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Crystalline Bi–amorphous MoOx interfaces anchored on RGO exhibit superior electrocatalytic NRR performance by enhancing the N2 adsorption/activation while suppressing the competitive HER process.

A novel functional flexible transparent film with excellent printability, swellability, degradability, and hydroxyl groups is directly developed from natural cotton.

Layered semiconductors, represented by transition metal dichalcogenides, have attached extensive attention due to their unique and tunable electrical and optical properties. In particular, lateral layered semiconductor multijunctions, including homojunctions, heterojunctions, hybrid junctions and superlattices, present a totally new degree of freedom in research on electronic devices beyond traditional materials and their structures, providing unique opportunities for the development of new structures and operation principle-based high performance devices. However, the advances in this field are limited by the precise synthesis of high-quality junctions and greatly hampered by ambiguous device performance limits. Herein, we review the recent key breakthroughs in the design, synthesis, electronic structure and property modulation of lateral semiconductor multijunctions and focus on their application-specific devices. Specifically, the synthesis methods based on different principles, such as chemical and external source-induced methods, are introduced stepwise for the controllable fabrication of semiconductor multijunctions as the basics of device application. Subsequently, their structure and property modulation are discussed, including control of their electronic structure, exciton dynamics and optical properties before the fabrication of lateral layered semiconductor multijunction devices. Precise property control will potentially result in outstanding device performances, including high-quality diodes and FETs, scalable logic and analog circuits, highly efficient optoelectronic devices, and unique electrochemical devices. Lastly, we focus on several of the most essential but unresolved debates in this field, such as the true advantages of few-layer

Efficient waste heat dissipation has become increasingly challenging as transistor size has decreased to nanometers. As governed by universal Umklapp phonon scattering, the thermal conductivity of semiconductors decreases at higher temperatures and causes heat transfer deterioration under high-power conditions. In this study, we realized simultaneous electrical and thermal rectification (TR) in a monolayer MoSe 2 -WSe 2 lateral heterostructure. The atomically thin MoSe 2 -WSe 2 heterojunction forms an electrical diode with a high ON/OFF ratio up to 10 4 . Meanwhile, a preferred heat dissipation channel was formed from MoSe 2 to WSe 2 in the ON state of the heterojunction diode at high bias voltage with a TR factor as high as 96%. Higher thermal conductivity was achieved at higher temperatures owing to the TR effect caused by the local temperature gradient. Furthermore, the TR factor could be regulated from maximum to zero by rotating the angle of the monolayer heterojunction interface. This result opens a path for designing novel nanoelectronic devices with enhanced thermal dissipation.

Developing bifunctional electrocatalysts with both high catalytic activity and high stability is crucial for efficient water splitting in alkaline media. Herein, a Fe-incorporated dual-metal selenide on nickel foam (Co0.9Fe0.1-Se/NF) is synthesized via a facile one-step electrodeposition method. As-synthesized materials could serve as self-supported bifunctional electrocatalysts with excellent catalytic activity towards oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline media. Experimental results show that delivering a 10 mA cm−2 water splitting current density only requires a cell voltage of 1.55 V. In addition, a very stable performance could be kept for about 36 hours, indicating their excellent working stability. Moreover, by means of phase analysis, we have identified that the evolution of the synthesized Co0.9Fe0.1-Se/NF experiences two entirely different processes in HER and OER, which hydroxide and oxyhydroxide are regarded as the real active sites, respectively. This work may pave the way to further understanding the relationships between the reactivity and stability of chalcogenide-based electrocatalysts and facilitating the rational design of efficient electrocatalysts for future renewable energy system applications.

MoS2 nanomaterials show excellent high theoretical performance in energy storage and hydrogen evolution reaction (HER), whereas they typically suffer from agglomeration and poor electrical conducti...

In the present study, graphitic carbon nitride (g-C3N4) was synthesized in a tube furnace and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR). Different concentrations (0-200 mg/L) of g-C3N4 were prepared in nutrient solution amended with or without 20 mg/L CdCl2 for the greenhouse study. Rice seedlings were exposed to g-C3N4 and Cd for 20 days. Our results suggest that 200 mg/L g-C3N4 significantly increased the fresh weight and root and shoot length as compared with the control, and notably alleviated Cd-induced toxicity. The addition of 200 mg/L g-C3N4 significantly reduced the root and shoot Cd content by approximately 14% and 23%, respectively. In addition, 200 mg/L g-C3N4 significantly elevated the nitrogen content and decreased C/N ration in rice shoots; most importantly, it alleviated Cd-induced nitrogen reduction. Our findings demonstrated the potential of g-C3N4 in regulating plant growth and minimizing the Cd-induced phytotoxicity, and shed light on providing a new strategy to maintain heavy metal contamination in agriculture using a low-cost and environmental friendly NMs.

