The Crystallization Process of Vaterite Microdisc Mesocrystals via Proto-Vaterite Amorphous Calcium Carbonate Characterized by Cryo-X-ray Absorption Spectroscopy

Li, Qiao; Žižak, Ivo; Zaslansky, Paul; Ma, Yurong

doi:10.3390/cryst10090750

Cited by 8 publications

(4 citation statements)

References 40 publications

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“…This is broadly consistent with the split Sr–Ca shells in this study, with improvements in data quality and k -range a likely reason for the resolution of 2 Ca shells in this study. In the literature, Ca K -edge spectra for vaterite often varies considerably, 107 , 108 referred to without experimental data, 53 , 54 not modeled at R > 3 Å 103 or at all, 109 not accompanied by model fitting parameters, 110 or are fit poorly/only in conjunction with the “conventional” 6 Ca atoms at approximately 4.2 Å (in accordance with ref ( 111 )). 55 , 112 Splitting the Ca shell at approximately 3.9–4.3 Å has not been conducted in studies analyzing the structure of vaterite using Ca K -edge.…”

Section: Resultssupporting

confidence: 69%

Enhanced Strontium Removal through Microbially Induced Carbonate Precipitation by Indigenous Ureolytic Bacteria

White-Pettigrew,

Shaw,

Hughes

et al. 2024

ACS Earth Space Chem.

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Microbial ureolysis offers the potential to remove metals including Sr2+ as carbonate minerals via the generation of alkalinity coupled to NH4 + and HCO3 – production. Here, we investigated the potential for bacteria, indigenous to sediments representative of the U.K. Sellafield nuclear site where 90Sr is present as a groundwater contaminant, to utilize urea in order to target Sr2+-associated (Ca)CO3 formation in sediment microcosm studies. Strontium removal was enhanced in most sediments in the presence of urea only, coinciding with a significant pH increase. Adding the biostimulation agents acetate/lactate, Fe(III), and yeast extract to further enhance microbial metabolism, including ureolysis, enhanced ureolysis and increased Sr and Ca removal. Environmental scanning electron microscopy analyses suggested that coprecipitation of Ca and Sr occurred, with evidence of Sr associated with calcium carbonate polymorphs. Sr K-edge X-ray absorption spectroscopy analysis was conducted on authentic Sellafield sediments stimulated with Fe(III) and quarry outcrop sediments amended with yeast extract. Spectra from the treated Sellafield and quarry sediments showed Sr2+ local coordination environments indicative of incorporation into calcite and vaterite crystal structures, respectively. 16S rRNA gene analysis identified ureolytic bacteria of the genus Sporosarcina in these incubations, suggesting they have a key role in enhancing strontium removal. The onset of ureolysis also appeared to enhance the microbial reduction of Fe(III), potentially via a tight coupling between Fe(III) and NH4 + as an electron donor for metal reduction. This suggests ureolysis may support the immobilization of 90Sr via coprecipitation with insoluble calcium carbonate and cofacilitate reductive precipitation of certain redox active radionuclides, e.g., uranium.

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Section: Resultssupporting

confidence: 69%

Enhanced Strontium Removal through Microbially Induced Carbonate Precipitation by Indigenous Ureolytic Bacteria

White-Pettigrew,

Shaw,

Hughes

et al. 2024

ACS Earth Space Chem.

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“…3d also demonstrate that with the addition of Ag, the structure of Cu in CuAg undergoes significant evolution. Specifically, the intensity of the peak located at around 4.3 Å decreases significantly with the increase in Ag content within the CuAg samples, indicating a reduction in long-range order of Cu atom arrangement 73 , 74 . Combining observations from both STEM and XRD analyses, we believe that this reduction in long-range order of Cu can be attributed to both the incorporation of Ag foreign atoms, as well as the formation of amorphous Cu layer.…”

Section: Resultsmentioning

confidence: 94%

Revealing the structural evolution of CuAg composites during electrochemical carbon monoxide reduction

Wang,

Jung,

Liu

et al. 2024

Nat Commun

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Comprehending the catalyst structural evolution during the electrocatalytic process is crucial for establishing robust structure/performance correlations for future catalysts design. Herein, we interrogate the structural evolution of a promising Cu-Ag oxide catalyst precursor during electrochemical carbon monoxide reduction. By using extensive in situ and ex situ characterization techniques, we reveal that the homogenous oxide precursors undergo a transformation to a bimetallic composite consisting of small Ag nanoparticles enveloped by thin layers of amorphous Cu. We believe that the amorphous Cu layer with undercoordinated nature is responsible for the enhanced catalytic performance of the current catalyst composite. By tuning the Cu/Ag ratio in the oxide precursor, we find that increasing the Ag concentration greatly promotes liquid products formation while suppressing the byproduct hydrogen. CO2/CO co-feeding electrolysis and isotopic labelling experiments suggest that high CO concentrations in the feed favor the formation of multi-carbon products. Overall, we anticipate the insights obtained for Cu-Ag bimetallic systems for CO electroreduction in this study may guide future catalyst design with improved performance.

