Vinyl-bearing sp2 carbon-conjugated covalent organic framework composites for enhanced electrochemical performance in hydrogen evolution reaction and lithium-sulfur batteries.

Vinyl-bearing triazine-functionalized covalent organic frameworks (COFs) have emerged as promising materials for electrocatalysis and energy storage. Guided by density functional theory calculations, a vinyl-enriched COF (VCOF-1) featuring a donor-acceptor structure was synthesized based on the Knoevenagel reaction. Moreover, the VCOF-1@Ru without pyrolysis was obtained through chemical coordination interactions between VCOF-1 and RuCl3, exhibiting enhanced electrocatalytic performance in the hydrogen evolution reaction when exposed to 0.5 M H2SO4. The results demonstrated that the protonation of VCOF-1@Ru enhanced the electrical conductivity and accelerated the generation of H2 on the catalytically active site Ru. Additionally, VCOF-1@CNT with a tubular structure was prepared by uniformly wrapping VCOF-1 onto carbon nanotubes (CNTs) and using it as a cathode for lithium-sulfur batteries by chemically and physically encapsulating S. The enhanced performance of VCOF-1@CNT was attributed to the effective suppression of lithium polysulfide migration. This suppression was achieved through several mechanisms, including the inverse vulcanization of vinyl on VCOF-1@CNT, the enhancement of material conductivity, and the interaction between N in the materials and Li ions. This study demonstrated a strategy for enhancing material performance by precisely modulating the COF structure at the molecular level.

Multi-functional carbon nanotube encapsulated by covalent organic frameworks for lithium-sulfur chemistry and photothermal electrocatalysis.

It is significant to tailor multifunctional electrode materials for storing sustainable energy in lithium-sulfur (Li-S) batteries and converting intermittent solar energy into H2, facilitated by electricity. In this context, COF-1@CNT obtained through interfacial interaction fulfilled both requisites via post-functionalization. Upon integrating COF-1@CNT with S as the cathode for Li-S batteries, the system exhibited an initial discharge capacity of 1360 mAh g-1. Subsequently, it maintained a sustained actual capacity even after undergoing 200 charge-discharge cycles at 0.5C. The performance improvement was attributed to the optimized conductivity due to the addition of carbon nanotubes (CNTs). Furthermore, the synergistic interaction between the nitrogen of COF-1 and lithium mitigated the shuttle effect in Li-S batteries. In the modified three-electrode electrolytic cell system, COF-1@CNT-Ru produced by COF-1@CNT with RuCl3 showed better electrochemical reactivity for photothermal-assisted hydrogen evolution reaction (HER). This effect was demonstrated by reducing the overpotential to 140 mV relative to the no-photothermal condition (180 mV) at a current density of 10 mA cm-2. This study marked the first simultaneous application of covalent organic frameworks (COFs) based materials in Li-S batteries and photothermal-assisted electrocatalysts. The modified electrocatalytic system held promise as a novel avenue for exploring solar thermal energy utilization.

Matched Redox Kinetics on Triazine-Based Carbon Nitride/Ni(OH)2 for Stoichiometric Overall Photocatalytic CO2 Conversion.

Mismatched reaction kinetics of CO2 reduction and H2 O oxidation is the main obstacle limiting the overall photocatalytic CO2 conversion. Here, a molten salt strategy is used to construct tubular triazine-based carbon nitride (TCN) with more adsorption sites and stronger activation capability. Ni(OH)2 nanosheets are then grown over the TCN to trigger a proton-coupled electron transfer for a stoichiometric overall photocatalytic CO2 conversion via "3CO2 + 2H2 O = CH4 + 2CO + 3O2 ." TCN reduces the energy barrier of H2 O dissociation to promote H2 O oxidation to O2 and supply sufficient protons to Ni(OH)2 , whereby the CO2 conversion is accelerated due to the enhanced proton-coupled electron transfer process enabled by the sufficient proton supply from TCN. This work highlights the importance of matching the reaction kinetics of CO2 reduction and H2 O oxidation by proton-coupled electron transfer on stoichiometric overall photocatalytic CO2 conversion.

