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LiMn2O4 (LMO) is an attractive positive electrode material for aqueous lithium-ion batteries (ALIBs), but its inferior cycle performance limits the practical application. The degradation mechanism of LMO in ALIBs is still unclear, resulting in inability to predictably improve its structural stability. The electrode/electrolyte interface is believed to play an important role in electrode degradation. However, the interactions of the water-containing electrode/electrolyte interface of LMO are underexplored. In this work, we demonstrate the insertion of H3O+ into LMO during cycling in aqueous electrolyte and elucidate the paradoxical effects of H3O+. The crystal H3O+ enhances the structural stability of LMO by forming a gradient Mn4+-rich protective shell, but an excess amount of crystal H3O+ leads to poor Li+ conductivity, resulting in rapid capacity fading. Combining electrochemical analyses, structural characterizations, and first-principles calculations, we reveal the intercalation of H3O+ into LMO and its associated mechanism on the structural evolution of LMO. Furthermore, we regulate the crystal H3O+ content in LMO by modifying the hydrogen bond networks of aqueous electrolyte to restrict H2O molecule activity. This approach utilizes an appropriate amount of crystal H3O+ to enhance the structural stability of LMO while maintaining sufficient Li+ diffusion.
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The electrochemical nitrogen reduction reaction is a crucial process for the sustainable production of ammonia for energy and agriculture applications. However, the reaction's efficiency is highly dependent on the activation of the inert N≡N bond, which is hindered by the electron back-donation to the π* orbitals of the N≡N bond, resulting in low eNRR capacity. Herein, we report a main-group metal-non-metal (O-In-S) eNRR catalyst featuring a dynamic proton bridge, with In-S serving as the polarization pair and O functioning as the dynamic electron pool. In-situ spectroscopic analysis and theoretical calculations reveal that the In-S polarization pair acts as asymmetric dual-sites, polarizing the N≡N bond by concurrently back-donating electrons to both the πx* and πy* orbitals of N2, thereby overcoming the significant band gap limitations, while inhibiting the competitive hydrogen evolution reaction. Meanwhile, the O dynamic electron pool acts as a "repository" for electron storage and donation to the In-S polarization pair. As a result, the O-In-S dynamic proton bridge exhibits exceptional NH3 yield rates and Faradaic efficiencies (FEs) across a wide potential window of 0.3 V, with an optimal NH3 yield of 80.07 ± 4.25 µg h-1 mg-1 and an FE of 38.01 ± 2.02%, outperforming most previously reported catalysts.
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Improving the slow redox kinetics of sulfur species and shuttling issues of soluble intermediates induced from the multiphase sulfur redox reactions are crucial factors for developing the next-generation high-energy-density lithium-sulfur (Li-S) batteries. In this study, we successfully constructed a novel molecular electrocatalyst through in situ polymerization of bis(3,4-dibromobenzene)-18-crown-6 (BD18C6) with polysulfide anions on the cathode interface. The crown ether (CE)-based polymer acts as a spatial "fence" to precisely control the unique redox characteristics of sulfur species, which could confine sulfur substance within its interior and interact with lithium polysulfides (LiPSs) to optimize the reaction barrier of sulfur species. The "fence" structure and the double-sided Li+ penetrability of the CE molecule may also prevent the CE catalytic sites from being covered by sulfur during cycling. This new fence-type electrocatalyst mitigates the "shuttle effect", enhances the redox activity of sulfur species, and promotes the formation of three-dimensional stacked lithium sulfide (Li2S) simultaneously. It thus enables lithium-sulfur batteries to exhibit superior rate performance and cycle stability, which may also inspire development facing analogous multiphase electrochemical energy-efficient conversion process.
