Effect of sulfur on enhancing nitrogen-doping and magnetic properties of carbon nanotubes

Sulfur (S) is introduced as an additive in the growth atmosphere of carbon nanotubes (CNTs) in the range of 940-1020°C. CNT products with distorted sidewalls can be obtained by S-assisted growth. Moreover, many fascinating CNT structures can also be found in samples grown with S addition, such as bamboo-like CNTs, twisted CNTs, arborization-like CNTs, and bead-like CNTs. Compared with CNTs grown without S, more nitrogen-doping content is achieved in CNTs with S addition, which is beneficial for the properties and applications of nitrogen-doped CNTs. In addition, S can also enhance the encapsulation of ferromagnetic materials and thus improve the soft magnetic properties of CNTs, which is favorable to the applications of CNTs in the electromagnetic wave-absorbing and magnetic data storage areas

Hydrothermal Synthesis of Iodine-Doped Nanoplates with Enhanced Visible and Ultraviolet-Induced Photocatalytic Activities

The iodine-doped Bi2WO6 (I-BWO) photocatalyst was prepared via a hydrothermal method using potassium iodide as the source of iodine. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. The photocatalytic activity of I-BWO for the degradation of rhodamine B (RhB) was higher than that of pure BWO and I2-BWO regardless of visible light (>420 nm) or ultraviolet light (<400 nm) irradiation. The results of DRS analysis showed that the I-BWO and I2-BWO catalysts had narrower band gaps. XPS analysis proved that the multivalent iodine species including I0 and were coadsorbed on the defect surface of Bi2WO6 in I-BWO. The enhanced PL intensity revealed that a large number of defects of oxygen vacancies were formed by the doping of iodine. The enhanced photocatalytic activity of I-BWO for degradation of RhB was caused by the synergetic effect of a small crystalline size, a narrow band gap, and plenty of oxygen vacancies

Sol-Gel-Hydrothermal Synthesis of the Heterostructured TiO

The heterostructured TiO2/N-Bi2WO6 composites were prepared by a facile sol-gel-hydrothermal method. The phase structures, morphologies, and optical properties of the samples were characterized by using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive spectroscopy (EDS), and UV-vis diffuse reflectance spectroscopy. The photocatalytic activities for rhodamine B of the as-prepared products were measured under visible and ultraviolet light irradiation at room temperature. The TiO2/N-Bi2WO6 composites exhibited much higher photocatalytic performances than TiO2 as well as Bi2WO6. The enhancement in the visible light photocatalytic performance of the TiO2/N-Bi2WO6 composites could be attributed to the effective electron-hole separations at the interfaces of the two semiconductors, which facilitate the transfer of the photoinduced carriers

High-Power and Ultralong-Life Aqueous Zinc-Ion Hybrid Capacitors Based on Pseudocapacitive Charge Storage

© 2019, © 2019, The Author(s). Rechargeable aqueous zinc-ion hybrid capacitors and zinc-ion batteries are promising safe energy storage systems. In this study, amorphous RuO2·H2O for the first time was employed to achieve fast and ultralong-life Zn2+ storage based on a pseudocapacitive storage mechanism. In the RuO2·H2O||Zn zinc-ion hybrid capacitors with Zn(CF3SO3)2 aqueous electrolyte, the RuO2·H2O cathode can reversibly store Zn2+ in a voltage window of 0.4–1.6 V (vs. Zn/Zn2+), delivering a high discharge capacity of 122 mAh g−1. In particular, the zinc-ion hybrid capacitors can be rapidly charged/discharged within 36 s with a very high power density of 16.74 kW kg−1 and a high energy density of 82 Wh kg−1. Besides, the zinc-ion hybrid capacitors demonstrate an ultralong cycle life (over 10,000 charge/discharge cycles). The kinetic analysis elucidates that the ultrafast Zn2+ storage in the RuO2·H2O cathode originates from redox pseudocapacitive reactions. This work could greatly facilitate the development of high-power and safe electrochemical energy storage.[Figure not available: see fulltext.]