Developing high-performance electrode materials for energy-storage devices with high energy-power densities, such as sodium ion hybrid capacitors (SIHCs), is of vital importance for applications in electric vehicles and portable electronics. Porous hard carbon is one of the most fascinating anode materials for SIHCs due to the rapid Na+ diffusion. Doping with heteroatoms, such as pyridinic N and thiophene S, may boost both the rate performance and specific capacity. However, it is still very challenging to modulate the content and configuration of N and S dopants efficiently. Furthermore, the trade-off for several storage mechanisms, which is vital for carbon anodes with rapid storage and release of sodium ions, is still scarce. Herein, a simple and efficient method is proposed to regulate the configuration of nitrogen dopants, increase the content of thiophene S, create micropores and adjust the structure of curved graphitic domains of hard carbon. Besides, the evolution mechanism of the structure and component is explored through ex situ XRD and XPS analysis. As-prepared NS-pHC-1.348 (N and S co-doped porous hard carbon with 1.348 g MgCl2 precursor) delivers high reversible capacity (383.9 mA h g−1 at 0.05 A g−1), excellent rate ability (183.2 mA h g−1 at 20 A g−1) and fine cycle stability (287.2 mA h g−1 at 1 A g−1 after 1000 cycles). The ratio of pseudocapacitive behaviors in NS-pHC-1.348 reaches up to 70.19% at 0.2 mV s−1, which could balance the electrochemical kinetics of the cathode and anode in SIHCs. Therefore, SIHCs, assembled from the presodiated NS-pHC-1.348 anode and NPC (N-doped porous carbon) cathode, showed superb power characteristics (92.03 kW kg−1 at 5.98 W h kg−1). This work will contribute to the design of high-performance anodes with tunable multi-active sites and the construction of high-power SIHCs.

Although electrocatalytic nitrogen reduction reaction (NRR) has been considered as an emerging pathway to produce ammonia (NH3) under ambient conditions owing to its low energy consumption, it still lacks efficient the electrocatalysts to dissociate inert N N bonds. Here, we develop an efficient approach to produce vanadium carbide with abundant periodic carbon vacancies (12.5 at. %) and mesoporous structure as electrocatalysts for NRR via a carbothermic reaction. The typical synthesis protocol involves the use of zinc vanadate decorated vanadium pentoxide nanosheets to homogeneously guide the nucleation and growth of metal organic frameworks (MOFs) on their surface, thus facilitating the in-situ formation of unique vanadium carbide during the subsequent carbothermic reaction. Owing to the optimized substrate-adsorbate binding strength, the intrinsic periodic carbon vacancies of the resultant vanadium carbide could act as coordinatively unsaturated sites to adsorb and activate nitrogen through π-back-donation process, thus promoting the reduction of N2 to NH3. As a consequence, a high yield rate and high Faradaic efficiency with good stabilities are achieved for producing NH3 under ambient conditions.

Van der Waals solids with tunable band gaps and interfacial properties have been regarded as a class of promising active materials for electrocatalytic hydrogen evolution reaction (HER). However, due to the anisotropic features, their basal planes are usually electrochemically inert, only a few unsaturated edge atoms could serve as active centers to actuate H2 generation. Hence, material utilization and productivity efficiency are insufficient for practical applications. Recently, diverse defects have been confirmed to enable tailoring atomic configurations and electronic properties of van der Waals solids, thus triggering their superior catalytic activity of in-plane atoms while introducing high amount of new active sites. In this minireview, we summarize the state-of-the-art progress of defect engineering in van der Waals solids for HER, focusing in particular on their advantages in material modification and corresponding catalytic mechanisms. We also propose the challenges and perspectives of these catalytic materials in terms of both experimental synthesis and fundamental understanding of the defect structures.

We report a simple process to connect graphene sheets forming graphene hollow microtubes (GHMs), where the tube diameter can be adjusted in the 100–500 nm range by changing reaction conditions. We discovered that graphene sheets can be seamlessly linked to each other if C atoms are substituted for N atoms at the edges of the sheets during annealing of graphene oxide(G-O)-coated electrospun PAN carbon fibers in ammonia atmosphere. The G-O/carbon hybrid nanofibers framework served as a confining template around which graphene sheets curved to form tubular structures. The GHMs formed by this process are similar to (very) large diameter carbon nanotubes (CNTs) with relatively low curvature whose electron field-emission properties include a low turn-on voltage of 0.18 V/μm (at J = 10 μA/cm2), low threshold field of 0.35 V/μm (at J = 10 mA/cm2), and high field-emission stability. This process to produce GHMs can be scaled up to fabricate GHMs of variable diameter in bulk quantities.

