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Vanderbilt University’s role in this collaborative multi-PI project with Savannah River National Laboratory (lead) and Clemson University was to synthesize 2D materials and characterize them for applications specific to Electrochemical hydrogen isotope fractionation - fundamental insights leading to process scale up.
The surface geology and geomorphology of Mars indicates that it was once warm enough to maintain a large body of liquid water on its surface, though such a warm environment might have been transient. The transition to the present cold and dry Mars is closely linked to the history of surface water, yet the evolution of surficial water is poorly constrained. This study presents insights from hydrogen isotopes for the origin and evolution of Martian water reservoirs.
On-line and real-time analysis of a chemical process is a major analytical challenge that can drastically change the way the chemical industry or chemical research operates. With in situ analyses, new and powerful understanding of chemistry can be gained; however, building robust tools for long-term monitoring faces many challenges that include compensating for instrument drift, instrument replacement, and sensor or probe replacement. Accounting for these changes by recollecting calibration data and rebuilding quantification models can be costly and time consuming. Here, in this study, methods to overcome these challenges are demonstrated with an application of Raman spectroscopy to monitoring hydrogen isotopes with varied speciation within dynamic gas streams. Specifically, chemical data science tools such as chemometric modeling are leveraged along with several examples of calibration transfer approaches. Furthermore, the optimization of instrument and sensors cell parameters for targeted gas phase analyses is discussed. While the particular focus on hydrogen is highly beneficial within the nuclear energy sector, mechanisms built and demonstrated here are widely applicable to optical spectroscopy monitoring in numerous other chemical systems that can be leveraged in other hazardous processes.
Intramolecular carbon, hydrogen, and sulfur isotope ratios were measured on a homologous series of organic sulfonic acids discovered in the Murchison meteorite. Mass-independent sulfur isotope fractionations were observed along with high deuterium/hydrogen ratios. The deuterium enrichments indicate formation of the hydrocarbon portion of these compounds in a low-temperature environment that is consistent with that of interstellar clouds. Sulfur-33 enrichments observed in methanesulfonic acid could have resulted from gas-phase ultraviolet irradiation of a precursor, carbon disulfide. The source of the sulfonic acid precursors may have been the reactive interstellar molecule carbon monosulfide.
The Mars Science Laboratory Curiosity rover sampled the aeolian bedform called Rocknest as its first solid samples to be analyzed by the analytical instruments CheMin and SAM. The instruments ingested aliquots from a sieved sample of less than 150 micrometer grains. As discussed in other reports at this conference [e.g., 1], CheMin discovered many crystalline phases, almost all of which are igneous minerals, plus some 10s of percent of x-ray amorphous material. The SAM instrument is focused on understanding volatiles and possible organics in the fines, performing evolved gas analysis (EGA) with the SAM quadrapole mass spectrometer (QMS), isotope measurements using both the QMS and the tunable laser spectrometer (TLS), which is sensitive to CO2, water and methane, and organics with the gas chromatograph mass spectrometer (GCMS). As discussed in the abstract by Franz et al. [2] and others, EGA of Rocknest fines revealed the presence of significant amounts of H2O as well as O-, C- and S-bearing materials. SAM has also tasted the martian atmosphere several times, analyzing the volatiles in both the TLS and QMS [e.g., 3,4]. This abstract will focus on presentation of initial hydrogen isotopic data from the TLS for Rocknest soils and the atmosphere, and their interpretation. Data for CO2 isotopes and O isotopes in water are still being reduced, but should be available by at the conference.
The geology and geomorphology of Mars provide clear evidence for the presence of liquid water on its surface during the Noachian and Hesperien eras (i.e., >3 Ga). In contrast to the ancient watery environment, today the surface of Mars is relatively dry. The current desert-like surface conditions, however, do not necessarily indicate a lack of surface or near-surface water/ice. In fact, massive deposits of ground ice and/or icy sediments have been proposed based on subsurface radar sounder observations. Hence, accurate knowledge of both the evolution of the distribution of water and of the global water inventory is crucial to our understanding of the evolution of the climate and near-surface environments and the potential habitability of Mars. This study presents insights from hydrogen isotopes for the interactive evolution of Martian water reservoirs. In particular, based on our new measurement of the D/H ratio of 4 Ga-old Noachian water, we constrain the atmospheric loss and possible exchange of surface and subsurface water through time.