Compositional Engineering of Hybrid Organic-Inorganic Lead-Halide Perovskite and PVDF-Graphene for High-Performance Triboelectric Nanogenerators.

Triboelectric nanogenerators (TENGs) have attracted a great deal of attention since they can convert ubiquitous mechanical energy into electrical energy and serve as a continuous power source for self-powered sensors. Optimization of the dielectric material composition is an effective way to improve the triboelectric output performance of TENGs. Herein, the hybrid organic-inorganic lead-iodide perovskite Cs0.05FA0.95-xMAxPbI3 was prepared by blade coating and used as a positive friction layer material. Moreover, PVDF-graphene (PG) nanofibers were prepared as negative friction layer materials by electrostatic spinning. The output performance of the TENG was enhanced by varying the MA content of the pervoskite films and the graphene content of the PG nanofibers. The champion output TENG based on Cs0.05FA0.9MA0.05PbI3/PG-0.15 achieved an open-circuit voltage of 245 V, a short-circuit current of 24 µA, and a charge transfer of 80.2 nC. Meanwhile, a maximum power density of 11.23 W m-2 was obtained at 100 MΩ. Moreover, the device exhibits excellent energy-harvesting properties, including excellent stability and durability, rapidly charges capacitors, and lights commercial LEDs and digital tubes.

Electrolyte Modulation of Biological Chelation Additives toward a Dendrite-Free Zn Metal Anode.

Aqueous zinc-ion batteries are considered promising energy storage devices due to their superior electrochemical performance. Nevertheless, the uncontrolled dendrites and parasitic side reactions adversely affect the stability and durability of the Zn anode. To cope with these issues, inspired by the chelation behavior between metal ions and amino acids in the biological system, glutamic acid and aspartic acid are selected as electrolyte additives to stabilize the Zn anode. Experimental characterizations in conjunction with theoretical calculation results indicate that these additives can simultaneously modify the solvation structure of hydrated Zn2+ and preferentially adsorb onto the Zn anode, thereby restricting the occurrence of interfacial side reactions and enhancing the performance of the Zn anode. Benefiting from these synergistic effects, the as-assembled Zn-based batteries containing additive electrolytes achieved admirable electrochemical performance. From the viewpoint of electrolyte regulation, this work provides a bright direction toward the development of aqueous batteries.

Pure and Metal-confining Carbon Nanotubes through Electrochemical Reduction of Carbon Dioxide in Ca-based Molten Salts.

To be successfully implemented, an efficient conversion, affordable operation and high values of CO2 -derived products by electrochemical conversion of CO2 are yet to be addressed. Inspired by the natural CaO-CaCO3 cycle, we herein introduce CaO into electrolysis of SnO2 in affordable molten CaCl2 -NaCl to establish an in situ capture and conversion of CO2 . In situ capture of anodic CO2 from graphite anode by the added CaO generates CaCO3 . The consequent co-electrolysis of SnO2 and CaCO3 confines Sn in carbon nanotube (Sn@CNT) in cathode and increases current efficiency of O2 evolution in graphite anode to 71.9 %. The intermediated CaC2 is verified as the nuclei to direct a self-template generation of CNT, ensuring a CO2 -CNT current efficiency and energy efficiency of 85.1 % and 44.8 %, respectively. The Sn@CNT integrates confined responses of Sn cores to external electrochemical or thermal stimuli with robust CNT sheaths, resulting in excellent Li storage performance and intriguing application as nanothermometer. The versatility of the molten salt electrolysis of CO2 in Ca-based molten salts for template-free generation of advanced carbon materials is evidenced by the successful generation of pure CNT, Zn@CNT and Fe@CNT.

Hierarchical structure design of sea urchin Shell-Based evaporator for efficient omnidirectional Solar-Driven steam generation.

