High-conductivity Layer Research Articles

Three-Dimensional Electromagnetic Imaging of Geothermal System in Gonghe Basin

To better understand the geothermal system of the Gonghe Basin, we deployed 471 magnetotelluric survey points with an average distance of 2~3 km, covering the eastern and southern areas of the Basin. We used ModEM inversion software to carry out 3D inversion of 431 survey points and established a 3D-electrical model at a depth of 50 km in the area. The resistivity model shows that the low resistivity in the shallow part of the basin is related to the Cenozoic loose sedimentary cover, while the resistivity values of the mountains around the basin and the magmatic rock uplift zone are higher. The electrical model also shows that the high-conductivity layer is widely distributed in the middle and lower crust (15~35 km) of the basin, and direction of the high-conductivity layer is consistent with that of NW–SE fault in the basin. These high-conductivity layers may be the principal reason for the high heat flow values in the Gonghe Basin. Our resistivity model also shows that there is an obvious discontinuity between high- and low-resistivity blocks at different depths in the middle and upper crust. These discontinuities are consistent with the faults observed on the surface, which are related to the strong topographic relief. Our electrical model shows that these faults in the middle and upper crust are connected with the high-conductivity layer as the channel of heat transfer to the shallow part. Finally, the heat energy is enriched in the Triassic granite to form dry hot rock (HDR). The 3D-magnetotelluric imaging results depict the 3D-distribution characteristics of the geothermal system in the eastern and southern parts of the Gonghe Basin.

Crustal structure beneath the Jiamusi Block and the Nadanhada Terrane from seismic and magnetotelluric studies: Implications for the subduction of the Pacific Plate

The Nadanhada terrane is considered to accrete to the eastern end of the Jiamusi Block during the Pacific Plate subduction. Constraints on the deep structure of the Nadanhada terrane and Jiamusi Block are essential to study the evolution, transformation and current activity of the eastern Asian continental margin. To reconstruct the accretion processes, two magnetotelluric sounding sections and a seismic reflection section were conducted in the eastern part of Jiamusi Block, the middle, and the southern end of the Nadanhada terrane respectively. Geophysical data revealed resistant stable structures and west-dipping discontinuous reflections with a thickness of around 15 km in the upper crust of Jiamusi Block. In contrast, the lower crust of the Jiamusi block exhibited high conductivity and short sub-horizontal reflections that suggest upwelling of mantle material under Pacific Plate subduction. Moreover, the low resistivity zone observed connecting the shallow crust with the upper mantle in the Tongjiang-Yuejinshan fault was interpreted as the boundary line between the Jiamusi block and Nadanhada terrane. The Nadanhada terrane can be subdivided into the Yuejinshan and Raohe complexes based on their distinct geophysical features. The Yuejinshan Complex is characterized by irregular bodies with high resistivity and short arc reflections with a thickness of about 10 km. In contrast, the Raohe Complex displays high-resistivity blocks and west-dipping thrust nappe strong reflections with a thickness of about 5 km. Additionally, the high-conductivity layer located between the Raohe Complex and the underlying basement is believed to be the detachment zone. Since the Cretaceous, the continuous subduction of the Pacific Plate has caused magmatism that has led to the high conductivity crust. The observation of low-resistivity channels and arcuate reflections within the crust supports the notion of upwelling of mantle-derived materials brought about by the subduction of the Pacific Plate in the Cenozoic era.

Electrical structures in the central part of the North China Craton and their implications for the mechanism of Craton destruction

The North China Craton is a stable cratonic block that emerged in the Paleozoic era. During the late Mesozoic era, lithospheric stretching and thinning, as well as volcanic activities, caused extensive destruction of the craton. In this study, we conducted a magnetotelluric profile within the North China Craton, covering the western (Ordos Block), middle (Taihangshan Uplift), and eastern (North China Plain) segments of the craton. The electrical structure along the profile was obtained. Our analysis revealed that the Huoshan fault and the piedmont fault of the Taihangshan are large-scale high- and low-resistivity boundaries, which traverse the entire crust. These two faults divide the three major secondary blocks within the North China Craton. The crust of the Taihangshan Uplift is characterized by a layered high-resistivity body, while the lower and middle crust exhibits widespread high conductivity layer. The crustal-scale structures of the North China Plain and the Ordos Block on both sides are dominated by stable layered resistivity structures. This indicates that the lithospheric destruction near the profile may have mainly concentrated beneath the central Taihangshan Uplift. The seismogenic environment of the 1303 Hongtong earthquake may have been controlled by multiple factors. The upwelling of mantle-derived materials in the lower and middle crust beneath the Taihangshan Uplift caused the extension of the Shanxi Graben fault system where the Linfen Graben is located. The main controlling factor of this earthquake is the southeastward sliding of the Huoshan fault. We speculate that the destruction process beneath the central Taihangshan Uplift of the North China Craton exhibited a bottom-up process, and the thermo-mechanical-chemical erosion mechanism may have dominated the destruction of craton.

