Search

Bismuth sulfide (Bi2S3) has attracted particular interest as a potential anode material for sodium-ion batteries (SIBs). However, the low electrical conductivity and dramatic volumetric change greatly restrict its practical applications. In view of the apparent structural and compositional advantages of metal-organic frameworks (MOFs) derived carbon-based composite, herein, as a proof of concept, Bi2S3 spheres coated with the MOF-derived Co9S8 and N-doped carbon composite layer (Bi2S3@Co9S8/NC composite spheres) have been rational designed and synthesized. As expected, the core-shell Bi2S3@Co9S8/NC composite spheres exhibit remarkable electrochemical performance in terms of high reversible capacity (597 mAh g−1 after 100 cycles at 0.1 A g−1), good rate capability (341 mAh g−1 at 8 A g−1) and long-term cycling stability (458 mAh g−1 after 1000 cycles at 1 A g−1) when investigated as anode materials for SIBs. Electrochemical analyses further reveal the favorable reaction kinetics in the Bi2S3@Co9S8/NC composite spheres. In addition, the possible sodium storage mechanism has been studied by ex-situ X-ray diffraction technique. More importantly, a sodium-ion full cell based on Na3V2(PO4)3/rGO as cathode and Bi2S3@Co9S8/NC as anode is also fabricated, suggesting their potential for practical applications. It is anticipated that the present work could be extended to construct other advanced electrode materials using MOFs-derived carbon-based composites as surface coating materials for various energy storage-related applications.

Searching for high-performance Ni-based cathodes plays an important role in developing better aqueous nickel-zinc (Ni-Zn) batteries. For this purpose, herein, we demonstrate the design and synthesis of ultrathin α-Ni(OH)2 nanosheets branched onto metal-organic frameworks (MOFs)-derived 3D cross-linked N-doped carbon nanotubes encapsulated with tiny Co nanoparticles (denoted as Co@NCNTs/α-Ni(OH)2), which are directly supported on a flexible carbon cloth (CC). An aqueous Ni-Zn battery employing the hierarchical CC/Co@NCNTs/α-Ni(OH)2 as the binder-free cathode and a commercial Zn plate as the anode is fabricated, which displays an ultrahigh capacity (316 mAh g-1) and energy density (540.4 Wh kg-1) at 1 A g-1 as well as excellent rate capability (238 mAh g-1 at 10 A g-1) and superior cycling performance (about 84% capacity retention after 2000 cycles at 10 A g-1). The impressive electrochemical performance might benefit from the rich active sites, rapid electron transfer, cushy electrolyte access, rapid ion transport, and robust structural stability. In addition, the quasi-solid-state CC/Co@NCNTs/α-Ni(OH)2//Zn batteries are also successfully assembled with polymer electrolyte, indicating the great potential for portable and wearable electronics. This work might provide important guidance for constructing carbon-based hybrid materials directly supported on conductive substrates as high-performance electrodes for energy-related devices.

Developing high-performance cathode host materials is fundamental to solve the low utilization of sulfur, the sluggish redox kinetics, and the lithium polysulfide (LiPS) shuttle effect in lithium-sulfur batteries (LSBs). Here, a multifunctional Ag/VN@Co/NCNT nanocomposite with multiple adsorption and catalytic sites within hierarchical nanoreactors is reported as a robust sulfur host for LSB cathodes. In this hierarchical nanoreactor, heterostructured Ag/VN nanorods serve as a highly conductive backbone structure and provide internal catalytic and adsorption sites for LiPS conversion. Interconnected nitrogen-doped carbon nanotubes (NCNTs), in situ grown from the Ag/VN surface, greatly improve the overall specific surface area for sulfur dispersion and accommodate volume changes in the reaction process. Owing to their high LiPS adsorption ability, outer Co nanoparticles at the top of the NCNTs catch escaped LiPS, thus effectively suppressing the shuttle effect and enhancing kinetics. Benefiting from the multiple adsorption and catalytic sites of the developed hierarchical nanoreactors, Ag/VN@Co/NCNTs@S cathodes display outstanding electrochemical performances, including a superior rate performance of 609.7 mAh g-1 at 4 C and a good stability with a capacity decay of 0.018% per cycle after 2000 cycles at 2 C. These properties demonstrate the exceptional potential of Ag/VN@Co/NCNTs@S nanocomposites and approach LSBs closer to their real-world application.

The efficient nondestructive assessment of quality and homogeneity for two-dimensional (2D) MoS2 is critically important to advance their practical applications. Here, we presented a rapid and large-area assessment method for visually evaluating the quality and uniformity of chemical vapor deposition (CVD)-grown MoS2 monolayers simply with conventional optical microscopes. This was achieved through one-pot adsorbing abundant sulfur particles selectively onto as-grown poorer-quality MoS2 monolayers in a CVD system without any additional treatment. We further revealed that this favorable adsorption of sulfur particles on MoS2 originated from their intrinsic higher-density sulfur vacancies. Based on unadsorbed MoS2 monolayers, superior performance field effect transistors with a mobility of ∼49 cm2 V-1 s-1 were constructed. Importantly, the assessment approach was noninvasive due to the all-vapor-phase and moderate adsorption-desorption process. Our work offers a new route for the performance and yield optimization of devices by quality assessment of 2D semiconductors prior to device fabrication.

Sodium–ion hybrid capacitors (SIHCs) hold great promise in large-scale energy storage by compromising the merits of sodium–ion batteries and electrochemical capacitors; however, the mismatch of kinetics and capacity between battery-type anode and capacitive-type cathode is still the Achilles’ heel of this technology. Herein, nanohybrids with Mn single atoms implanted in N, F co-doped ultrathin porous carbon nanosheets (MnSAs/NF-CNs) have been developed as both the anode and cathode of SIHCs. The systematic experimental study coupled with theoretical calculations reveal that N-coordinated Mn atoms (Mn–N4) can act as sites not only for reversible Na+ storage with reduced energy barrier but also for improving the pseudocapacitance, thus making great contribution to accelerating the reaction kinetics of the anode and enhancing the capacity for the cathode in SIHCs. We demonstrate that the Janus-featured MnSAs/NF-CNs endows SIHCs with an impressively high energy/power density (maximum 197 W h kg−1/9350 W kg−1) and ultralong cycling life over 10 000 cycles.