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Nitrogen doping has been recognized as an important strategy to enhance the oxygen reduction reaction (ORR) activity of carbon-encapsulated transition metal catalysts (TM@C). However, previous reports on nitrogen doping have tended to result in a random distribution of nitrogen atoms, which leads to disordered electrostatic potential differences on the surface of carbon layers, limiting further control over the materials' electronic structure. Herein, a gradient nitrogen doping strategy to prepare nitrogen-deficient graphene and nitrogen-rich carbon nanotubes encapsulated cobalt nanoparticles catalysts (Co@CNTs@NG) is proposed. The unique gradient nitrogen doping leads to a gradual increase in the electrostatic potential of the carbon layer from the nitrogen-rich region to the nitrogen-deficient region, facilitating the directed electron transfer within these layers and ultimately optimizing the charge distribution of the material. Therefore, this strategy effectively regulates the density of state and work function of the material, further optimizing the adsorption of oxygen-containing intermediates and enhancing ORR activity. Theoretical and experimental results show that under controlled gradient nitrogen doping, Co@CNTs@NG exhibits significantly ORR performance (Eonset = 0.96 V, E1/2 = 0.86 V). At the same time, Co@CNTs@NG also displays excellent performance as a cathode material for Zn-air batteries, with peak power density of 132.65 mA cm-2 and open-circuit voltage (OCV) of 1.51 V. This work provides an effective gradient nitrogen doping strategy to optimize the ORR performance.
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Electrochemical nitrogen reduction reaction (eNRR) offers a sustainable route for ammonia synthesis; however, current electrocatalysts are limited in achieving optimal performance within narrow potential windows. Herein, inspired by the heliotropism of sunflowers, we present a biomimetic design of Ru-VOH electrocatalyst, featuring a dynamic Ru-O-V pyramid electron bridge for eNRR within a wide potential range. In situ spectroscopy and theoretical investigations unravel the fact that the electrons are donated from Ru to V at lower overpotentials and retrieved at higher overpotentials, maintaining a delicate balance between N2 activation and proton hydrogenation. Moreover, N2 adsorption and activation were found to be enhanced by the Ru-O-V moiety. The catalyst showcases an outstanding Faradaic efficiency of 51.48% at -0.2 V (vs RHE) with an NH3 yield rate exceeding 115 µg h-1 mg-1 across the range of -0.2 to -0.4 V (vs RHE), along with impressive durability of over 100 cycles. This dynamic M-O-V pyramid electron bridge is also applicable to other metals (M = Pt, Rh, and Pd).
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Construction of a built-in electric field has been identified as an attractive improvement strategy for photoelectrochemical (PEC) water splitting by facilitating the carrier extraction from the inside to the surface. However, the promotion effect of the electric field is still restrained by the confined built-in area. Herein, we construct a microscale built-in electric field via gradient oxygen doping. The octahedral configuration of the synthesized CdIn2S4 (CIS) provides a structural basis, which enables the subsequent oxygen doping to reach a depth of â¼100 nm. Accordingly, the oxygen-doped CIS (OCIS) photoanode exhibits a microscale built-in electric field with band bending. Excellent PEC catalytic activity with a photocurrent density of 3.69 mA cm-2 at 1.23 V vs. RHE is achieved by OCIS, which is 3.1 times higher than that of CIS. Combining the results of thorough characterization and theoretical calculations, accelerating migration and separation of charge carriers have been determined as the reasons for the improvement. Meanwhile, the recombination risk at the doping centers has also been reduced to the minimum via optimal experiments. This work provides a new-generation idea for constructing a built-in electric field from the view point of bulky configuration towards PEC water splitting.
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Aqueous zinc ion batteries have been extensively researched due to their distinctive advantages such as low cost and high safety. Vanadium oxides are important cathode materials, however, poor cycle life caused by vanadium dissolution limits their application. Recent studies show that the lattice NH4 + in vanadium oxides can act as a pillar to enhance structural stability and play a crucial role in improving its cycling stability. Nevertheless, there is still a lack of research on the effect of the lattice NH4 + content on structural evolution and electrochemical performance. Herein, we synthesize vanadium oxides with different contents of lattice NH4 + by a one-step hydrothermal reaction. The vanadium oxides with lattice NH4 + exhibit high initial capacity, as well as good cycling stability and rate performance compared to bare vanadium oxide. Combined with electrochemical analyses, ex-situ structural characterizations, and in-situ X-ray diffraction tests, we reveal that the lattice NH4 + content plays a positive role in vanadium oxides' structural stability and cation diffusion kinetics. This work presents a direction for designing high-performance vanadium cathodes for aqueous zinc ion batteries.