Enhanced Magnetic Properties and Thermal Conductivity of FeSiCr Soft Magnetic Composite with Al2O3 Insulation Layer Prepared by Sol-Gel Process

FeSiCr soft magnetic composites (SMCs) were fabricated by the sol-gel method, and an Al2O3/resin composite layer was employed as the insulation coating. By the decomposition of boehmite (AlOOH) gel into Al2O3 in the temperature range of 606–707 °C, a uniform Al2O3 layer could be formed on the FeSiCr powder surface. The Al2O3 insulation coating not only effectively reduced the core loss, increased the resistivity, and improved the quality factor, but it also increased the thermal conductivity of SMCs. The best overall properties with saturation magnetization Ms = 188 emu/g, effective permeability μe = 39, resistivity ρ = 8.28 × 105 Ω·cm, quality factor Q = 94 at 1 MHz, and core loss = 1173 mW/cm3 at 200 kHz and 50 mT were obtained when the SMC was prepared with powders coated by 0.5 wt.% Al2O3 and resin. The optimized SMC exhibited the lowest core loss with 27% reduction compared to the resin only-insulated sample and 71% reduction compared to the sample without insulation treatment. Importantly, the thermal conductivity of the SMCs is 5.3 W/m·K at room temperature, which is higher than that of the samples prepared by phosphating and SiO2 coating owing to the presence of a high thermal conductive Al2O3 layer. The high thermal conductivity is beneficial to enhancing the high temperature performance, lifetime, and reliability of SMCs. This work is expected to be a valuable reference for the design and fabrication of SMCs to be applied in high-temperature and high-frequency environments.

Electrical structure of the fault system in the Tangyin graben, eastern margin of the Taihangshan uplift, China: Inferences from magnetotelluric imaging

We present three-dimensional magnetotelluric images across the southern segment of the Taihangshan uplift and the Tangyin graben. Distinct electrical structures are recognized between these two regions. The upper crust of the southern segment of the Taihangshan uplift is characterized by a high resistivity structure, and the underlying middle and lower crust contain a high conductivity layer. On the eastern side of the uplift, the upper crust contains a high conductivity structure in the Tangyin graben and a high resistivity structure in the Neihuang uplift. The lower crust is dominated by a single coherent high resistivity structure. The Tangxi fault, Tangdong fault, and the western margin fault of the Neihuang uplift collectively form a flower structure, wherein the Tangdong fault is dominant. Three-dimensional inversion is also carried out for magnetotelluric profiles across the central-northern segment of the Taihangshan uplift and the Shijiazhuang-Jinxian depression to serve as a comparison for the southern portion of the Taihangshan uplift. The central-northern segment of the Taihangshan uplift is characterized by a high resistivity structure. The upper crust of the Shijiazhuang-Jinxian depression is characterized by a combination of a high conductivity graben and a high resistivity adjacent uplift. The deep electrical structure of the Tangdong fault and the associated concealed subvertical electrical boundary zone are quite similar to the electrical structure in the vicinity of the 1966 Xingtai earthquake. We conclude that the existence of tectonic conditions in the middle and lower crust of the Tangyin graben might be capable of creating moderate to strong earthquakes.

