Anhydrous Proton Conduction Through a Chemically Robust Electrolyte Enabling a High-Temperature Non-Precious Metal Catalyzed Fuel Cell

Fuel cells offer great promise for portable electricity generation, but their use is currently limited by their low durability, excessive operating temperatures, and expensive precious metal electrodes. It is therefore essential to develop fuel cell systems that can perform effectively using more robust electrolyte materials, at reasonable temperatures, with lower-cost electrodes. Recently, proton exchange membrane fuel cells have attracted attention due to their generally favorable chemical stability and quick start-up times. However, in most membrane materials, water is required for proton conduction, severely limiting operational temperatures. Here, for the first time it is demonstrated that when acidified, PAF-1 can conduct protons at high temperatures, via a unique framework diffusion mechanism. It shows that this acidified PAF-1 material can be pressed into pellets with high proton conduction properties even at high temperatures and pellet thickness, highlighting the processibility, and ease of use of this material. Furthermore, a fuel cell is shown with high power density output is possible using a non-precious metal copper electrode. Acid-doped PAF-1 therefore represents a significant step forward in the potential for a broad-purpose fuel cell due to it being cheap, robust, efficient, and easily processible

NMR-Based Structural Modeling of Graphite Oxide Using Multidimensional 13C Solid-State NMR and ab Initio Chemical Shift Calculations

Chemically modified graphenes and other graphite-based materials have attracted growing interest for their unique potential as lightweight electronic and structural nanomaterials. It is an important challenge to construct structural models of noncrystalline graphite-based materials on the basis of NMR or other spectroscopic data. To address this challenge, a solid-state NMR (SSNMR)-based structural modeling approach is presented on graphite oxide (GO), which is a prominent precursor and interesting benchmark system of modified graphene. An experimental 2D C-13 double-quantum/single-quantum correlation SSNMR spectrum of C-13-labeled GO was compared with spectra simulated for different structural models using ab initio geometry optimization and chemical shift calculations. The results show that the spectral features of the GO sample are best reproduced by a geometry-optimized structural model that is based on the Lerf-Klinowski model (Lerf, A. et al. Phys. Chem. B 1998, 102, 4477); this model is composed of interconnected sp(2), 1,2-epoxide, and COH carbons. This study also convincingly excludes the possibility of other previously proposed models, including the highly oxidized structures involving 1,3-epoxide carbons (Szabo, I. et al. Chem. Mater. 2006, 18, 2740). C-13 chemical shift anisotropy (CSA) patterns measured by a 2D C-13 CSA/isotropic shift correlation SSNMR were well reproduced by the chemical shift tensor obtained by the ab initio calculation for the former model. The approach presented here is likely to be applicable to other chemically modified graphenes and graphite-based systems

Geology and Physical Properties Investigations by the InSight Lander

Although not the prime focus of the InSight mission, the near-surface geology and physical properties investigations provide critical information for both placing the instruments (seismometer and heat flow probe with mole) on the surface and for understanding the nature of the shallow subsurface and its effect on recorded seismic waves. Two color cameras on the lander will obtain multiple stereo images of the surface and its interaction with the spacecraft. Images will be used to identify the geologic materials and features present, quantify their areal coverage, help determine the basic geologic evolution of the area, and provide ground truth for orbital remote sensing data. A radiometer will measure the hourly temperature of the surface in two spots, which will determine the thermal inertia of the surface materials present and their particle size and/or cohesion. Continuous measurements of wind speed and direction offer a unique opportunity to correlate dust devils and high winds with eolian changes imaged at the surface and to determine the threshold friction wind stress for grain motion on Mars. During the first two weeks after landing, these investigations will support the selection of instrument placement locations that are relatively smooth, flat, free of small rocks and load bearing. Soil mechanics parameters and elastic properties of near surface materials will be determined from mole penetration and thermal conductivity measurements from the surface to 3–5 m depth, the measurement of seismic waves during mole hammering, passive monitoring of seismic waves, and experiments with the arm and scoop of the lander (indentations, scraping and trenching). These investigations will determine and test the presence and mechanical properties of the expected 3–17 m thick fragmented regolith (and underlying fractured material) built up by impact and eolian processes on top of Hesperian lava flows and determine its seismic properties for the seismic investigation of Mars’ interior

SEIS: Insight’s Seismic Experiment for Internal Structure of Mars

By the end of 2018, 42 years after the landing of the two Viking seismometers on Mars, InSight will deploy onto Mars’ surface the SEIS (Seismic Experiment for Internal Structure) instrument; a six-axes seismometer equipped with both a long-period three-axes Very Broad Band (VBB) instrument and a three-axes short-period (SP) instrument. These six sensors will cover a broad range of the seismic bandwidth, from 0.01 Hz to 50 Hz, with possible extension to longer periods. Data will be transmitted in the form of three continuous VBB components at 2 sample per second (sps), an estimation of the short period energy content from the SP at 1 sps and a continuous compound VBB/SP vertical axis at 10 sps. The continuous streams will be augmented by requested event data with sample rates from 20 to 100 sps. SEIS will improve upon the existing resolution of Viking’s Mars seismic monitoring by a factor of ∼ 2500 at 1 Hz and ∼ 200 000 at 0.1 Hz. An additional major improvement is that, contrary to Viking, the seismometers will be deployed via a robotic arm directly onto Mars’ surface and will be protected against temperature and wind by highly efficient thermal and wind shielding. Based on existing knowledge of Mars, it is reasonable to infer a moment magnitude detection threshold of Mw ∼ 3 at 40◦ epicentral distance and a potential to detect several tens of quakes and about five impacts per year. In this paper, we first describe the science goals of the experiment and the rationale used to define its requirements. We then provide a detailed description of the hardware, from the sensors to the deployment system and associated performance, including transfer functions of the seismic sensors and temperature sensors. We conclude by describing the experiment ground segment, including data processing services, outreach and education networks and provide a description of the format to be used for future data distribution

