Confinement Effect and 3D Design Endow Unsaturated Single Ni Atoms with Ultrahigh Stability and Selectivity toward CO2 Electroreduction.

Developing single-atomic catalysts with superior selectivity and outstanding stability for CO2 electroreduction is desperately required but still challenging. Herein, confinement strategy and three-dimensional (3D) nanoporous structure design strategy are combined to construct unsaturated single Ni sites (Ni-N3) stabilized by pyridinic N-rich interconnected carbon nanosheets. The confinement agent chitosan and its strong interaction with g-C3N4 nanosheet are effective for dispersing Ni and restraining their agglomeration during pyrolysis, resulting in ultrastable Ni single-atom catalyst. Due to the confinement effect and structure advantage, such designed catalyst exhibits a nearly 100% selectivity and remarkable stability for CO2 electroreduction to CO, exceeding most reported state-of-the-art catalysts. Specifically, the CO Faradaic efficiency (FECO) maintains above 90% over a broad potential range (-0.55 to -0.95 V vs. RHE) and reaches a maximum value of 99.6% at a relatively low potential of -0.67 V. More importantly, the FECO is kept above 95% within a long-term 100 h electrolyzing. Density functional theory (DFT) calculations explain the high selectivity for CO generation is due to the high energy barrier required for hydrogen evolution on the unsaturated Ni-N3. This work provides a new designing strategy for the construction of ultrastable and highly selective single-atom catalysts for efficient CO2 conversion.

Regulating Zinc Storage Behaviors of Tunnel Structure Cathodes Via Tungsten Induction.

Aqueous zinc-ion batteries have received continuous interests because of applying low-cost and eco-friendly aqueous electrolytes and having high safety. Beyond energetically to explore new-type cathode materials, it is of great significance to regulate the zinc storage behavior of the existing cathodes in order to understand the underlying working mechanism. Therefore, as a proof of concept, this work achieves the regulation of zinc storage behaviors of the tunnel structure tunnel structure B-phase vanadium dioxide (VO2 (B)) and vanadium oxide (V6 O13 ) cathodes via a simple chemical tungsten-doping induction approach. Under low-concentration tungsten-doping induction of 1, 2 and 3 at.%, the tunnel sizes of VO2 (B) can be controlled readily. Moreover, the V6 O13 with large size tunnels can be achieved by medium-concentration tungsten induction of 6 and 9 at.%. It is demonstrated that tungsten induced VO2 (B) can achieve zinc storage without lattice structure change via operando X-ray diffraction analyses. Remarkably, via operando and non-operando analyses, tungsten induced V6 O13 with lager size tunnels can realize the oriented 1D zinc ion intercalation/deintercalation. The further kinetics analysis shows that the zinc storage is mainly diffusion control, which is different from most of vanadium-based cathodes with capacitance control. This viable tungsten-doping induction strategy provides a new insight into achieving the controllable regulation of zinc storage behaviors.

Advances in Template Prepared Nano-Oxides and their Applications: Polluted Water Treatment, Energy, Sensing and Biomedical Drug Delivery.

The nano-oxide materials with special structures prepared by template methods have a good dispersion, regular structures and high specific surface areas. Therefore, in some areas, improved properties are observed than conventional bulk oxide materials. For example, in the treatment of dye wastewater, the treatment efficiency of adsorbents and catalytic materials prepared by template method was about 30 % or even higher than that of conventional samples. This review mainly focuses on the progress of inorganic, organic and biological templates in the preparation of micro- and nano- oxide materials with special morphologies, and the roles of the prepared materials as adsorbents and photocatalysts in dye wastewater treatment. The characteristics and advantages of inorganic, organic and biological template are also summarized. In addition, the applications of template method prepared oxides in the field of sensors, drug carrier, energy materials and other fields are briefly discussed with detailed examples.

Research Progress in the Field of Adsorption and Catalytic Degradation of Sewage by Hydrotalcite-Derived Materials.

With the rapid development of industry and agriculture and the greatly improved living conditions, the resultant gradually deteriorated environments threaten the human beings. Refractory or even toxic pollutants, which are from different industries such as printing and dyeing, pesticides, chemicals, petrochemicals, plastics and rubber, seriously threat the ecosystems and human health. Having the advantages of flexible composition, unique structure, high stability, memory effect, easy preparation and low cost, hydrotalcite compounds have a great potential in sewage degradation and environmental protection. This study focuses on the adsorption and catalytic properties (such as photocatalysis, electrocatalysis and photoelectrocatalysis) of hydrotalcite-derived materials for treating organic, inorganic and heavy metal ion sewage. The types of adsorption and catalysis, and the effects of various influencing factors on the degradation efficiency were discussed as well.

3D porous graphene composite film embedded by Ni/NiO nanoparticles as freestanding electrodes for efficient energy storage devices.

A 3D porous graphene composite film containing Ni/NiO hybrid nanoparticles (Ni/NiO NPs) is prepared by combining electrophoresis deposition and thermal H2 annealing techniques. The Ni/NiO NPs with a mean diameter of 45 nm are uniformly embedded on both the exterior and interior surfaces of reduced graphene, forming a 3D porous reduced graphene oxide composite film (Ni/NiO rGO). The insertion of Ni/NiO NPs into rGO greatly improves the electric conductivity and charge storage capability of the resultant Ni/NiO rGO film. By directly using it as freestanding electrodes, the fabricated lithium-ion battery and supercapacitor respectively exhibited high capacities of 758 mAh g-1@ 0.2 A g-1 and 430.8 F g-1@0.5 A g-1, an increase of 82.3-fold and 20.2-fold compared to the pure rGO electrode-based counterparts under the same condition.

Anionic Se-Substitution toward High-Performance CuS1- x Sex Nanosheet Cathode for Rechargeable Magnesium Batteries.

Rechargeable magnesium batteries (rMBs) are promising as the most ideal further energy storage systems but lack competent cathode materials due to sluggish redox reaction kinetics. Herein, developed is an anionic Se-substitution strategy to improve the rate capability and the cycling stability of 2D CuS1- x Sex nanosheet cathodes through an efficient microwave-induced heating method. The optimized CuS1- x Sex (X = 0.2) nanosheet cathode can exhibit high reversible capacity of 268.5 mAh g-1 at 20 mA g-1 and good cycling stability (140.4 mAh g-1 at 300 mA g-1 upon 100 cycles). Moreover, the CuS1- x Sex (X = 0.2) nanosheet cathode can deliver remarkable rate capability with a reversible capacity of 119.2 mAh g-1 at 500 mA g-1 , much higher than the 21.7 mAh g-1 of pristine CuS nanosheets. The superior electrochemical performance can be ascribed to the enhanced reaction kinetics, enriched cation storage active sites, and shortened ion diffusion pathway of the CuS1- x Sex nanosheet. Therefore, tuning anionic chemical composition demonstrates an effective strategy to develop novel cathode materials for rMBs.

Multicomponent Co9S8@MoS2 nanohybrids as a novel trifunctional electrocatalyst for efficient methanol electrooxidation and overall water splitting.

In view of the importance of multifunctional catalysts that can drive different electrocatalytic reactions in the same electrolyte solution, we designed and prepared a series of multicomponent nanohybrids composed of Co9S8 and MoS2 derived from cobalt-doped polyoxometalate (Co-POMs) by one-pot calcination method. The obtained Co9S8@MoS2 nanohybrids were composed of Co9S8, MoS2, Co-Mo-S phases and assembled nanosheets, and therefore were explored as trifunctional electrocatalysts for hydrogen evolution reaction, oxygen evolution reaction, and methanol oxidation reaction (MOR) in an alkaline medium. The nanostructure and chemical components of the series of Co9S8@MoS2 nanohybrids can be modulated by changing the mole ratios of H5Mo12O41P to Co(NO3)2 precursor. Compared with the sole component and other reported Co9S8@MoS2 nanohybrids, the Co9S8@MoS2 nanohybrid prepared from the 1:1 ratio of PMo12 and Co(NO3)2 exhibited superior MOR catalysis efficiency (121.4 mA cm-2) and an extremely low overpotential (1.49 V) for overall water splitting at a current density of 10 mA cm-2 owning to the effective synergism among Co9S8, MoS2, and Co-Mo-S phase. Overall, this study provides a feasible approach to developing efficient and stable trifunctional bimetal electrocatalysts for clean-energy applications.

A highly Li+-conductive HfNb24O62 anode material for superior Li+ storage.

Highly Li+-conductive HfNb24O62 is explored as a new intercalation-type niobium-based oxide anode material for superior Li+ storage. HfNb24O62 owns a Wadsley-Roth shear structure with a large unit-cell volume, leading to a large Li+ diffusion coefficient. HfNb24O62 shows a large capacity, safe operating potential, high rate performance and good cyclability.

Carbon nitride nanoplatelet photocatalysts heterostructured with B-doped carbon nanodots for enhanced photodegradation of organic pollutants.

Decorating electron-accepting materials on carbon nitride (C3N4) is a promising strategy to construct heterostructure catalysts for improved photocatalytic abilities. In this study, B-doped carbon-dots (B-C-dots) decorated C3N4 (C3N4/B-C-dots) catalysts were fabricated through the surface deposition. The benefits from integration of B-C-dots and C3N4 are four folds: (i) increasing surface area; (ii) improving visible light absorption; (iii) promoting the transfer of photoinduced carriers; and (iv) reducing the recombination of photoinduced carriers. The optimum photocatalytic activity of B-C-dots/C3N4 for Rhodamine B (Rh B) (or tetracycline hydrochloride (TC)) degradation was about 7.21 (6.56) and 4.80 (4.35) times higher than that of C3N4 and C-dots/C3N4, respectively, exhibiting both remarkable stability and repeatability. Moreover, enhanced photocatalytic activity of C3N4/B-C-dots could also be attributed to the type-II heterojunction formed between C3N4 and B-C-dots caused by B doping.

Hierarchically Porous MoS2-Carbon Hollow Rhomboids for Superior Performance of the Anode of Sodium-Ion Batteries.

It is always challenging to fabricate two-dimensional transition-metal dichalcogenides into multiple hollow micro-/nanostructures with improved properties for various potential applications. Here, hierarchically porous MoS2-C hollow rhomboids (MCHRs) have been creatively synthesized via a facile self-templated solvothermal approach. It has been clarified that the obtained MCHRs assembled beneath ultrathin γ-MnS and carbon cohybridized MoS2 nanosheets under the structural direction of the MnMoO4·0.49H2O self-template. The prepared MCHR anode of sodium-ion batteries exhibited a reversible capacity of 506 mA h g-1 at 0.1 A g-1, ultrahigh rate capabilities up to 10 A g-1 with 310 mA h g-1, and exceptional stability over 3000 cycles. This study provides inspiration for the rational design of hierarchically porous hollow nanostructures with specific geometries as an excellent electrode material for outstanding performance energy storage equipment.

Sodium-ion capacitors: Materials, Mechanism, and Challenges.

Sodium-ion capacitors (SICs), designed to attain high energy density, rapid energy delivery, and long lifespan, have attracted much attention because of their comparable performance to lithium-ion capacitors (LICs), alongside abundant sodium resources. Conventional SIC design is based on battery-like anodes and capacitive cathodes, in which the battery-like anode materials involve various reactions, such as insertion, alloying, and conversion reactions, and the capacitive cathode materials usually depend on activated carbon (AC). However, researchers have attempted to construct SICs based on battery-like cathodes and capacitive anodes or a combination of both in recent years. In this Minireview, charge storage mechanisms and material design strategies for SICs are summarized, with a focus on the battery-like anode materials from both inorganic and organic sources. Additionally, the challenges in the fabrication of SICs and future research directions are discussed.

N self-doped ZnO derived from microwave hydrothermal synthesized zeolitic imidazolate framework-8 toward enhanced photocatalytic degradation of methylene blue.