Цифровая осциллография полимерных мембран с протонной проводимостью

Polyvinyl alcohol-based cast membranes have promising application in creating commonly available fuel cells and fuel synthesizers, as well as inexpensive water sources and microelectromechanical systems. In order to control the properties of such membranes a deep understanding of the charge transfer mechanisms and their relationship with the structure formed at a certain composition and manufacturing technology is required. A method for studying the structure of the proton-conductive polymer membranes using digital oscillography of ion currents excited by the low-frequency rectangular pulses with the amplitudes below the threshold voltage of the ionic conductivity in a dehydrated membrane, and for the analysis of the resulting ion current pulses (spikes) in the frames of the model of a proton pump acting in each layer of the membrane is proposed in this paper. Fast Fourier transform of these oscillograms reveals from 2 to 4 branches or spike sequences corresponding to the phases with different ionic conductivity and makes it possible to determine the thicknesses of both high-conductivity phase layers (7–30 µm) and low-conductivity phase interlayers (1–7 µm) formed in the process of polymerization. The reason of spike merging into bursts is described in terms of successively induced increase in the excited proton density over a threshold value in highly conductive layers. The resonance observed in dry proton membranes at the frequencies of about 2.2 to 3.0 kHz is interpreted as the burst merge point with the further increase in impedance due to proton lagging and respective decrease in the effective thickness of active layers. The effective charge carrier concentrations (as small as 1012 to 1013 cm−3) and the velocity (from 5 to 18 cm/s for the highly conductive phases which turned out to be much higher than those observed in solutions) are estimated. The asymmetry of the cast membranes, which becomes apparent at low frequencies and causes the generation of a direct ion current in response to excitation by a purely alternating current, is studied. It is found that the apparent conductivity determining contribution to the total ohmic resistance is made by a thin interlayer with a very low ion velocity, presumably surface layer, rather than the main layers. The conclusion on the optimization of the production technology and the composition of the proton membranes for various applications is made.

Granite thermal reservoirs in Lingshui area of Hainan Island and their significance to geothermal resources, China

Hainan Island located at the southernmost tip of the continental crust of the South China Plate, has high terrestrial heat-flow values, widely-distributed hot springs, and rich geothermal resources. Intensified researches on the origin and potentials of geothermal resources can promote Hainan Island's development into a clean energy island. To determine the geological conditions for the formation of geothermal resources in southern Hainan Island, we collected core samples of granites from the Baocheng batholith in southern Hainan Island and conducted systematic analysis in respect of petrology, geochronology, geochemistry, and petrophysical property. The results of this study are as follows. The Baocheng batholith in the southern Hainan Island has a crystallization age of 98.42 ± 0.56 Ma, making it the product of magmatism in the early stage of the Late Cretaceous. It mainly consists of high-K calc-alkaline granites, which were intruded by intermediate-to-mafic veins. The Baocheng batholith has a high radioactive heat generation rate of 2.712–6.843 μW/m3, with an average of 3.846 μW/m3, a radioactive heat-flow value of 30.768 mW/m2 and a heat-flow contribution rate of 38.95%–43.95%. As shown by the results of their thermophysical property analysis, the granites have high thermal conductivity and can serve as high-quality geothermal reservoirs. In combination with previous geological and geophysical data, the geothermal model of the Lingshui area was established in this study. The deep structure indicates the presence of high-conductivity and low-resistivity layers in the basement of the Baocheng batholith. It can be inferred thereby that asthenospheric upwelling may occur and that there exist two magma vents at depth in the batholith. Therefore, magmatic heat at depth and granites with high radioactive heat generation rate serve as the main heat sources in the Lingshui area.

3-D Inversion of Gravity Data of the Central and Eastern Gonghe Basin for Geothermal Exploration

The Gonghe Basin is one of the most important regions for the exploration and development of hot dry rock geothermal resources in China. However, there is still some controversy about the main heat source of hot dry rock geothermal resources in the Gonghe Basin. Combined with previous research results including three-dimensional magnetotelluric imaging and linear inversion of Rayleigh wave group and phase velocity result, we obtained a high-resolution underground spatial density distribution model of the Gonghe Basin based on satellite gravity data by using 3-D gravity focusing inversion method. According to the results, there are widely distributed low density anomalies relative to surrounding rock in the middle crust of the study area. The low-density layer is speculated to be a low-velocity, high-conductivity partial melting layer in the crust of the Gonghe Basin. The inversion result confirms for the first time the existence of a partial melt layer from the gravity point of view, and this high temperature melt layer may be the main heat source of the hot dry rock geothermal resources in the Gonghe Basin. It can provide a new basis for further research on the genesis of the hot dry rock geothermal system in the Gonghe Basin.

Application of geophysical techniques for shallow groundwater investigation using 1D-lateral constrained and 2D inversions in Ras Gara area, southwestern Sinai, Egypt

There is an urgent need for greater water resources to support sustainable development in Ras Gara area of southwestern Sinai. Determining the water-bearing zones of the shallow Quaternary aquifer of the Araba Formation in the study region is therefore the main objective of the research. This will be done by using a variety of geophysical techniques, such as DC resistivity sounding and shallow seismic refraction surveys. Using the Schlumberger array (max. AB = 1200 m), the DC data were gathered at 27 VES locations along five primary profiles. At the same locations, 27 spreads totaling 115 m in length of seismic data were also performed. One-dimensional laterally constrained (1D-LCI) inversion is only applied to the DC data in order to generate a best-fit model, whereas 2D inversion is applied to other datasets. The area is divided up into five geo-electrical layers based on the results of 1D-LCI inversion of DC data, and the aquifer is classified into fresh (third layer) and saline bearing-zones (fourth layer). The resistivity values of the fresh-zone range from 8.7 to 26.7 Ω.m, with only low values (5–7.5 Ω.m) found at some VES sites, while the resistivity values of the saline-zone range between 0.9 and 3 Ω.m, except for (14.4 Ω.m) at VES-04. At depths of (2.4–15.6 m) and (8.7–28.5 m) for the fresh and saline zones, respectively. In this region, the shallow low resistive (about 10–100 Ω.m) and intermediate high conductive (< 10 Ω.m) layers of the 2D-DC inverted model represent the fresh and saline zones of the aquifer, respectively. The basement rocks were represented by a deep, extremely high resistive layer that can reach 40,000 Ω.m. Three subsurface layers are identified from the results of the 2D inversion of seismic data (VP1 = 400–1100 m.s−1, VP2 = 1200–1900 m.s−1 and VP3 = 2400–5400 m.s−1). The saturated zone of this aquifer is represented by the second layer (depth, 3.7–20.5 m). The basement rocks are also reflected in the last layer of high velocity. The inversion results and the previously available hydro-geological map data show a good degree of concordance. In the eastern portion of the study area, additional water wells could be drilled for additional water resources.

Analysis of Impact of Bioimpedance on Performance of Implant coil of Artificial Retina for Optimizing Q factor & Bandwidth.

Spiral coils are indispensable part of implantable electronics for facilitating wireless power and data transfer. Although many advanced high Q receiver design have emerged, implementing and retaining high Q in biological medium so as to improve link efficiency is challenging. This article bridges the gap between advanced techniques towards improving link efficiency and the tissue losses that deteriorates the Q factor of coil in heterogeneous tissue medium. The purpose of this research is to improve the Q factor and bandwidth of the coil in tissue medium by reducing the net conductance of the coil in tissue medium, which is comparable to the net conductance in air. Bioimpedance of each layer of the eye is modelled to identify the highly capacitive and highly conductive tissue layer in the eye. To investigate the worst-case and best-case scenario, Q factor and bandwidth of the implant coil is analysed in the eye with and without aqueous humor which is a highly conductive and capacitive tissue layer in the eye. The coil is encapsulated with breast fat which possess lowest permittivity of all body tissue. After removing the high conductive tissue layer from the implantation zone, the Q factor and bandwidth of the coil is improved by 87.5 % and 97.7 % respectively. It is observed that 100 % Q at 10 MHz and 76.75 % of bandwidth is recovered in tissue medium after using breast fat as encapsulation layer. This demonstration of coil for various test cases in tissue medium aids to device a reliable, safe and efficient wireless power/data transfer system for artificial retina.

Origin of the high conductivity anomalies in the mid-lower crust of the Tibetan Plateau: Dehydration melting of garnet amphibolites

High-conductivity layers of 0.1–1 S/m distributed in the mid-lower crust of the Tibetan Plateau are traditionally explained as the fluid/melt related crustal flow. Dehydration of amphibole-bearing rocks may play an important role in explaining these anomalies. To survey the anomalies' origin, the electrical conductivities of amphibole-bearing samples are measured at 1.5 GPa and 600–1300 K. Our experiments show that dehydration melting of amphibole occurs at about 1100 K. Before dehydration melting of amphibolites, proton conduction together with small polaron conduction dominate the conduction process, whereas ionic conduction plays a more important role after the dehydration melting of amphibolites. The dehydration melting of polycrystalline amphibole yields a conductivity of up to 1 S/m under the lower-crust conditions beneath the Tibetan Plateau. Combining the calculated thermal gradient in the crust of Tibetan Plateau with the petrology proof and seismic data, dehydration melting of garnet amphibolites likely contributes to the high conductivity anomalies within the Tibetan crust. MW and cube model simulation indicates that the melt fraction is 3.8–36 vol% in the partial molten region.