Vanadium(V)-based cathode materials hold great potential for rechargeable aqueous zinc-ion batteries (AZIBs). However, the shortcomings of poor electrical conductivity, large volume changes, serious V dissolution and the complicated electrochemical reaction mechanism seriously restrict their practical applications. Herein, we demonstrate the synthesis of unique amorphous Mo–V–O and Mo–V–N hybrid nanoplate arrays directly grown on a carbon cloth substrate (CC@a-MVO/MVN HNPAs) as an additive- and binder-free cathode for AZIBs. This electrode design offers multiple advantages including high electrical conductivity, abundant active sites, favorable ion diffusion kinetics and robust mechanical stability. As expected, the CC@a-MVO/MVN cathode exhibits outstanding performance in terms of high discharge capacity (1.06 mA h cm−2 at a current density of 0.5 mA cm−2), good rate capability (0.67 mA h cm−2 at 10 mA cm−2) and exceptional long-term cycle stability (94% capacity retention at 6 mA cm−2 for 2000 cycles). Furthermore, flexible soft-packaged AZIBs are successfully assembled to demonstrate their ability for practical applications. More importantly, various ex situ characterization studies reliably demonstrate the reversible formation/decomposition of two different kinds of zinc-containing byproducts, which could correspond to the H+/Zn2+ co-insertion mechanism. This study might contribute to the rational development of V-based cathode materials for high-performance AZIBs and provide reliable insights into the reaction mechanism.

Covalent triazine frameworks (CTFs), as a burgeoning type of porous organic material, have attracted increasing attention in a lot of research fields, including gas separation, heterogeneous catalysis, etc. In particular, stemming from their heteroatom effect (HAE), incorporated with the merits of π-conjugated frameworks, electron-rich triazine units and extraordinary chemical stability, they exhibit prospective potential applications in chemical sensing. In this paper, a triazine-based conjugated porous organic polymer (DPA-CTF) containing anthracene units was used to study the sensing effects on nitroaromatic compounds and metal ions. Intriguingly, DPA-CTF showed sensitive detection performance towards nitroaromatic explosives, especially p-nitroaniline (p-NA). Besides, it also exhibited high sensitivity toward Fe3+ ions compared to other metal ions. A series of characterization studies and computational simulations were used to explain the mechanism of the luminescence quenching effect. These results manifest that the new synthesized CTF is a promising candidate as a chemical sensor for p-NA and Fe3+ ions.

A novel core-substituted naphthalenediimide derivative (DPyNDI-TPA) capped with electroactive triphenylamine was employed as an electroactive precursor to prepare p(DPyNDI-TPA) polymer films through in-situ electropolymerization on FTO substrates. In contrast to the non-core-substituted NDI-TPA, the introduction of pyrrolidine groups endows p(DPyNDI-TPA) films a distinct morphology and a capability of ionization. Under an electric field, the pyrrolidine group could release an electron and combined with counterions in electrolyte solution. Moreover, compared to p(NDI-TPA) films, the wrapped counter anions in p(DPyNDI-TPA) films could serve as balancing charges in electrochromic processes, which render the film a much better electrochromic performance (e.g., switching stability, coloring-bleaching speed and coloration efficiency). This meaningful design provides new conceptions for the design of organic electrochromic materials and shows great prospect in optoelectrical materials.

Covalent organic frameworks (COFs) represent an emerging class of two- or three-dimensional crystalline porous materials with delicate control over topology, composition, and porosity. Here, we develop a new COF made up of 1,3,6,8-tetrakis(p-formylphenyl)pyrene (TFPPy) and 4,4'-diaminobenzophenone (DABP) that exhibits a rare one-dimensional (1D) structure. The resulting frameworks possess good crystallinity, comparatively high Brunauer-Emmett-Teller (BET) surface area (426 m2/g), and good thermal stability (360 °C). Impressively, this 1D COF shows strong fluorescence and can be used as an excellent H+ sensor in an acidic aqueous solution.

Directly growing nickel/cobalt-based cathode materials on current collectors as binder-free electrodes for rechargeable aqueous nickel/cobalt-Zn-based (NiCo//Zn) batteries have attracted tremendous attentions. However, most of the present binder-free cathodes suffer from low areal capacity and energy density, which severely restrict their practical applications. Herein, we demonstrate an efficient metal-organic framework (MOF)-involved strategy to rationally integration of the active NiCo2O4, CoMoO4 and Co3O4 cathode materials into one hierarchical arrayed structure that uniformly grown on nickel foam (NF) substrate (denoted as NF–NCO@CMO@CO) with a high mass loading of 9.6 ​mg ​cm−2. Such electrode design possesses favorable merits in the aspects of high electrical conductivity, robust arrayed architectures, abundant electrochemical active sites, rich redox reactions, facile ion diffusion and components’ synergetic effect. As a result, the aqueous NiCo//Zn battery based on NF–NCO@CMO@CO binder-free cathode exhibits an ultrahigh areal capacity of 2.51 ​mAh cm−2 at a current density of 2 ​mA ​cm−2, as well as good rate capability and long-term cycling stability. Impressively, the aqueous NF–NCO@CMO@CO//Zn battery shows a maximum areal energy density of 4.09 ​mWh cm−2 (corresponding to 424.5 ​Wh kg−1), which is superior to most of the previously reported aqueous NiCo//Zn batteries. Electrode reaction kinetics analysis reveals that both capacitive and diffusion-controlled behaviors are involved during the charge storage processes. Moreover, a quasi-solid-state NF–NCO@CMO@CO//Zn battery is also assembled by replacing the liquid electrolyte with gel electrolyte, suggesting the potential for practical applications. This work might shed light on the rational construction of advanced binder-free cathodes for high-performance aqueous NiCo//Zn batteries.

One-dimensional bunched nanostructures have attracted particular research interest for their applications in energy-relate fields. However, developing a reasonable strategy to realize such unique s...

