust grains, such as dust scattering, near-edge X-ray absorption fine structures, and shielding. We show how the cross sections of the photon–gas interaction change depending on the fraction of metals in dust grains (i.e., the dust depletion factor). We compare RefleX simulations to the most widely used absorption model that includes dust and show how X-ray spectra are affected by the presence of dust in the absorbing/reprocessing medium for different geometries. We also show how RefleX can be used to reproduce the dust scattering halos observed in Galactic sources, and we release the first torus X-ray spectral model that considers dust absorption and scattering (RXTorusD), to reproduce the spectra of active galactic nuclei (AGNs). RXTorusD also considers other physical processes that are not included in the most widely used AGN torus models, such as Rayleigh scattering and scattering on molecular gas, which can lead to remarkable differences in the predicted X-ray spectra for the same set of geometrical and physical parameters.

Phosphate interactions with iron-titanium oxide composites: Implications for phosphorus removal/recovery from wastewater

Understanding the interactions between phosphate (P) and mineral adsorbents is critical for removing and recovering P from wastewater, especially in the presence of both cationic and organic components. To this end, we investigated the surface interactions of P with an iron-titanium coprecipitated oxide composite in the presence of Ca (0.5–3.0 mM) and acetate (1–5 mM), and quantified the molecular complexes and tested the possible removal and recovery of P from real wastewater. A quantitative analysis of P K-edge X-ray absorption near edge structure (XANES) confirmed the inner-sphere surface complexation of P with both Fe and Ti, whose contribution to P adsorption relies on their surface charge determined by pH conditions. The effects of Ca and acetate on P removal were highly pH-dependent. At pH 7, Ca (0.5–3.0 mM) in solution significantly increased P removal by 13–30% by precipitating the surface-adsorbed P, forming hydroxyapatite (14–26%). The presence of acetate had no obvious influence on P removal capacity and molecular mechanisms at pH 7. At pH 4, the removal amount of P was not obviously affected by the presence of Ca and acetate. However, acetate and high Ca concentration jointly facilitated the formation of amorphous FePO4 precipitate, complicating the interactions of P with Fe-Ti composite. In comparison with ferrihydrite, the Fe-Ti composite significantly decreased the formation of amorphous FePO4 probably by decreasing Fe dissolution due to the coprecipitated Ti component, facilitating further P recovery. An understanding of these microscopic mechanisms can lead to the successful use and simple regeneration of the adsorbent to recover P from real wastewater.

Parsimonious methodology for synthesis of silver and copper functionalized cellulose.

The online version contains supplementary material available at 10.1007/s10570-023-05099-7.

Spectroscopic studies for identifying the chemical states of the periostracum of the Corbicula species in Lake Biwa

Corbicula clam shells consist of thin periostracum and calcareous layers made of calcium carbonate (CaCO3). Depending on habitat conditions, the shell exhibits various colorations, such as yellow, brown, and black. The chemical state of the periostracum of the Corbicula species in Lake Biwa was studied by X-ray absorption fine structure (XAFS) and Raman scattering spectroscopies. Fe K-edge X-ray absorption near edge structure (XANES) revealed that the Fe3+ intensity increases as the color of the shell changes from yellow to black. Raman spectra suggested that quinone-based polymers cover the yellow shell, and the black shell is further covered by dihydroxyphenylalanine (DOPA) rings of amino acid derivatives. From Fe K-edge extended X-ray absorption fine structure (EXAFS), it was found that Fe3+ in the periostracum was surrounded by five to six oxygen atoms with an average Fe-O ligand distance of 2.0 Å. Accordingly, a tris-DOPA-Fe3+ complex is formed, which is responsible for the periostracum’s black color.

Role of the Gd2O3 increment on the cerium oxidation state and luminescence behavior in the CeF3 doped silicoborate glass

This study aimed to investigate the effect of Gd2O3 on the cerium oxidation state and studied their luminescence in the silicoborate glass. Glass samples of a silicoborate glass containing cerium fluoride were prepared by doping the glass with varying amounts of Gd2O3 in the chemical formula xGd2O3: 40Na2O: 5SiO2: (54.5)B2O3: 0.5CeF3 (x = 0.0, 2.5, 5.0, 7.5, and 10.0 mol%). Density and refractive index tend to increase with increasing Gd2O3 content, whereas molar volume decreases. High-resolution XPS spectra confirm the chemical composition in the glass structure and found that the B1s and O1s regions illustrated more BO4 and bridging oxygen, respectively. X-ray absorption near edge structure (XANES) at the Ce LIII-edge was used to investigate the proportion between trivalent cerium (Ce3+) and tetravalent cerium (Ce4+). The ratio of Ce3+/Ce4+ decreased with the addition of Gd2O3. A higher concentration of Gd2O3 content showed more Ce4+ related to the reduction of photoluminescence and X-ray-induced luminescence spectra. Alpha-induced luminescence was used to calculate the light yield of the 7.5Gd:0.5CeF glass. Decay time was measured by pulsed light sources at 286 nm and X-ray excitation.

Unveiling the Mechanical and Electrochemical Evolution of Nanosilicon Composite Anodes in Sulfide‐Based All‐Solid‐State Batteries

AbstractThe utilization of silicon anodes in all‐solid‐state lithium batteries provides good prospects for facilitating high energy density. However, the compatibility of sulfide solid‐state electrolytes (SEs) with Si and carbon is often questioned due to potential decomposition. Herein, operando X‐ray absorption near‐edge structure (XANES) spectroscopy, ex situ scanning electron microscopy (SEM), and ex situ X‐ray nanotomography (XnT) are utilized to investigate the chemistry and structure evolution of nano‐Si composite anodes. Results from XANES demonstrate a partial decomposition of SEs during the first lithiation stage, which is intensified by the presence of carbon. Nevertheless, the performances of first three cycles in Si–SE–C are stable, which proves that the generated media is ionically conductive. XnT and SEM results show that the addition of SEs and carbon improves the structural stability of the anode, with fewer pores and voids. A chemo‐elasto‐plastic model reveals that SEs and carbon buffer the volume expansion of Si, thus enhancing mechanical stability. The balance between the pros and cons of SEs and carbon in enhancing reaction kinetics and structural stability enables the Si composite anode to demonstrate the highest Si utilization with higher specific capacities and a better rate than pure Si and Si composite anodes with only SEs.

Selective CO2 Photoreduction to Acetate at Asymmetric Ternary Bridging Sites.

Photoreduction of CO2 is a promising strategy to synthesize value-added fuels or chemicals and realize carbon neutralization. Noncopper catalysts are seldom reported to generate C2 products, and the selectivity over these catalysts is low. Here, we design rich-interface, heterostructured In2O3/InP (r-In2O3/InP) for highly competitive photocatalytic CO2-to-CH3COOH conversion with a productivity of 96.7 μmol g-1 and selectivity > 96% along with water oxidation to O2 in pure water (no sacrificial agent) under visible light irradiation. The hard X-ray absorption near-edge structure (XANES) shows that the formation of r-In2O3/InP with the isogenesis cation adjusts the coordination environment via interface engineering and forms O-In-P polarized sites at the interface. In situ FT-IR and Raman spectra identify the key intermediates of OCCO* for acetate production with high selectivity. Density functional theory (DFT) calculations reveal that r-In2O3/InP with rich O-In-P polarized sites promotes C-C coupling to form C2 products because of the imbalanced adsorption energies of two carbon atoms. This work reports an interesting indium-based photocatalyst for selective CO2 photoreduction to acetate under strict solution and irradiation conditions and provides significant insights into fabricating interfacial polarization sites to promote the process.

Formation and Segregation of a Pd-MgO Solid Solution Studied by X-ray Absorption Spectroscopy.

Thermal treatment of Pd nanoparticles or Pd(NH3)4(NO3)2 supported on MgO resulted in the formation of a solid solution of Pd-MgO, as evidenced by Pd K-edge X-ray absorption fine structure (XAFS). The valence of Pd in the Pd-MgO solid solution was determined to be 4+ from the comparison of X-ray absorption near edge structure (XANES) with reference compounds. A characteristic shrinkage of the Pd-O bond distance was observed in comparison with that of the nearest-neighboring Mg-O bond in MgO, which agreed with the density functional theory (DFT) calculations. The two-spike pattern was observed in the dispersion of Pd-MgO owing to the formation and successive segregation of solid solutions above 1073 K.