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“…Decreases in second and third shell coordination numbers, relative to bulk metal oxide, have been correlated to nanoparticles of defined sizes. , These results in tandem with DFT calculations have predicted specific structures of supported metal oxide clusters with 9–13 metal atoms . There have been few studies that use Ca K-edge extended X-ray absorption fine structure (EXAFS) to inform on Ca-containing nanoparticle sizes and structure of highly dispersed , and nanoparticle Ca species. , Changes in Ca–O coordination can be observed during mineral crystallization as the solid phases become larger and more ordered . Ca deposition on coal via impregnation and ion exchange yielded catalysts that lacked any Ca–Ca coordination due to a high degree of dispersion .…”

Section: Introductionmentioning

confidence: 99%

“… 27 , 28 Changes in Ca–O coordination can be observed during mineral crystallization as the solid phases become larger and more ordered. 29 Ca deposition on coal via impregnation and ion exchange yielded catalysts that lacked any Ca–Ca coordination due to a high degree of dispersion. 25 The aggregation of CaCO 3 and CaO species was observed after high-temperature treatments.…”

Section: Introductionmentioning

confidence: 99%

Impact of Local Structure in Supported CaO Catalysts for Soft-Oxidant-Assisted Methane Coupling Assessed through Ca K-Edge X-ray Absorption Spectroscopy

Filardi,

Vila,

Hong

et al. 2024

J. Phys. Chem. C

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Soft-oxidant-assisted methane coupling has emerged as a promising pathway to upgrade methane from natural gas sources to high-value commodity chemicals, such as ethylene, at selectivities higher than those associated with oxidative (O 2 ) methane coupling (OCM). To date, few studies have reported investigations into the electronic structure and the microscopic physical structure of catalytic active sites present in the binary metal oxide catalyst systems that are known to be effective for this reaction. Correlating the catalyst activity to specific active site structures and electronic properties is an essential aspect of catalyst design. Here, we used X-ray absorption spectroscopy at the Ca K-edge to ascertain the most probable local environment of Ca in the ZnO-supported Ca oxide catalysts. These catalysts are shown here to be active for N 2 O-assisted methane coupling (N 2 O-OCM) and have previously been reported to be active for CO 2 -assisted methane coupling (CO 2 -OCM). X-ray absorption near edge structure features at multiple Ca loadings are interpreted through simulated spectra derived from ab initio full multiple scattering calculations. These simulations included consideration of CaO structures organized in multiple spatial arrangements�linear, planar, and cubic�with separate analyses of Ca atoms in the surfaces and bulk of the threedimensional structures. The morphology of the oxide clusters was found to influence the various regions of the X-ray absorption spectrum differently. Experiment and theory show that for low-Ca-loading catalysts (≤1 mol %), which contain sites particularly active for methane coupling, Ca primarily exists in an oxidized state that is consistent with the coordination environment of Ca ions in one-and two-dimensional clusters. In addition to their unique nanoscale structures, the spectra also indicate that these clusters have varying degrees of undercoordinated surface Ca atoms that could further influence their catalytic activities. The local Ca structure was correlated to methane coupling activity from N 2 O-OCM and previously reported CO 2 -OCM reactor studies. This study provides a unique perspective on the relationship between the catalyst physical and electronic structure and active sites for soft-oxidant-assisted methane coupling, which can be used to inform future catalyst development.

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The Crystallization Process of Vaterite Microdisc Mesocrystals via Proto-Vaterite Amorphous Calcium Carbonate Characterized by Cryo-X-ray Absorption Spectroscopy

Cited by 8 publications

References 40 publications

Enhanced Strontium Removal through Microbially Induced Carbonate Precipitation by Indigenous Ureolytic Bacteria

Enhanced Strontium Removal through Microbially Induced Carbonate Precipitation by Indigenous Ureolytic Bacteria

Revealing the structural evolution of CuAg composites during electrochemical carbon monoxide reduction

Impact of Local Structure in Supported CaO Catalysts for Soft-Oxidant-Assisted Methane Coupling Assessed through Ca K-Edge X-ray Absorption Spectroscopy

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