Pedestrian Crossing Action Recognition and Trajectory Prediction with 3D Human Keypoints

Accurate understanding and prediction of human behaviors are critical prerequisites for autonomous vehicles, especially in highly dynamic and interactive scenarios such as intersections in dense urban areas. In this work, we aim at identifying crossing pedestrians and predicting their future trajectories. To achieve these goals, we not only need the context information of road geometry and other traffic participants but also need fine-grained information of the human pose, motion and activity, which can be inferred from human keypoints. In this paper, we propose a novel multi-task learning framework for pedestrian crossing action recognition and trajectory prediction, which utilizes 3D human keypoints extracted from raw sensor data to capture rich information on human pose and activity. Moreover, we propose to apply two auxiliary tasks and contrastive learning to enable auxiliary supervisions to improve the learned keypoints representation, which further enhances the performance of major tasks. We validate our approach on a large-scale in-house dataset, as well as a public benchmark dataset, and show that our approach achieves state-of-the-art performance on a wide range of evaluation metrics. The effectiveness of each model component is validated in a detailed ablation study.Comment: ICRA 202

Silicon-Encapsulated Hollow Carbon Nanofiber Networks as Binder-Free Anodes for Lithium Ion Battery

Silicon-encapsulated hollow carbon nanofiber networks with ample space around the Si nanoparticles (hollow Si/C composites) were successfully synthesized by dip-coating phenolic resin onto the surface of electrospun Si/PVA nanofibers along with the subsequent solidification and carbonization. More importantly, the structure and Si content of hollow Si/C composite nanofibers can be effectively tuned by merely varying the concentration of dip solution. As-synthesized hollow Si/C composites show excellent electrochemical performance when they are used as binder-free anodes for Li-ion batteries (LIBs). In particular, when the concentration of resol/ethanol solution is 3.0%, the product exhibits a large capacity of 841 mAh g−1 in the first cycle, prominent cycling stability, and good rate capability. The discharge capacity retention of it was ~90%, with 745 mAh g−1 after 50 cycles. The results demonstrate that the hollow Si/C composites are very promising as alternative anode candidates for high-performance LIBs

2023 roadmap for potassium-ion batteries

The heavy reliance of lithium-ion batteries (LIBs) has caused rising concerns on the sustainability of lithium and transition metal and the ethic issue around mining practice. Developing alternative energy storage technologies beyond lithium has become a prominent slice of global energy research portfolio. The alternative technologies play a vital role in shaping the future landscape of energy storage, from electrified mobility to the efficient utilization of renewable energies and further to large-scale stationary energy storage. Potassium-ion batteries (PIBs) are a promising alternative given its chemical and economic benefits, making a strong competitor to LIBs and sodium-ion batteries for different applications. However, many are unknown regarding potassium storage processes in materials and how it differs from lithium and sodium and understanding of solid–liquid interfacial chemistry is massively insufficient in PIBs. Therefore, there remain outstanding issues to advance the commercial prospects of the PIB technology. This Roadmap highlights the up-to-date scientific and technological advances and the insights into solving challenging issues to accelerate the development of PIBs. We hope this Roadmap aids the wider PIB research community and provides a cross-referencing to other beyond lithium energy storage technologies in the fast-pacing research landscape

Synthesis and Enhanced Field-Emission of Thin-Walled, Open-Ended, and Well-Aligned N-Doped Carbon Nanotubes

Thin-walled, open-ended, and well-aligned N-doped carbon nanotubes (CNTs) on the quartz slides were synthesized by using acetonitrile as carbon sources. As-obtained products possess large thin-walled index (TWI, defined as the ratio of inner diameter and wall thickness of a CNT). The effect of temperature on the growth of CNTs using acetonitrile as the carbon source was also investigated. It is found that the diameter, the TWI of CNTs increase and the Fe encapsulation in CNTs decreases as the growth temperature rises in the range of 780–860°C. When the growth temperature is kept at 860°C, CNTs with TWI = 6.2 can be obtained. It was found that the filed-emission properties became better as CNT growth temperatures increased from 780 to 860°C. The lowest turn-on and threshold field was 0.27 and 0.49 V/μm, respectively. And the best field-enhancement factors reached 1.09 × 105, which is significantly improved about an order of magnitude compared with previous reports. In this study, about 30 × 50 mm2 free-standing film of thin-walled open-ended well-aligned N-doped carbon nanotubes was also prepared. The free-standing film can be transferred easily to other substrates, which would promote their applications in different fields

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead