N-doped Carbon Framework Research Articles

NiS2/FeS2 binary nanoparticles confined in interconnected carbon framework with regulated pore structure enabled by citric acid for enhanced sodium storage properties

Recently, pyrite iron disulfide (FeS2) has emerged as a promising anode candidate for sodium-ion batteries (SIBs) due to its high theoretical capacity, affordability, non-toxicity and abundant resource in nature. However, the utilization of FeS2 still confronts the challenges of inferior rate capability and cycling instability for sodium storage, stemming from its low electronic conductivity and substantial volume changes during cycling. Herein, to address these obstacles, NiS2/FeS2 binary nanoparticles encapsulated within a network of interconnected N-doped porous carbon framework (NiS2/FeS2@NPC) are prepared by a successive solid-state ball milling, carbonization and sulfurization strategy with coordination complex of nickel iron Prussian blue analogue (NiFe-PBA) as precursor. The introduction of citric acid plays a critical role for the formation of interconnected carbon framework with regulated internal porous structure, thereby achieving heterostructured NiS2/FeS2@NPC with modulated specific surface area and pore volume. The rational design of interconnected N-doped porous carbon framework and heterogeneous structure guarantees rapid ion/electron transport kinetics, alleviated mechanical stress, and enhanced structural integrity. Benefitting from these advantages, the optimal NiS2/FeS2@NPC-1 electrode exhibits a high reversible capacity (545 mAh/g at 1 A/g), superior rate capability (267 mAh/g at 5 A/g) and ultrastable long-term cycling performance (98.5 % retention over 1000 cycles at 5 A/g). This study presents a novel and efficient design approach for creating durable and high-rate anode materials based on metal sulfides for SIBs.

Construction of honeycomb-like N-doped porous carbon framework with effective aperture distribution toward advanced supercapacitors and sodium-ion batteries

Smart synthesis of porous carbon with appropriate aperture distribution and high area utilization still retains an enormous challenge for efficient charge storage. Herein, a simple freeze-drying along with subsequent one-step carbonization/activation process is ingeniously devised to fabricate honeycomb-like nitrogen-doped porous carbon (NPC) framework with high-level active N/O-functional groups and hierarchical porous structure including substantial ultra-micropores (<0.7 nm). The underlying formation mechanism of such porous NPC framework is tentatively proposed. By finely regulating the dosage of NaHCO3, the optimized NPC (i.e., NPC114) is endowed with ultra-high surface area utilization of ∼26.4 μF/cm2 at 1 A/g in KOH electrolyte, which is close to theoretical value of electrochemical double-layer capacitance (15 – 25 μF/cm2), and even larger than the case (∼22.4 μF/cm2) with H2SO4 electrolyte due to the inaccessible ultra-micropores by SO42− of larger size. Similarly, as for the organic system, the as-prepared NPC115 with higher meso- and macropore surface area exhibits higher energy density of 22.36 Wh/kg than other counterparts. Furthermore, NPC114, when evaluated as anode material for sodium-ion batteries, exhibited more attractive high-rate Na+-storage properties as well. The in-depth understanding into intrinsic relationship between aperture distribution and electrochemical behaviors will provide meaningful guidance for electrode material design.

Insight into the polysulfides conversion kinetics and its activation energy relationship on ultrafine V8C7 in Li-S batteries

Catalytic conversion of lithium polysulfides (LiPSs) is regarded as an effective approach to boosting kinetics and suppressing shuttling effect in lithium-sulfur (Li-S) batteries, but developing efficient catalysts and understanding of its catalytic mechanism still remain challenges. Herein, the ultrafine V8C7 nanocrystals embedded into the porous N-doped carbon frameworks (V8C7/NC) was designed for accelerating the LiPSs catalytic-conversion kinetics toward high-performance Li-S batteries. We propose that the ultrafine V8C7 nanocrystals with abundant unsaturated coordination atoms increase the active sites for catalytic-conversion of LiPSs and also accelerate the corresponding kinetics by reducing its reaction activation energy, meanwhile the interlinked nano-channels of V8C7/NC can effectively confine LiPSs and also promote electron/ion transfer. These attributes enable the Li-S cell equipped with V8C7/NC to deliver a large discharge capacity of 1393.3 mAh g−1 at 0.2 C, excellent rate capability (496.0 mAh g−1 at 10 C), and robust cycling stability (1000 cycles with a negligible capacity decay rate of 0.019 % per cycle even at 5 C). The innovative concept of ultrafine V8C7 nanocrystals embedded into the porous carbon toward improved LiPSs catalytic-conversion kinetics could be extended to develop other electrocatalytic hosts for high-performance Li-S batteries.