Traditional slurry-based electrodes consist of heavy current collectors and electroactive materials with a low weight percentage, which inevitably increase the total weight and cost of lithium-ion batteries (LIBs). Consequently, the development of low-cost, lightweight, flexible and binder-free electrodes for LIBs is highly desirable but also greatly challenging. In this work, we report the synthesis of small ZnO nanoparticles uniformly embedded in N-doped carbon (NC) nanoplate arrays (NPAs) tightly grown on a N-doped carbon paper (NCP) substrate (ZnO/NC NPAs@NCP) through a facile metal-organic framework-engaged strategy. This electrode design not only avoids the utilisation of insulating polymer binders but also offers other advantages, including large electrode/electrolyte contact areas, abundant electroactive sites, good wettability of the electrolyte, fast electron/ion transport and efficient volume accommodation. Notably, the freestanding ZnO/NC NPAs@NCP electrode displays a high reversible capacity of 610 mA h g−1 (based on the mass of entire electrode) at a current density of 100 mA g−1 for 50 cycles and excellent long-term cycling stability (363 mA h g−1 at 500 mA g−1 for 200 cycles). Furthermore, a full cell employing ZnO/NC NPAs@NCP as the anode and commercial LiFePO4 as the cathode is constructed, indicating the feasibility for practical application. Moreover, an analysis of the electrode kinetics confirms the favourable lithium-ion storage kinetics within the ZnO/NC NPAs@NCP electrode. The present work could provide a new approach to develop low-cost, lightweight and flexible electrodes for advanced energy storage.

A major impediment of the incorporation of extra functional groups on skeletons of covalent organic frameworks (COFs) is the long-ordered microporosity over their networks. This problem has delayed the practical applications of these highly porous materials for chemical sensing, CO2 capture, and heterogeneous catalysis. In this work, we demonstrated a facile method named the nonstoichiometric synthon strategy to introduce functional groups onto the network of the COFs for further metallic nanoparticle confinement. By simply adjusting the ratio of primitive synthons, we can deliberately decorate the interior pores of the resultant COF materials with amine groups from the excess synthon fragments, while maintaining the structure of the parent COF. Benefiting from the excess dangling amine groups on the network, these COFs are readily available as catalytic support for the confinement of ultrasmall metallic Pd nanoclusters and further used for the benzyl alcohol oxidation reaction.

Manganese-based oxides with high capacity and moderate operation voltage have been extensively studied as promising cathode materials for aqueous zinc ion batteries (ZIBs). However, the inherent poor electrical conductivity, sluggish reaction kinetics, huge volume expansion and dissolution of manganese species in electrolyte greatly restrict their practical applications. Herein, ultrasmall ZnMn2O4 nanodots uniformly anchored on reduced graphene oxide with strong interfacial interaction (ZnMn2O4 NDs/rGO composite) is synthesized. Compared with the pure ZnMn2O4 microspheres, the ZnMn2O4 NDs/rGO composite displays a much higher discharge capacity of 207.6 mA h g−1 at a current density of 0.2 A g−1, as well as better rate capability and long-term cycling stability. Impressively, the aqueous Zn//ZnMn2O4 NDs/rGO battery exhibits a high energy density of 266 W h kg−1 at a power density of 137 W kg−1, indicating great potential for practical applications. The excellent performance could be attributed to the abundant active sites, shortened ion diffusion pathway, improved electrical conductivity and good structure stability. Furthermore, electrochemical analyses reveal that favorable reaction kinetics towards efficient zinc ion storage is achieved in the composite. The present work might shed light on the rational design and synthesis of advanced strongly coupled graphene based composites as cathode materials for aqueous ZIBs.

Here we present the design and synthesis of a new robust microporous organic polymer (TPBP) decorated with phenazine groups which endowed reversibly redox-active properties. The obtained TPBP possesses relatively high surface area (359 m2/g) and good thermal stability. TPBP exhibits excellent catalytic capability for the oxidative homocoupling of amines with high activity and selectivity toward target products. Besides, this metal-free catalyst demonstrated excellent recyclability after 6 cycles under the investigated conditions. By means of EPR and UV-vis spectroscopy, a plausible mechanism of the amine oxidative coupling reaction was deduced via a single electron transfer from TPBP radical cations to amine substrates.

When designing Fe–N–C electrocatalysts as platinum group metal-free catalysts for the oxygen reduction reaction, pore engineering is crucial, in addition to creating active sites. In this study, g-C3N4 was added during the pyrolysis process of polyaniline and cyanamide, increasing the density of active sites and pore volume of the final product. The uniform distribution of atoms and relatively high ratio of pores resulted in the unprecedented electroreduction of oxygen through a 4e− pathway in acidic and alkaline media. In 0.1 M KOH solution, the half-wave potential of the modified catalyst (E1/2 = 0.912 V vs. RHE) was 50 mV more positive than that of a commercial 20% Pt/C catalyst. The durability of the catalyst was also better than that of the commercial Pt/C catalyst in acidic and alkaline media.

Aggregation-induced emission (AIE) properties have been widely investigated not only because they thoroughly circumvent the notorious aggregation-caused quenching effect encountered in conventional fluorophores but also due to their promising applications in organic light-emitting diodes, fluorescent sensors and bioimaging. In this work, we reported a study of the molecular packing and luminescence properties of AIE active positional isomers (m-BPCDM and p-BPCDM) with carbazole and dicyanovinyl groups. The compound m-BPCDM based on meta-substitution showed more evident AIE processes than the compound p-BPCDM based on para-substitution, which can be attributed to the strong π–π stacking effect brought by the spatial structure of p-BPCDM. Moreover, the two positional isomers also exhibited distinct mechanochromic luminescence properties.