Slag/dust formation is one of the critical issues regarding tritium retention in advanced fusion reactors. We upgraded an ultrahigh vacuum device, the sample exposure station (SES), to perform temperature-programmed desorption (TPD), also known as thermal desorption spectroscopy, to investigate deuterium (D) retention in powder samples that are utilized as proxies for slag/dust particles formed in fusion reactors. TPD analysis, calibrated for the desorption rate, was successfully performed on commercially available crystalline/amorphous boron (B) powder after D 2 neutral gas or D + ion exposure. We calibrated the B powder temperature measurement for TPD analysis utilizing a D 2 desorption peak from B-D bonding known for its desorption temperature ~700 K. We introduce a separation procedure of observed D TPD signals, convoluted for corresponding D retention pathways, that was necessary for TPD analysis. This is the first report on the retention of D 2 neutral gas to B, and this observation was enabled by utilizing the B powder sample, which has a larger surface area than films commonly used in laboratory experiments. In conclusion, the upgraded SES system will enable us to investigate hydrogen isotope behaviors for powder/dust samples of various elemental compositions, including metals.
The role of nonadiabatic electrons in regulating the hydrogenic isotope-mass scaling of gyrokinetic turbulence in tokamak fusion plasmas is assessed in the transition from ion-dominated core transport regimes to electron-dominated edge transport regimes. We propose a new isotope-mass scaling law that describes the electron-to-ion mass-ratio dependence of turbulent ion and electron energy fluxes. Here, the massratio dependence arises from the nonadiabatic response associated with fast electron parallel motion and plays a key role in altering—and in the case of the DIII-D edge, favorably reversing—the naive gyro-Bohm scaling behavior. In the reversed regime hydrogen energy fluxes are larger than deuterium fluxes, which is the opposite of the naive prediction.
Isotopic measurements have been made on organic sulfur and phosphorus compounds recently discovered in the Murchison meteorite. Carbon, hydrogen and sulfur measurements were performed on individual members of the organic sulfur compounds, alkyl sulfonates; and carbon and hydrogen measurements were made on bulk alkyl phosphonates. Cooper and Chang reported the first carbon isotopic measurements of Murchison organic sulfonates, providing insight into the potential synthetic mechanisms of these and, possibly, other organic species. Hydrogen isotopic measurements of the sulforiates now reveal deuterium excesses ranging from +660 to +2730 %. The deuterium enrichments indicate formation of the hydrocarbon portion of these compounds in a low temperature astrophysical environment consistent with that of dense molecular clouds. Measurements of the sulfur isotopes provide further constraints on the origin and mechanism of formation of these organic molecules. Recently, there has been growing documentation of sulfur isotopic anomalies in meteoritic material. Thiemens and Jackson have shown that some bulk ureilites possess excess S-33 and Thiemens et al. have reported excess S-33 in an oldhamite separate from the Norton County meteorite. Rees and Thode reported a large S-33 excess in an Allende acid residue, however, attempts to verify this measurements have been unsuccessful, possibly due to the heterogeneous nature of the carrier phase. With the recognition that sulfur isotopes may reflect chemistry in the protosolar nebula or the precursor molecular cloud, identification of potential carriers is of considerable interest. In the present study, the stable isotopes of sulfur were measured in methane sulfonic acid extracted from the Murchison meteorite. The isotopic composition was found to be: (delta)S-33 = 2.48 %, (delta)S-34 = 2.49 % and (delta)S-36 = 6.76 %. Based upon analysis of more than 60 meteoritic and numerous terrestrial samples, the mass fractionation lines are defined by Delta-33 = (delta)S-33 -0.50(delta)S-34 and Delta-36 = (delta)s-36 - 1.97 (delta)S-34. From these relationships Delta-33 = 1.24 % and Delta-36 = 0.89 % are observed. These anomalies, particularly the Delta-33, lie well outside the range of analytical uncertainty. They are the largest observed in any meteoritic component and the first found in an organosulfur compound. As discussed by Thiemens and Jackson, due to it's position on the periodic chart, sulfur undergoes chemically induced mass independent isotopic fractionations as does oxygen. Experiments by Mauersberger et. al. show that in such processes, the magnitude of fractionation for the different isotopically substituted species varies with mass and angular momentum; thus, anomalies are expected for both S-33 and S-36, but not necessarily of the same magnitude. Laboratory experiments have also confirmed that chemically produced, mass independent fractionations are mediated by molecular symmetry factors. A chemical source of fractionation requires that the sulfur isotopic anomaly was established in the gas phase, probably in reactions involving symmetric CS2. The discovery of an anomalous sulfur isotopic composition in a specific molecule containing excess deuterium is an important advance in the understanding of the cosmochemistry of sulfur. This evidence suggests that methanesulfonic acid was synthesized by interstellar processes. Further measurements and details of possible synthesis and fractionation mechanisms will be presented.