Herein, a salt-assisted hydrothermal carbonization (HTC) strategy is applied to fabricate low-surface-area carbon microspheres (as low as 5.5 m2 g−1) for sodium ion batteries (SIBs) by using water containing eutectic salt melt (e.g. NaCl) and sugar (e.g. glucose) as reaction media. The small amount of salt increases the carbon conversion efficiency from 15.0 to 58.3%, and microsphere size from the nanoscale to the microscale. Meanwhile, the specific surface area of carbon microsphere is minimized and the microstructure is optimized. Ex-situ X-ray diffraction (XRD) and kinetic analysis revealed that the narrower lateral width of pseudographitic domains and lower micropore volume are the key factors to promote sodium storage ability and Na ion diffusion. The carbon microsphere anode delivers a capacity of 350 mAh g−1 with 73.0% from the low potential (0–0.2 V) at 100 mA g−1, a high initial Coulombic efficiency (ICE) of 86.1% (excluding conductive carbon black), and an excellent rate capability with capacity of 261 mAh g−1 even at 500 mA g−1. This research highlights a salt-assisted HTC method to synthesize low-surface-area carbon microspheres with superior ICE and energy/power density.

Hard carbon is regarded as one of the most promising anode material for sodium-ion batteries in virtue of the low cost and stable framework. However, the correlation between pore structures of hard carbon and sodium-ion storage is still ambiguous. In this work, based on precise control of pore-size distribution, the capacity, ion diffusion, and initial Coulombic efficiency were improved. Meanwhile, the relationship between pore structure and capacity was investigated. Our result indicates that the micropores hinder ion diffusion and hardly ever accommodate Na+ ions, while mesopores facilitate Na+ ion intercalation. Hard carbon with negligible micropores and abundant mesopores delivers a maximum capacity of 283.7 mAh g−1 at 20 mA g−1, which is 83% higher than that of micropore-rich one. Even after 320 cycles at 200 mA g−1, the capacity still remains 189.4 mAh g−1.

Intensive attempts have been devoted to solving the inferior cycling stability of Si-based electrode induced by the large volume change of Si. However, the complex synthesis procedures make many strategies much low practical significances. Together with the inferior cycling stability, an easy and scalable fabrication strategy is still a great challenge for implementing Si anode in commercial batteries. This work uses a simple water steam selective etching method to simultaneously engineer the pores and the confinement of commercial Si/SiOx in carbon paper electrodes, leading to a significant improvement in electrode flexibility and cycle life. The as-prepared freestanding lotus-seed-pod-like steam-etched Si/SiOx@CNF electrode shows a high capacity retention of 137% after 1000 cycles at 3 A g−1. It also possesses outstanding electrochemical performance in a flexible lithium-ion full battery with LiCoO2/steam-etched CNF as the cathode, even under bended condition. This simple approach may offer a pathway for the application of Si-based anode in commercialization and/or flexible energy storage devices.

Lithium-ion hybrid supercapacitors (Li-HSCs) and dual-ion batteries (DIBs) are two types of energy storage devices that have attracted extensive research interest in recent years. Li-HSCs and DIBs have similarities in device structure, tendency for ion migration, and energy storage mechanisms at the negative electrode. However, these devices have differences in energy storage mechanisms and working potentials at the positive electrode. Here, we first realize the integration of a Li-HSC and a DIB to form a dual-ion hybrid supercapacitor (DIHSC), by employing mesocarbon microbead (MCMB)-based porous graphitic carbon (PGC) with a partially graphitized structure and porous structure as a positive electrode material. The MCMB-PGC-based DIHSC exhibits a novel dual-ion battery-capacitor hybrid mechanism: it exhibits excellent electronic double-layer capacitor (EDLC) behavior like a Li-HSC in the low-middle wide potential range and anion intercalation/de-intercalation behavior like a DIB in the high-potential range. Two types of mechanisms are observed in the electrochemical characterization process, and the energy density of the new DIHSC is significantly increased.

