N-doped Amorphous Carbon Research Articles

Synthesis of Co/Co3O4 Heterostructure in N-Doped Porous, Amorphous Carbon: A Superior Electrochemical Sensor for Sensitive Determination of Alectinib in Various Fluids.

Highly crystallized Co and Co3O4 nanoparticles embedded in an N-doped amorphous carbon matrix have been successfully fabricated by the molten-salt-assisted method using KClO3 and zeolitic imidazolate framework-12 (ZIF-12). Pyrolysis of ZIF-12 with different concentrations of KClO3 leads to embedded Co and Co3O4 nanoparticles in a conductive amorphous carbon network. The impact of salt concentration on the morphology and electrochemical performance of these composites was investigated for electrochemical sensor applications. By employing a straightforward and efficient technique, Co/Co3O4 heterostructures were successfully synthesized in N-doped porous amorphous carbon. The Co/Co3O4 carbon heterostructures were optimized by varying the salt concentration, resulting in a significant electrochemical sensor performance for detecting ALC in both bulk and biological fluids. The sensor demonstrates excellent sensitivity (62.97 nmol/L) and selectivity toward ALC, with a wide linear range (0.2-2 μM) and a low detection limit (18.89 nM). Furthermore, it displays remarkable stability and reproducibility, positioning it as a strong contender for practical use in pharmaceutical analysis and biomedical research. This study presents a significant advancement in electrochemical sensing technology and underscores the potential of Co/Co3O4 heterostructures in the development of high-performance sensors for detecting bioactive compounds in complex matrices.

Superior Electrochemical Sensor Application of Co3O4/C Heterostructure in Rapid Analysis of Anticancer Drug Palbociclib in Pharmaceutical Formulations and Biological Fluids.

In this work, we report a study examining how different salt concentrations affect the structure and electrochemical performance of two Co3O4/C materials designed for the fabrication of an easy, cheap, fast, safe, and useful electrochemical sensor for the detection of Palbociclib (PLB). Co3O4 nanoparticles were successfully created by encapsulating them in N-doped amorphous carbon matrices by using the molten salt-assisted approach. In this process, different amounts of potassium iodate and zeolitic imidazolate framework-12 (ZIF-12) were used, followed by pyrolysis at 800 °C. Optimum Co3O4 embedded porous carbon structures were obtained, and the composite with the highest electrochemical properties was modified to a glassy carbon electrode (GCE) surface for PLB detection. The linear response spanned from 1.0 to 5.0 μM, featuring a limit of detection (LOD) of 0.122 μM and a limit of quantification (LOQ) of 0.408 μM; the correlation coefficient was calculated as 0.995. The high sensitivity of the method in detecting PLB in pharmaceutical samples and human urine demonstrated its feasibility, with recovery percentages ranging from 99.3% to 101.3% and relative standard deviation (RSD) values of <3%. Therefore, this technique will make a significant contribution to monitoring and improving existing cancer treatment options.

Corrosion-Resistant Ultrathin Cu Film Deposited on N-Doped Amorphous Carbon Film Substrate and Its Use for Crumpleable Circuit Board.

Copper (Cu) is widely used as an industrial electrode due to its high electrical conductivity, mechanical properties, and cost-effectiveness. However, Cu is susceptible to corrosion, which degrades device performance over time. Although various methods (alloying, physical passivation, surface treatment, etc.) are introduced to address the corrosion issue, they can cause decreased conductivity or vertical insulation. Here, using the nitrogen-doped amorphous carbon (a-C:N) thin film is proposed as a substrate on which Cu is directly deposited. This simple method significantly inhibits corrosion of ultrathin Cu (<20nm) films in humid conditions, enabling the fabrication of ultrathin electronic circuit boards without corrosion under ambient conditions. This study investigates the origin of corrosion resistance through comprehensive microscopic/spectroscopic characterizations and density-functional theory (DFT) calculations: i) diffusion of Cu atoms into the a-C:N driven by stable C-Cu-N bond formation, ii) diffusion of N atoms from the a-C:N to the Cu layer heading the top surface, which is the thermodynamically preferred location for N, and iii) the doped N atoms in Cu layer suppress the inclusion of O into the Cu lattice. By leveraging the ultrathinness and deformability of the circuit board, a transparent electrode and a crumpleable LED lighting device are demonstrated.

