Search

The Chile subduction zone is known to host megathrust earthquakes. This study investigates the near‐field co‐seismic ionospheric perturbations (CIP) associated with recent large to great, shallow depth (22–25 km) earthquakes that occurred in the Chile subduction zone. These earthquakes are (a) 16 September 2015, Mw 8.3 (EQ1) (b) 03 April 2014, Mw 7.7 (EQ2) (c) 01 April 2014, Mw 8.2 (EQ3) (d) 02 January 2011, Mw 7.1 (EQ4), and (e) 27 February 2010, Mw 8.8 (EQ5). Using the Global Navigation Satellite System (GNSS) measured total electron content (TEC), we found that despite the lower magnitude of EQ3 than EQ1 and EQ5, the CIP observed during EQ3 had higher amplitudes than that of EQ5 and EQ1. The amplitude of CIP also depends on non‐seismic parameters in addition to the concerning earthquake magnitude. The comparison of relative CIP amplitudes, in light of the non‐seismic parameters of the geomagnetic field and satellite geometry indicates that background electron density (due to different local times of earthquake occurrence) might contributed to CIP amplitudes. We believe that this thorough analysis leads to a better understanding of non‐seismic factors that can largely influence the CIP amplitudes apart from the earthquake magnitudes. Key Points: GNSS‐TEC measured co‐seismic ionospheric perturbation during the shallow depth earthquakes in Chile‐subduction zoneInvestigating the role of seismic and non‐seismic parameters in manifesting co‐seismic ionospheric perturbationEstimating the dependency between the co‐seismic ionospheric perturbation amplitude and earthquake magnitude [ABSTRACT FROM AUTHOR]

The development of inexpensive and efficient bifunctional electrocatalysts for water splitting is very important but still a challenging task. In the present research, a mixed-valent molecular cluster, [Mn9L4(μ2-O)4(μ3-Cl)2] (1; 5MnII, 4MnIII) possessing cubic Ia3¯d symmetry has been synthesized as an efficient bifunctional water-splitting electrocatalyst for the first time. This synthesis is achieved by adopting a molecular library approach that utilizes an inorganic metal salt, MnCl2·4H2O and a multidentate organic linker, H3L as building blocks (H3L = N,N′-bis[2-carboxybenzomethyl]-N,N′-bis[2-pyridylmethyl]-1,3-diaminopropan-2-ol). The organic linker is so flexible and the inclination towards cubic symmetry is so high that this cluster is readily formed through subcomponent self-assembly. Structural investigation reveals that the metallic hub of 1 consists of a central [MnII(μ2-O)4(μ3-Cl)2] backbone that connects four MnII and four MnIII ions, located at eight vertices of a body-centered cubic (BCC) structure, via the μ2-oxido and μ3-chlorido groups. A total of 24 discrete [Mn9] cluster units are packed together in the unit cell through a number of intramolecular π⋯π stacking interactions among the adjoining benzoate and pyridyl moieties, forming aesthetically attractive 3D polyhedral topologies with essentially large unit cell dimensions, and a cell volume of 113 112(9) Å3. When working as both a hydrogen evolution reaction (HER) and an oxygen evolution reaction (OER) catalyst, 1 exhibits excellent activity with overpotential values of 209 mVHER and 410 mVOER to attain a current density of 10 mA cm−2, and the Tafel slopes of 180 mV decHER−1 and 113.54 mV decOER−1. The chronoamperometric studies reveal the commendable stability of 1, accompanied by minimal degradation of current density which is the key yardstick for HER and OER activities. The mechanistic insight obtained from DFT calculations on the intermediate species show that the MnII–Ooxido–MnIII linkage is the active site for the formation of H2 and O2. [ABSTRACT FROM AUTHOR]

Overall water-splitting reactions provide significant challenges for the rational design and manufacture of electrocatalysts with exceptional capabilities and long-term durability. NiV-LDH is a promising electrocatalyst for OER; however, its low conductivity limits its performance towards total water splitting. This study describes the development of a novel composite material, NiV-LDH@Mn2O3. Mn2O3 indirectly enhances the conductivity of the composite by pulling electrons from NiV-LDH via formed heterojunction. The band gap (1.35 eV) from the Tauc plot analysis further shows the increased electrical conductivity after the heterostructure. Furthermore, the number of active sites increased by 5.34 and 18 times compared with the bare NiV-LDH and Mn2O3, respectively. This increased active sites facilitate a simultaneous enhancement in TOF values of 6.945 × 10−4 and 0.001 s−1 for OER and HER, respectively. In 1 M KOH solution, NiV-LDH@Mn2O3 requires overpotentials of 298 and 185 mV for OER and HER to achieve a 50 mA cm−2 current density with 54 and 48 h of long-term stability, respectively. Moreover, it shows a low cell voltage of 1.604 V to reach a 10 mA cm−2 current density with 70 h stability. Besides, the specific activity after the formation of the heterostructure is increased by 1.8 times compared with the bare materials. This heterostructure strategy paves a unique way for the sustainable production of hydrogen from the electrocatalytic water splitting technique. [ABSTRACT FROM AUTHOR]

