Nitrogen-doped Carbon Framework Research Articles

Dual-function CoP on nitrogen doped carbon framework with induced interfacial coupling for overall water splitting

Strong interfacial coupling in the hybrid catalysts could enhance catalytic performances. In this work, N, P were co-doped in zeolitic imidazolate framework-67 (ZIF-67) derived Co-based materials (denoted as CoP/NC) via in-situ carbonization and phosphating strategy, which accordingly induced strong interfacial coupling, leading to promote the catalytic activity in overall water splitting. In detail, the CoP/NC-2 presents the overpotential of 98 and 139 mV for hydrogen evolution reaction (HER) in 0.5 M H2SO4 and 1.0 M KOH at 10 mA cm−2, respectively, and 295 mV for oxygen evolution reaction (OER) in 1.0 M KOH at 20 mA cm−2, which is excellent during the non-noble metal-based catalysts. It also achieved a potential of 1.69 V (η20) in the overall water splitting. Density functional theory (DFT) based calculation reveals that the in-situ N, P co-doping induced strong interface coupling, which enhances the interaction in the interface of catalysts and improves electron conduction. More importantly, it contributes to adjusting electronic structure and d-band center, optimizing the adsorption energy for HER and/or OER and improving the kinetics of water splitting reaction. This work sheds new light on the heteroatom doping strategy to construct bifunctional transition metal-based electrocatalyst with boosting electrocatalytic performance in energy conversion application.

Interfacial "Double-Terminal Binding Sites" Catalysts Synergistically Boosting the Electrocatalytic Li2S Redox for Durable Lithium-Sulfur Batteries.

Catalytic conversion of polysulfides emerges as a promising approach to improve the kinetics and mitigate polysulfide shuttling in lithium-sulfur (Li-S) batteries, especially under conditions of high sulfur loading and lean electrolyte. Herein, we present a separator architecture that incorporates double-terminal binding (DTB) sites within a nitrogen-doped carbon framework, consisting of polar Co0.85Se and Co clusters (Co/Co0.85Se@NC), to enhance the durability of Li-S batteries. The uniformly dispersed clusters of polar Co0.85Se and Co offer abundant active sites for lithium polysulfides (LiPSs), enabling efficient LiPS conversion while also serving as anchors through a combination of chemical interactions. Density functional theory calculations, along with in situ Raman and X-ray diffraction characterizations, reveal that the DTB effect strengthens the binding energy to polysulfides and lowers the energy barriers of polysulfide redox reactions. Li-S batteries utilizing the Co/Co0.85Se@NC-modified separator demonstrate exceptional cycling stability (0.042% per cycle over 1000 cycles at 2 C) and rate capability (849 mAh g-1 at 3 C), as well as deliver an impressive areal capacity of 10.0 mAh cm-2 even in challenging conditions with a high sulfur loading (10.7 mg cm-2) and lean electrolyte environments (5.8 μL mg-1). The DTB site strategy offers valuable insights into the development of high-performance Li-S batteries.

Ir nanoclusters on ZIF-8-derived nitrogen-doped carbon frameworks to give a highly efficient hydrogen evolution reaction

Ir nanoclusters on ZIF-8-derived nitrogen-doped carbon frameworks to give a highly efficient hydrogen evolution reaction

NiFe layered double hydroxide (LDH) anchored, Fe single atom and nanoparticle embedded on nitrogen-doped carbon-CNT (carbon nanotube) framework as a bifunctional catalyst for rechargeable zinc-air batteries

