Browsing by Author "Hamilton, JL"
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- ItemInfluence of carbon support on the pyrolysis of cobalt phthalocyanine for the efficient electroreduction of CO2(American Chemical Society, 2022-11-14) Hamonnet, J; Bennington, MS; Johannessen, B; Hamilton, JL; Brooksby, PA; Brooker, S; Golovko, VB; Marshall, ATUnderstanding the nature of the reactive sites of CO2reduction catalysts is crucial to developing efficient and selective materials to help mitigate the greenhouse effect. In this research, materials based on cobalt phthalocyanine supported by carbon black and pyrolyzed at various temperatures under argon are fabricated and tested for CO2electroreduction. The results show that the high reactivity of the catalysts for the electroreduction of CO2to CO is maintained for materials prepared at temperatures up to 700 °C, with CO Faradaic efficiencies of >85% and CO current densities consistently at >40 mA cm-2at -0.86 V vs RHE. The materials annealed up to 900 °C are also remarkably active, with CO Faradaic efficiencies of >40% and CO current densities of >12 mA cm-2. The combination of X-ray diffraction, infrared and Raman spectroscopies, and X-ray absorption analysis show that the annealed materials exhibit chemical structures drastically different from those of the original CoPC and unsupported pyrolyzed catalyst while highlighting the role of the carbon black support in the formation of active species. These results give crucial insight into the reactive structure of CoPC and open the way for the development of pyrolyzed Co-N4macrocycles as a new class of materials efficient for the electroreduction of CO2,. © 2022 American Chemical Society.
- ItemPreservation of terrestrial microorganisms and organics within alteration products of chondritic meteorites from the Nullarbor Plain, Australia(Mary Ann Liebert, Inc., 2022-04-13) Tait, AW; Wilson, SA; Tomkins, AG; Hamilton, JL; Gagen, EJ; Holman, AI; Grice, K; Preston, LJ; Paterson, DJ; Southam, GMeteorites that fall to Earth quickly become contaminated with terrestrial microorganisms. These meteorites are out of chemical equilibrium in the environments where they fall, and equilibration promotes formation of low-temperature alteration minerals that can entomb contaminant microorganisms and thus preserve them as microfossils. Given the well-understood chemistry of meteorites and their recent discovery on Mars by rovers, a similarly weathered meteorite on Mars could preserve organic and fossil evidence of a putative past biosphere at the martian surface. Here, we used several techniques to assess the potential of alteration minerals to preserve microfossils and biogenic organics in terrestrially weathered ordinary chondrites from the Nullarbor Plain, Australia. We used acid etching of ordinary chondrites to reveal entombed fungal hyphae, modern biofilms, and diatoms within alteration minerals. We employed synchrotron X-ray fluorescence microscopy of alteration mineral veins to map the distribution of redox-sensitive elements of relevance to chemolithotrophic organisms, such as Mn-cycling bacteria. We assessed the biogenicity of fungal hyphae within alteration veins using a combination of Fourier-transform infrared spectroscopy and pyrolysis gas chromatography-mass spectrometry, which showed that alteration minerals sequester and preserve organic molecules at various levels of decomposition. Our combined analyses results show that fossil microorganisms and the organic molecules they produce are preserved within calcite–gypsum admixtures in meteorites. Furthermore, the distributions of redox-sensitive elements (e.g., Mn) within alteration minerals are localized, which qualitatively suggests that climatically or microbially facilitated element mobilization occurred during the meteorite's residency on Earth. If returned as part of a sample suite from the martian surface, ordinary chondrites could preserve similar, recognizable evidence of putative past life and/or environmental change. © 2022 Mary Ann Liebert, Inc
- ItemSpeciation and mobility of antimony and arsenic in a highly contaminated freshwater system and the influence of extreme drought conditions(CSIRO Publishing, 2021-12-22) Doherty, S; Tighe, MK; Milan, LA; Lisle, L; Leech, C; Johannessen, B; Mitchell, VD; Hamilton, JL; Johnston, SG; Wilson, SCEnvironmental context Toxicity and mobility of antimony and arsenic in aqueous systems are largely determined by their speciation and redox chemistry. In a highly contaminated freshwater system, one antimony species (dissolved SbV) dominated, while dissolved arsenic was more responsive to environmental conditions. Arsenic (as AsV) increased significantly during a drought period; this increase in As mobility presents a threat for first flush events and water contamination in a changing climate. Abstract Aqueous and solid-state antimony (Sb) and arsenic (As) speciation is assessed in an Australian freshwater system contaminated by mining of primary sulfide minerals. The study aims to understand metalloid transformation and mobilisation in the system, and coincides with a severe drought providing the opportunity to examine the influence of extreme low-flow conditions. X-ray absorption spectra identified only SbV in <2 mm sediments, despite boulder size stibnite evident in the creek. Roméite-group minerals were detected by X-ray diffraction in oxidation rims of creek-bed stibnite, which potentially limit the contribution of dissolved SbIII to the waterway. Arsenic in <2 mm sediments was dominated by AsV (17–91 %) and orpiment (16–93 %), while the co-occurrence of AsIII (11–36 %) with orpiment suggests that primary As minerals are an important ongoing source of AsIII to the system. Dissolved metalloids (<45 µm filtered) dominated total water column concentrations and comprised mainly pentavalent species. Arsenic(III) was however identified in most water samples (up to 6.6 µg L−1), while dissolved SbIII was only detected in one sample (3.4 µg L−1) collected during the drought period. Dissolved AsV increased significantly in samples collected in low-flow conditions, considered a result of reductive dissolution of sediment Fe-oxyhydroxide host phases, but a similar increase in dissolved Sb was not observed. This study highlights a greater risk from As in this system, and the likelihood of increased As mobility under the warmer and drier environmental conditions predicted with climate change, especially during first-flush events.