In the search for alternative energy sources due to the depletion of fossil fuels, green hydrogen energy produced from the water splitting reaction is considered to be a promising candidate owing to its high energy density and zero carbon emission. This reaction involves two electrons for the production of hydrogen at the cathode and four electrons for the production of oxygen at the anode. Therefore, the oxygen evolution reaction (OER) is as crucial as the hydrogen evolution reaction (HER). However, due to the sluggish kinetics of OER and the low abundance and high cost of the state-of-the-art RuO2 and IrO2 catalysts (noble metals), it is necessary to develop alternative low-cost, highly abundant, reasonably active, and stable catalysts to realize their industrial application in the water splitting reaction. In this case, the sol–gel process involves wet chemical synthesis using low-cost transition metal precursors for the production of various nanostructures, specifically oxide materials. In recent decades, a plethora of sol–gel-synthesized materials including metal oxides, hydroxides, phosphides, sulfides, and their derivatives have demonstrated remarkable efficiency as heterostructure catalysts in promoting water splitting activities including oxygen evolution reactions. In this method, the precursor molecules are mainly dissolved in alcohol or water, forming a sol, and then converted to gel via various approaches, and eventually dried to obtain the resultant catalyst. Accordingly, anticipating continuous growth in the research on these materials due to their cost-effective, easy fabrication, and ability to realize industrial applications, a comprehensive review addressing the enhancement of sol–gel-synthesized composites becomes imperative. This review aims to provide a thorough analysis of the recent research advancements in the sol–gel approach and resulting materials for OER. Particularly, we focus on the recent developments, showcasing their potential applications and reasons why the prepared materials display enhanced catalytic properties. Furthermore, a detailed discussion of prospective avenues for future research is presented. [ABSTRACT FROM AUTHOR]

Ebselen (EbSe), a therapeutically significant molecule, is shown to exhibit chalcogen bonding interaction with nitrite anion (ONO−). This report suggests that the σ-holes of EbSe are powerful for offering weak but influential interactions towards biologically relevant ONO−, thereby assisting oxidative transformations like N-nitrosation of aromatic amines. [ABSTRACT FROM AUTHOR]

Developing acid-stable oxygen evolution/reduction reaction (OER/ORR) electrocatalysts is essential for high-performance water splitting. Still, the slow kinetics of the ORR and OER during the discharge and charge processes seriously impede their advancement in these performances. This report outlines the creation of a nitrogen-doped porous carbon matrix (NC) produced from a zeolitic imidazolate framework (ZIF-8). The matrix includes spatially engineered ultra-low loaded Ru atomic sites and is examined in the context of electrocatalytic oxygen evolution studies. The systematic analysis and computational studies reveal that the Ru atomic sites act as central driving forces, and their formation is confirmed through X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) analyses, specifically X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). These analyses emphasize the presence of Ru–O bonds at approximately 1.4 Å. Moreover, these results were validated by HRTEM, STEM, and HAADF investigations which emphasize the dispersion of atom-scale Ru on the NC(ZnO). Ru1.75@NC(ZnO) shows a low overpotential (320 mV) at a current density of 10 mA cm−2 for the OER because of the high active site utilization. Importantly, the Ru1.75@NC(ZnO) electrode displays an admirable specific capacitance value of 0.0501 mF cm−2 with notable durability of the capacitor after 500 cycles. The studies revealed that the introduction of monometallic Ru into ZIF-derived ZnO tunes intermediate adsorption energies and promotes the reactions by demanding lesser free energy in the water dissociation process. This research advances the pursuit of creating high-efficiency electrocatalysts with single-site structures, aiming for maximum atomic utilization efficiency in oxygen evolution reactions (OERs), particularly on templates derived from ZIFs. [ABSTRACT FROM AUTHOR]