Solar-driven steam generation (SSG) is regarded as a feasible solution to the problem of fresh water scarcity. Although several attempts have been devoted to increase the efficiency of solar-to-steam conversion, it remains difficult to fabricate cost-effective, steady, and multi-angle sunlight-absorbing evaporators from readily available biomass materials. Herein, a novel hierarchical structured SSG evaporator (PDA@Shell-NaClO) is developed through a simple, low-cost, and scalable etching treatment on discarded sea urchin (SU) shells. Attributing to the dedicatedly designed microneedles array structure and porous skeleton structure of the SU shell, this PDA@Shell-NaClO evaporator shows an outstanding average light absorption performance (>90%) in a broad range of angles from 0° to 60° and exceedingly high evaporation rate of 2.81 kg m-2 h-1 under one sun condition. Furthermore, the prepared evaporator also maintains an overall stable evaporation performance and exhibits an excellent durability for a long time of up to two weeks in actual seawater. This full-ocean biomass-based SSG evaporator with plentiful raw material availability offers innovative opportunities for large-scale fresh water production.

Feasibility analysis of coexistence between plantation and tower concentrating solar system.

There are large-scale thermal utilization needs in rural and urban fringes in China that can provide many employment opportunities. However, due to the limited use of small and medium-sized coal-fired boilers, thermal energy is actually in short supply. If embedding these spaces including plantations with solar heliostat fields, a large number of nodes for cheap thermal energy supply can be obtained through solar energy, which can create more small-scale industrial and commercial employment opportunities near user side. However, to ensure the crop harvest, plantations are often prohibited from being used for other purposes. In order to verify the idea of coexistence between tower concentrating solar system with sparse heliostat field and plantation, the clean-sky model was used to analyze the shading rate of the heliostat to the ground in each month and the proportion of the area with a relative sunshine duration of less than 80% for the heliostat fields at low, middle, and high latitude areas, and further gave the correction of the above analysis results using typical meteorological year conditions. The results show that heliostats in mid latitude area have obvious adverse effects on overwintering crops. In high latitude area, although the heliostats are more severely blocked in the cold season, there is no planting activity in this season, so the impact on planting can be ignored. The shade ratio of the heliostats to the ground in low, middle and high latitude regions is tolerable in the months suitable for planting, and shade-tolerant crops can also be interplanted in the shaded area to enrich the variety structure. Therefore, by embedding the tower concentrating solar system with a sparse heliostat field, the plantation can meet the two functions of planting and thermal energy supply at the same time to further increase its income.

Overall Carbon-neutral Electrochemical Reduction of CO2 in Molten Salts using a Liquid Metal Sn Cathode.

An overall carbon-neutral CO2 electroreduction requires enhanced conversion efficiency and intensified functionality of CO2 -derived products to balance the carbon footprint from CO2 electroreduction against fixed CO2 . A liquid Sn cathode is herein introduced into electrochemical reduction of CO2 in molten salts to fabricate core-shell Sn-C spheres (Sn@C). An in situ generated Li2 SnO3 /C directs a self-template formation of Sn@C. Benefitting from the accelerated reaction kinetics from the liquid Sn cathode and the core-shell structure of Sn@C, a CO2 -fixation current efficiency higher than 84 % and a high reversible lithium-storage capacity of Sn@C are achieved. The versatility of this strategy is demonstrated by other low melting point metals, such as Zn and Bi. This process integrates energy-efficient CO2 conversion and template-free fabrication of value-added metal-carbon, achieving an overall carbon-neutral electrochemical reduction of CO2 .

Modulating Surface Electron Density of Heterointerface with Bio-Inspired Light-Trapping Nano-Structure to Boost Kinetics of Overall Water Splitting.