Thermally-activated electron hopping in Fe-rich amphiboles: Implications for the high-conductivity anomalies in subduction zones

Anomalous high-conductivity layers are typical of subduction zones, the largest recycling systems of the Earth. Understanding the mineral physics underlying the high conductivity of rocks has paramount implications for several planetary-scale processes, including global water cycling, earthquake activity, and arc magmatism.Here, by using in situ polarized Raman spectroscopy, we provide a direct proof for the development of anisotropic electron-phonon excitations (polarons) and delocalized H+ in riebeckite, a Fe-bearing sodic amphibole typical of blue-schist metamorphic facies. The activation of polarons starts at 500 K (227 °C) and is complete at 650 K (377 °C) under both reducing and oxidizing conditions. At higher temperatures external oxygen triggers the expulsion of H+ and e− from the crystal bulk. The temperature range observed for the development of charge carriers is in excellent agreement with the conductivity trends measured for riebeckite in previous studies, and nicely fits the temperatures for the development of high-conductivity layers in warm and cold subduction zones.The study directly demonstrates the activation of polarons at temperatures characteristic of convergent plate margins provides the atomic-scale picture whose macroscopic-scale expression is the anomalous conductivity measured in subduction zones.

Shallow and Deep Electric Structures in the Tolhuaca Geothermal System (S. Chile) Investigated by Magnetotellurics

The geoelectric properties of the geothermal system associated with the Tolhuaca volcano were investigated by three-dimensional (3D) inversion of magnetotelluric (MT) data. This study presents the first resistivity model of the Tolhuaca volcano derived from 3D MT inversion to have a better understanding of its magmatic and hydrothermal system. We selected data from 54 MT stations for 3D inversion. We performed a series of 3D MT inversion tests by changing the type of data to be inverted, as well as the starting model to obtain a model in agreement with the geology. The final 3D MT model presents a conductive body (&lt;20 Ωm) located 2 km below the summit of Tolhuaca volcano, inferred as a shallow magmatic storage compartment. We also distinguish a ~300 m thick layer of high conductivity (&lt;10 Ωm) corresponding to argillic hydrothermal alteration. The MT model includes two resistive bodies (~200 Ωm) in the upper crust below the laterally displaced argillic alteration layer to the west beneath the extinct Tolhuaca, which would correspond to a shallow reservoir (~1000 m from the surface) and a deep reservoir (&gt;1800 m from the surface) that had so far not been identified by previous resistivity models. The result of this study provides new insights into the complexity of the Tolhuaca geothermal system.

Observation of a Strong Decoupling Phenomenon in Pt/Si Hybrid Structures for In-Plane Thermoelectric Properties

The performance of thermoelectric (TE) materials is limited by the intrinsic coupling of the Seebeck coefficient and the electrical conductivity such that an increase in one leads to a decrease in the other with respect to the carrier concentration. This coupling makes it particularly difficult to enhance the TE power factor in TE materials. In this study, we added a Pt top layer over a silicon wafer, forming a hybridized Pt/Si structure to drive a strong decoupling of the Seebeck coefficient and electrical conductivity. The results show that the electrical resistance in the Pt/Si hybrid structure decreased by ∼94 times compared to that of a single-layer lightly doped Si substrate at 300 K, while the Seebeck coefficient in the hybrid structure decreased slightly compared to that of the single layer. The remarkably high TE performance of the Pt/Si hybrid structure is brought about by the hybridization of the intrinsic high-conductivity Pt layer and the high-Seebeck coefficient Si substrate. In addition, we demonstrate that this novel and effective decoupling method enables the assessment of the in-plane intrinsic Seebeck coefficient of a lightly doped Si wafer, which typically has an electrical resistance that is extremely high to measure the Seebeck coefficient even with a high-resolution voltmeter. These results represent a significant advancement in the understanding of electrical transport in TE materials, which will invigorate further research on Si-based devices for realizing large-area watt-scale TE generation at room temperature.