A water-stable and pH-independent sensor for qualitative and quantitative detection of nicotine in urine solution and living cell was successfully developed. This material, named MB@UiO-66-NH2, can be synthesized by encapsulating methylene blue (MB) with a well-known metal-organic framework (MOF) UiO-66-NH2 through a simple impregnation method. The fluorescence intensity of the system was significantly enhanced when a certain amount of nicotine was added. In the meanwhile, MB is reduced by reductive nicotine to form leucomethylene blue (LB). The proposed sensor displayed excellent selectivity and sensitivity toward nicotine with limit of detection (LOD) of 0.98 μM, which is comparable or even better than that of the electrochemistry detecting methods for nicotine. The obvious enhancement and blue shift of the emission arise from the photoinduced electron transfer (PET) from LB to the UiO-66-NH2. The photophysical properties and the sensing applications of MB@UiO-66-NH2 suggest that this composite can be acted as a sensitive, selective, recyclable, and fluorogenic sensor for nicotine determination in urine solution and living cell.

Developing facile strategies to synthesize transition metal oxides and nitrogen-doped carbon (NC) hybrid materials is important for lithium-ion batteries (LIBs) but also challenging. Herein, unique one-dimensional multicomponent MoO2@CoO-CoMoO4-NC hybrid nanorods have been successfully synthesized. Benefiting from the unique morphology, structure and components, the MoO2@CoO-CoMoO4-NC hybrid nanorods exhibit a high reversible discharge capacity of 1164.0 mA h g−1 at 200 mA g−1 for 80 cycles, good rate performance (394.5 mA h g−1 at 4000 mA g−1) and cycling stability (688.8 mA h g−1 at 1000 mA g−1 for 350 cycles). It is believed that the MoO2@CoO-CoMoO4-NC hybrid nanorods could be very promising anode materials for LIBs.

In solid oxide fuel cells (SOFCs), it is important that the sealing glass has adequate mechanical strength (rigidity) to withstand stack loads while simultaneously having appropriate resiliency to release the internal stress and thus resist cracking. However, at present, sealing glass is either resilient or rigid. Animal teeth exhibit a bilayer structure that combines remarkable surface hardness to withstand mastication loads with the high resiliency of the inner layer to resist crack propagation. Drawing from this, in this study, we selected a heat-treatment temperature of 700 °C to simulate the operating temperature of the sealing glass and SOFCs, and carried out experimental and theoretical investigation of a typical borosilicate sealing-glass system. The results revealed that surface strengthening occurs within 200 nm depth as the heat-treatment time increases; that is, there is a gradient change in the mechanical property from the surface to the interior of glass, indicating that the surface has greater hardness and elastic modulus to bear stack loads, while the interior has better resiliency and may help resist crack initiation and propagation. A possible mechanism for this strengthening is proposed. The 4-coordinated B and Al centred BO4 and AlO4 can form a glass network structure with SiO4 (i.e., B–O–Si, Al–O–Si), which may lead to surface strengthening due to the increase in the degree of network crosslinking.

Heptazine units with highly rich nitrogen sites were employed to fabricate a new porous organic polymer (POP-HE) via direct coupling of 2,5,8-trichloro-s-heptazine and 4,4′,4″,4‴-(ethene-1,1,2,2-tetrayl)tetraaniline with the mild base N, N′-diisopropylethylamine (DIPEA) in tetrahydrofuran (THF) solution. POP-HE displays good CO2 uptake capacity (50.6 cm3 g−1, 10 wt%, 1 bar/273 K) and highly selectively adsorptive separation of CO2 over CH4 under ambient conditions. Impressively, at 273 K, the predicted IAST selectivity of POP-HE is 47.0-13.4 for the natural gas mixture (CO2/CH4 = 5:95) at pressures varying from 0 to 1 atm. Meanwhile, the result of calculated band gap value based on Tauc plot motivated us to investigate its photocatalytic activity. POP-HE was applied as heterogeneous photocatalyst for visible light-induced selective oxidation of benzyl alcohol to benzaldehyde, and exhibited great conversion of 33.6% under irradiation of white LED light, which is much higher than that of g-C3N4. Moreover, POP-HE can be recycled up to three times without significant decrease in catalytic activity.

Crack formation at the interface between sealing glass and other cell components is one of the key issues in constraining the development of solid oxide fuel cells (SOFCs). Herein, we report our finding on tuning the mechanical and thermal properties of borosilicate glass by doping Nb2O5. We observe the formation of Ba3Nb10O28 crystalline phase in the Nb2O5-doped glass, leading to significantly enhanced crack-resistant and self-healing abilities of the glass. In addition, we demonstrate long-term thermal and chemical stability at the sealing interface between the Nb2O5-doped glass-ceramics and Y2O3-ZrO2 electrolyte after heat-treatment at 700 °C for 1000 h. The possible mechanism for the improved crack-resistant and self-healing properties is discussed.

Anisotropic two-dimensional materials with direction-dependent mechanical and optical properties have attracted significant attention in recent years. In this work, based on density functional theory calculations, unexpected elastic anisotropy and optical isotropy in van der Waals (vdW) heterostructures have been theoretically proposed by assembling the well-known anisotropic black phosphorene (BP) and transition-metal trisulfides MS3 (M = Ti, Hf) together. It is interesting to see that the BP/MS3 vdW heterostructures show anisotropic flexibility in different directions according to the elastic constants, Young’s modulus, and Poisson’s ratio. We have further unraveled their physical origin of the type-II band structure nature with their conduction band minimum and valence band maximum separated in different layers. In particular, our results on the optical response functions including the excitonic effects of the BP/MS3 vdW heterostructures suggest their unexpected optical isotropies together with the enhancements of the solar energy conversion efficiency.

The practical applications of transition metal sulfides as electrode materials for lithium-ion batteries (LIBs) is greatly hindered by the fast capacity fading owing to the large volume expansion. To address this issue, construction of transition metal sulfide and carbon nanocomposites with unique yolk–shell structures is an effective strategy but also remains a great challenge. In this work, we reported a facile approach to synthesize the unique yolk–shell FeS2@carbon (FeS2@C) spheres via calcination treatment of the resorcinol–formaldehyde (RF) resin-coated Prussian blue (FeFe PB) core–shell spheres in Ar atmosphere and a subsequent sulfidation treatment. The synthetic method herein was quite simple and convenient. Such unique structure design could effectively prevent the large volume expansion and dissolution of the active materials in the electrolytes during lithiation. As expected, the yolk–shell FeS2@C spheres exhibited good electrochemical performance as anode materials for LIBs, which displayed a...