Herein, inspired by natural sunflower heads' properties increasing the temperature of dish-shaped flowers by tracking the sun, a novel hybrid heterostructure (MoS2 /Ni3 S2 @CA, CA means carbon nanowire arrays) with the sunflower-like structure to boost the kinetics of water splitting is proposed. Density functional theory (DFT) reveals that it can modulate the active electronic states of NiMo atoms around the Fermi-level through the charge transfer between the metallic atoms of Ni3 S2 and MoMo bonds of MoS2 to boost overall water splitting. Most importantly, the finite difference time domain (FDTD) could find that its unique bio-inspired micro-nano light-trapping structure has high solar photothermal conversion efficiency. With the assistance of the photothermal field, the kinetics of water-splitting is improved, affording low overpotentials of 96 and 229 mV at 10 mA cm-2 for HER and OER, respectively. Moreover, the Sun-MoS2 /Ni3 S2 @CA enables the overall alkaline water splitting at a low cell voltage of 1.48 and 1.64 V to achieve 10 and 100 mA cm-2 with outstanding catalytic durability. This study may open up a new route for rationally constructing bionic sunflower micro-nano light-trapping structure to maximize their photothermal conversion and electrochemical performances, and accelerate the development of nonprecious electrocatalysts for overall water splitting.

Silicate-Mediated Electrolytic Silicon Nanotube from Silica in Molten Salts.

Electrochemical preparation/processing of functional silicon from abundant silica is an ideal protocol to promote sustainability of energy sectors. Such an imperative task is challenged by poor electrical conductivity of Si/SiO2 and inadequate mass diffusion of bulk silicon. Herein, a template-free and one-step preparation of silicon nanotubes (Si-NT) from electrochemical reduction of silica in molten salts is reported. An in situ oriented growth of silicate nanorods (NRs) from silica is clarified as the key step to direct a self-template evolution of Si-NT from silica. The silicate-mediated construction of Si-based NT is versatile and successfully extended to prepare Si-NT/graphite and Tix Siy -NT. Benefitting from fast longitudinal motorways for fast transport of electrons and ions along/inside NTs, an energy consumption 30% lower than industrial silicon production is achieved. When evaluated as anode of lithium ion battery, the Si-NT-based electrodes show outstanding initial Coulombic efficiency and high reversible capacity. The silicate-mediated construction of Si-based NT integrates straightforward preparation and intriguing functionality of Si-based materials, bridging a closed-loop Si-based energy infrastructure.

Functionalized triazine-based covalent organic frameworks containing quinoline via aza-Diels-Alder reaction for enhanced lithium-sulfur batteries performance.

The development of functional covalent organic frameworks (COFs) with specific properties is an emerging research field. In the current work, COF-SQ-Ph was synthesized through the aza-Diels-Alder reaction between phenylacetylene and the matrix COF-SQ (triazine-based COF) generated from the organic monomers 2, 4, 6-tris(4-aminophenyl)-1, 3, 5-triazine and 2, 5-dimethoxyterephthalaldehyde in flask. The functionalized COF-SQ-Ph with an extended π-conjugated structure and enhanced structural stability was used as the sulfur loading recipient to prepare sulfur cathodes for lithium-sulfur batteries. Sulfur-impregnated COF-SQ-Ph marked as COF-SQ-Ph-S displayed better cycling stability with a specific capacity of 618 mA h g-1 after 150 cycles due to the lithiophilic interaction between lithium polysulfides and nitrogen atoms from quinoline and triazine moieties in COF-SQ-Ph-S. The functionalization of triazine-based COFs through a cycloaddition reaction in flask could promote the large-scale preparation of tailored COFs and the post-synthesis modification of COF-SQ.

Molten Salt Electrochemical Modulation of Iron-Carbon-Nitrogen for Lithium-Sulfur Batteries.

Sulfur hosts with rationally designed chemistry to confine and convert lithium polysulfides are of prime importance for high-performance lithium-sulfur batteries. A molten salt electrochemical modulation of iron-carbon-nitrogen is herein demonstrated as formation of hollow nitrogen-doped carbon with grafted Fe3 C nanoparticles (Fe3 C@C@Fe3 C), which is rationalized as an excellent sulfur host for lithium-sulfur batteries. Fe3 C over nitrogen-doped carbon contributes to enhanced adsorption and catalytic conversion of lithium polysulfides. The sulfur-loaded Fe3 C@C@Fe3 C electrodes hence show a high capacity, good cyclic stability, and enhanced rate performance. This work highlights the unique chemistry of metal carbides on facilitating adsorption-conversion process of lithium polysulfides, and also extends the scope of molten salt electrolysis to elaboration of energy materials.