Magnetotelluric Sounding in the Arctic Using a Drifting Station on an Ice Floe (Numerical Experiment)

Abstract —The magnetotelluric sounding (MTS) method implemented on drifting ice floes in the Arctic is suitable for detection of 3D inhomogeneities in crustal conductivity while recording the transverse magnetic (TM) mode potential of the electromagnetic field. Highconductivity layers of seawater and sediments shield the underlying 3D inhomogeneity. Their presence virtually does not affect changes in the standard responses of the medium used in MTS but is quite noticeable in the characteristics of the TM mode. To register them, one can use a circular electric dipole (CED) located at the surface of an ice floe. During the drift, the electric field can be measured on the ice floe using electrodes in seawater. We propose to lower the magnetic sensors beneath the ice, in seawater, because ice deformations interfere with the magnetic-field component measurements. The coordinates of the observation station during MT soundings on the ice floe in the Arctic (similarly to earlier observations at the North Pole stations) can change significantly. To take into account the effect of horizontal movements of the drifting station, we propose to complement all the recorded time series with the coordinates of measurement points. We have developed a technique for processing such data to take into account nonplane-wave effects, which can occur in the Arctic because of the proximity of ionospheric current jets. We carry out the synchronization of all observations in the investigated area, using a model of spatial and temporal field variations and data accumulation. To test our approach, we use the synthetic experimental data for the model that considers the existence of seawater, sediment, resistive crust, crustal object, and underlying mantle. We determine the crustal 3D object parameters with account of the TM-mode potential distributions at the seawater surface restored from the synthetic experimental data obtained at the drifting station during the drift. We use the Nelder–Mead method for optimization of the object characteristics. The parameters of the object become highly similar to their test values if the trajectory of the drifting station passes through an object, covering it most fully.

In-situ directly anchored CoMoS4 particles on reduced graphene oxide nanosheets for the high-efficiency asymmetric supercapacitor

The well-designed CoMoS4/reduced graphene oxide (RGO) composite was directly synthesized by a simple one-step hydrothermal method, in virtue of the uniformly-distributed oxygen-containing functional groups on the precursor graphene oxide (GO) surface. As expected, the optimized CoMoS4/RGO exhibits the high specific capacity of 123 mAh/g at 1 A/g, about 152% higher than that of pure CoMoS4. The reason is as follows: (1) the structure with no serious aggregation can be favor of rapid electrolyte ion transport process; (2) the RGO phase cannot only provide the high specific surface area, moderate conductivity and electrochemical double layer capacitance from the Π conjugated carbon skeleton, but also contribute to some extra Faradaic redox capacitance from a few oxygen-containing functional groups. As for practical application, the fabricated CoMoS4/RGO//AC asymmetric supercapacitor can deliver the good energy storage performances, such as the high energy density of 59 Wh/kg at 1125 W/kg (almost superior to the reported CoMoS4 based asymmetric supercapacitor devices to our best knowledge), especially for the good cycle stability with 99.3% capacity retention after 6000 cycles. Therefore, this work can provide a feasible strategy to improve the supercapacitor performances of CoMoS4.

Co-doped 1T‐MoS2 nanosheets anchored on carbon cloth as self-supporting anode for high-performance lithium storage

The widespread use of wearable devices has triggered a huge demand for flexible power source. Flexible lithium-ion batteries (LIBs) are widely regarded as an ideal power source for wearable devices because of their high energy density and long cycle life, but their application is limited by traditional rigid electrodes. A promising strategy is to prepare flexible electrodes by synthesising active materials with high capacity on flexible carbon substrates. In this study, Co-doped 1T‐MoS2 nanosheets were successfully anchored on a pretreatment carbon cloth (CC) by using a facile one-step solvothermal method, which is denoted as Co-MoS2/CC. Benefiting from the high conductivity and large layer spacing of the metallic 1T‐MoS2, self-supporting CC framework, doping of cobalt and their synergistic effect, when used as a self-supporting anode for LIBs, Co-MoS2/CC delivers a high reversible capacity of 1392 mAh g−1 at 0.1 A g−1 and retains 611 mAh g−1 at 2 A g−1 over 300 cycles. Furthermore, it delivers a remarkable rate performance of 230 mAh g−1 at 10 A g−1. The facile and scalable synthesis method can also be applied to other similar flexible free-standing electrodes for the application of electrochemical energy storage.