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Flue-cured tobacco (Nicotiana tabacum L.) is a significant cash crop globally. In August 2022, necrotic lesions on stem associated with root rot and wilting were observed on flue-cured tobacco (Cv. Yunyan 87) in fields located in Banxin village (27.95N,109.60E) of Fenghuang county in Xiangxi Autonomous Prefecture, Hunan Province, China. The affected and damaged area of tobacco is approximately 10 hectares, with adisease incidence of 60%. Lots of small black speckling within the lower stem of the affected plant, vascular tissue changed to black, dry rot, and looked like charcoal breezes. Small pieces were cut from healthy and diseased tissues, surface sterilized with 5% NaClO for 3 min and 75% ethanol for 1 min, rinsed with sterile distilled water and air-drying, incubated on oat medium incubated at 28â for five days. These isolates grew fast and produced typical black microsclerotia. The morphological were septate hyphae and microsclerotia. The microsclerotia were black and regularly round, with a 42.5 - 92.9 µm diameter. These morphological features were consistent with Macrophomina phaseolina (Smith and Wyllie 1999). The internal transcribed spacer (ITS) rDNA and translation elongation factor 1-α (TEF1-α) genes of three representative isolates were amplified and sequenced using the primers ITS1/ITS4 and EF1-728F/EF2R (Machado et al. 2019). Our resulting sequences (GenBank accessions OR435093, OR435101, OR435102 for ITS; OR891780, OR891781 and OR891782 for EF1-α) showed 99-100% similarity with M. phaseolina by NCBI blast. Phylogenetic analysis was conducted using MEGA-X software with the NJ method. The combined sequences grouped with isolates to M. phaseolina with 100% bootstrap support. The strain XF22 has been sent to the China General Microbiological Culture Collection Center (CGMCC3.25349). Pathogenicity tests were conducted by inoculating potted plants (six plants per isolate, three times) from 45 day-old tobacco seedlings cv. Yunyan 87. Stems were randomly gently scratched with sterile needles, and a 5 mm agar disc with mycelium of the pathogen was attached to the surface of each wound, with a sterilized agar disc as control. Inoculated seedlings were incubated in growth chambers at 26â and 60% RH with a 12 h photoperiod/day. After ten days, symptoms that brown or black lesions on the inoculated lesions were dotted with numerous black, hard microsclerotia similar to those naturally occurring on the diseased plants, but not on the control plants. The same pathogen was re-isolated consistently, fulfilling Koch's postulates. Based on morphological, molecular, and pathogenicity test results, these isolates were identified as M. phaseolina. Charcoal rot of tobacco, caused by M. phaseolina was previously found in Guangxi in 1989 (Zhu et al. 2002), while this is the first report of M. phaseolina causing charcoal rot on flue-cured tobacco in Hunan, China. We speculate that the planting area is influenced by the preceding crop sesame. The soil carries M. phaseolina, which can cause stem rot of sesame, leading to the occurrence of tobacco charcoal rot. Our results indicated that charcoal rot caused by M. phaseolina is a new threat to flue-cured tobacco production and lue-cured tobacco might be acting as a reservoir and spreading this pathogen to other economically crops in China.
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Investigating the process of crystalline transformation in metal-organic frameworks (MOFs) has significant implications in advancing our understanding of the growth mechanisms and design of innovative materials. This study achieves a theoretically impossible transformation direction from three-dimensional (3D) zeolitic imidazolate nanocubes (ZIF) to two-dimensional (2D) ZIF nanoframes through the Marangoni effect in droplets. This transformation challenges the established belief that only a transition from 2D ZIF-L to 3D ZIF-67 is possible, which neglects the reverse process. Finite element analysis indicates that the conversion from 3D ZIF to 2D ZIF is feasible when uniform mass distribution and heat transport are guaranteed under Marangoni flow. This research not only demonstrates an alternative pathway for MOF crystalline transformation but also provides a fresh perspective on the construction of MOF nanoframes.