Synthesis of boron carbonitride nanosheets using for delivering paclitaxel and their antitumor activity.

As a structural analog of graphene and boron nitride, hexagonal boron carbonitride nanosheets (BCNNSs) are supposed to be a potential drug deliverer. In the present work, an improved solid-state reaction method combined with ultrasonic exfoliating was reported for preparing BCNNSs. Vapor-solid (VS) mechanism was proposed to be responsible for the formation of BCNNSs. The BCNNSs were further modified by DSPE-mPEG-5000 to improve their dispersion in aqueous solution. It was found that the BCNNSs-PEG nanocomplex could be efficiently taken in by MDA-MB-231 breast cancer cells evidenced by inverted fluorescence microscopy. The PEGylated BCNNSs showed an outstanding ability to load paclitaxel through π-π interaction and hydrophobic interaction, and BCNNSs-PEG-loaded paclitaxel presented higher cytotoxicity in comparison with free paclitaxel. BCNNSs may become a promising candidate for delivering paclitaxel and other hydrophobic drugs.

Electrochemical Reduction of Carbon Dioxide and Iron Oxide in Molten Salts to Fe/Fe3 C Modified Carbon for Electrocatalytic Oxygen Evolution.

Non-noble electrocatalyst for the oxygen evolution reaction (OER) is essential for water electrolysis and electrochemical conversion of CO2 . Integrating electrochemical fixation of CO2 and electrochemical metallurgy to prepare advanced OER electrocatalyst is a promising solution to promote carbon neutrality and renewable energy. Herein, the electrochemical reduction of CO2 and Fe2 O3 are combined in molten salts to prepare cathodic Fe3 C-based electrocatalyst and anodic oxygen at 600 °C with enhanced current efficiency. The resulting Fe3 C-based electrocatalyst outperforms precious electrocatalyst towards the OER operation in 1 M KOH due to a dynamic structural evolution to form an interface of Fe3 C-FeOOH.

DNA nano-pocket for ultra-selective uranyl extraction from seawater.

Extraction of uranium from seawater is critical for the sustainable development of nuclear energy. However, the currently available uranium adsorbents are hampered by co-existing metal ion interference. DNAzymes exhibit high selectivity to specific metal ions, yet there is no DNA-based adsorbent for extraction of soluble minerals from seawater. Herein, the uranyl-binding DNA strand from the DNAzyme is polymerized into DNA-based uranium extraction hydrogel (DNA-UEH) that exhibits a high uranium adsorption capacity of 6.06 mg g-1 with 18.95 times high selectivity for uranium against vanadium in natural seawater. The uranium is found to be bound by oxygen atoms from the phosphate groups and the carbonyl groups, which formed the specific nano-pocket that empowers DNA-UEH with high selectivity and high binding affinity. This study both provides an adsorbent for uranium extraction from seawater and broadens the application of DNA for being used in recovery of high-value soluble minerals from seawater.

Atomic-Scale Control of Magnetism at the Titanite-Manganite Interfaces.

Complex oxide thin-film heterostructures often exhibit magnetic properties different from those known for bulk constituents. This is due to the altered local structural and electronic environment at the interfaces, which affects the exchange coupling and magnetic ordering. The emergent magnetism at oxide interfaces can be controlled by ferroelectric polarization and has a strong effect on spin-dependent transport properties of oxide heterostructures, including magnetic and ferroelectric tunnel junctions. Here, using prototype La2/3Sr1/3MnO3/BaTiO3 heterostructures, we demonstrate that ferroelectric polarization of BaTiO3 controls the orbital hybridization and magnetism at heterointerfaces. We observe changes in the enhanced orbital occupancy and significant charge redistribution across the heterointerfaces, affecting the spin and orbital magnetic moments of the interfacial Mn and Ti atoms. Importantly, we find that the exchange coupling between Mn and Ti atoms across the interface is tuned by ferroelectric polarization from ferromagnetic to antiferromagnetic. Our findings provide a viable route to electrically control complex magnetic configurations at artificial multiferroic interfaces, taking a step toward low-power spintronics.