The precursor particles were successfully prepared by a facile microwave hydrothermal method. Compared with solvothermal and precipitation method, microwave hydrothermal method can greatly shorten the reaction time and increase the product yields. Nitrogen (N) doped zinc oxide (ZnO) nanoparticles were derived via one-step controllable pyrolysis of zeolitic imidazolate framework-8 (Zif-8) precursors under 550 °C. The powder X-ray diffraction (XRD) analysis, elemental mapping image, energy dispersive spectrometry (EDS) spectra and X-ray photoelectron spectroscopy (XPS) analysis proved that Zif-8 particles were converted to ZnO and the N atoms were successfully doped into ZnO lattice. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results demonstrated that N doped ZnO retained the morphology of Zif-8 with a particle size of approximately ~70 nm and the UV-visible diffuse reflectance spectra (UV-vis DRS) showed that the as-prepared N doped ZnO possessed a lower band gap (3.16 eV) than commercial ZnO (3.26 eV). The photocatalytic activities of the as-prepared samples were evaluated by the degradation rate of methylene blue (MB) upon irradiation with solar-simulated light. The photocatalytic degradation efficiency of N doped ZnO was 95.3% after 80 min illumination, which was much higher than that of other samples prepared by other methods. Quenching tests proved that the photo-generated holes (h+) played a main role in the photodegradation of MB under solar-simulated light irradiation.

Magnetic nanocellulose-magnetite aerogel for easy oil adsorption.

HYPOTHESIS: Cellulose aerogels are a new category of high-efficiency adsorbents for treating oil spills and water pollution. However, the hydrophilic properties and recyclability of aerogels after adsorption hamper developments and applications. Combining both hydrophobic and magnetic properties are expected to improve their adsorption capacity and functionality. EXPERIMENTS: In this study, the effect of oleic acid (OA) and nanomagnetite on the preparation of magnetic nanocellulose aerogels (called as NCA/OA/Fe3O4) by a mechanical mixing combined with freeze-drying method have been investigated. FINDINGS: It has been found that the optimal condition for fabricating this NCA/OA/Fe3O4 aerogel is 0.4 wt% nanocellulose, 3 mg mL-1 OA and 0.5 wt% Fe3O4 in the aqueous solution. This aerogel has a very low density of 9.2 mg cm-3 and demonstrates a high adsorption capacity of 68.06 g g-1 for cyclohexane. In addition, this aerogel adsorbent demonstrates an excellent magnetic responsivity and can be easily recycled by a permanent magnet after adsorption. As a consequence, this hydrophobic magnetic NCA/OA/Fe3O4 aerogel is promising not only for easy oil and organic solvent adsorption but also potentially for other magnetic related applications.

A polyether amine modified metal organic framework enhanced the CO2 adsorption capacity of room temperature porous liquids.

Based on both the compatibility principle of similar polymeric structures and the steric interaction, a polyether amine (D2000) modified MOF (UIO-66) was dispersed into an ionic liquid with a polyether structure to form a new porous liquid (called the UIO-66-liquid) at room temperature. This unique UIO-66-liquid showed an outstanding CO2 uptake capacity among the existing porous liquids.

Fe3O4 hard templating to assemble highly wrinkled graphene sheets into hierarchical porous film for compact capacitive energy storage.

Highly wrinkled graphene film (HWGF) with high packing density was synthesized by combining an electrostatically self-assembling process, a vacuum filtration-induced film assembling process and capillary compression. Fe3O4 nanoparticles were used as a low-cost and environment-friendly hard template. Hierarchical porosity and high packing density were achieved with the aid of capillary compression in the presence of Fe3O4 nanoparticles. This strategy enables integration of highly wrinkled graphene sheets to form highly compact carbon electrodes with a continuous ion transport network. The generated HWGF exhibited a high packing density of 1.53 g cm-3, a high specific surface area of 383 m2 g-1 and a hierarchically porous structure. The HWGF delivered a high capacitance of 242 F g-1 and 370 F cm-3 at 0.2 A g-1 in 6 M KOH aqueous electrolyte system with excellent rate capability (202 F g-1 and 309 F cm-3 retained at 20 A g-1). The capacity retention rate reached 97% after 10 000 cycles at 1 A g-1. The HWGF-based supercapacitor exhibited a high energy density of 17 W h kg-1 at the power density of 49 W kg-1. Such high capacitive performances could be attributed to the highly dense but porous graphene assemblies composed of highly wrinkled graphene sheets.

Synthesis of Heterocyclic Core-Expanded Bis-Naphthalene Tetracarboxylic Diimides.