A facile one-pot synthesis of ultrafine Sn/N-doped carbon/graphene oxide composite for superior lithium-ion storage

Metallic Sn is considered as a promising candidate of anode materials for lithium-ion batteries (LIBs) owing to its high capacity and ease of preparation. However, it undergoes severe mechanical damage after several lithiation/delithiation cycles due to the large volume change (∼300%). In this study, ultrafine Sn nanograins are embedded in N-doped amorphous carbon and then anchored onto reduced graphene oxide (rGO) via a facile one-pot synthesis route. The resulting composite consists of highly active Sn nanograins, three-dimensional carbon frameworks and highly conductive graphene oxide matrices. This unique configuration endows the composite with promising electrochemical performance. It delivers a reversible capacity of 1392 mAh g−1 at a current density of 50 mA g−1. When cycled after 300 times at 500 mA g−1, it still maintains a reversible capacity of 805 mAh g−1.

Hybrid Molecular Layer Deposition of Molybdenum-Aminates as Hydrogen Evolution Reaction Electrocatalysts

The development of high-performance hydrogen evolution reaction (HER) electrocatalysts from noble metal-free materials is critical to achieving cost-effective water splitting and ultimately realizing affordable hydrogen based on renewable energy. Compounds based on earth-abundant transition metals have been the subject of great research interest for this purpose, with metal nitrides gaining recent attention due to their high conductivity and corrosion resistance. Molybdenum nitride-based electrocatalysts have shown particular promise, with many of the best reported activities occurring in composite systems wherein crystalline MoNx domains are embedded in an amorphous N-doped carbon matrix. The present work demonstrates the formation of such uniquely active morphologies in films deposited by organic-inorganic hybrid molecular layer deposition (MLD).Hybrid MLD is a hybridization of other well-established layer-by-layer deposition techniques – namely atomic layer deposition (used to deposit inorganic films) and purely organic MLD. This family of techniques involves the cyclical exposure of a growth surface to alternating vapor-phase chemical precursors which react in a self-limiting fashion to saturate available surface sites, offering atomic- and molecular-level control over the resulting films. This presentation will introduce the successful development of hybrid MLD deposition procedures for new Mo-aminate materials using Mo(CO)6 as a Mo precursor and various amine precursors, including ethylenediamine, p-phenylenediamine, and tris(2-aminoethyl)amine.We will describe how the molecular level of control offered by this technique enables tunable variations in film composition and structure, lending unique insights into how the local bonding environment of Mo active sites affects their catalytic properties towards HER. Increased nitrogen loading in the MLD films was shown to decrease the overpotentials required to drive HER in acidic media (0.5 M H2SO4) and improve film stability. Catalysts with N/Mo ratios above 2 demonstrated the best performance, with overpotentials lower than 400 mV at -10 mA/cm2. By incorporating organic components in the MLD films, it was possible to induce desirable morphological changes in the catalytic material – notably including the development of increased active site density – simply through initial exposure to HER testing conditions. The choice of organic precursor affected the rate and extent of these changes through structural effects like crosslinking and crystallinity, which led to more stable catalysts, slowed the rate of morphological changes, and impacted final film structure.

Amorphous carbon intercalated MoS2 nanosheets embedded on reduced graphene oxide for excellent high‐rate and ultralong cycling sodium storage

AbstractMoS2 as a typical layered transition metal dichalcogenide (LTMD) has attracted considerable attention to work as sodium host materials for sodium‐ion batteries (SIBs). However, it suffers from low semiconducting behavior and high Na+ diffusion barriers. Herein, intercalation of N‐doped amorphous carbon (NAC) into each interlayer of the tiny MoS2 nanosheets embedded on rGO conductive network is achieved, resulting in formation of rGO@MoS2/NAC hierarchy with interoverlapped MoS2/NAC superlattices for high‐performance SIBs. Attributed to intercalation of NAC, the resulting MoS2/NAC superlattices with wide MoS2 interlayer of 1.02 nm facilitates rapid Na+ insertion/extraction and accelerates reaction kinetics. Theoretical calculations uncover that the MoS2/NAC superlattices are beneficial for enhanced electron transport, decreased Na+ diffusion barrier and improved Na+ adsorption energy. The rGO@MoS2/NAC anode presents significantly improved high‐rate capabilities of 228, 207, and 166 mAh g−1 at 20, 30, and 50 A g−1, respectively, compared with two control samples of pristine MoS2 and MoS2/NAC counterparts. Excellent long‐term cyclability over 10 000 cycles with extremely low capacity decay is demonstrated at high current densities of 20 and 50 A g−1. Sodium‐ion full cells based on the rGO@MoS2/NAC anode are also demonstrated, yielding decent cycling stability of 200 cycles at 5C. Our work provides a novel interlayer strategy to regulate electron/Na+ transport for fast‐charging SIBs.image