We developed a novel operando Raman spectroscopy method for investigation of hydrogen (H) isotope exchange reactions in the lithium aluminate (γ-LiAlO 2 ) that allows modeling of tritium behaviors in high temperature and in an irradiated environment. The lithium aluminate pellet is a main component in the Tritium-Producing Burnable Absorber Rod (TPBAR). We used deuterium ( 2 H or D) as a surrogate to simulate tritium ( 3 H or T). We used a surface analysis tools in situ/operando Raman spectroscopy to observe the transformation OH and OD compositional changes. We also used ToF-SIMS to analyze the lithium aluminate pellet control sample to build the base line for future in situ/operando analysis. To conduct operando Raman spectroscopy, we developed a custom reaction cell with a detachable micro heater using microelectromechanical systems (MEMS) and 3D printing techniques. Multiple versions were developed and tested. Using the new reaction cell, we demonstrated operando Raman spectroscopy of water (H 2 O) and deuterated water (D 2 O) with nitrogen (N 2 ) exposure onto the lithium aluminate (LiAlO2) pellet specimen, respectively, using a wet gas injection setup. We also successfully developed a detachable microheater that can heat up to ~250°C for ~90 mins. The Raman spectra did not show clear H 2 O and D 2 O characteristic peaks, which indicates that introducing H 2 O and D 2 O onto the surface of the pellet is challenging due to its dense structure nature. Our efforts suggest that various improvements are needed, such as increasing reaction cell operating gas pressure and thinning pellet sample thickness, to obtain meaningful measurements.
The detection of indigenous water in mare basaltic glass beads has challenged the view established since the Apollo era of a "dry" Moon. Since this discovery, measurements of water in lunar apatite, olivine-hosted melt inclusions, agglutinates, and nominally anhydrous minerals have confirmed that lunar igneous materials contain water, implying that some parts of lunar mantle may have as much water as Earth's upper mantle. The interpretation of hydrogen (H) isotopes in lunar samples, however, is controversial. The large variation of H isotope ratios in lunar apatite (delta Deuterium = -202 to +1010 per mille) has been taken as evidence that water in the lunar interior comes from the lunar mantle, solar wind protons, and/or comets. The very low deuterium/H ratios in lunar agglutinates indicate that solar wind protons have contributed to their hydrogen content. Conversely, H isotopes in lunar volcanic glass beads and olivine-hosted melt inclusions being similar to those of common terrestrial igneous rocks, suggest a common origin for water in both Earth and Moon. Lunar water could be inherited from carbonaceous chondrites, consistent with the model of late accretion of chondrite-type materials to the Moon as proposed by. One complication about the sources of lunar water, is that geologic processes (e.g., late accretion and magmatic degassing) may have modified the H isotope signatures of lunar materials. Recent FTIR analyses have shown that plagioclases in lunar ferroan anorthosite contain approximately 6 ppm H2O. So far, ferroan anorthosite is the only available lithology that is believed to be a primary product of the lunar magma ocean (LMO). A possible consequence is that the LMO could have contained up to approximately 320 ppm H2O. Here we examine the possible sources of water in the LMO through measurements of water abundances and H isotopes in plagioclase of two ferroan anorthosites and one troctolite from lunar highlands.
This report provides a final technical report and listing of products from the research on a research project from Clemson university, focused on use of two-dimensional materials within membranes to accomplish hydrogen ion separations. The project used CVD graphene and related 2D materials to accomplish hydrogen / deuterium / tritium (H/D/T) separation during water electrolysis in proton-exchange-membrane (PEM)-style cells. 2D materials were incorporated into PEM cells at varying places with the aim of accomplishing isotopic sieving through 2D materials by selective hydron transport at high rates and with high selectivity. The project work scope included studies on H/D separation with small-scale cells at Clemson, collaborative work between Clemson and SRNL on computational modeling and tritium separations, and issues associated with scaleup.