N-doped one-dimensional carbon framework embedded with CoSe2 nanoparticles as superior electrode for advanced sodium ion storage

Cobalt selenide (CoSe2) is acknowledged as a negative electrode material for sodium-ion batteries (SIBs) due to its high theoretical capacity. However, the significant volume change and inadequate electrochemical performance during charge and discharge processes have limited its practical use in batteries. In this investigation, a straightforward and practical electrospinning method combined with selenization reaction was utilized to fabricate CoSe2 nanoparticles enclosed in nitrogen-doped carbon nanofibers with a three-dimensional self-supporting network structure (CoSe2/N-PCNFs).The CoSe2/N-PCNFs electrode has self-supporting and high conductivity properties, as an anode material for sodium-ion batteries, the discharge capacity of the composite material can reach 450.1 mAh/g after 100 cycles at a current density of 0.2 A/g, and can still maintain a large discharge capacity of 396.9 mAh/g after 500 cycles at a high current density of 1 A/g. The outstanding electrochemical performance is mainly attributed to the superior specific surface area, controllable porous structure, and high pore volume of CoSe2/N-PCNFs Experimental and density functional theory calculations both indicate that the heterojunction interface between CoSe2 and nitrogen-doped carbon can not only promote the adsorption of Na+, but also facilitate electron transfer to significantly improve the rate capability of the material.

P-Block anion compressed d/p band center of bifunctional oxygen electrocatalysts for durable aqueous Zn–air batteries

Robust bifunctional electrocatalysts that accelerate the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are vital for rechargeable aqueous Zn–air batteries (AZABs). In this study, a three-dimensional foam-like N-doped carbon frameworks (NCFs) catalyst with abundant NCoTe2 active sites (CoTe2@NCFs) was successfully constructed using the carbon dots (CDs)-assisted strategy as the efficient bifunctional ORR/OER catalyst. In situ Raman spectra were used to monitor the formation of Co-OOH, which confirmed the dynamic change in oxygen intermediates on the surface of the CoTe2@NCFs catalyst. Both theoretical calculations and experimental results demonstrate that the integrated Te element in the p-block results in a reduction in the difference between d/p band centers (Δεd-p), which effectively enhances the rapid adsorption/desorption capability of *OOH/*OH, thereby improving the ORR/OER performance. Impressively, the CoTe2@NCFs catalyst shows excellent bifunctional oxygen catalytic performance (ΔE = 0.66 V). Moreover, the assembled CoTe2@NCFs-based rechargeable AZABs exhibit a high peak power density of 177.8 mW cm−2, substantial specific capacity of 793.4 mAh g−1, and excellent long-term cycling durability over 1000 cycles. The compressed d/p-band synergistic center provides novel insights into the design of bifunctional oxygen electrocatalysts for efficient energy storage and conversion devices.

Iron-Cobalt Phosphide Encapsulated in a N-Doped Carbon Framework as a Promising Low-Cost Oxygen Reduction Electrocatalyst for Zinc-Air Batteries.

The oxygen reduction reaction (ORR) plays a vital role in many next-generation electrochemical energy conversion and storage devices, motivating the search for low-cost ORR electrocatalysts possessing high activity and excellent durability. In this work, we demonstrate that iron-cobalt phosphide (FeCoP) nanoparticles encapsulated in a N-doped carbon framework (FeCoP@NC) represent a very promising catalyst for the ORR in alkaline media. The core-shell structured FeCoP@NC catalyst offered outstanding ORR activity with a half-wave potential (E1/2) of 0.86 V vs reversible hydrogen electrode (RHE) and excellent stability in a 0.1 M KOH electrolyte, outperforming commercial Pt/C and many recently reported noble-metal-free ORR electrocatalysts. The superiority of FeCoP@NC as an ORR electrocatalyst relative to Pt/C was further verified in prototype zinc-air batteries (ZABs), with the aqueous and flexible ZABs prepared using FeCoP@NC offering excellent stability, impressive open circuit voltages (1.56 and 1.44 V, respectively), and high maximum power densities (183.5 and 69.7 mW cm-2, respectively). Density functional theory calculations revealed that encapsulating FeCoP nanoparticles in N-doped carbon shells resulted in favorable electron penetration effects, which synergistically regulated the adsorption/desorption of ORR intermediates for optimal ORR performance while also boosting the electronic conductivity. Our findings offer valuable new insights for rational design of transition metal phosphide-based catalysts for the ORR and other electrochemical applications.