Na-ion capacitors (NICs) are promising energy storage devices in virtue of their merits in combining the high energy densities of secondary batteries and the high power densities of supercapacitors. However, it is still very challenging to achieve a balanced energy-power performance in NIC device due to the kinetic imbalance between the battery-type anode and the capacitive-type cathode. In this work, an NIC device based on carbon materials for both anode and cathode has been reported. As-prepared (polyimide/graphene oxide)-derived carbon (PIGC) anode material shows excellent rate capability, which can deliver a specific capacity of 110 mAh g−1 at high current densities of 5 A g−1. In addition, the N, B co-doped expanded reduced graphite oxide (NBEG) cathode demonstrates a high specific capacitance of 328 F g−1. Due to the improved rate capability of PIGC anode and specific capacitance of NBEG cathode, the imbalance on the energy and power densities between anode and cathode is well addressed. As-assembled PIGC//NBEG device can deliver an energy density of 55 W h kg−1 even at a high power density of 9500 W kg−1. The energy-power properties of PIGC//NBEG are superior to many state-of-the-art NIC devices that using carbon or non-carbon based electrodes. This work offers not only a promising device configuration with superior energy-power properties, but also a guidance for the design strategies on electrode materials for high-throughput energy storage systems. Keywords: Carbon materials, Doping, Porous structure, Sodium ion capacitors, Energy storage

Hybrid ion capacitors that combined high-power density of supercapacitor and high-energy density of battery are drawing attention to insufficient power densities of currently-used lithium-ion batteries (LIBs). Two kinds of layered carbon-based pseudocapacitive materials were used as both anode and cathode for lithium/sodium ion capacitors (LICs/NICs) with balanced energy/power properties. As-assembled NIC and LIC could deliver the energy densities of 125.7 Wh kg−1 and 119.6 Wh kg−1 at the power density of 7941.2 W kg−1 and 8823.5 W kg−1, respectively. The electrochemical properties of NICs were better than that of LICs when the current density was below 4 A g−1, although the working voltage of LIC is higher than that of NICs, and the size of Na+ is larger than that of Li+. Using an instantaneous potential technique, it is found that the increase of the capacity for anode material in low potential region will effectively enhance the electrochemical performance for the full device. Keywords: Sodium/lithium-ion capacitors, High energy-power density, Pseudocapacitive electrodes, Layered materials

The electrocatalytic nitrogen reduction reaction (NRR) has been regarded as a promising strategy for producing ammonia (NH

Noble-metal-free, durable, and high-efficiency electrocatalysts for oxygen reduction and evolution reaction (ORR/OER) are vital for rechargeable Zn-air batteries (ZABs). Herein, a flexible and free-standing carbon fiber membrane immobilized with atomically dispersed Fe-N

An ultrasensitive enzyme-free glucose sensor was facilely prepared by electrodepositing three-dimensional dendritic Cu on a room temperature exfoliated graphite-derived film (RTEG-F). An excellent electrocatalytic performance was demonstrated for glucose by using Cu/RTEG-F as an electrode. In terms of the high conductivity of RTEG-F and the good catalytic activity of the dendritic Cu structures, the sensor demonstrates high sensitivities of 23.237 mA/mM/cm2, R2 = 0.990, and 10.098 mA/mM/cm2, R2 = 0.999, corresponding to the concentration of glucose ranging from 0.025 mM to 1.0 mM and 1.0 mM to 2.7 mM, respectively, and the detection limit is 0.68 μM. In addition, the Cu/RTEG-F electrode demonstrates excellent anti-interference to interfering species and a high stability. Our work provides a new idea for the preparation of high-performance electrochemical enzyme-free glucose sensor.

Ti3C2Tx MXene has drawn considerable attention as anode materials to store sodium ions because of the capability of accommodating the large sodium ions, enabling their intercalation without substantial structural change. However, the limited sodium-ion storage capacity of Ti3C2Tx hinders its real application in sodium-ion batteries (SIBs). To enhance its performance as anode materials in SIBs, here, we introduce nanopores into Ti3C2Tx sheets by sonication, and after which we assemble them with rGO and cellulose nanofibers into an elastic freestanding composite structure by mimicking the wasp nest. The wasp nest-like structure endows the resulting composite with more accessible surfaces of electrode materials to the electrolyte. Further, the nanopores on the Ti3C2Tx sheets and the TiO2 formed from the sonication provide more active sites for sodium storage. As a result, the resulting composite shows a high capacity of 280 mAh g−1 at 100 mA g−1 and remarkable cyclic life with a capacity retention of 84.8% after 1000 cycles at 1 A g−1.