Halide Layer Cathodes for Compatible and Fast-Charged Halides-Based All-Solid-State Li Metal Batteries.

Insertion-type compounds based on oxides and sulfides have been widely identified and well-studied as cathode materials in lithium-ion batteries. However, halides have rarely been used due to their high solubility in organic liquid electrolytes. Here, we reveal the insertion electrochemistry of VX3 (X=Cl, Br, I) by introducing a compatible halide solid-state electrolyte with a wide electrochemical stability window. X-ray absorption near-edge structure analyses reveal a two-step lithiation process and the structural transition of typical VCl3 . Fast Li+ insertion/extraction in the layered VX3 active materials and favorable interface guaranteed by the compatible electrode-electrolyte design enables high rate capability and stable operation of all-solid-state Li-VX3 batteries. The findings from this study will contribute to developing intercalation insertion electrochemistry of halide materials and exploring novel electrode materials in viable energy storage systems.

Local structure and magnetic properties of a nanocrystalline Mn-rich Cantor alloy thin film down to the atomic scale

The huge atomic heterogeneity of high-entropy materials along with a possibility to unravel the behavior of individual components at the atomic scale suggests a great promise in designing new compositionally complex systems with the desired multi-functionality. Herein, we apply multi-edge X-ray absorption spectroscopy (extended X-ray absorption fine structure (EXAFS), X-ray absorption near edge structure (XANES), and X-ray magnetic circular dichroism (XMCD)) to probe the structural, electronic, and magnetic properties of all individual constituents in the single-phase face-centered cubic (fcc)-structured nanocrystalline thin film of Cr20Mn26Fe18Co19Ni17 (at.%) high-entropy alloy on the local scale. The local crystallographic ordering and component-dependent lattice displacements were explored within the reverse Monte Carlo approach applied to EXAFS spectra collected at the K absorption edges of several constituents at room temperature. A homogeneous short-range fcc atomic environment around the absorbers of each type with very similar statistically averaged interatomic distances (2.54–2.55 Å) to their nearest-neighbors and enlarged structural relaxations of Cr atoms were revealed. XANES and XMCD spectra collected at the L2,3 absorption edges of all principal components at low temperature from the oxidized and in situ cleaned surfaces were used to probe the oxidation states, the changes in the electronic structure, and magnetic behavior of all constituents at the surface and in the sub-surface volume of the film. The spin and orbital magnetic moments of Fe, Co, and Ni components were quantitatively evaluated. The presence of magnetic phase transitions and the co-existence of different magnetic phases were uncovered by conventional magnetometry in a broad temperature range.

X-ray Absorption Spectroscopy Studies of a Molecular CO2-Reduction Catalyst Deposited on Graphitic Carbon Nitride

Metal–ligand complexes have been extensively explored as well-defined molecular catalysts in small molecule activation reactions such as carbon dioxide (CO2) reduction. Many hybrid photocatalysts have been prepared by coupling such complexes with photoactive surfaces for use in solar CO2 reduction. In this work, we employ X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopies, density functional theory (DFT) and computational XANES modeling to interrogate the structure of a hybrid photocatalyst consisting of a macrocyclic cobalt complex deposited on graphitic carbon nitride (C3N4). Results show that the cobalt complex binds on C3N4 through surface OH or NH2 groups. By refining the local geometry and binding sites of this well-defined molecular cobalt complex on C3N4, we established an important benchmark for modeling a large class of molecular catalysts that can be adapted to in situ/operando studies and further enhanced by applying chemometrics-based approaches and machine learning methods of XANES data analysis.

Deciphering the Structural and Chemical Transformations of Oxide Catalysts during Oxygen Evolution Reaction Using Quick X-ray Absorption Spectroscopy and Machine Learning.

Bimetallic transition-metal oxides, such as spinel-like CoxFe3-xO4 materials, are known as attractive catalysts for the oxygen evolution reaction (OER) in alkaline electrolytes. Nonetheless, unveiling the real active species and active states in these catalysts remains a challenge. The coexistence of metal ions in different chemical states and in different chemical environments, including disordered X-ray amorphous phases that all evolve under reaction conditions, hinders the application of common operando techniques. Here, we address this issue by relying on operando quick X-ray absorption fine structure spectroscopy, coupled with unsupervised and supervised machine learning methods. We use principal component analysis to understand the subtle changes in the X-ray absorption near-edge structure spectra and develop an artificial neural network to decipher the extended X-ray absorption fine structure spectra. This allows us to separately track the evolution of tetrahedrally and octahedrally coordinated species and to disentangle the chemical changes and several phase transitions taking place in CoxFe3-xO4 catalysts and on their active surface, related to the conversion of disordered oxides into spinel-like structures, transformation of spinels into active oxyhydroxides, and changes in the degree of spinel inversion in the course of the activation treatment and under OER conditions. By correlating the revealed structural changes with the distinct catalytic activity for a series of CoxFe3-xO4 samples, we elucidate the active species and OER mechanism.

Coke evolution during the air- and oxy-firing regeneration of a spent Ni/ZnO sulfur adsorbent

Reactive adsorption desulfurization (RADS) is an effective desulfurization technology in refineries to reduce the sulfur contents in oil products. To ameliorate the desulfurization technology, the evolution of coke was first studied in the air-firing regeneration of a typical spent Ni/ZnO sulfur adsorbent used in RADS. Efforts were made to elaborate the conversion of carbon and sulfur during the oxy-firing regeneration of the spent adsorbent to test the possibility of applying that carbon capture technology – oxy-fuel combustion to the sulfur adsorbent regeneration. A lab-scale drop-tube furnace was employed to conduct the combustion experiments; and the speciation of carbon and sulfur in the regenerated adsorbents was characterized by advanced techniques including near-edge X-ray absorption fine structure (NEXAFS), Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). The catalytic role of metals (Ni/Zn) in the coke combustion was also verified by acid leaching and temperature-programmed oxidation (TPO) experiments. It has been founded that the carbonaceous materials deposited on the adsorbent comprise five groups, including polyaromatic and graphitic carbon with a fraction of around 27 mol% of the entire carbon, and the other groups which are mostly light aliphatic compounds and oxygen-containing functional groups. During the air-firing regeneration process, most of the light coke species were oxidized into oxygenated intermediates and then desorbed as CO and CO2, with a small portion being polymerized into heavy molecules. Oxy-firing regeneration was verified to improve the efficiency of coke combustion due to the metal-catalyzed CO2 gasification reaction and improved the sulfur conversion under the oxygen-lean condition such as 3 vol% O2 in CO2. The carbon conversion increased from 23% in 3%O2/N2 to 31% in 3%O2/CO2 at 510 ℃. In the meantime, the sulfur conversion was also increased from 50% to 57% at 750 ℃, which is probably due to that the CO2 gasification of coke alleviated the competition of oxygen between carbon and sulfur.

Aluminum speciation in forest soils and forest floor density fractions using synchrotron-based XANES spectroscopy

The speciation of aluminum (Al) in soils is important for Al cycling and Al toxicity in terrestrial ecosystems. Current soil Al speciation methods are mostly wet-chemical, discriminating among operationally defined fractions rather than distinct Al species. We performed synchrotron-based X-ray absorption near edge structure (XANES) spectroscopy at the Al K-edge (1560 eV) for Al speciation in different horizons of three forest soil profiles and O layer density fractions. We deconvoluted the spectra by linear combination fitting (LCF; 1550–1690 eV), using reference spectra of 22 diluted inorganic and organic Al-bearing soil constituents. Our first time application of Al XANES spectroscopy + LCF for soil Al speciation revealed methodological challenges and difficulties. Thus, a minimum sample Al content of 5 mg g−1 was necessary to yield spectra with satisfactory signal-to-noise ratio in reasonable acquisition time, and Al contents > 15 mg g−1 resulted in spectrum distortion by self absorption, requiring adequate sample dilution prior to XANES analysis. Nevertheless, Al K-edge XANES spectroscopy allowed for estimating the relative contribution of different Al species to total Al in our soil and density fraction samples. The Al XANES spectra of different Al carboxylates were very similar. The same was true for different Al phenol species, different 2:1 clay minerals (illite, montmorillonite, chlorite), different 1:1 clay minerals (kaolinite, halloysite), and different feldspars (orthoclase, anorthite), jeopardizing a reliable differentiation and quantification of these specific compounds. We therefore combined these compounds into the groups SOM carboxyl(ate)-bound Al, SOM phenol-bound Al, 1:1 clay mineral-bound Al, 2:1 clay mineral-bound Al, and feldspar-bound Al. XANES results showed a decreasing contribution of organically bound Al to total soil Al with soil depth (O layers 20–43 %; Ah horizons 10–22 %; B horizons 0–12 %). Major inorganic Al-bearing constituents in the fine earth of all soils were 2:1 clay minerals and feldspars, followed by 1:1 clay minerals (kaolinite), and Fe oxyhydroxides with partial Al substitution. Gibbsite or allophane did contribute only marginally to fine-earth Al in our soils. Different Oa layer density fractions with different SOM content and SOM decomposition status also differed in Al content and Al speciation, indicating the existence of spatially separated forest floor constituents with different Al speciation. Aluminum in the mineral-dominated density fraction > 1.6 g cm−3 with advanced SOM decomposition, comprising about 50 % of total Oa mass, was entirely bound in clay minerals (65–70 % of total Al) and feldspars (30–35 % of total Al). In contrast, Al in the mineral-poor density fraction < 1.0 g cm−3 was entirely bound to SOM as Al-organo complex, with Al bound to SOM phenol groups (>75 % of total Al) being more relevant than Al bound to SOM carboxyl(ate) groups. However, the latter density fraction comprised only 4 % of total Oa mass in both soils. Aluminum K-edge XANES spectroscopy, particularly when combined with total element analysis and XRD, is a promising novel tool for speciation of Al in soils and in SOM-mineral associations, with a great potential to promote our understanding of Al biogeochemistry in terrestrial ecosystems.

XAFS Analysis of Sulfuric Acid Solution Related to the Effect of Bi in Suppressing the Disproportionation Reaction of Mn&lt;sup&gt;3+&lt;/sup&gt; in Mn/Ti Redox Flow Cells

In sulfuric acid (H2SO4) aqueous solutions containing manganese (Mn) and titanium (Ti) ions, which are used for the positive electrolyte in redox flow (RF) batteries, the addition of a small quantity of bismuth (Bi) has been found to be very effective in suppressing the MnO2 precipitation in the charging process from Mn2+ to Mn3+. The effect of the addition of Bi on the structural change in these solutions has been analyzed using x-ray absorption fine structure (XAFS) techniques. X-ray absorption near edge structure (XANES) spectra indicated that some Mn4+ ions were generated only when Bi was not added. It was also confirmed that the Mn-O octahedral coordination was maintained at a high state of charge (SOC). On the other hand, no change was observed in the valence of Ti and Bi ions even at high SOCs. Extended x-ray absorption fine structure (EXAFS) measurements combined with fitting analysis clarified that the addition of Bi resulted in the generation of Mn-O-Bi coordination at the SOCs of 70 and 90 %. Bi-O-Mn coordination may suppress the MnO2 precipitation at a high SOC.

Engineered Cobalt Single-Atoms@BiFeO3 Heteronanostructures for Highly Efficient Solar Water Oxidation.