Enhancing Electrocatalytic CO2-to-CO Conversion by Weakening CO Binding through Nitrogen Integration in the Metallic Fe Catalyst.

Metallic iron (Fe) typically demonstrates the unfavorable catalytic activity for the CO2 reduction reaction (CO2RR), mainly attributed to the excessively strong binding of CO products on Fe sites. Toward this end, we employed an effective approach involving electronic structure modulation through nitrogen (N) integration to enhance the performance of the CO2RR. Here, an efficient catalyst has been developed, composed of N-doped metallic iron (Fe) nanoparticles encapsulated in a porous N-doped carbon framework. Notably, this N-integrated Fe catalyst displays significantly enhanced performance in the electrocatalytic reduction of CO2, yielding the highest CO Faradaic efficiency of 97.5% with a current density of 6.68 mA cm-2 at -0.7 V versus the reversible hydrogen electrode. The theoretical calculations, combined with the in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy study, reveal that N integration modulates the electron density around Fe, resulting in the weakening of the binding strength between the Fe active sites and *CO intermediates, consequently promoting the desorption of CO and the overall CO2RR process.

Facile synthesis of flower-like NiCo/NiO–CoO surrounded by N-doped porous carbon derived from covalent organic framework for aqueous asymmetric supercapacitor

The persisting quest for improving charge density, electronic conductivity and cyclic stability of the electrode material in supercapacitor (SC) applications still demands intensive research and advancements. This study also aims the aforementioned pursuit with the construction of hybrid supercapacitor using mixed metal oxides with the incorporation of metal and supported with porous carbon to improve the charge density, electrical conductivity and cyclic stability, respectively. A covalent organic framework (COF) was synthesized and doped with nickel (Ni2+) and cobalt (Co2+) ions followed by carbonization at 1000 °C for 3 h to generate NiCo/NiO–CoO surrounded N-doped porous carbon (NPC) framework. The X-ray diffraction reveals that nickel considerably impacts the crystallinity of NiCo/NiO–CoO and the Raman spectroscopy revealed that the NiCo/NiO-CoO-NPC with an equal molar ratio of Ni2+ and Co2+ ions (NiCo/NiO-CoO-NPC-2) offered the highest degree of graphitization. The electron microscopic images showed the formation of flower-like morphology of NiCo/NiO-CoO-NPC-2 with a size of 250 nm and the greater number of flowers on NPC's surface could augment the electrochemical activity of the composite material. The NiCo/NiO–CoO-NPC-2 offered an attractive specific capacitance (Cs) of 845 F g−1 @ 1 A g−1 and preserves 93% capacity retention @ 10 A g−1 after 6000 charge-discharge cycles while exploited in SC application. The metal-free COF carbonized at 900 °C (CCOF-900) is utilized as the negative electrode with a Cs of 286 F g−1 @ 1 A g−1 for the construction of an asymmetric supercapacitor device and the NiCo/NiO-CoO-NPC-2//CCOF-900 device delivered efficient energy of 54 Wh kg−1 at a power density of 633 W kg−1.

3D hierarchical porous N-doped carbon nanoarchitecture coated bimetallic phosphides as a highly efficient bifunctional electrocatalyst for overall water splitting

As the energy and ecological crises are increasingly grim, it is challengeable but extremely attractive to fabricate highly efficient and low-cost bifunctional electrocatalysts for overall water splitting (OWS). Herein, a bimetallic phosphide embedded in N-doped hierarchical porous carbon (CoP/Ni2P@NHPC) framework was successfully constructed by calcination and phosphorization of cobalt–nickel coordination polymer nanoflowers (Co/Ni CPNFs), which were obtained by a facile hydrothermal process. Benefitting from their fascinating architecture and composition, the as-prepared CoP/Ni2P@NHPC exhibits outstanding electrochemical properties for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) with small Tafel slopes (103.9 mV dec-1, 62.58 mV dec-1) and ultralow overpotentials (275 mV, 159 mV at 10 mA cm−2) in alkaline medium. Additionally, the CoP/Ni2P@NHPC can be used as a bifunctional catalyst in a two-electrode water splitting device, and it only requires a low cell voltage of 1.55 V to attain the current density of 10 mA cm−2. Meanwhile, the CoP/Ni2P@NHPC also present admirable durability (at least 20 h) under long-term electrolysis. This work gives inspiration for the preparation of highly active bifunctional electrocatalysts for OWS.

Iron phosphide nanoparticles anchored on N-doped carbon as efficient electrocatalysts for nitrate reduction reaction

Electrochemical transformation nitrate to ammonia at ambient conditions is a green alternative approach to the conventional Haber-Bosch process, while suffering from a restricted ammonia yield rate owing to the multi-step electron and proton transfer. Herein, we reported a quintessential bubble-like iron phosphides nanoparticles anchored on N-doped carbon framework (FeP@NC) electrocatalyst for nitrate reduction reaction (NO3RR). The FeP@NC catalyst exhibits 93.12 % NH3 faradaic efficiency (FE) at −0.5 V with the yield rate of 626.07 mmol h−1 gcat−1, superior over these for Fe@NC. DFT calculations indicate that the phosphorization promotes the absorption of NO3− and following hydrogenation, beneficial for NO3RR. This study provides a reference of transition metal phosphides for efficient NO3− removal and conversion.

MOF/LDH cross composites derived heterojunction nanospheres as highly efficient catalysts for ORR-OER and rechargeable Zn-air batteries

Exploiting high-stability and cost-effective cathode catalysts is still one of the most important issues in promoting the practical application of Zn-air batteries (ZABs). Herein, the MOF/LDH crossed composites are utilized as templates to construct the N-doped carbon framework carrying the CoFe/Fe3C heterojunction as highly efficient electrocatalysts for ORR-OER and ZABs. During pyrolysis, the Co-Fe-LDH transforms into the CoFe alloy nanoparticle, while the MOFs convert to the Fe3C phase, thus leading to the formation of the CoFe/Fe3C heterojunction. Owing to the strong interactions between the heterogeneous interface of MOF and LDH, more active sites can be obtained on the surface of the contact interface. Moreover, more oxygen vacancies are generated in the catalysts after the formation of heterojunction. The optimal CoFe/Fe3C@CN-900 catalysts exhibit excellent ORR-OER performance with a potential gap between ORR and OER of 0.713 V at 0.1 M KOH electrolyte. DFT calculations demonstrate that the electron redistributes and accumulates at the heterojunction interface between CoFe and Fe3C, resulting in a stronger electron-donating capacity and faster electron conductivity. The CoFe/Fe3C@CN-900-based aqueous and solid-state ZABs also display good battery performance with high power density, strong discharge stability, large capacity, and good charge–discharge cycling durability.

Facilely Fabricating F-Doped Fe3N Nanoellipsoids Grown on 3D N-Doped Porous Carbon Framework as a Preeminent Negative Material.

Transition metal nitride negative electrode materials with a high capacity and electronic conduction are still troubled by the large volume change in the discharging procedure and the low lithium ion diffusion rate. Synthesizing the composite material of F-doped Fe3N and an N-doped porous carbon framework will overcome the foregoing troubles and effectuate a preeminent electrochemical performance. In this study, we created a simple route to obtain the composite of F-doped Fe3N nanoellipsoids and a 3D N-doped porous carbon framework under non-ammonia atmosphere conditions. Integrating the F-doped Fe3N nanoellipsoids with an N-doped porous carbon framework can immensely repress the problem of volume expansion but also substantially elevate the lithium ion diffusion rate. When utilized as a negative electrode for lithium-ion batteries, this composite bespeaks a stellar operational life and rate capability, releasing a tempting capacity of 574 mAh g-1 after 550 cycles at 1.0 A g-1. The results of this study will profoundly promote the evolution and application of transition metal nitrides in batteries.

Seed-induced strategy for the construction of nitrogen-doped carbon coated MoSe2/ZnSe-NC nanotubes with enriched phase boundaries toward boosting Na/K-ion storage

It is a challenge to construct suitable hosts for the large-sized Na+/K+ to overcome the hampered reaction kinetics for the energy storage. Component regulation and ingenious structure design are significant for achieving high electrochemical performance in Na+/K+ ions batteries (SIBs/PIBs). Herein, though a seed-induced assembly and subsequent high-temperature selenization process, MoSe2/ZnSe nanotubes encapsulated in N-doped carbon (NC) framework (MoSe2/ZnSe-NC@NC) are rationally synthesized. In this MoSe2/ZnSe-NC@NC structure, there are abundant heterointerfaces, which can induce to form self-built electric field and increase the interfacial Na+/K+ storage, promoting charge transfer and accelerating reaction kinetics. This leads to enhance Na+/K+ storage performance in terms of high reversible capacity, superior rate performance and long term cycling stability. Simultaneously, MoSe2/ZnSe-NC@NC exhibits impressive electrochemical properties, including high rate capability of 236.3 mAh g−1 at high current denisity of 5.0 A g−1 for SIBs and stable capacity of 162.4 mAh g−1 at 0.2 A g−1after 500 cycles for PIBs. Moreover, high energy density of 121.2 Wh kg−1 at power densities of 11486.3 W kg−1 can be also obtained in MoSe2/ZnSe-NC@NC//Na3V2(PO4)3/C full cell, demonstrating a promising anode candidate for large-sized Na+/K+ storage.

Zinc sulfide quantum dots modified 3D Nitrogen-Doped framework carbon enhances the ion transport rate of potassium ion hybrid capacitors

The potassium-ion hybrid capacitor (PIHC) has garnered considerable attention due to its ability to leverage the advantages of both battery-type anodes and capacitor-type cathodes simultaneously. Nevertheless, the slow K+ transfer rate between the PIHC battery-type anode and capacitor-type cathode significantly impedes the overall performance. Herein, we have employed quantum-sized zinc sulfide (ZnS) immobilized within a three-dimensional N-doped porous carbon framework (ZnSQDS@3DNC) as a standalone anode. The corresponding three-dimensional N-doped porous carbon (3DNC) serves as the cathode, thereby constructing a PIHC device. The strong coupling between ZnS quantum dots and N-doped three-dimensional porous carbon material effectively enhances ion/electron transport, facilitating intercalation-conversion-exfoliation reactions and improving K+ transfer rates. The numerous active sites within the 3DNC significantly enhance the capacitance performance of the cathode, facilitating the reversible adsorption and desorption of FSI-. The values of DK+ have all been calculated to be within the range of 10-10 to 10-9 cm2 s−1, indicating the rapid diffusion capability of this ZnSQDs@3DNC structure. More impressively, the assembled PIHC device can achieve high energy densities of 179.9 Wh kg−1 at power densities of 200 W kg−1, with an ultralong cycling life over 10,000 cycles. This study serves to advance the development of metal-ion hybrid capacitors and provides direction for improving ion transport kinetics.

P-doped NiS2/Ni nanoheteroparticles embedded into N-doped carbon framework anchored on multi-walled carbon nanotubes as an efficient counter electrode for Pt-free dye-sensitized solar cells

Designing of inexpensive counter electrode (CE) material with robust electrochemical properties and perfect electrical conductivity is of great essential to improve the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). Herein, the catalytic nickel nanoparticles are in-situ embedded into nitrogen-doped carbon framework (Ni-NC) by high-temperature carbonization. Next, the formed Ni-NC hybrid is subjected to simultaneous sulfurization/phosphorization treatment in the N2 atmosphere to acquire P–NiS2/Ni-NC. Finally, the acquired P–NiS2/Ni-NC hybrid is anchored on functional carboxylated multi-walled carbon nanotubes (MWCNTs) by ultrasonication to obtain P–NiS2/Ni-NC@MWCNTs. According to the electrochemical results, the P–NiS₂/Ni-NC@MWCNTs CE displays remarkable catalytic activities, great electron transfer ability, and high stability in the iodine/iodide electrolyte. DSSC assembled with P–NiS2/Ni-NC@MWCNTs CE yields an impressive PCE of 9.57 %, surpassing those of platinum (Pt) electrode (PCE = 7.84 %) and other corresponding counterparts. Such notable photovoltaic performance can be ascribed to the structural advantages and synergistic coupling effect of NiS2/Ni nanoheterostructure, P doping effect, and the support role of porous carbon network, which offer abundant catalytic active sites, high porosity, and exceptional electrical conductivity. Our work suggests a novel strategy to fabricate Pt-like CE materials based on transition metal sulfides/carbon-based nanostructures with excellent performances for large-scale energy conversion devices to reach the consumer market.

