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1. Mechanical, thermal, and electrochemical properties of Pr doped ceria from wafer curvature measurements

   https://doi.org/10.1039/c8cp04802a  

   Ma, Yuxi ; Nicholas, Jason D. ( November 2018 , Physical Chemistry Chemical Physics)

   This work demonstrates, for the first time, that a variety of disparate and technologically-relevent thermal, mechanical, and electrochemical oxygen-exchange material properties can all be obtained from in situ , current-collector-free wafer curvature measurements. Specifically, temperature or oxygen partial pressure induced changes in the curvature of 230 nm thick (100)-oriented Pr 0.1 Ce 0.9 O 1.95−x (10PCO) films atop 200 μm thick single crystal yttria stabilized zirconia or magnesium oxide substrates were used to measure the biaxial modulus, Young's modulus, thermal expansion coefficient, thermo-chemical expansion coefficient, oxygen nonstoichiometry, chemical oxygen surface exchange coefficient, oxygen surface exchange resistance, thermal stress, chemical stress, thermal strain, and chemical strain of the model mixed ionic electronic conducting material 10PCO. The (100)-oriented thin film 10PCO thermal expansion coefficient, thermo-chemical expansion coefficient, oxygen nonstoichiometry, and Young's modulus (which is essentially constant, at ∼200 MPa, over the entire 280–700 °C temperature range in air) measured here were similar to those from other bulk and thin film 10PCO studies. In addition, the measured PCO10 oxygen surface coefficients were in agreement with those reported by other in situ , current-collector-free techniques. Taken together, this work highlights the advantages of using a sample's mechanical response, instead of the more traditional electricalmore »response, to probe the electrochemical properties of the ion-exchange materials used in solid oxide fuel cell, solid oxide electrolysis cell, gas-sensing, battery, emission control, water splitting, water purification, and other electrochemically-active devices.« less
2. Solution- and gas-phase behavior of decavanadate: implications for mass spectrometric analysis of redox-active polyoxidometalates

   https://doi.org/10.1039/d1qi01618k  

   Favre, Daniel ; Bobst, Cedric E. ; Eyles, Stephen J. ; Murakami, Heide ; Crans, Debbie C. ; Kaltashov, Igor A. ( March 2022 , Inorganic Chemistry Frontiers)

   Decavanadate (V 10 O 28 6− or V10) is a paradigmatic member of the polyoxidometalate (POM) family, which has been attracting much attention within both materials/inorganic and biomedical communities due to its unique structural and electrochemical properties. In this work we explored the utility of high-resolution electrospray ionization (ESI) mass spectrometry (MS) and ion exclusion chromatography LC/MS for structural analysis of V10 species in aqueous solutions. While ESI generates abundant molecular ions representing the intact V10 species, their isotopic distributions show significant deviations from the theoretical ones. A combination of high-resolution MS measurements and hydrogen/deuterium exchange allows these deviations to be investigated and interpreted as a result of partial reduction of V10. While the redox processes are known to occur in the ESI interface and influence the oxidation state of redox-active analytes, the LC/MS measurements using ion exclusion chromatography provide unequivocal evidence that the mixed-valence V10 species exist in solution, as extracted ion chromatograms representing V10 molecular ions at different oxidation states exhibit distinct elution profiles. The spontaneous reduction of V10 in solution is seen even in the presence of hydrogen peroxide and has not been previously observed. The susceptibility to reduction of V10 is likely to be shared bymore »other redox active POMs. In addition to the molecular V10 ions, a high-abundance ionic signal for a V 10 O 26 2− anion was displayed in the negative-ion ESI mass spectra. None of the V 10 O 26 cations were detected in ESI MS, and only a low-abundance signal was observed for V 10 O 26 anions with a single negative charge, indicating that the presence of abundant V 10 O 26 2− anions in ESI MS reflects gas-phase instability of V 10 O 28 anions carrying two charges. The gas-phase origin of the V 10 O 26 2− anion was confirmed in tandem MS measurements, where mild collisional activation was applied to V10 molecular ions with an even number of hydrogen atoms (H 4 V 10 O 28 2− ), resulting in a facile loss of H 2 O molecules and giving rise to V 10 O 26 2− as the lowest-mass fragment ion. Water loss was also observed for V 10 O 28 anions carrying an odd number of hydrogen atoms ( e.g. , H 5 V 10 O 28 − ), followed by a less efficient and incomplete removal of an OH˙ radical, giving rise to both HV 10 O 26 − and V 10 O 25 − fragment ions. Importantly, at least one hydrogen atom was required for ion fragmentation in the gas phase, as no further dissociation was observed for any hydrogen-free V10 ionic species. The presented workflow allows a distinction to be readily made between the spectral features revealing the presence of non-canonical POM species in the bulk solution from those that arise due to physical and chemical processes occurring in the ESI interface and/or the gas phase.« less
3. Accelerating water dissociation in bipolar membranes and for electrocatalysis

   https://doi.org/10.1126/science.aaz1487  

   Oener, Sebastian Z. ; Foster, Marc J. ; Boettcher, Shannon W. ( July 2020 , Science)