Efficient charge-carrier separation and their utilization are the key factors in overcoming sluggish four-electron reaction kinetics involved in photocatalytic oxygen evolution. Here, a novel study demonstrates the significance of Na2 S2 O8 as a sacrificial agent in comparison to AgNO3 . Resultantly, BiFeO3 (BFO) and titanium doped-oxygen deficient BiFeO3 (Ti-BFO-R) nanostructures achieve ≈64 and 44.5 times higher O2 evolution in the presence of Na2 S2 O8 compared to AgNO3 as a sacrificial agent, respectively. Furthermore, the presence of Co single atoms (Co-SAs) deposited via immersion method on BFO and Ti-BFO-R nanostructures led to achieving outstanding O2 evolution at a rate of 16.11 and 23.89mmol g-1 h-1 , respectively, which is 153 and 227.5 times higher compared to BFO (in the presence of AgNO3 ), the highest O2 evolution observed for BFO-based materials to date. The successful deposition of Co-SAs is confirmed by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC HAADF-STEM) and X-ray absorption near-edge structure (XANES). The charge transfer investigations confirm the significance of Co-SAs on BFO-based photocatalysts for improved charge-carrier separation, transport, and utilization. This novel study validates the excellent role of Na2 S2 O8 as a sacrificial agent and Co-SAs as a cocatalyst for BFO-based nanostructures for efficient O2 evolution.

Characterization of Phosphate Compounds along a Catena from Arable and Wetland Soil to Sediments in a Baltic Sea lagoon

Phosphorus (P) is an indispensable nutrient for arable crops, but at the same time, contributes to excessive eutrophication in aquatic ecosystems. Knowledge about P is essential to assess the possible risks of P being transported towards vulnerable aquatic ecosystems. Our objective was to characterize P along a catena from arable and wetland soils towards aquatic sediments of a shallow lagoon of the Baltic Sea. The characterization of P in soil and sediment samples included a modified sequential P fractionation and P K-edge X-ray absorption near edge structure (XANES) spectroscopy. The concentrations of total P ranged between 390 and 430 mg kg−1 in the arable soils, between 728 and 2258 mg kg−1 in wetland soils and between 132 and 602 mg kg−1 in lagoon sediments. Generally, two sinks for P were revealed along the catena. The wetland soil trapped moderately stable P, Al-P and molybdate-unreactive P (MUP), which are most likely organically bound phosphates. Sediments at the deepest position of the catena acted as a sink for, MUP compounds among the lagoon sediments. Thus, wetlands formed by reed belts can help to prevent the direct transfer of P from arable soils to adjacent waters and deeper basins and help to avoid excessive eutrophication in shallow aquatic ecosystems.

Vanadium Speciation in Ancient Shales Revealed through Synchrotron-Based X-ray Spectroscopy

Redox-sensitive trace elements, such as vanadium, are frequently used as paleoredox proxies to infer the redox status of ancient marine depositional environments. When applied to vanadium, this approach relies on an accurate understanding of vanadium geochemistry in marine sediments. This, in turn, requires the application of analytical techniques capable of providing reliable chemical information on vanadium host phases of vanadium and thus the ability to distinguish authigenic from detrital phases. The increasing availability of synchrotron-based X-ray spectroscopic techniques capable of providing chemical speciation information at both the bulk and micro-scale presents an opportunity to refine our understanding of vanadium geochemistry in ancient marine sediments. Here, we show the utility of synchrotron-based X-ray absorption near-edge structure (XANES) spectroscopy and scanning X-ray fluorescence microscopy (SXFM) for investigating vanadium host phases in ancient marine sediments. The studied samples from the 1400 Ma Xiamaling Formation came from strongly contrasting depositional settings (ranging from oxic to euxinic) with a wide range of vanadium enrichments (enrichment factors from 0.7 to 9.6), yet vanadium speciation determined by XANES was consistently found to be phyllosilicate-hosted vanadium (III). High-resolution elemental imaging by SXFM coupled with global statistical colocalization analyses revealed strong associations between vanadium and potassium, consistent with vanadium hosted by potassium-rich clay minerals. These findings, while demonstrating the power of synchrotron-based X-ray methods, imply that differentiating authigenic and detrital vanadium in ancient marine sediments is unlikely to be possible given that post-depositional processes result in similar chemical speciation for both fractions. This will also limit the reliability of vanadium isotope system studies that depend on differentiating authigenic and detrital fractions using selective extraction procedures.