Towards reliable three-electrode cells for lithium–sulfur batteries

Three-electrode measurements are valuable to the understanding of the electrochemical processes in a battery system. However, their application in lithium–sulfur chemistry is difficult due to the complexity of the system...

Reversible electrochemical oxidation of sulfur in ionic liquid for high-voltage Al−S batteries

Sulfur is an important electrode material in metal−sulfur batteries. It is usually coupled with metal anodes and undergoes electrochemical reduction to form metal sulfides. Herein, we demonstrate, for the first time, the reversible sulfur oxidation process in AlCl3/carbamide ionic liquid, where sulfur is electrochemically oxidized by AlCl4− to form AlSCl7. The sulfur oxidation is: 1) highly reversible with an efficiency of ~94%; and 2) workable within a wide range of high potentials. As a result, the Al−S battery based on sulfur oxidation can be cycled steadily around ~1.8 V, which is the highest operation voltage in Al−S batteries. The study of sulfur oxidation process benefits the understanding of sulfur chemistry and provides a valuable inspiration for the design of other high-voltage metal−sulfur batteries, not limited to Al−S configurations.

Microbial diversity in an early earth analogue: From ancient novelty to modern commonality

Life emerged and diversified in the absence of molecular oxygen 1. The prevailing anoxia and unique sulfur chemistry in the Paleo-, Meso- and Neoarchean, and early Proterozoic eons may have supported microbial communities that are drastically different than those currently thriving on the earth’s surface 2–4. Zodletone spring in southwestern Oklahoma represents a unique habitat where spatial sampling could substitute for geological eons: from the anoxic, surficial light-exposed sediments simulating a preoxygenated earth, to overlaid water column where air exposure simulates the relentless oxygen intrusion during the Neo-Proterozoic 5. We discovered a remarkably diverse microbial community in the spring sediments, with two thirds (340/516) of the metagenomic assembled genomes belonging to 200 bacterial and archaeal families that were either previously undescribed or are extremely rare elsewhere on earth. Such diversity is underpinned by the widespread occurrence of sulfite-, thiosulfate-, tetrathionate-, and sulfur-reduction, in contrast with a paucity of sulfate-reduction metabolism in those taxa. This greatly expands the diversity of lineages mediating reductive sulfur cycling processes in the tree of life. In the overlaying water community oxygen intrusion leads to the establishment of a significantly less diverse community dominated by well-characterized lineages and the prevalence of oxidative sulfur cycling processes. Such transition from ancient novelty to modern commonality underscores the profound impact of the great oxygenation event on the earth’s surficial anoxic community.. It also suggests that novel and rare lineages encountered in current anaerobic habitats could represent taxa once thriving on the anoxic earth that have failed to adapt to the progressive oxygenation.

Ground-based measurements of HCl abundance at the cloud top of Venus

<p>The atmosphere of Venus can be vertically divided into three regions with different chemical conditions. High temperature and pressure and the absence of effective photolysis processes are dominant in the lower atmosphere up to 60 km. The middle atmosphere between 60 and 110 km is controlled by photochemistry driven by solar UV radiation. In the upper atmosphere above 110 km, dissociation, ionization, and ionospheric reactions are important processes.</p> <p>HCl is the primary chlorine reservoir in the Venus’ atmosphere below 110 km. Highly reactive chlorine species (ClO<sub>x</sub>) is produced by solar UV photolysis of HCl and has been proposed to play an important role in catalysis of CO and O recombination to CO<sub>2</sub>, thereby stabilizing the CO<sub>2</sub> atmosphere. Chlorine chemistry is also linked to sulfur chemistry and its understanding is necessary to explain the observed vertical distribution of SO<sub>2</sub>.</p> <p>Interestingly, there is a large inconsistency between the HCl abundances measured by spacecraft and ground-based telescopes. The SOIR instrument onboard Venus Express measured its abundance as less than ~50 ppb at the cloud top (~70 km) increasing with altitude, reaching to 1 ppm in the upper atmosphere (~110 km) [Mahieux et al., 2015]. Such a vertical trend conflicts with the results obtained by sub-mm ground-based observations which inferred a vertically constant profile (up to ~80 km) [Sandor and Clancy, 2012]. Near-infrared ground-based observations also showed the HCl abundance at the cloud top as ~500 ppb [Iwagami et al., 2008; Krasnopolsky, 2010], which are nearly one order of magnitude larger than the SOIR results. The reason for this inconsistency has not been understood yet.</p> <p>In order to re-examine HCl abundance at the cloud top, we carried out a high-resolution spectroscopy of Venus’ dayside at wavelengths of 3.580-3.934 μm with IRTF/iSHELL on August 5-7, 2018 and August 18-20, 2020 (UT). Venus was near its greatest eastern and western elongations, respectively, in the observation periods. Taking the full advantages of iSHELL’s high spectral resolution of R ~ 75,000, iSHELL resolved individual HCl lines with sufficient separation from terrestrial lines. We analyzed three cross-dispersed echelle orders (orders 141, 142, and 144). For each order, retrievable lines of HCl<sup>35</sup>, HCl<sup>37</sup>, and O<sup>16</sup>C<sup>12</sup>O<sup>18</sup> were included. With using radiative transfer modeling, HCl<sup>35</sup> and HCl<sup>37</sup> abundances were derived after cloud top altitude was retrieved from several O<sup>16</sup>C<sup>12</sup>O<sup>18</sup> lines. Our preliminary results showed that HCl abundance at the cloud top is at least larger than 100 ppb and does not vary with the observation period (i.e., no difference between the morning and evening hemispheres).</p> <p>In this presentation, we show latitudinal distribution of HCl abundance and its isotopic (HCl<sup>35</sup>/HCl<sup>37</sup>) ratio at the cloud top, retrieved from the iSHELL spectra and compare them with the previous studies.</p>