   Catalyzing water dissociation (WD) into protons and hydroxide ions is important both for fabricating bipolar membranes (BPMs) that can couple different pH environments into a single electrochemical device and for accelerating electrocatalytic reactions that consume protons in neutral to alkaline media. We designed a BPM electrolyzer to quantitatively measure WD kinetics and show that, for metal nanoparticles, WD activity correlates with alkaline hydrogen evolution reaction activity. By combining metal-oxide WD catalysts that are efficient near the acidic proton-exchange layer with those efficient near the alkaline hydroxide-exchange layer, we demonstrate a BPM driving WD with overpotentials of <10 mV at 20 mA·cm⁻²and pure water BPM electrolyzers that operate with an alkaline anode and acidic cathode at 500 mA·cm⁻²with a total electrolysis voltage of ~2.2 V.
4. Green synthesis of nanoscale anion exchange resin for sustainable water purification

   https://doi.org/10.1039/C8EW00593A  

   Sahu, Abhispa ; Blackburn, Kayla ; Durkin, Kayla ; Eldred, Tim B. ; Johnson, Billy R. ; Sheikh, Rabia ; Amburgey, James E. ; Poler, Jordan C. ( January 2018 , Environmental Science: Water Research & Technology)

   The challenge of providing safe and reliable drinking water is being exacerbated by accelerating population growth, climate change, and the increase of natural and anthropogenic contamination. Current water treatment plants are not effective at the removal of pervasive, hydrophilic, low molecular weight contaminants, which can adversely affect human health. Herein, we describe a green all-aqueous synthesis of an ion exchange resin comprised of short chain polyelectrolyte brushes covalently bound to single walled carbon nanotubes. This composite material is incorporated onto a membrane and the active sites are tested against analyte adsorption. Our control studies of water or brine pushed through these materials, found no evidence of single-walled carbon nanotubes (SWCNTs) or carbon/polymer coming out of the membrane filter. We have measured the adsorption capacity and percentage removal of ten different compounds (pharmaceuticals, pesticides, disinfection byproducts and perfluoroalkylated substances). We have measured their removal with an efficiency up to 95–100%. The synthesis, purification, kinetics, and characterization of the polyelectrolytes, and the subsequent nanoresin are presented below. The materials were tested as thin films. Regeneration capacity was measured up to 20 cycles and the material has been shown to be safe and reusable, enabling them as potential candidates for sustainable water purification.
5. A Hybrid Catalytic Hydrogenation/Membrane Distillation Process for Nitrogen Recovery from Nitrate-Contaminated Waste Ion Exchange Brine

   https://doi.org/10.1016/j.watres.2020.115688  

   Huo, X. ; Vanneste, J. ; Cath, T.Y. ; Strathmann, T.J. ( January 2020 , Water research)

   Ion exchange is widely used to treat nitrate-contaminated groundwater, but high salt usage for resin regeneration and management of waste brine residuals increase treatment costs and add environmental burdens. Development of palladium-based catalytic nitrate treatment systems for brine treatment and reuse has showed promising activity for nitrate reduction and selectivity towards the N2 over the alternative product ammonia, but this strategy overlooks the potential value of nitrogen resources. Here, we evaluated a hybrid catalytic hydrogenation/membrane distillation process for nitrogen resource recovery during treatment and reuse of nitrate-contaminated waste ion exchange brines. In the first step of the hybrid process, a Ru/C catalyst with high selectivity towards ammonia was found to be effective for nitrate hydrogenation under conditions representative of waste brines, including expected salt buildup that would occur with repeated brine reuse cycles. The apparent rate constants normalized to metal mass (0.30 ± 0.03 mM min−1 gRu−1 under baseline condition) were comparable to the state-of-the-art bimetallic Pd catalyst. In the second stage of the hybrid process, membrane distillation was applied to recover the ammonia product from the brine matrix, capturing nitrogen as ammonium sulfate, a commercial fertilizer product. Solution pH significantly influenced the rate of ammonia mass transfer through themore »gas-permeable membrane by controlling the fraction of free ammonia species (NH3) present in the solution. The rate of ammonia recovery was not affected by increasing salt levels in the brine, indicating the feasibility of membrane distillation for recovering ammonia over repeated reuse cycles. Finally, high rates of nitrate hydrogenation (apparent rate constant 1.80 ± 0.04 mM min−1 gRu−1) and ammonia recovery (overall mass transfer coefficient 0.20 m h−1) with the hybrid treatment process were demonstrated when treating a real waste ion exchange brine obtained from a drinking water utility. These findings introduce an innovative strategy for recycling waste ion exchange brine while simultaneously recovering potentially valuable nitrogen resources when treating contaminated groundwater.« less