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Stable hydrogen, carbon, and nitrogen isotopic ratios (oD, 013C, and olSN) of organic compounds can revcal information about their origin and formation pathways. Several formation mechanisms and environments have been postulated for the amino acids detected in carbonaceous chondrites. As each proposed mechanism utilizes different precursor molecules, the isotopic signatures of the resulting amino acids may indicate the most likely of these pathways. We have applied gas chromatography with mass spectrometry and combustion isotope ratio mass spectrometry to measure the compound-specific C, N, and H stable isotopic ratios of amino acids from seven CM and CR carbonaceous chondrites: CM1I2 Allan Hills (ALH) 83100, CM2 Murchison, CM2 Lewis Cliff (LEW) 90500, CM2 Lonewolf Nunataks (LON) 94101, CRZ Graves Nunataks (GRA) 95229, CRZ Elephant Moraine (EET) 92042, and CR3 Queen Alexandra Range (QUE) 99177. We compare the isotopic compositions of amino acids in these meteorites with predictions of expected isotopic enrichments from potential formation pathways. We observe trends of decreasing ODC and increasing oD with increasing carbon number in the aH, (l-NH2 amino acids that correspond to predictions made for formation via Streckercyanohydrin synthesis. We also observe light ODC signatures for ~-alanine, which may indicate either formation via Michael addition or via a pathway that forms primarily small, straight-chain, amine-terminal amino acids (n-ro-amino acids). Higher deuterium enrichments are observed in amethyl amino acids, indicating formation of these amino acids or their precursors in cold interstellar or nebular environments. Finally, individual amino acids are more enriched in deuterium in CR chondrites than CM chondrites, reflecting different parent-body chemistry.
Hydrogen in nominally anhydrous minerals (NAMs) in meteorites provides insight to mantle sources of indigenous water on differentiated bodies: e.g. Peslier et al. 2017 [1], including Mars [2-4]. However, all meteorite samples, including Martian shergottites, record impact events as fractures, deformation, silicate darkening, shock melt veins and pockets, etc. The effect of shock on hydrogen in NAMs is poorly constrained, and must be understood prior to using these data to infer planetary indigenous water. Here we present water contents and D/H ratios (calculated as dD, i.e. the variation of the D/H ratio relative to a standard, in this case sea water "SMOW") in pyroxene, olivine and maskelynite in the olivine-phyric shergottite Larkman Nunatak 06319 (LAR 06319) as a function of proximity to impact melt. While the results suggest impact may have a role in fractionating H isotopes, the magmatic signature of H2O in Mars can be preserved in some pyroxene.
Observations from several experimental scenarios by various research groups found that releasing deuterium gas from hydrided palladium (Pd) metal can result in unexplained temperature increases. This heating is possible evidence of heat generation in what is ostensibly an endothermic process. Creating a method for identifying and repeating this unusual scenario is beneficial for understanding the occurrence of such temperature increases. It is suspected that x-ray radiation and significant deuterium concentrations may contribute to such reactions. The work, described here, attempted to determine if x-ray stimulation, combined with diffusion of hydrogen or deuterium gas, can cause anomalous nuclear behavior in thin Pd-silver (Ag) and titanium (Ti)-carbide coated Pd-Ag sample disks.
This final report summarizes the PhD research of Dr. Mayura Silva who was supported on the project from inception in August 2021 to his graduation in December 2023. Dr. Silva undertook a detailed examination of the eGicacy of graphene interlayers on H/D selectivity in electrochemical proton / deuteron pump cells. His work focused on the role of impurity cations (especially NH 4 * and Cu 2+ which are resident in membranes as a residual from the ammonium persulfate treatment used to remove copper backing from the graphene during membrane preparation), and on the composition of evolved gases from hydrogen / deuterium pump cells that were fed a 50:50 mixture of H 2 and D 2 gas. The key finding is that previous reports of very high H/D selectivity in hydrogen pump cells having Nafion | graphene | Nafion membranes installed were not reproduced.