A highly reactive bis-naphthalene tetracarboxylic diimide (bis-NDI) intermediate, TBrDNDI, was designed and synthesized for core-expanded NDIs. Based on this intermediate, we achieved 9- and 11-membered core-expanded bis-NDI derivatives. Through expanding the NDI core and introducing electron-donor or electron-acceptor groups, the frontier energy orbitals, optical and electrical properties of these bis-NDIs can be finely tuned to obtain air-stable ambipolar or n-type materials.

Sandwich-like NiCo layered double hydroxide/reduced graphene oxide nanocomposite cathodes for high energy density asymmetric supercapacitors.

Nanocomposites with a well-defined sandwich-like nanostructure were prepared via in situ growing NiCo-layered double hydroxide nanosheets with tunable Ni/Co ratios on reduced graphene oxide (rGO). Electrochemical impedance spectra and N2 adsorption/desorption isotherms confirmed that these sandwich nanostructures effectively promoted charge transport and enlarged the specific surface area. The nanocomposites with Ni : Co = 2 : 1 exhibited a maximum specific capacitance of 2130 F g-1 at 2 A g-1, excellent rate capability (72.7% retention at 15 A g-1), and cycling stability. Asymmetric supercapacitors were assembled with these nanocomposite cathodes and rGO as a negative electrode (anode), and demonstrated an energy density of 34.5 W h kg-1 at a power density of 772 W kg-1, while maintaining a capacity retention of 86.7% after 10 000 cycles at 5 A g-1. The robust electrochemical properties indicate the composites as promising electrodes for electrochemical energy storage devices.

Zinc oxide/vanadium pentoxide heterostructures with enhanced day-night antibacterial activities.

Low photocatalytic efficiency of visible light and fast recombination of photo-generated carriers are two challenges facing the applications of photocatalyst sterilant zinc oxide (ZnO). Meanwhile, both light and dark photocatalytic activities are important. It is of great theoretical and practical significance to construct a day-night photocatalytic antibacterial material, which is beneficial to the effective use of energy and to tackle the limitation of using photocatalytic bacteriostat. ZnO nanoflowers decorated vanadium pentoxide (V2O5) nanowires heterojunction (ZVH) was firstly fabricated using a facile water-bathing method. The designed ZVH structure efficiently produced abundant reactive oxygen species (ROS) in both light and darkness. It yielded 99.8% and 99.0% of antibacterial rate against S. aureus due to oxidative stress induced by ROS in light and darkness, respectively. The generation of ROS played a major role in the antibacterial activities against S. aureus under both light and dark conditions. The prepared ZVH with improved antibacterial properties provides an alternative for day-night antibacterial agents.

Controllable organic magnetoresistance in polyaniline coated poly(p-phenylene-2,6-benzobisoxazole) short fibers.

Herein, we first report a tunable organic magnetoresistance (OMAR) effect in polyaniline (PANI) coated acid treated poly(p-phenylene-2,6-benzobisoxazole) (t-PBO) short fibers. This unique OMAR is interpreted using the paramagnetic nature of PBO molecules combined with the localization length a0 calculated from the wave-function shrinkage model and forward interference model.

Surface intercalated spherical MoS2xSe2(1-x) nanocatalysts for highly efficient and durable hydrogen evolution reactions.

An efficient hydrogen evolution reaction (HER) depends essentially on high-performing electrocatalysts. The aggregation of catalysts normally deteriorates their activity and stability. In this study, a two-step route was used to synthesize surface intercalated well-dispersed spherical MoS2xSe2(1-x) nanocatalysts. The resulting catalysts present a highly active and stable performance towards the HER with an overpotential of -143 mV at 10 mA cm-2, and a Tafel slope of 53.8 mV dec-1. The mechanism for the enhanced HER was analyzed and was attributed to three factors: (i) large numbers of defects and edge active sites arising from the coexistence of S and Se elements; (ii) enhanced electric conductivity arising from the phase transition from the semiconducting 2H-phase to metallic 1T-phase during the intercalation process; and (iii) enlarged contact areas between active sites and electrolyte caused by the increased surface roughness due to the surface intercalation. This work not only deepens our understanding of the improved HER performance of surface intercalated catalysts, but also provides novel strategies for preparing durable electrocatalysts through surface engineering.