Structure and performance of N-doped amorphous carbon films (a-C: N) on stainless steel surfaces for bipolar plates in proton exchange membrane fuel cells

Stainless steel bipolar plates (BPPs) are anticipated to supersede traditional graphite BPPs in proton exchange membrane fuel cells (PEMFCs) owing to their superior machinability, enhanced mechanical strength, and cost-effectiveness. Nevertheless, stainless steel BPPs are susceptible to corrosion and dissolution in acidic environments over extended periods, leading to the formation of a passivation film that diminishes conductivity. In this study, amorphous carbon (a-C) films with varying N doping contents were deposited onto 304L stainless steel foil using the cathodic arc ion plating technique. This was achieved by manipulating the N2 flow rate. The research investigated the impact of N doping on the microstructure, corrosion resistance, interfacial contact resistance (ICR), and hydrophobicity of the a-C films on stainless steel surfaces. The findings reveal that the various a-C films significantly enhance the performance of 304L stainless steel under simulated PEMFCs operating conditions. While N-doped a-C (a-C: N) films are advantageous for reducing ICR, incorporating N results in a decrease in C-sp3 content and density, ultimately leading to a decrease in the corrosion resistance of films. Additionally, the hydrophobicity of the a-C films diminishes with increasing N content. Consequently, N doping is not conducive to improving the overall performance of a-C films on the surface of 304L stainless steel bipolar plates under simulated PEMFCs operating conditions.

Dual Strategy of Morphology Optimization and Interlayer Expansion in VS2 Cathode Toward High-Performance Mg-Li Hybrid Ion Batteries.

Combining the merits of the dendrite-free formation of a Mg anode and the fast kinetics of Li ions, the Mg-Li hybrid ion batteries (MLIBs) are considered an ideal energy storage system. However, the lack of advanced cathode materials limits their further practical application. Herein, we report a dual strategy of morphology optimization and interlayer expansion for the construction of hierarchical flower-like VS2 architecture coated by N-doped amorphous carbon layers. This tailored hierarchical flower-like structure coupled with homogeneous N-doped amorphous carbon layers cooperatively provide more active sites and buffer volume changes, thus realizing the enhancement of capacity and structural stability. Moreover, the enlarged interlayer spacing caused by the cointercalation of polyvinylpyrrolidone and ammonium ions can effectively promote the charge transfer rate and facilitate the rapid ion diffusion, as further demonstrated by electrochemical results and theoretical calculations. These features endow the hierarchical flower-like VS2 cathode with superior specific energy density (644.4 Wh kg-1, average voltage of 1.2 V vs Mg2+/Mg) and excellent rate capability (181.1 mAh g-1 at 2000 mA g-1). Systematic ex situ characterization measurements are employed to reveal the ion storage mechanism, which confirms that Li+ storage plays a leading role in the capacity contribution of MLIBs. Our strategy is in favor of providing useful insights to design and construct MLIBs with high energy density and excellent rate performance.

Surface-Pore-Modified N-Doped Amorphous Carbon Nanospheres Tailored with Toluene as Anode Materials for Lithium-Ion Batteries.

The surface modification of amorphous carbon nanospheres (ACNs) through templates has attracted great attention due to its great success in improving the electrochemical properties of lithium storage materials. Herein, a safe methodology with toluene as a soft template is employed to tailor the nanostructure, resulting in ACNs with tunable surface pores. Extensive characterizations through transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption/desorption isotherms elucidate the impact of surface pore modifications on the external structure, morphology, and surface area. Electrochemical assessments reveal the enhanced performance of the surface-pore-modified carbon nanospheres, particularly ACNs-100 synthesized with the addition of 100 μL toluene, in terms of the initial discharge capacity, rate performance, and cycling stability. The interesting phenomenon of persistent capacity increase is ascribed to lithium ion movement within the graphite-like interlayer, resulting in ACNs-100 experiencing a capacity upswing from an initial 320 mAh g-1 to a zenith of 655 mAh g-1 over a thousand cycles at a rate of 2 C. The findings in this study highlight the pivotal role of tailored nanostructure engineering in optimizing energy storage materials.