Constraints on the shallow elastic and anelastic structure of Mars from InSight seismic data

Mars’s seismic activity and noise have been monitored since January 2019 by the seismometer of the InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) lander. At night, Mars is extremely quiet; seismic noise is about 500 times lower than Earth’s microseismic noise at periods between 4 s and 30 s. The recorded seismic noise increases during the day due to ground deformations induced by convective atmospheric vortices and ground-transferred wind-generated lander noise. Here we constrain properties of the crust beneath InSight, using signals from atmospheric vortices and from the hammering of InSight’s Heat Flow and Physical Properties (HP3) instrument, as well as the three largest Marsquakes detected as of September 2019. From receiver function analysis, we infer that the uppermost 8–11 km of the crust is highly altered and/ or fractured. We measure the crustal diffusivity and intrinsic attenuation using multiscattering analysis and find that seismic attenuation is about three times larger than on the Moon, which suggests that the crust contains small amounts of volatiles

Preface to the virtual special issue on advanced NMR on glasses

International audienceSince the end of the 50’s, Nuclear Magnetic Resonance (NMR) has proven to be a valuable technique for the characterisation of glasses. With the introduction of the high resolution technique of magic angle spinning (MAS) and together with the availability of high magnetic fields, 1D MAS-NMR has now become the standard technique to determine and quantify the boron or aluminium coordination states as well as the silicate or phosphate Qn speciation. But the last 20 years have seen a tremendous amount of more sophisticated NMR techniques becoming - almost routinely- available, which can also be used to provide additional structural information at a larger length scale and/or with a better resolution. This family of NMR techniques, referred to as advanced NMR, has also greatly benefitted from technical and methodological improvements and can now be used to edit 2D map showing spatial proximity or chemical connectivity, to produce better resolution spectra for quadrupolar nuclei, to provide new insights into impact on structural disorder on NMR lineshape, or to determine interatomic distances...In this Virtual Special Issue of the Journal of Non-Crystalline Solids, worldwide-recognized teams were asked for reviews or scientific articles showing how advanced solid state NMR can be applied to vitreous materials. Special attention was paid to publish pedagogic papers that can be easily handled by the whole glass community researchers. Phosphate based glasses have been extensively studied by advanced NMR within the last twenty years. This VSI contains two papers using combination of advanced 1D/2D NMR techniques to investigate the structure of fluoro-phosphate (Jinjun Ren et al., Shanghai Institute of Optics and Fine Mechanics) [1] and boro-phosphate (Grégory Tricot et al., University of Lille) [2] based glasses. Very detailed analysis of 1D NMR spectra lineshape of quadrupolar nuclei (I> ½) in amorphous materials was investigated by Josef Zwanziger et al. (Dalhousie university) in a paper focusing on the Czjzek model [3]. Hellmut Eckert et al. (University of Muenster, University of Sao Paulo) provided a complete reviewing of NMR and EPR applications on rare-earth containing glasses and glass ceramics [4]. Analysis of chalcogenide glasses by 29Si, 31P, 77Se and 125Te 1D and 2D homonuclear correlation NMR was reviewed by Sabyasachi Sen et al. (University of California at Davis) [5]. Sung Keun Lee et al. (Seoul National University) used 1D and MQ-MAS 11B, 27Al and 17O NMR experiments and 11B DQ-SQ experiments to investigate the structure of Na2O-B2O3 and Na2O-B2O3-Al2O3-SiO2 systems [6]. Mattias Eden et al. (Stockholm university) used 17O MAS-NMR and 27Al 1D and 2D DQ-SQ to highlight the presence of unexpected [4]Al-O-[4]Al and [4]Al-NBO bonds in rare earth aluminosilicate glasses [7]To conclude, we would like to thank all the contributors and we do hope that this VSI will be helpful for the entire glass community. We believe that many users of standard 1D NMR will see how advanced NMR can be used to complete structural models and we are looking forward to seeing more and more groups using these advanced NMR techniques within the next years

Through-bond phosphorus-phosphorus connectivities in crystalline and disordered phosphates by solid-state NMR

2D P-31 refocused INADEQUATE NMR experiments have been used to determine through-bond P-O-P connectivities in crystalline and disordered phosphates

Solid-State 19F MAS NMR Investigation of Fluoride Ion Mobility in Lead Fluorides: Correlation with Anionic Conductivity

International audienc