Two novel isomeric polymers P(DPPT-TT) and P(DPPTT-T) based on thiophene-flanked diketopyrrolopyrrole, thieno[3,2-b]thiophene and thiophene building units were designed and synthesized via a new skeletal isomerization strategy. This study emphasizes on the impact of this skeletal isomerization on the photoelectric properties and organic field-effect transistor (OFET) performances of the resulting isomeric polymers. Both polymers show similar light absorption properties and excellent thermostability and have a comparable molecular weight. They also display typical p-type characteristics in air-tested OFETs. However, P(DPPTT-T) exhibits significantly better OFET performances. In particular, its average hole mobility reaches 2.14 cm2 V−1 s−1, triple that of P(DPPT-TT). The higher mobility of P(DPPTT-T) might be attributed to the interconnected, smooth and thicker nanofibrillar network morphology and the relatively higher crystallinity of its thin films, and its conjugated chains possess a smaller π–π stacking distance.

Black phosphorene has been proposed as a high-efficiency metal-free two-dimensional photocatalyst for hydrogen production by visible light-driven water splitting. In this work, based on the screening of materials by density functional theory calculations, the potentials of group IV and group VI isoelectronic co-doped black phosphorenes (BPs) as candidate photocatalysts were comprehensively evaluated. According to the essential criteria of stability, electronic structure features, as well as visible light photocatalytic hydrogen production performance, we identified Si–S, Si–Se, Ge–S and Ge–Se co-doped BPs as promising catalysts. We highlighted that the isoelectronic co-doping process is geometrically and thermodynamically favorable. Interestingly, the isoelectronic co-dopants did not affect the direct and clean band gap nature of pure BP, and they also enhanced the photocatalytic hydrogen production properties, retaining a strong anisotropic feature. We believe that our findings will shed light on the modulation and development of BP based metal-free two-dimensional photocatalysts.

Metal-organic frameworks (MOFs) derived ternary transition metal oxide nanostructures have attracted considerable attention for their important applications in energy-related fields. However, most of the present reports on MOFs-derived materials are in the powder form, which should be further mixed with polymer binder and conductive agents before they are coated on current conductor. In this work, we demonstrate a facile solution method to grow the bimetallic zinc/cobalt zeolitic imidazolate frameworks nanoplate arrays (Zn/Co-ZIF NPAs) on carbon cloth (CC) substrate and then they are well converted to porous ternary ZnCo2O4 NPAs on CC after an annealing treatment in air. When investigated as binder-free electrodes for lithium-ion batteries (LIBs), the ZnCo2O4 NPAs/CC electrode exhibits a high area capacity of 3.01 mA h cm−2 (corresponding to 1341.7 mA h g−1 for the ZnCo2O4 NPAs) at the current density of 0.24 mA cm−2 for 100 cycles, which is much higher than that of the Co3O4 NPAs/CC electrode (1.93 mA h cm−2). Moreover, at a high current density of 1.20 mA cm−2, the ZnCo2O4 NPAs/CC electrode can still maintain a high capacity of 2.05 mA h cm−2. The excellent electrochemical performance could be attributed to the unique morphology, structure and composition of the porous ternary ZnCo2O4 NPAs, as well as directly grown on current collector.

Synthesis of nanostructured composites containing multiple components with distinctive structure and composition is important for high-performance energy storage but challenging. Starting form metal-organic frameworks (MOFs), we herein successfully synthesize a series of advanced nanocomposites consisting of composition-tailored nickel cobalt sulfoselenide (NiCo2(SxSe1−x)5) nanoparticles confined in graphitic carbon hollow spheres (GC HSs). For pseudocapacitors, the NiCo2(S0.78Se0.22)5/GC HSs exhibit the highest specific capacity (560.7 C g−1 at 1 A g−1) with good rate capability and cycling performance. An asymmetric supercapacitor (ASC) based on the NiCo2(S0.78Se0.22)5/GC HSs cathode and Bi2O2.33/rGO nanocomposite anode displays an energy density of 47.2 Wh kg–1 at a high power density of 801 W kg–1. Besides, the NiCo2(S0.78Se0.22)5/GC HSs are also promising anode materials for lithium-ion batteries, which deliver a high reversible capacity of 865.2 mA h g−1 at 200 mA g−1 after 100 cycles. The excellent performance could be attributed to the high electrical conductivity, facile electron and ion transport, good structural robustness and components’ synergistic effect. We believe this synthetic strategy could be extended to prepare other anions doped bimetallic compounds and carbon composites for next-generation energy storage.

Rational design and synthesis of advanced sulfur host materials has been regarded as an effective strategy to address the critical challenges of lithium-sulfur (Li-S) batteries including shuttle effect of lithium polysulfides (LiPSs), sluggish reaction kinetics, and huge volume change of sulfur. In this work, we demonstrate the rational construction of a multifunctional sulfur host grown on carbon cloth consisting of self-supported porous VN arrays coupled with MOF-derived N-doped carbon nanotubes embedded with tiny Co nanoparticles (named CC/VN/Co@NCNTs). This unique electrode design possesses a series of advantages such as high electrical conductivity, strong physical/chemical confinement of LiPSs, favorable catalytic activity, fast reaction kinetics, effective volumetric accommodation, good mechanical stability and high sulfur loading. As expected, when evaluated as self-standing and binder-free cathode for Li-S batteries, the CC/VN/Co@NCNTs/S exhibits a high initial discharge capacity of 1130.4 mAh g−1 at 0.1C and maintains 864.1 mAh g−1 after 100 cycles, along with outstanding rate performance (625.3 mAh g−1 at 5C) and superior long-term cycling stability with a low capacity decay rate of 0.063% per cycle at 1C for 500 cycles. Moreover, the CC/VN/Co@NCNTs/S delivers high reversible capacities of 847.6, 668.3, and 581.1 mAh g−1 at 0.1C after 100 cycles at different high sulfur loadings of 2.8, 5.2, and 7.8 mg cm−2, respectively. The present work might provide an effective strategy to directly construct multifunctional sulfur host materials on current collectors for high-performance Li-S batteries.