- ItemTotal scattering measurements at the Australian Synchrotron Powder Diffraction beamline: capabilities and limitations(International Union of Crystallography, 2023-03-01) D'Angelo, AM; Brand, HEA; Mitchell, VD; Hamilton, JL; Oldfield, DT; Liu, ACY; Gu, QFThis study describes the capabilities and limitations of carrying out total scattering experiments on the Powder Diffraction (PD) beamline at the Australian Synchrotron, ANSTO. A maximum instrument momentum transfer of 19 Å−1 can be achieved if the data are collected at 21 keV. The results detail how the pair distribution function (PDF) is affected by Qmax, absorption and counting time duration at the PD beamline, and refined structural parameters exemplify how the PDF is affected by these parameters. There are considerations when performing total scattering experiments at the PD beamline, including (1) samples need to be stable during data collection, (2) highly absorbing samples with a μR > 1 always require dilution and (3) only correlation length differences >0.35 Å may be resolved. A case study comparing the PDF atom–atom correlation lengths with EXAFS-derived radial distances of Ni and Pt nanocrystals is also presented, which shows good agreement between the two techniques. The results here can be used as a guide for researchers considering total scattering experiments at the PD beamline or similarly setup beamlines. © 2023 The Authors - Open Access CC-BY Licence 4.0
- ItemTotal scattering measurements at the Australian Synchrotron Powder Diffraction beamline: capabilities and limitations(Australian Nuclear Science and Technology Organisation, 2021-11-24) D'Angelo, AM; Gu, QF; Brand, HEA; Mitchell, VD; Hamilton, JL; Liu, ACY; Oldfield, DTThe PD beamline at the Australian Synchrotron (ANSTO) consistently receives requests to carry out total scattering experiments for various materials including battery electrodes, piezoelectrics and coordination frameworks. In this study we describe the capabilities and limitations of carrying out total scattering experiments on the Powder Diffraction beamline. A maximum instrument momentum transfer of 19 Å-1 can be achieved. Our results detail how the pair distribution function is affected by Qmax, absorption, and counting time duration at the PD beamline. We also trial a variable counting time strategy using the Mythen II detector. Refined structural parameters exemplify how the PDF is affected by these parameters. Total scattering experiments can be carried out at PD although there are limitations. These are: (1) only measurements on stable systems and at non-ambient conditions is possible if the temperature is held during data collection, (2) it is essential to dilute highly absorbing samples (μR>1), and (3) only correlation lengths >0.35 Å may be resolved. A case study comparing the PDF atom-atom correlation lengths with EXAFS derived radial distances of Ni and Pt nanoparticles is also presented, which shows good agreement between the two techniques. The results here can be used as a guide for researchers considering total scattering experiments at the PD beamline. © The Authors
- ItemTransition metal mobility and recoverability from weathered serpentinite and serpentinite skarn tailings from Lord Brassey Mine, Australia and Record Ridge, British Columbia, Canada(Goldschmidt, 2022-07-14) Honda-McNeil, M; Wilson, SA; Locock, A; Mililli, B; Zeyen, N; Wang, B; Turvey, C; Vessey, CJ; Patel, AS; Hamilton, JL; Southam, G; Poitras, J; Jones, TR; Jowitt, S; Lowock, AAs mineral resources become scarcer, companies are lowering their ore cut-off grades and resorting to exploring deeper underground and in more isolated areas. Incorporating tailings storage facilities and tailings reprocessing as part of the ore processing circuit can potentially extend the lives of mines and save on future exploration costs. Ultramafic and mafic mine tailings host resources including first and second row transition metals, such as nickel (Ni), cobalt (Co), and platinum group elements (PGE), whose high value and recovery could serve as a motivator for existing mines to reprocess their tailings. Many of these target metals are initially hosted by olivine, are repartitioned during serpentinization to form sulfides, oxides and alloys, and then are remobilized during weathering to form authigenic carbonates, sulfates and oxyhydroxides. Reprocessing tailings may further provide environmental benefits, including a reduction in waste output and the ability to offset greenhouse gas emissions by enhanced silicate-weathering and carbonation reactions. Here we use powder X-ray diffraction, scanning electron microscopy, electron probe micro-analysis and synchrotron X-ray fluorescence mapping to demonstrate how first and second row transition metals are mobilized to their final sinks. Samples of serpentinite, skarn and weathered tailings from the historical Lord Brassey nickel mine in Tasmania, Australia and weathered outcrops of serpentinite ore from the proposed magnesium mine in Record Ridge, BC, Canada are analyzed and compared. Preliminary results from these climatically similar localities indicate clear transition metal dissemination patterns across alteration zones and distinct partitioning behavior (ex. homogenous distribution of Ni within sulfides) in weathering products. By developing an understanding of the sinks for metals across the mining lifecycle, we aim to cultivate an economically.