Probing the Ionic and Electrochemical Phenomena during Resistive Switching of NiO Thin Films.

Ionic transport and electrochemical reactions underpin the functionality of the memory devices. NiO, as a promising transition metal oxide for developing resistive switching random access memory, has been extensively explored in the terms of the resistive switching. However, there is limited experimental evidence to visualize the ionic processes of the NiO under the external electrical field. In addition, the correlation between the ionic processes and the resistive switching has not been established. To close this gap and also to determine the role of the ionic processes in resistive switching of the NiO, in this study, a series of scanning probe microscopy techniques, including electrochemical strain microscopy (ESM), conductive atomic force microscopy, Kelvin probe force microscopy, and a newly developed first-order reversal curve-IV, are employed to measure the ESM response, the resistive switching performance, the work function, and the ionic dynamics of NiO, respectively. The results in this work have clearly visualized the ionic transport and electrochemical reactions of NiO when subjected to the electrical field. It has been found that the ionic processes and the resistive switching accompanied each other. Furthermore, it is found that the electrochemical reactions play a determinative role in the resistive switching of the NiO, and this electrochemically induced resistive switching performance can be explained by an integrated mechanism that has combined the filamentary and the interfacial effects underlying resistive switching. In addition to providing a better understanding of the resistive switching of NiO, this work also provides effective methods to probe the ionic processes and to correlate these ionic processes to the performance of functional materials.

Multi-Nonvolatile State Resistive Switching Arising from Ferroelectricity and Oxygen Vacancy Migration.

Resistive switching phenomena form the basis of competing memory technologies. Among them, resistive switching, originating from oxygen vacancy migration (OVM), and ferroelectric switching offer two promising approaches. OVM in oxide films/heterostructures can exhibit high/low resistive state via conducting filament forming/deforming, while the resistive switching of ferroelectric tunnel junctions (FTJs) arises from barrier height or width variation while ferroelectric polarization reverses between asymmetric electrodes. Here the authors demonstrate a coexistence of OVM and ferroelectric induced resistive switching in a BaTiO3 FTJ by comparing BaTiO3 with SrTiO3 based tunnel junctions. This coexistence results in two distinguishable loops with multi-nonvolatile resistive states. The primary loop originates from the ferroelectric switching. The second loop emerges at a voltage close to the SrTiO3 switching voltage, showing OVM being its origin. BaTiO3 based devices with controlled oxygen vacancies enable us to combine the benefits of both OVM and ferroelectric tunneling to produce multistate nonvolatile memory devices.

Enhanced Thermoelectric Properties of Polyaniline Nanofilms Induced by Self-Assembled Supramolecules.

Polyaniline (PANI) is one of the most promising candidates for flexible organic thermoelectric (TE) applications owing to its relatively low cost and high stability. Herein, the self-assembled supramolecule (SAS) (3,6-dioctyldecyloxy-1,4-benzenedicarboxylic acid) was used as an additive and was introduced into PANI films as a template. Raman spectroscopy, X-ray diffraction, and conductive atomic force microscopy analyses demonstrated that the highly ordered chain structure of PANI was achieved by chemical interactions between PANI and the SAS. Moreover, the ordered regions in the PANI-SAS film increased with a decrease in the film thickness. Consequently, the TE properties of PANI-SAS films were not only much higher than those of PANI films, but they also increased with a decrease in film thickness. The maximum TE power factor of the PANI-SAS film reached 31 µW m(-1) K(-2) , which is approximately six times higher than the power factor of a PANI film with a similar thickness. This work offers a promising way to prepare PANI thin films with enhanced TE properties.