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Osmotic power, a clean energy source, can be harvested from the salinity difference between seawater and river water. However, the output power densities are hampered by the trade-off between ion selectivity and ion permeability. Here we propose an effective strategy of double angstrom-scale confinement (DAC) to design ion-permselective channels with enhanced ion selectivity and permeability simultaneously. The fabricated DAC-Ti0.87 O2 membranes possess both Ti atomic vacancies and an interlayer free spacing of ≈2.2â Å, which not only generates a profitable confinement effect for Na+ ions to enable high ion selectivity but also induces a strong interaction with Na+ ions to benefit high ion permeability. Consequently, when applied to osmotic power generation, the DAC-Ti0.87 O2 membranes achieved an ultrahigh power density of 17.8â W m-2 by mixing 0.5/0.01â M NaCl solution and up to 114.2â W m-2 with a 500-fold salinity gradient, far exceeding all the reported macroscopic-scale membranes. This work highlights the potential of the construction of DAC ion-permselective channels for two-dimensional materials in high-performance nanofluidic energy systems.
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The catalytic performance of metal-organic frameworks (MOFs) in Li-S batteries is significantly hindered by unsuitable pore size, low conductivity, and large steric contact hindrance between the catalytic site and lithium polysulfide (LPSs). Herein, the smallest π-conjugated hexaaminobenzene (HAB) as linker and Ni(II) ions as skeletal node are in situ assembled into high crystallinity Ni-HAB 2D conductive MOFs with dense Ni-N4 units via dsp2 hybridization on the surface of carbon nanotube (CNT), fabricating Ni-HAB@CNT as separator modified layer in Li-S batteries. As-obtained unique π-d conjugated Ni-HAB nanostructure features ordered micropores with suitable pore size (≈8 Å) induced by HAB ligands, which can cooperate with dense Ni-N4 chemisorption sites to effectively suppress the shuttle effect. Meanwhile, the conversion kinetics of LPSs is significantly accelerated owing to the small steric contact hindrance and increased delocalized electron density endued by the planar tetracoordinate structure. Consequently, the Li-S battery with Ni-HAB@CNT modified separator achieves an areal capacity of 6.29 mAh cm-2 at high sulfur loading of 6.5 mg cm-2 under electrolyte/sulfur ratio of 5 µL mg-1 . Moreover, Li-S single-electrode pouch cells with modified separators deliver a high reversible capacity of 791 mAh g-1 after 50 cycles at 0.1 C with electrolyte/sulfur ratio of 6 µL mg-1 .
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Hydrovoltaic energy technology that generates electricity directly from the interaction of materials with water has been regarded as a promising renewable energy harvesting method. With the advantages of high specific surface area, good conductivity, and easily tunable porous nanochannels, two-dimensional (2D) nanomaterials have promising potential in high-performance hydrovoltaic electricity generation applications. Herein, this review summarizes the most recent advances of 2D materials for hydrovoltaic electricity generation, including carbon nanosheets, layered double hydroxide (LDH), and layered transition metal oxides and sulfides. Some strategies were introduced to improve the energy conversion efficiency and the output power of hydrovoltaic electricity generation devices based on 2D materials. The applications of these devices in self-powered electronics, sensors, and low-consumption devices are also discussed. Finally, the challenges and perspectives on this emerging technology are outlined.
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Functionalized porous carbons are central to various important applications such as energy storage and conversion. Here, a simple synthetic route to prepare oxygen-rich carbon nitrides (CNOs) decorated with stable Ni and Fe-nanosites is demonstrated. The CNOs are prepared via a salt templating method using ribose and adenine as precursors and CaCl2 ·2H2 O as a template. The formation of supramolecular eutectic complexes between CaCl2 ·2H2 O and ribose at relatively low temperatures facilitates the formation of a homogeneous starting mixture, promotes the condensation of ribose through the dehydrating effect of CaCl2 ·2H2 O to covalent frameworks, and finally generates homogeneous CNOs. As a specific of the recipe, the condensation of the precursors at higher temperatures and the removal of water promotes the recrystallization of CaCl2 (T < Tm = 772 °C), which then acts as a hard porogen. Due to salt catalysis, CNOs with oxygen and nitrogen contents as high as 12 and 20 wt%, respectively, can be obtained, while heteroatom content stayed about unchanged even at higher temperatures of synthesis, pointing to the extraordinarily high stability of the materials. After decorating Ni and Fe-nanosites onto the CNOs, the materials exhibit high activity and stability for electrochemical oxygen evolution reaction with an overpotential of 351 mV.