A Metal-Organic Framework-Derived Strategy for Constructing Synergistic N-Doped Carbon-Encapsulated NiCoP@N-C-Based Anodes toward High-Efficient Lithium Storage.

Transition metal phosphides (TMPs) have been regarded as the prospective anodes for lithium-ion batteries (LIBs). However, their poor intrinsic conductivity and inevitable large volume variation result in sluggish redox kinetics and the collapse of electrode structure during cycling, which substantially hinders their practical use. Herein, an effective composite electrodes design strategy of "assembly and phosphorization" is proposed to construct synergistic N-doped carbon-encapsulated NiCoP@N-C-based composites, employing a metal-organic frameworks (MOFs) as sacrificial hosts. Serving as the anodes for LIBs, one representative P-NCP-NC-600 electrode exhibits high reversible capacity (858.5mAhg-1, 120 cycles at 0.1Ag-1) and superior long-cycle stability (608.7mAhg-1, 500 cycles at 1Ag-1). The impressive performances are credited to the synergistic effect between its unique composite structure, electronic properties and ideal composition, which achieve plentiful lithium storage sites and reinforce the structural architecture. By accompanying experimental investigations with theoretical calculations, a deep understanding in the lithium storage mechanism is achieved. Furthermore, it is revealed that a more ideal synergistic effect between NiCoP components and N-doped carbon frameworks is fundamentally responsible for the realization of superb lithium storage properties. This strategy proposes certain instructive significance toward designable high-performance TMP-based anodes for high-energy density LIBs.

A polymer tethering strategy to achieve high metal loading on catalysts for Fenton reactions

The development of heterogenous catalysts based on the synthesis of 2D carbon-supported metal nanocatalysts with high metal loading and dispersion is important. However, such practices remain challenging to develop. Here, we report a self-polymerization confinement strategy to fabricate a series of ultrafine metal embedded N-doped carbon nanosheets (M@N-C) with loadings of up to 30 wt%. Systematic investigation confirms that abundant catechol groups for anchoring metal ions and entangled polymer networks with the stable coordinate environment are essential for realizing high-loading M@N-C catalysts. As a demonstration, Fe@N-C exhibits the dual high-efficiency performance in Fenton reaction with both impressive catalytic activity (0.818 min−1) and H2O2 utilization efficiency (84.1%) using sulfamethoxazole as the probe, which has not yet been achieved simultaneously. Theoretical calculations reveal that the abundant Fe nanocrystals increase the electron density of the N-doped carbon frameworks, thereby facilitating the continuous generation of long-lasting surface-bound •OH through lowering the energy barrier for H2O2 activation. This facile and universal strategy paves the way for the fabrication of diverse high-loading heterogeneous catalysts for broad applications.

In-situ constructing porous N-doped carbon skeleton with rich defects from modified polyamide acid to boost the high performance of Na3V2(PO4)3 cathode for full sodium-ion batteries