Zinc-air batteries (ZAB) have significant potential for practical energy storage, but their rechargeability has been limited by the lack of a suitable bifunctional catalyst. Here, we developed NiFe LDH-A-Fe/NC-CNT, a remarkable bifunctional catalyst that is built on a hierarchically porous nitrogen-doped carbon and carbon nanotube (NC-CNT) framework enriched with iron single atoms and nanoparticles, with nickel‑iron layered double hydroxides (NiFe LDH) anchored onto it. The NiFe LDH-A-Fe/NC-CNT exhibited remarkable performance in the ORR, with Eonset of 0.94 V, a half-wave potential of 0.84 V, and a limited current of 6.89 mA cm−2. A remarkable Eonset of 1.47 V and a potential of 1.59 V at 10 mA cm−2 (Ej = 10) in the OER were also observed. Significantly, the difference in potential (ΔE) between the ORR and OER was only 0.74 V. The stability tests, tolerance assessments, and poisoning experiments consistently demonstrated the superior performance of this cutting-edge catalyst in comparison to the commercial Pt/C and RuO2. In ZAB tests, it achieves a discharge capacity of 818 mAhg−1 and an impressive power density of 293 mWcm−2, enduring nearly 1000 cycles (320h). Flexible ZABs with this catalyst maintain a 629 mAhg−1 capacity, a power density of 195 mWcm−2, and a lifespan of 95 h (280 cycles), outperforming benchmark catalysts. In conclusion, a remarkable bifunctional catalyst was synthesized, demonstrating its immense capacity for utilization in zinc-air batteries.

Ir nanoclusters on ZIF-8-derived nitrogen-doped carbon frameworks to give a highly efficient hydrogen evolution reaction

The precise change of the electronic structure of active metals using low-active supports is an effective way of developing high-performance electrocatalysts. The electronic interaction of the metal and support provides a flexible way of optimizing the catalytic performance. We have fabricated an efficient hydrogen evolution reaction (HER) electrocatalyst, in which Ir nanoclusters are uniformly loaded on a nitrogen-doped carbon framework (Ir@NC). The synthesis process entails immersing an annealed zeolitic imidazolate framework-8 (ZIF-8), prepared at 900 °C as a carbon source, into an IrCl3 solution, followed by a calcination-reduction treatment at 400 °C under a H2/Ar atmosphere. The three-dimensional porous structure of the nitrogen-doped carbon framework exposes more active metal sites, and the combined effect of the Ir clusters and the N-doped carbon support efficiently changes the electronic structure of Ir, optimizing the HER process. In acidic media, Ir@NC has a remarkable HER electrocatalytic activity, with an overpotential of only 23 mV at 10 mA cm−2, an ultra-low Tafel slope (25.8 mV dec−1) and good stability for over 24 h at 10 mA cm−2. The high activity of the electrocatalyst with a simple and scalable synthesis method makes it a highly promising candidate for the industrial production of hydrogen by splitting acidic water.

Cobalt-vanadium sulfide yolk-shell nanocages from surface etching and ion-exchange of ZIF-67 for ultra-high rate-capability sodium ion battery

Development of high-performance metal sulfides anode materials is a great challenge for sodium-ion batteries (SIBs). In this work, a cobalt-based imidazolate framework (ZIF-67) were firstly synthesized and applied as precursor. After the successive surface etching, ion exchange and sulfidation processes, the final cobalt-vanadium sulfide yolk-shell nanocages were obtained (CoS2/VS4@NC) with VS4 shell and CoS2 yolk encapsulated into nitrogen doped carbon frameworks. This yolk-shell nanocage structure effectively increases the specific surface area and provides enough space for inhibiting the volume change during charge/discharge processes. Besides, the nitrogen doped carbon skeleton greatly improves the ionic conductivity and facilitates ion transport. When used as the anode materials for SIBs, the yolk-shell nanocages of CoS2/VS4@NC electrode exhibits excellent rate capability and stable cycle performance. Notably, it displays a long-term cycling stability with excellent capacity of 417.28 mA h g−1 after 700 cycles at a high current density of 5 A/g. This developed approach here provides a new route for the design and synthesis of various yolk-shell nanocages nanomaterials from enormous MOFs with multitudinous compositions and morphologies and can be extended to the application into other secondary batteries and energy storage fields.