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SLAM (Simultaneous Localization and Mapping) is mainly composed of five parts: sensor data reading, front-end visual odometry, back-end optimization, loopback detection, and map building. And when visual SLAM is estimated by visual odometry only, cumulative drift will inevitably occur. Loopback detection is used in classical visual SLAM, and if loopback is not detected during operation, it is not possible to correct the positional trajectory using loopback. Therefore, to address the cumulative drift problem of visual SLAM, this paper adds Indoor Positioning System (IPS) to the back-end optimization of visual SLAM, and uses the two-label orientation method to estimate the heading angle of the mobile robot as the pose information, and outputs the pose information with position and heading angle. It is also added to the optimization as an absolute constraint. Global constraints are provided for the optimization of the positional trajectory. We conducted experiments on the AUTOLABOR mobile robot, and the experimental results show that the localization accuracy of the SLAM back-end optimization algorithm with fused IPS can be maintained between 0.02 m and 0.03 m, which meets the requirements of indoor localization, and there is no cumulative drift problem when there is no loopback detection, which solves the problem of cumulative drift of the visual SLAM system to some extent.
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Dispositivos Ópticos , AlgoritmosRESUMEN
The development of green primary explosives has become a "holy grail" of energetic materials research. Cu-based 5-nitrotetrazolate is considered one of the most promising candidates due to its excellent blasting power and environmentally benign nature. However, synthesizing Cu-based 5-nitrotetrazolate controllably and securely remains highly challenging. Herein, room-temperature anodization of metallic Cu and a Cu(I)-imidazole nanowire array on copper substrates in a sodium 5-nitrotetrazolate electrolyte leads to in situ electrosynthesis of Cu(I) 5-nitrotetrazolate (DBX-1, CuNT) and its analogue, Cu(II) 5-nitrotetrazolate [Cu(NT)2], respectively. Both obtained CuNT and Cu(NT)2 films demonstrate remarkable energy output and good laser-induced ignition performance. The thermal stability (Tp = 291 °C) and electrostatic safety (E50 = 2.54 mJ) of CuNT proved to be superior to those of Cu(NT)2 (Tp = 257 °C, and E50 = 0.57 mJ). Remarkably, this study provides an exciting new method for the rational design and development of Cu-based 5-nitrotetrazolate as a primary explosive for advanced initiating applications.
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As COVID-19 continues to spread, people are unable to move freely when their residence region is temporarily lockdown, supplies cannot normally enter into such zones, leading to the shortage of supplies in these areas. Thus to ensure the delivery of supplies while reducing contact, the unmanned aerial vehicle (UAV) deliveries have become a common way. In order to efficiently use UAV resources and reduce energy loss in data transmission while performing the tasks, clustering is often used for achieving the above objectives, where the selected cluster heads centrally plan tasks so that reduce the communication times. However, problems such as unreasonable clustering, high energy consumption of cluster heads, and high mortality of cluster heads, directly lead the low cooperation efficiency and short life cycle of UAVs. Considering the nodes often died earlier through the k-means algorithm and ant colony algorithm, and highly dependent on the base station, these factors affect the working cycle and coordination efficiency of the UAVs. Facing the issues above, the cluster head selection algorithm of UAV based on game (CHSA) is proposed, where the mixed game model is adopted to select cluster heads for each region after regional division, and selecting the representative node to perform the cluster head selection algorithm, which help to reduce the energy consumption of each round of communication between nodes. Moreover, the key properties of the CHSA algorithm are proved, and the comparison experiment are conducted to prove the CHSA algorithm can effectively reduce energy consumption and prolong the network life cycle.