Fabricating composites of multicomponent active substances embedded in carbon matrix for enhancing structural stability and redox kinetics of cathode in aqueous zinc-ion batteries

Rechargeable aqueous zinc-ion batteries (ZIBs) are recognized as a potential candidate for large-scale energy storage due to its high-security and low-expense aspects. However, the poor structural stability and sluggish redox kinetics of cathode material lead to the serious capacity fading and bad rate performances, which hinders its practical applications. Herein, a novel one-step pyrolysis strategy is conducted for fabricating the composites of multicomponent active substances (including WO3, Bi and Bi2O3) embedded in amorphous N-doped carbon matrix (BWO@C) using polydopamine-coated Bi2WO6 micro-flowers as the precursors. The amorphous nitrogen-doped carbon endows BWO@C composite to possess more active-sites and higher electrical conductivity for rapid electrons/ions transport, and meanwhile the active substances could be effectively utilized even undergoing thousands of charge/discharge cycles. Therefore, the resulting BWO@C as cathode for aqueous ZIBs exhibits satisfying rate performances as well as outstanding cycling stability. This work provides a simple and efficient pathway for designing the cathode materials with high conductivity and high structural stability to achieve remarkable performances and long life-span of aqueous ZIBs.

Recyclable fabrication of hollow N-doped amorphous carbon nanospindles with abundant short-range curved carbon fragments as bifunctional anode for lithium/sodium ion storage

A recyclable hard-template method is proposed to exploit spindle-shaped hollow nitrogen-doped amorphous carbon (h-NAC) with a large number of short-range curved carbon fragments as anodes for lithium/sodium ion batteries (LIBs/SIBs). Besides providing adsorption sites due to the high existence of oxygen-containing functional groups (CO and COOH), the heavily exposed edge regions also provide a favorable storage environment with high adsorption energy for Li+/Na+ due to their short-range curved structure. Importantly, the etching solution of hard templates can be recycled to generate the FeOOH nanospindles as a precursor through a simple chemical titration, which supplies a new idea for the green preparation of hollow materials. The h-NAC electrode is proven to be bifunctional for storing lithium and sodium ions, displaying favorable rate capability (255 mAh g−1 and 106 mAh g−1 at 5 A g−1 for LIBs and SIBs, respectively). After 1000 cycles at 1 A g−1, the reproducible capacities of the LIBs and SIBs kept 496 mAh g−1 and 181 mAh g−1, respectively.

Interlayer engineering and electronic regulation of MoSe2 nanosheets rolled hollow nanospheres for high-performance sodium-ion half/full batteries

Layered transition metal dichalcogenides are promising candidates for sodium storage but suffering from low intrinsic electronic conductivity and limited interlayer spacing for fast electron/ion transport, which restricts their high-rate capability and cycling stability. In this work, rGO@MoSe2/NAC hierarchical architectures, consisting of conductive reduced graphene oxide (rGO) supported by hollow nanospheres that are rolled from superlattices of alternatively overlapped MoSe2 and N-doped amorphous carbon (NAC) monolayers, are synthesized as a high-performance sodium storage anode. Theoretical calculations reveal the intercalation of NAC monolayer between two adjacent MoSe2 monolayers improving electronic conductivity of MoSe2 in both surface and internal bulk to fully accelerate electron transport and enhance Na+ ​adsorption. The interoverlapped MoSe2/NAC superlattice featuring a wide interlayer expansion (72.3 ​%) of MoSe2 dramatically decreases Na+ ​diffusion barriers for fast insertion/extraction. Moreover, the hollow nanospheres and the rGO conductive network contribute to a robust hiberarchy that can well release internal stress and buffer the volume expansion, thereby enabling outstanding structural stability. Consequently, the rGO@MoSe2/NAC anode exhibits excellent high-rate capability of 194 mAh g−1 and ultralong cyclability of 12 ​000 cycles with a low capacity fading rate of 0.0038 ​% per cycle at an ultra-high current of 50 ​A ​g−1, delivering the best high-rate cycling performance to date. Remarkably, the Na3V2(PO4)3‖rGO@MoSe2/NAC full cells also present outstanding cycling stability (600 cycles) at 10C rate, which proves the great potential in fast-charging applications.