Sodium-selenium (Na-Se) battery has been emerging as one of the most prospective energy storage systems owing to their high volumetric energy density and cost effectiveness. Nevertheless, the shuttle effect of sodium polyselenide (NaPSe) and sluggish electrochemical reaction kinetics present the main bottlenecks for its practical implementation. Herein, a new Se host of 3D nitrogen-doped hierarchical multicavity carbon nanospheres (3D NHMCs) is designed and synthesized via a facile self-sacrifice templating strategy. The 3D NHMCs are verified to hold a favorable structure of a hollow macropore core and numerous micro/mesopores hollow shell for hosting Se, which can not only maximize Se utilization and alleviate the volumetric expansion but also promote the electrical/ionic conductivity and electrolyte infiltration. Moreover, the abundant self-functionalized surfaces as an efficient NaPSe scavenger via robust physical-chemical dual blocking effects demonstrate high-efficiency in situ anchoring-diffusion-conversion of NaPSe, rendering rapid reaction kinetics and remarkable suppressive shuttle effect, as evidenced by systematic experimental analysis and density functional theory calculations. As a result, the high-Se-loading 3D NHMCs/Se cathode exhibits an ultrahigh volumetric capacity (863 mAh cm-3 ) and rate capability (377 mAh g-1 at 20 C) and unexceptionable stability over 2000 cycles at 2 C.

Covalent organic frameworks (COFs) are typically isolated as microcrystalline powders. It remains fundamentally challenging to fabricate COFs into high-quality self-standing films to take full advantage of their ordered pore channels for molecular separation. Here, we report a new strategy for fabricating self-standing imine-linked COF films via homogeneous polymerization where films emerge from clear solutions without forming amorphous precipitates. The abundant basic nitrogen atoms of the monomers acted as a reaction controller to realize the homogeneous polymerization and also promoted the tight self-aggregation of COF crystallites to form compact films via H-bonding. The chemically supported self-standing COF films on nylon membranes were also developed via an in situ growth method. The resulting films showed an unprecedentedly ultrafast permeance of 2822 L m-2 h-1 MPa-1 with a high rejection rate (99.8%) in the filtration of a congo red (CR) solution, demonstrating the advantage of this new strategy in fabricating high-quality self-standing COF films.

Heptazine-based conjugated polymeric carbon nitrides (PCNs) are promising metal-free photocatalysts, yet their synthesis is challenging due to the electron-deficiency and insolubility of heptazine units. Indeed, heptazine-containing polymers have only been prepared through nucleophilic substitution with amines by using toxic cyameluric chloride as the starting material. Herein, we report the novel and environmentally friendly method for preparing heptazine-based mesoporous PCNs with hydrazone links formed through a simple Schiff base condensation of melem-NH2 and aldehydes. Unlike cyameluric chloride, melem-NH2 is non-toxic, stable, and can be readily obtained from melem and hydrazine in solution. We demonstrate that the hydrazone linkages and the heptazine units synergistically enhance the photocatalytic activity of PCNs in visible-light-driven aerobic oxidation of benzyl alcohol to benzaldehyde. In particular, the polymer constructed from melem-NH2 and p-phthalaldehyde shows 17 times more activity than graphitic carbon nitride (g-C3 N4 ).

Three porous lanthanide metal-organic frameworks (Ln-MOFs) [Ln(BCB)(DMF)]∙(DMF)m(H2O)n (Ln = Yb3+ (1), Er3+ (2), Dy3+ (3), DMF = N,N′-dimethylformamide) have been successfully prepared using 4,4′,4″-benzenetricarbonyltribenzoic acid (H3BCB) as organic linkers. X-ray diffraction analysis reveals that these ketone group decorated complexes are isostructural, and each form a three-dimensional structure possessing two types of one-dimensional channels along the c axis. Moreover, the near-infrared luminescence properties of the three complexes were also investigated.

Exploring suitable electrode materials with high rate capability and long-term cycling stability for sodium-ion batteries (SIBs) is of great importance but still challenging. In this work, we report a facile strategy to synthesize the nanocomposite of porous NaTi2(PO4)3 nanoparticles coated with a thin carbon layer (NTP/C). The unique structural and component merits endow the NTP/C nanocomposite with excellent charge transfer kinetics and enhanced structural stability. Compared with the pristine NTP nanoparticles, the NTP/C nanocomposite exhibits significant enhanced rate capability (108.9 mA h g−1 at 0.2C and 55.0 mA h g−1 at 20C) and long-term cycling performance (capacity retention of 78.8% after 2000 cycles at 10C). The electrochemical results indicate the NTP/C nanocomposite could be a high-performance anode material for SIBs.

The exploration of anode materials for lithium ion batteries (LIBs) or sodium ion batteries (SIBs) represents a grand technological challenge to meet the continuously increased demand for the high-performance energy storage market. Here we report a facile and reliable synthetic strategy for in situ growth of few-layer MoS2 nanosheets on reduced graphene oxide (rGO) cross-linked hollow carbon spheres (HCS) with formation of three-dimensional (3D) network nanohybrids (MoS2-rGO/HCS). Systematic electrochemical studies demonstrate, as an anode of LIBs, the as-developed MoS2-rGO/HCS can deliver a reversible capacity of 1145 mAh g–1 after 100 cycles at 0.1 A g–1 and a revisible capacity of 753 mAh g–1 over 1000 cycles at 2 A g–1. For SIBs, the as-developed MoS2-rGO/HCS can also maintain a reversible capacity of 443 mAh g–1 at 1 A g–1 after 500 cycles. The excellent electrochemical performance can be attributed to the 3D porous structures, in which the few-layer MoS2 nanosheets with expanded interlayers can prov...