Generally, the transport of electrons and Na+ is seriously constrained in Na3V2(PO4)3 (NVP) due to intense interactions of V-O and PO bonds. Besides, polyamide acid (PAA) is hardly used in the sol–gel route due to insolubility. This work develops a facile liquid synthesis strategy based on modified PAA, achieving in-situ construction of a porous N-doped carbon framework with rich defects to improve the kinetics of NVP. The addition of triethylamine (TEA) reacts with carboxyls in PAA to achieve acid-base neutralization, turning PAA into polyamide salts with good solubility. The special morphology construction mechanism of this unique system was observed by ex-situ scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). Specifically, PAA undergoes in-situ conversion into chain-like polyimide (PI) through a thermal polymerization mechanism during the pre-sintering process. Meanwhile, NVP precursors are evenly dispersed in the PI fibers, efficiently reducing the particle size. After the final treatment, the favorable porous carbon skeleton could be generated derived from the partial decomposition of PI, on which small active grains are in situ grown. The resulting N-doped carbon substrate contains rich defects, benefiting from the migration of Na+. Furthermore, the porous construction is conducive to alleviating the stress and strain generated by the high current impact, increasing the contact area between electrodes/electrolytes to improve the utilization efficiency of active substances. Comprehensively, the optimized samples exhibit a capacity of 82.1 mAh g−1 at 15C with a retention rate of 95.45 % after 350 cycles. It submits a capacity of 67.6 mAh g−1 at 90C and remains 52.2 mAh g−1 after 1500 cycles. Even in full cells, it reveals a value of 110.6 mAh g−1. This work guides the application of in-situ multiple modifications of polymers in electrode materials.

Ultra-Dispersed α-MoC1-x Embedded in a Plum-Like N-Doped Carbon Framework as a Synergistic Adsorption-Electrocatalysis Interlayer for High-Performance Li-S Batteries.

The shuttle effect and sluggish redox kinetics of lithium polysulfides (LiPSs) severely hinder the scalable application of lithium-sulfurr (Li-S) batteries. Herein, the highly dispersed α-phase molybdenum carbide nano-crystallites embedded in a porous nitrogen-doped carbon framework (α-MoC1-x @NCF) are developed via a simple metal-organic frameworks (MOFs) assisted strategy and proposed as the multifunctional separator interlayer for Li-S batteries. The inlaid MoC1-x nanocrystals and in situ doped nitrogen atoms provide a strong chemisorption and outstanding electrocatalytic conversion toward LiPSs, whereas the unique plum-like carbon framework with hierarchical porosity enables fast electron/Li+ transfer and can physically suppress LiPSs shuttling. Benefiting from the synergistic trapping-catalyzing effect of the MoC1-x @NCF interlayer toward LiPSs, the assembled Li-S battery achieves high discharge capacities (1588.1mAhg-1 at 0.1C), impressive rate capability (655.8mAhg-1 at 4.0C) and ultra-stable lifespan (a low capacity decay of 0.059% per cycle over 650 cycles at 1.0C). Even at an elevated sulfur loading (6.0mgcm-2 ) and lean electrolyte (E/S is ≈5.8µLmg-1 ), the battery can still achieve a superb areal capacity of 5.2mAhcm-2 . This work affords an effective design strategy for the construction of muti-functional interlayer in advanced Li-S batteries.

Controllable Preparation of a N-Doped Hierarchical Porous Carbon Framework Derived from ZIF-8 for Highly Efficient Capacitive Deionization.

Capacitive deionization (CDI) is a promising desalination technology, and metal-organic framework (MOF)-derived carbon as an electrode material has received more and more attention due to its designable structure. However, MOF-derived carbon materials with single-pore structures have been difficult to meet the technical needs of related fields. In this work, the ordered hierarchical porous carbon framework (OMCF) was prepared by the template method using zeolitic imidazolate frameworks-8 (ZIF-8) as a precursor. The pore structures, surface properties, electrochemical properties, and CDI performances of the OMCF were investigated and compared with the microporous carbon framework (MCF), also derived from ZIF-8. The results show that the hierarchical porous carbon OMCF possessed a higher specific surface area, better hydrophilic surface (with a contact angle of 13.45°), and higher specific capacitance and ion diffusion rate than those of the MCF, which made the OMCF exhibit excellent CDI performances. The adsorption capacity and salt adsorption rate of the OMCF in a 500 mg·L-1 NaCl solution at 1.2 V and a 20 mL·min-1 flow rate were 12.17 mg·g-1 and 3.34 mg·g-1·min-1, respectively, higher than those of the MCF. The deionization processes of the OMCF and MCF closely follow the pseudo-first-order kinetics, indicating the double-layer capacitance control. This work serves as a valuable reference for the CDI application of N-doped hierarchical porous carbon derived from MOFs.