MOF-derived N-doped carbon nanocages trap CoP nanoparticles anchored on rGO to modulate dielectric polarization behavior for microwave absorption

In order to gain a deeper insight into the effect of dielectric polarization behavior caused by defects and heterogeneous interfaces on microwave absorption capability, the structure of in situ grown cobalt phosphide in MOF-derived N-doped amorphous carbon nanocages (CoP/NC) anchored on reduced graphene oxide (rGO) sheets was used to control the number of defects and heterogeneous interfaces. The different dielectric polarization behaviors are expressed by the amplitude and range of the polarization relaxation peaks. More defects and heterogeneous interfaces not only cause more intense polarization loss, but also modulate the electromagnetic parameters to improve the impedance matching performance. The CoP/NC@rGO achieves strong absorption of −67.5 dB and absorption bandwidth of 7 GHz with only 4 wt%. First principles calculation shows the formation of interfacial dipole at the CoP-NC heterogeneous interface. This work provides a strategy for regulating microwave absorption properties by defect and heterogeneous interface-controlled polarization behavior.

Partial oxidation of methane to methyl oxygenates with enhanced selectivity using a single-atom copper catalyst on amorphous carbon support

In this study, we report a single-atom Cu catalyst on the amorphous carbon support for direct methane partial oxidation. The catalyst was prepared by the carbonization of Cu-doped ZIF-8 to implant single-atom Cu active centers that coordinate with four nitrogen (CuN4) on the amorphous N-doped carbon. Carbonization enhanced the oxidation resistance of the catalyst by preventing the oxidation of Cu-coordinating ligands, leading to a 40% reduction in CO2 production. Our prepared catalyst showed higher methanol selectivity than other single-atom copper catalysts. Mechanistic studies revealed that Cu and the surface carbon atom facilitated the dissociation of H2O2 into OOH and H, which further transformed into Cu–O and led to proton abstraction from methane. We highlight a simple approach to prepare a single-atom catalyst that is supported on amorphous N-doped carbon, derived from a metal-doped ZIF. This catalyst exhibits enhanced selectivity and stability for the partial oxidation of methane.

Joule heating-assisted tailoring Co-MOC derived chainmail catalyst to regulate peroxymonosulfate activation for tetracycline destruction: Singlet oxygen integrated direct electron transfer pathways

Rational design of stable and high-efficiency non-precious catalysts to activate peroxymonosulfate (PMS) is crucially important for recalcitrant pollutant elimination. In this study, we present a microwave-assisted combustion heat method to fabricate stable Co-MOC-800 as a highly efficient peroxymonosulfate (PMS) activator for tetracycline hydrochloride (TCH) degradation. Joule heating from short-time microwave irradiation enables the expeditious fabrication of Co-based metal–organic-complex (Co-MOC) precursor, which is carbonized to form the representative Co-MOC-800 chainmail catalyst with a maximum degradation rate of 97% in 10 min. This catalyst still possesses an excellent stability with highly remained activity of the initial cycle after five consecutive runs. The N-doped amorphous carbon encapsulated Co nanoparticles integrated Co-Nx sites play an essential role in activating PMS for TCH degradation through non-radial dominant pathways including singlet oxygen and direct electron transfer. Attributing to the non-radical pathways, the Co-MOC-800-catalyzed PMS activation exhibits relatively high anti-interference ability under different solution pH, inorganic anions and humic acid. Three reaction pathways for TCH degradation are proposed by recording the degradation intermediates, and the toxicity of the detected intermediates was evaluated. The present work provides a vivid example for simply fabricating efficient Co-based catalysts for recalcitrant pollutant elimination via activating PMS.

Nitrogen-Doped Carbon Coated Na3V2(PO4)2F3 Derived from Polyvinylpyrrolidone as a High-Performance Cathode for Sodium-Ion Batteries

Na super ionic conductor (NASICON)-type Na3V2(PO4)2F3 (NVPF) has been regarded as a prospective candidate of cathode materials for sodium-ion batteries due to its excellent structural stability, relatively high capacity and working voltage. However, the poor cyclability and rate capability, resulting from its low intrinsic electronic conductivity, have become a serious obstacle to their practical large-scale application. In this work, N-doped carbon coated NVPF composites (NVPF@NC) were successfully synthesized via a simple sol–gel method, in which low-cost polyvinylpyrrolidone was introduced as a nitrogen source. After high-temperature pyrolysis, a highly conductive N-doped carbon layer was in-situ constructed on the particle surface to enhance the sodium storage performance of NVPF. The optimized NVPF@NC cathode delivered high reversible capacity, excellent rate capability and long-term cycle life compared to pristine NVPF@C. The remarkable electrochemical performance of NVPF@NC cathode benefits from the modification strategy of introducing a heteroatom-doped carbon layer, triggering the formation of extrinsic defects and active sites in the N-doped amorphous carbon layer, which greatly enhances the electrical conductivity and the diffusion rate of sodium ions. This work provides a facile and effective approach for the preparation of N-doped carbon coated NVPF with remarkable sodium storage properties, which could be extended to other electrode materials electrochemical for energy storage.