Exploring high-performance and low-priced electrode materials for supercapacitors is important but remains challenging. In this work, a unique sandwich-like nanocomposite of reduced graphene oxide (rGO)-supported N-doped carbon embedded with ultrasmall CoNiSx nanocrystallites (rGO/CoNiSx/N–C nanocomposite) has been successfully designed and synthesized by a simple one-step carbonization/sulfurization treatment of the rGO/Co–Ni precursor. The intriguing structural/compositional/morphological advantages endow the as-synthesized rGO/CoNiSx/N–C nanocomposite with excellent electrochemical performance as an advanced electrode material for supercapacitors. Compared with the other two rGO/CoNiOx and rGO/CoNiSx nanocomposites, the rGO/CoNiSx/N–C nanocomposite exhibits much enhanced performance, including a high specific capacitance (1028.2 F g−1 at 1 A g−1), excellent rate capability (89.3% capacitance retention at 10 A g−1) and good cycling stability (93.6% capacitance retention over 2000 cycles). In addition, an asymmetric supercapacitor (ASC) device based on the rGO/CoNiSx/N–C nanocomposite as the cathode and activated carbon (AC) as the anode is also fabricated, which can deliver a high energy density of 32.9 W h kg−1 at a power density of 229.2 W kg−1 with desirable cycling stability. These electrochemical results evidently indicate the great potential of the sandwich-like rGO/CoNiSx/N–C nanocomposite for applications in high-performance supercapacitors.

We describe a highly sensitive chemical sensor for the detection of the hydrazine hydrate. The chemical sensor was synthesized by simply doping a UiO-66 type metal–organic framework (MOF) with Eu3+ through a well-known post-synthetic modification method. The Eu3+@MOF was characterized by powder X-ray diffraction (PXRD), nitrogen gas adsorption isotherm measurements, FTIR, and ICP-MS. This luminescent probe exhibits strong emission intensity, and more significantly, displays various merits, such as high selectivity with notable photoluminescence quenching effect, rapid response time, and remarkable sensitivity with low detection of limit for hydrazine recognition. Under the optimal experimental conditions, hydrazine hydrate can be detected by this method in concentrations as low as 0.18 μM, which is much lower than the threshold limit value (10 ppb, ≈0.3 μM) of hydrazine exposure recommended by the U.S. Environmental Protection Agency (EPA). More interestingly, a portable film sensing device derived from this MOF display quick response to hydrazine hydrate within 90 s. A possible luminescent quenching mechanism for hydrazine hydrate was also investigated.

The efficient design and synthesis of new tert-butoxycarbonyl (t-Boc) and t-Boc-removed diketopyrrolopyrrole (DPP) polymers with regioregular conjugated backbones via a new route of combining random copolymerization and the classical t-Boc precursor approach are reported. The resulting new type of DPP polymer, named P(40/1)-H, is found to possess good solubility, film-forming ability, and reasonable optoelectronic properties. Importantly, it displays a significantly improved field-effect mobility (∼0.91 cm2 V−1 s−1) as compared to the recognized reference polymer P(100/0) (∼0.56 cm2 V−1 s−1), which indicates partially removing the long branched alkyl side chains of a regioregular conjugated backbone based DPP polymer is an alternative new strategy of molecular design for enhancing field-effect carrier mobility.

Borate bioactive glass (BBG) stimulates angiogenesis and promotes cell growth. However, controlling the degradation rate of BBG and maintaining the critical concentration of bioactive ions suitable for cell promotion and differentiation remain great challenges in soft tissue repair. In this study, a novel approach was proposed to produce nanosized CO32−-containing hydroxyapatite (HCA)-coated BBG (nano-HCA@BG). Unlike the previously reported hard-to-degrade hydroxyapatite (HA) coating after static soaking treatment of BBG, the nano-HCA@BG, obtained by dynamically immersing the BBG powder in a flowing buffer, had a porous structure and was surface-coated with a layer of amorphous HCA, which improved the biocompatibility and retained the biodegradability of BBG. The effects of nano-HCA@BG were evaluated and compared with those of powdered BBG at the cellular and animal levels. The formation of the HCA-coated nanoporous architecture significantly improves biocompatibility, promotes cell growth and proliferation, and is beneficial for wound healing in rodent skin defects.

Manganese oxide and carbon hybrid materials have attracted intensive research attention as advanced electrode materials for energy storage. Herein, starting form metal-organic frameworks (MOFs), the nanocomposites of mixed-valent manganese oxide nanoparticles in-situ grown on ultrathin carbon sheets (MnOx-CSs nanocomposites) have been synthesized via a simple method. Benefiting from the unique structural merits, the nanocomposite obtained at 600 °C (MnOx-CSs-600) exhibits excellent performance for both supercapacitors (SCs) and lithium-ion batteries (LIBs). A high specific capacitance of 220 F g−1 is achieved at the current density of 1 A g−1. An asymmetric supercapacitor (ASC) based on the MnOx-CSs-600 nanocomposite cathode and activated carbon anode exhibits a high energy density of 27.5 W h kg−1 at the power density of 225 W kg−1. Moreover, the MnOx-CSs-600 nanocomposite displays a high reversible capacity of 1217.7 mA h g−1 at 200 mA g−1 after 160 cycles as an anode material for LIBs. Remarkably, the discharge capacity is still as high as 612.1 mA h g−1 even at high current density of 2000 mA g−1, indicating good rate capability. This synthetic strategy is quite simple, cost-effective and environmental friendly, which is highly promising for scaled-up production.

Binary metal sulfides have been considered as promising electrode materials for supercapacitors with excellent performance. Herein, we demonstrate a simple two-step hydrothermal method to grow the interconnected Co9S8/NiCo2S4 nanosheet arrays (denoted as Ni-Co sulfide NSAs) on nickel foam with robust adhesion for high performance supercapacitors. Remarkably, the as-synthesized Ni-Co sulfide binder-free electrode exhibits an ultrahigh areal capacitance of 7.4 F cm−2 for supercapacitors, which is about five times higher than 1.5 F cm−2 of the Ni-Co oxide electrode at the current density of 5 mA cm−2. The Ni-Co sulfide binder-free electrode also exhibits a good cycling stability, which still displays a high capacitance retention of 90.7% after 2000 cycles even at a high current density of 40 mA cm−2. The good electrochemical performance could be ascribed to the high electrical conductivity and porous nanosheet structure of the Ni-Co sulfide nanosheets, as well as the robust adhesion with the current collector. These electrochemical results suggest that such Ni-Co sulfide NSA binder-free electrode might hold some potential for electrochemical energy applications.