Strontium doped Fe-based porous carbon for highly efficient electrocatalytic ORR and MOR reactions

The catalytic activity improvement of Fe-based active sites derived from metal organic frameworks toward oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) remains a major challenge. In this study, the growth of strontium decorated 2-methylimidazole zinc salt (Sr/ZIF-8) is prepared as a carrier to vapor deposited iron formation Sr doped Fe-based nitrogen-doped carbon framework (named as Sr/FeNC). After high-temperature pyrolysis and vapor deposition, strontium carbonate nanocrystals are evenly dispersed on the shrunk dodecahedron carbon frame and multitudinous Fe-based active catalytic sites are embedded in carbon skeleton. The optimal Sr/FeNC-2 catalyst demonstrates the outstanding ORR performance in terms of a half-wave potential of 0.851 V and an onset potential of 0.90 V, while Sr/FeNC-2 exhibits a high current density of 18.2 mA cm−2 and a lower Tafel slope of 21 mV dec-1 in MOR. The exceptional catalytic activity could be ascribed to the synergistic coupling effect of strontium compounds with Fe-based catalytic sites (Fe-Nx, Fe, and iron oxide). In particular, the formation of SrCO3 affects the bonding configuration of the iron species sites, leading to an optimization of the electronic structure within the multihole carbon matrix. The synthetic approach presents a prospective strategy for future endeavors in developing innovative and advanced bifunctional catalysts for ORR and MOR.

3D nitrogen-doped carbon frameworks with hierarchical pores and graphitic carbon channels for high-performance hybrid energy storages.

In principle, hybrid energy storages can utilize the advantages of capacitor-type cathodes and battery-type anodes, but their cathode and anode materials still cannot realize a high energy density, fast rechargeable capability, and long-cycle stability. Herein, we report a strategy to synthesize cathode and anode materials as a solution to overcome this challenge. Firstly, 3D nitrogen-doped hierarchical porous graphitic carbon (NHPGC) frameworks were synthesized as cathode materials using Co-Zn mixed metal-organic frameworks (MOFs). A high capacity is achieved due to the abundant nitrogen and micropores produced by the MOF nanocages and evaporation of Zn. Also, fast ion/electron transport channels were derived through the Co-catalyzed hierarchical porosity control and graphitization. Moreover, tin oxide precursors were introduced in NHPGC to form the SnO2@NHPGC anode. Operando X-ray diffraction revealed that the rescaled subnanoparticles as anodic units facilitated the high capacity during ion insertion-induced rescaling. Besides, the Sn-N bonds endowed the anode with a cycling stability. Furthermore, the NHPGC cathode and SnO2@NHPGC achieved an ultrahigh energy density (up to 244.5 W h kg-1 for Li and 146.1 W h kg-1 for Na), fast rechargeable capability (up to 93C-rate for Li and 147C-rate for Na) as exhibited by photovoltaic recharge within a minute and a long-cycle stability with ∼100% coulombic efficiency over 10 000 cycles.

Nanoarchitectonics of ultrafine molybdenum carbide nanocrystals into three-dimensional nitrogen-doped carbon framework for capacitive deionization.

Molybdenum carbide (MoC) has emerged as a promising material for capacitive deionization (CDI), but the poor electrochemical kinetics in conventional MoC owing to the bulk structure and low electric conductivity limit its CDI performance. To address this challenge, herein, we develop a novel strategy to synthesize ultrafine MoC nanocrystals that are embedded within a three-dimensional nitrogen-doped carbon framework (NC/MoC). This synthesis method involves the space-confined pyrolysis of molybdate precursors within metal-organic frameworks (MOFs). In this process, molybdates are confined into the MOF crystalline structure, where MOFs provide a confined reactor and carbon source. The resulting NC/MoC with the uniformly distributed MoC nanocrystals provides sufficient active sites for the electrosorption of salt ions, while the MOF-derived NC matrix facilitates charge transfer and provides the space-confined effect for preventing the possible aggregations of MoC nanocrystals during the CDI process. The NC/MoC exhibits an impressive salt adsorption capacity (SAC, 84.2 mg g-1, 1.2 V), rapid desalination rate, and high cycling stability (91.4% SAC retention after 200 cycles), better than those of most previously reported carbon-based CDI materials. Besides, the possible mechanisms are systematically investigated by ex situ characterization and density functional theory calculations. This study opens up new avenues for the construction of metal carbide-based nanocrystals for CDI and other electrochemical applications.

Structure and Defect Engineering of V3S4-xSex Quantum Dots Confined in a Nitrogen-Doped Carbon Framework for High-Performance Sodium-Ion Storage.

Constructing quantum dot-scale metal sulfides with defects and strongly coupled with carbon is significant for advanced sodium-ion batteries (SIBs). Herein, Se substituted V3S4 quantum dots with anionic defects confined in nitrogen-doped carbon matrix (V3S4-xSex/NC) are fabricated. Introducing element Se into V3S4 crystal expands the interlayer distance of V3S4, and triggers anionic defects, which can facilitate Na+ diffusions and act as active sites for Na+ storage. Meanwhile, the quantum dots tightly encapsulated by conductive carbon framework improve the stability and conductivity of the electrode. Theoretical calculations also unveil that the presence of Se enhances the conductivity and Na+ adsorption ability of V3S4-xSex. These properties contribute to the V3S4-xSex/NC with high specific capacity of 447 mAh g-1 at 0.2 A g-1, and prominent rate and cyclic performance with 504 mAh g-1 after 1000 cycles at 10 A g-1. The sodium-ion hybrid capacitors (SIHCs) with V3S4-xSex/NC anode and activated carbon cathode can achieve high energy/power density (maximum 144 Wh kg-1/5960 W kg-1), capacity retention ratio of 71% after 4000 cycles at 2 A g-1. This work not only synthesizes V3S4-xSex/NC, but also provides a promising opportunity for designing quantum dots and utilizing defects to improve the electrochemical properties.

Single iron atom embedded in dual-size nitrogen-doped carbon framework on reduced graphene oxide: An effective catalyst for proton exchange membrane fuel cells

The commercialization of Proton Exchange Membrane Fuel Cells (PEMFCs) is hindering by the cost of noble metal catalysts. We are introducing A-FeSAC-NCDS/rGO, a novel catalyst derived from metal-organic framework through carbonization and ammonia treatment. This catalyst is incorporating single iron atoms (FeSAC) within dual-sized porous nitrogen-carbon frameworks (NCDS, 30 nm and 100 nm), supporting on reduced graphene oxide (rGO). The catalyst is providing abundant active sites, with NCDS increasing active site density and rGO enhancing material conductivity. Consequently, catalyst is exceling in the oxygen reduction reaction, boasting an onset potential of 0.807 V and a half-wave potential of 0.779 V, near benchmark Pt/C catalyst. PEMFC tests employing A-FeSAC-NCDS/rGO achieved a power density of 780.7 mWcm−2 at 1.6 A cm−2 in an H2–O2 system. In durability tests at 0.6 Acm−2 in H2-air, voltage loss was 28.68 % after 50 h. These results position the catalyst as a promising choice for PEMFC.

A Ni-Fe layered double hydroxide anchored FeCo nanoalloys and Fe-Co dual single-atom electrocatalysts for rechargeable and flexible zinc-air and aluminum-air batteries

Developing bifunctional catalysts for the ORR and OER, along with a unique cathode structure, is essential for advancing rechargeable zinc-air batteries (ZABs) and aluminum-air batteries (AABs). Our catalyst (NiFe LDH A-FeSACoSA-FeCoAlloy-CNT/NC) integrates nickel-iron layered double hydroxide (NiFe LDH), iron-cobalt dual single atoms (FeSACoSA), and iron-cobalt nanoalloy (FeCoAlloy) within carbon nanotubes (CNTs) on a nitrogen-doped carbon framework (NC). Due to its distinctive features, this catalyst excels, achieving an ORR half-wave potential of 0.84 V and an OER potential of 1.56 V (Ej=10mAcm−2). In ZABs, it outperforms the Pt/C+RuO2, reaching a power density of 266 mWcm−2 and demonstrating impressive rechargeability over 495 h (1484 cycles). Flexible ZABs achieve 173 mWcm−2 and over 270 cycles (90 h), while flexible AABs reach 145 mWcm−2, surpassing Pt/C+RuO2. Exceptional performance in terms of capacity, power density, rechargeability, and lifespan is attributed to the catalyst's design and the cathode configuration's unique attributes.

An efficient heterostructure MoP2-CoMoP-NC electrocatalyst derived from ZIF-67 for hydrogen evolution reaction

The fabrication of heterostructure electrocatalysts is an effective method for optimizing catalytic activity and improving electrocatalytic performance. Herein, we designed a novel MoP2-CoMoP-NC heterostructure electrocatalyst derived from ZIF-67. The prepared MoP2-CoMoP-NC displays wheat-spike nanorods cross-linked with each other for providing a large electrochemically active surface area. Furthermore, the nitrogen-doped carbon framework derived from ZIF-67 successfully wrapped nanoparticles, which is advantageous for enhancing the stability and conductivity of the catalyst. The heterointerface between MoP2 and CoMoP facilitates mass transport and charge transfer. The MoP2-CoMoP-NC/NF heterostructure electrocatalyst shows enhanced electrocatalytic activity, with a relatively low overpotential of 88.2 mV at 10 mA cm−2 for the hydrogen evolution in alkaline conditions and a Tafel slope of only 65.9 mV dec−1. Furthermore, long-term measurements showed that MoP2-CoMoP-NC/NF has superior durability in alkaline solutions.

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.

The millisecond fabrication of medium-entropy alloy as a high-performance bifunctional electrocatalyst for ultralong-term rechargeable zinc–air batteries

Zinc air battery (ZAB) has widely recognized advantages such as high theoretical energy density, environmental friendliness, and safety. However, its cathodic reactions involve sluggish four-electron process oxygen reduction and oxygen evolution reactions (ORR and OER). Therefore, developing a cheap, efficient and durable dual functional oxygen electrocatalyst has important scientific significance and practical value for the development of ZAB. Herein, we applied noble metal free medium-entropy alloy (CoFeNi) nanoparticles which were in embedded nitrogen doped carbon framework (N-PCF) as a highly active and ultra-stable bifunctional electrocatalyst. The CoFeNi@N-PCF was prepared by high temperature thermal shock approach from ion-exchanged ZIF percussor to ensure the uniform dispersion of medium-entropy alloy, hierarchical porosity and strong metal-support interaction. Due to the medium-entropy induced synergistic effects, the as-prepared bifunctional electrocatalyst has a large ORR onset potential (Eonset) of 0.92 V and half-wave potential (E1/2) of 0.85 V (vs. RHE) in 0.1 M KOH. And the overpotential of OER in 1.0 M KOH is only 320 mV at 10 mA cm−2. When used in ZAB, the as-assembled rechargeable ZAB with the self-supported air electrode provides an extremely high-power density of 203 mW cm−2, a superior specific capacity of 812 mAh g−1, and amazing cycled steadily for 600 h. The assembled flexible ZAB with CoFeNi@N-PCF exhibits an excellent stability (over 45 h) and the excellent bending ability under different angles. This work can provide some new insights into the design and preparation of advanced bifunctional oxygen electrocatalysts for next-generation metal-air batteries.

Porous W/N/C nanoframework: A trifunctionally effective cathodic electrocatalyst for rechargeable Zn-Air/iodide hybrid battery

Different from the conventional Zinc-Air batteries which only involves oxygen reduction and evolution (ORR/OER) in the cathode, the cathode of rechargeable zinc–air/iodide hybrid batteries (ZAIHBs), with the addition of I− species, involves I− electrooxidation (IOR) during charging and oxygen/iodate reduction (ORR and IDR) during discharging. This work reports the synthesis of a hierarchically porous tungsten-based nitrogen-doped carbon framework (W/N/C) with abundant WNx active sites and numerous ultrafine WN nanoclusters and explores their application as a trifunctional IOR/ORR/IDR electrocatalyst for ZAIHBs. The formation mechanism of ZIF-8-derived W/N/C framework as well as its structural and compositional features were investigated. The catalyst demonstrates high trifunctional catalytic activity and robust durability towards IOR/ORR/IDR in alkaline condition, owing to the uniform copresence of the numerous sub-nanometer-sized WN nanoclusters and the abundant single atom WNx sites in the hierarchically structured carbon framework. When applied in homemade ZAIHBs, it revealed a high peak energy density (141.9 mW cm−2) and remarkable cycling stability (65 h), outperforming the commercial Pt/C catalysts. This work demonstrates the multi-functional electrocatalytic activity of tungsten-based non-noble metal electrocatalyst for high-performance ZAIHBs.