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Despite the high energy density of O3-type layered cathode materials, the short cycle life in aqueous electrolyte hinders their practical applications in aqueous lithium-ion batteries (ALIBs). In this work, it is demonstrated that the structural stability of layered LiCoO2 in aqueous electrolyte can be remarkably improved by altering the oxygen stacking from O3 to O2. As compared to the O3-type LiCoO2 , the O2-type LiCoO2 exhibits significantly improved cycle performance in neutral aqueous electrolyte. It is found that the structural degradation caused by electrophilic attack of proton can be effectively mitigated in O2-type layered structure. With O2 stacking, CoO6 octahedra in LiCoO2 possess stronger CoO bonds while Co migration from Co layer to Li layer is strongly hampered, resulting in enhanced structural stability against proton attack and prolonged cycle life in aqueous electrolyte. The findings in this work reveal that regulating oxygen stacking sequence is an effective strategy to improve the structural stability of layered materials for ALIBs.
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SignificanceMany crystallization processes occurring in nature produce highly ordered hierarchical architectures. Their formation cannot be explained using classical models of monomer-by-monomer growth. One of the possible pathways involves crystallization through the attachment of oriented nanocrystals. Thus, it requires detailed understanding of the mechanism of particle dynamics that leads to their precise crystallographic alignment along specific faces. In this study, we discover a particle-morphology-independent oriented attachment mechanism for hematite nanocrystals. Independent of crystal morphology, particles always align along the [001] direction driven by aligning interactions between (001) faces and repulsive interactions between other pairs of hematite faces. These results highlight that strong face specificity along one crystallographic direction can render oriented attachment to be independent of initial particle morphology.
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It is highly desired but still remains challenging to design a primary explosive-based nanoparticle-encapsulated conductive skeleton for the development of powerful yet safe energetic films employed in miniaturized explosive systems. Herein, a proof-of-concept electrochemical preparation of metal-organic frameworks (MOFs) derived porous carbon embedding copper-based azide (Cu(N3 )2 or CuN3 , CA) nanoparticles on copper substrate is described. A Cu-based MOF, i.e., Cu-BTC is fabricated based on anodized Cu(OH)2 nanorods, as a template, to achieve CA/C film through pyrolysis and electrochemical azidation. Such a CA/C film, which is woven by numerous ultrafine nanofibers, favorably demonstrates excellent energy release (945-2090 J g-1 ), tunable electrostatic sensitivity (0.22-1.39 mJ), and considerable initiation ability. The performance is superior to most reported primary explosives, since the CA nanoparticles contribute to high brisance and the protection of the porous carbon network. Notably, the growth mechanism of the CA/C film is further disclosed by detailed experimental investigation and density functional theory (DFT) calculation. This work will offer new insight to design and develop a CA-based primary explosive film for applications in advanced explosive systems.
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A small-scale standalone device of nitrogen (N2 ) splitting holds great promise for producing ammonia (NH3 ) in a decentralized manner as the compensation or replacement of centralized Haber-Bosch process. However, the design of such a device has been impeded by sluggish kinetics of its half reactions, i.e., cathodic N2 reduction reaction (NRR) and anodic oxygen evolution reaction (OER). Here, it is predicted from density function theory that high-entropy oxides (HEOs) are potential catalysts for promoting NRR and OER, and subsequently develop a facile procedure to synthesize HEOs in the morphology of sea urchin-shaped hollow nanospheres assembled from ultrathin nanosheets. The excellent electrocatalytic activities of HEOs for both NRR (NH3 yield rate: 47.58 µg h-1 mg-1 and Faradaic efficiency (FE): 10.74%) and OER (215 mV @10 mA cm-2 ) are demonstrated. Consequently, a prototype device of N2 electrolysis driven by commercial batteries is constructed, which can operate smoothly and deliver remarkable NH3 yield rate (41.11 µg h-1 mg-1 ) and FE (14.14%). Further mechanism study has attributed the excellent catalytic performances of HEOs to their unique electronic structures originated from multi-metal synergistic effects and entropy increase effects. The work will provide new clues for designing versatile catalysts and devices for large-scale industrialization.