Graphene and metal oxide nanocomposites have been demonstrated as promising electrode materials for high-performance lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). In this work, ultrafine CoMn2O4 nanoparticles uniformly anchored on reduced graphene oxide (rGO) sheets have been synthesized through a facile and effective two-step strategy. Owing to the rational combination of merits from both ternary CoMn2O4 and graphene sheets, the as-synthesized rGO/CoMn2O4 nanocomposite exhibits remarkable Li-battery performance with high reversible capacity, good cycling stability and excellent rate performance. Remarkably, the rGO/CoMn2O4 nanocomposite displays high reversible capacities of 1102.1 and 811.1 mA h g−1 at the current densities of 200 and 500 mA g−1 after 60 cycles, respectively. The discharge capacities of the rGO/CoMn2O4 nanocomposite are as high as 851.1, 835.3, 795.2, 755.9, 694.0, and 563.6 mA h g−1 at the current densities of 100, 200, 500, 1000, 2000 and 5000 mA g−1, respectively. These electrochemical results suggest the rGO/CoMn2O4 nanocomposite could be a promising anode material for high-performance LIBs. Besides, the rGO/CoMn2O4 nanocomposite also exhibits comparably promising electrochemical performance as an anode material for SIBs. Our study also highlights the importance of rational synthesis of graphene-based nanocomposite materials for high-performance LIBs and SIBs.

Construction of metal oxide/sulfide and carbon-based material nanocomposites is an effective strategy to obtain high-performance electrode materials for supercapacitors. In the present work, graphene oxide nanofibers (GONFs) are selected as the support materials, and the nanocomposite of reduced graphene oxide nanofiber and cobalt sulfide (rGONF/CoS2) is synthesized via a simple and facile method. As an electrode material for pseudocapacitors, the rGONF/CoS2 nanocomposite exhibits a high specific capacitance of 635.8 F g-1 at a current density of 1 A g-1 measured in 6 M KOH electrolyte, which is much higher than that of bare cobalt sulfide. Furthermore, the rGONF/CoS2 nanocomposite has also shown excellent cycling performance with 95.4% capacitance retention over 2000 cycles. In addition, the assembled asymmetric supercapacitor (ASC) device using rGONF/CoS2 nanocomposite as cathode material and activated carbon (AC) as anode material can work at a high operating voltage of 1.65 V and show a maximum energy density of 13.8 W h kg−1 at a power density of 824.6 W kg−1.

Nanostructured ZnO and ternary Zn-based oxides have been regarded as promising anode materials for lithium ion batteries. In the present work, we report a facile and simple method to synthesize the highly porous ZnO/ZnFe2O4 hybrid nanostructures using the prussian blue analogue as the sacrificial template. The synthetic process only contains the room temperature synthesis of the precursor with a subsequent annealing treatment. Benefiting from their unique structural/component merits, the ZnO/ZnFe2O4 hybrid nanostructures exhibit excellent lithium-storage performance as anode materials. The first discharge capacity is as high as 998.4 mA h g−1, and a high reversible discharge capacity of 704 mA h g−1 is still retained after 200 cycles, indicating good cycle stability. The porous ZnO/ZnFe2O4 hybrid nanostructures could be a high-performance anode materials for lithium ion batteries.

Defect-mediated engineering has been proven as a novel and effective strategy to integrate two individual materials into a nanocomposite to boost the performance. In the present work, nanocomposite of partially-unzipped stacked-cup carbon nanofibers (PUSCNFs) decorated with platinum nanoparticles (Pt NPs) have been successfully synthesized through the defect-mediated formation method. Owing to the introduction of abundant structural defects during the chemical oxidation process, Pt NPs with an average diameter of 2–3 nm were uniformly anchored on the PUSCNFs without any surfactant involved. As comparison, the Pt NPs grown on the stacked-cup carbon nanofibers (SCNFs) possessed markedly larger nanoparticle size and trended to aggregate. The electrochemical properties of the nanocomposite-modified electrodes for biosensing were examined. Our results showed the Pt-PUSCNFs nanocomposite possessed optimal electrocatalytic activities and biosensing performance for detection of biomolecules, which could be attributed to a synergistic effect between the PUSCNFs and Pt NPs on electron transport and catalytic properties. We anticipate that the PUSCNFs may be a potential support material for construction of nanocomposites with good performance.

C20H24N4O6, triclinic, P1̄ (no. 2), a = 8.2441(5) Å, b = 11.6409(6) Å, c = 12.0107(9) Å, α = 64.328(6)°, β = 70.778(6)°, γ = 86.678(4)°, V = 976.09(12) Å3, Z = 2, R gt(F) = 0.0671, wR ref(F 2) = 0.1702, T = 100 K.

Detection of disease-related small biomolecules was of great significance for clinical diagnostics and treatment. In this work, we synthesized defect-rich knotted graphene nanotubes (k-GNTs) via chemical oxidative etching of stacked-up carbon nanotubes (SC-CNTs) followed by chemical reduction, to detect disease-related small biomolecules. We further studied the electrochemical properties using three representative redox probes and analyzed their biosensitivity using five biomolecules. The k-GNT-modified electrodes exhibited excellent electrochemical response, with the lowest Δ E p and the highest k 0 . Besides, the modified electrodes could simultaneously detect and discriminate between dopamine (DA), ascorbic acid and uric acid (UA), as well as differentiate phenethylamine (PEA) and epinephrine (EP) existed in newborn rat serum, providing the wide linear detection ranges with high sensitivities for DA, UA, PEA, and EP. These excellent electrocatalytic properties could be ascribe to the unique knotted graphene nanotube structure with high proportion of defect/edge sites, large, accessible, three-dimensional, accessible surface area, fewer oxygen-containing groups and doped N atoms. Our work reveals defect-rich k-GNTs as a promising platform for further applications in electrochemical biosensing and electrocatalysis.