Nitrogen-doped oxygen-rich porous carbon framework towards aqueous zinc ion hybrid capacitors and zinc-iodine batteries

Zinc ion hybrid capacitors (ZIHCs) and zinc-iodine batteries (ZIBs) have attracted significant attention as promising components for large-scale energy storage owing to their excellent security, environmental friendness and high theoretical capacity of Zn anode. However, there still exist some respective obstacles for commercial applications, such as limited specific capacity, poor cycling stability of ZIHCs or shuttle effect of polyiodide of ZIBs. Here, to enhance electrochemical properties, we report a synergistic one-step activation strategy using KMnO4 and Zn(NO3)2 for nitrogen-doped oxygen-rich three-dimensional hierarchical porous carbon (NOPC). Benefiting from its high specific surface area, three-dimensional porous morphology and improved redox sites from heteroatom doping, the as obtained NOPC exhibits desired electrochemical performance as cathode for ZIHCs and ZIBs. The NOPC-based electrode achieves an ultra-high specific capacity of 230 mAh g−1 at 0.1 A g−1, and 118 mAh g−1 can be maintained at 10 A g−1. Besides, a distinguished energy density of 213.0 Wh kg−1 and a high-power density of 11.2 kW kg−1 are also achieved with a constructed ZIHCs device. Furthermore, the NOPC/I2 composite exhibited excellent rate performance (54 mAh g−1 at 10 A g−1) and cycling performance (∼88.3 % retention upon 5000 cycles) in ZIBs device. This work provides a facile but effective strategy to develop 3D porous electrodes for ZIHCs and ZIBs with remarkable rate and cycling performance.

Tailoring the d-band center of Ni on a dual-single-atom Ni–ZnNC catalyst for efficient H2O2 production

Electrocatalytic oxygen reduction reaction (ORR) for H2O2 production presents an alternative approach suitable for on-site applications. Although atomically dispersed earth-abundant metal species anchored in a nitrogen-doped carbon framework (M–N–C) have demonstrated significant 2e− ORR activity, the Ni–N–C catalyst exhibits unfavorable catalytic activity. It is well-recognized that the d-band center of the metal can be tailored by introducing transition metals, thereby altering the adsorption free energy of the OOH∗ reactive species. Herein, we have designed a dual-single-atom configuration (Ni–ZnNC), where the Zn atom serves as a modulator to adjust the d-band electronic energy of the Ni center, ultimately optimizing the intermediate adsorption and resulting in high 2e− ORR performance. The Ni–ZnNC catalyst demonstrates an H2O2 production rate of 5.6 mol/g/h at 0.0 VRHE with a notable H2O2 selectivity of approximately 60% in an acid electrolyte. Density-functional theory calculations reveal that the Zn atom effectively alters the d-band electronic energy of the Ni center, strengthening the Ni–OOH∗ binding affinity and thereby enhancing the adsorption process. This work provides valuable insights into the design of earth-abundant metal Ni-based electrocatalysts for H2O2 generation.

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.

In-situ surface reconstructed NiOOH/Ni-ZnSe composite electrocatalysts with high activity toward oxygen evolution reaction in alkaline media

Fabricating long-durability and high-activity electrodes for oxygen evolution reaction (OER) in alkaline electrolyte is of great importance for practical water electrolysis. In this work, we develop a composite catalyst composed of Ni-doped zinc selenide nanoparticles embedded in nitrogen-doped amorphous carbon framework (denoted as Ni-ZnSe composite). Concretely, the systematic investigations disclose that the amorphous nickel (oxy)-hydroxide (NiOOH) in-situ formed on the surface of the hybrid catalyst during the OER process is considered as the genuine active centers. This self-reconstructed electrocatalyst (denoted as NiOOH/Ni-ZnSe) only demands small overpotentials of 218, 242 and 292 mV at the 10, 20 and 50 mA cm-2, respectively, as well as low Tafel slope of 56 mV dec-1 in alkaline media. XPS characterization reveals that performance enhancement is attributed to the electronic interaction between Ni-ZnSe and nitrogen-doped carbon (NC) that facilitate interfacial electron transfer, which in turn favors improve the oxygen evolution activity. This work not only enhances the electrocatalytic activity of selenide-based catalyst, but also provides a judicious avenue for developing advanced heterometallic doped catalysts toward OER and beyond.