3D S-Wave Velocity Model of the Crust and Upper Mantle beneath the Sea of Okhotsk and the Kamchatka Peninsula

Abstract A 3D S-wave velocity model (from 0 to 350 km depth) is determined for the region of the Sea of Okhotsk and the Kamchatka peninsula, through Rayleigh wave analysis applied to the traces of 278 earthquakes registered by 12 seismic stations, both located within (and nearby) of the study area. This model reveals the principal geological and tectonics features present in the study area, e.g., the presence of two lower-crust hot plumes located at the northwest of the Sea of Okhotsk, which are shown as two zones of low S-wave velocity (from 20 to 30 km depth). Also, a conspicuous low S-wave velocity zone is determined at the southwest of the Sea of Okhotsk (from 35 to 60 km depth), which can be matched up with a high conductivity layer previously determined from 30 to 65 km depth. For the Kamchatka peninsula, low S-velocities are determined beneath the volcanic belt from the upper crust (~5 km-depth) down to a depth of ~60 for the southern part, and down to a depth of ~140 km for the northern part. This low S-wave velocity pattern is enlarged in size at the northwest (north of ~55°N), following the location of the Kliuchevskoi and Sheveluch volcanoes, which confirms that these volcanoes must be a part of the same subduction-induced volcanic process. The present model shows that the subducting Pacific slab terminates near to the Aleutian-Kamchatka junction, i.e., no relict slab underlies the extinct northern Kamchatka volcanic arc. This model shows that this slab shoals towards north, and there exists a gap associated with the loss of this slab beneath Sheveluch and Kliuchevskoi volcanoes. The low S-wave velocity pattern determined at northwest of the slab edge confirms the presence of the asthenospheric flow, which would pass through this gap to the northwest around the north slab edge. Finally, the present model shows the precise location and detailed structure of the asthenosphere, which is a new result that has not been determined in other previous studies.

Generation of a highly conductive and stable solid electrolyte interphase at lithium anode under additional electric filed

The solid electrolyte interphase (SEI) generated spontaneously on the surface of lithium anode, is a protective layer to inhibit further reaction of electrolyte with lithium and to prevent the formation of lithium dendrites. The composition and properties of SEI layers determine the cycling performance of lithium batteries to some extent. Here we report a novel solution to optimize the SEI layer by applying an additional alternating current (AC) electric field during the generation of SEI. The application of an AC field enhances the association of anions and cations in the electrolytes, which results in an improved delivery of anions to the surface of lithium anode. The decomposition of anions at the surface leads to the formation of an anion-derived SEI layer containing a mass of LiF and Li2S particles. The grain boundaries among these particles provide fast diffusion channels for lithium ions, forming a high conductive SEI layer. The optimized composition of SEI layer is confirmed by X-ray photoelectron spectroscopy analysis and electrochemical characterizations. Through this strategy, the cycle performance of lithium batteries is greatly improved, and the stable cycling life of Cu@Li | Li cells and Cu@Li | NMC811 cells increases more than 3 times.

Engineering hollow Ni–Fe-based mesoporous spherical structure derived from MOF for efficient photocatalytic hydrogen evolution

Endowing photocatalyst with functional nanostructure can effectively improve its performance towards solar energy conversion. Here, a unique Ni–Fe-based mesoporous hollow spherical nanostructure (NiFeOx/NC-t) was facilely constructed via the direct thermal decomposition of Ni-BTC@PBA composites. The hybrids consist of in-situ formed nitrogen-enriched carbon layers constituting the mesoporous walls of hollow spherical, and amorphous NiFeOx nanoparticles and a small fraction of FeNi3 are embedded on the spherical walls during carbonization. After loading EY molecules on NiFeOx/NC-t as solar light absorbers, an optimal photocatalytic hydrogen evolution rate of 5352.7 μmol g−1 h−1 was achieved with excellent stability under visible light (λ > 420 nm) in the absence of co-catalyst. The excellent photocatalytic activity was revealed to be ascribed to: ⅰ) mesoporous hollow spherical structure having a large surface area, thus exposing more active sites; ⅱ) efficient injection of photo-generated electrons from excited EY− into NiFeOx and FeNi3 by the bridge of high-conductive nitrogen-enriched carbon layer. In brief, the structural and compositional features synergistically strengthen the photocatalytic activity of NiFeOx/NC-t. It is worth noting that MOF-derived route can significantly simplify the preparation process of mesoporous hollow spherical nanostructure. This work provides an approach for facile preparation of versatile photocatalysts with high efficiency for solar energy conversion.