Ga2O3 Quantum Dots with N-Doped Amorphous Carbon Fixed for Efficient Storage and Transfer of Lithium Ions by Introduction of Dopamine Hydrochloride.

The Ga2O3 anode has great potential due to its self-healing and high theoretical capacity in lithium-ion batteries. Like anodes with other transition metal oxides, the Ga2O3 anode has the problems of structural change and low electrical conductivity. The electrochemical performance of the Ga2O3 anode still needs to be improved. In this work, we synthesized a Ga2O3 quantum dots@N-doped carbon (Ga2O3-QD@NC) composite by hydrothermal reaction with a carbon source of dopamine hydrochloride, in which Ga2O3 quantum dots were dispersed in the interior of the amorphous carbon. Such a special structure is conducive to the high-speed migration of lithium ions and electrons and effectively inhibits volume expansion and agglomeration. Smaller and more uniform quantum dots facilitate efficient repair of the structure. Due to these advantages, the Ga2O3-QD@NC electrode has great electrochemical performance. The Ga2O3-QD@NC electrode has an initial discharge capacity of 1580 mAh g-1 with a high first Coulombic efficiency of 62.8% and a cycling capacity of 953 mAh g-1 under 0.1 A g-1. It even has a capacity of 460 mAh g-1 at 1 A g-1 after 300 cycles. This strategy can provide a new direction for the Ga2O3 anode in lithium-ion batteries with high capacity.

Novel Ni3S4/NiS/NC composite with multiple heterojunctions synthesized through space-confined effect for high-performance supercapacitors

The construction of heterojunctions in composite materials to optimize the electronic structures and active sites of energy materials is considered to be the promising strategy for the fabrication of high-performance electrochemical energy devices. In this paper, a one-step, easy processing and cost-effective technique for generating composite materials with heterojunctions was successfully developed. The composite containing Ni3S4, NiS, and N-doped amorphous carbon (abbreviated as Ni3S4/NiS/NC) with multiple heterojunction nanosheets are synthesized via the space-confined effect of molten salt interface of recrystallized NaCl. Several lattice matching forms of Ni3S4 with cubic structure and NiS with hexagonal structure are confirmed by the detailed characterization of heterogeneous interfaces. The C–S bonds are the key factor in realizing the chemical coupling between nickel sulfide and NC and constructing the stable heterojunction. Density functional theory calculations further revealed that the electronic interaction on the heterogeneous interface of Ni3S4/NiS can contribute to high electronic conductivity. The heterogeneous interfaces are identified to be the good electroactive region with excellent electrochemical performance. The synergistic effect of abundant active sites, the enhanced kinetic process and valid interface charge transfer channels of Ni3S4/NiS/NC multiple heterojunction can guarantee high reversible redox activity and high structural stability, resulting in both high specific capacitance and energy/power densities when it is used as the electrode for supercapacitors. This work offers a new avenue for the rational design of the heterojunction materials with improved electrochemical performance through space-confined effect of NaCl.

Dense T-Nb2O5/Carbon Microspheres for Ultrafast-(Dis)charge and High-Loading Lithium-Ion Batteries.

Orthorhombic niobium pentoxide (T-Nb2O5) is regarded as a potential anode material for lithium-ion batteries (LIBs) due to ultrafast charge/discharge and high safety. However, the poor electronic conductivity and low mass loading of nanostructured T-Nb2O5 limit its practical application in LIBs. Herein, we design and construct dense microspheres consisting of nanostructured T-Nb2O5 embedded in amorphous N-doped carbon (Nb2O5@NC) via a facile method to achieve fast ionic and electronic transport as well as a high mass loading. The dense micro-sized particles with an interconnected carbon network avoid the low mass loading and volumetric energy density of conventional nanostructures. Interconnected pores in the range of a few nanometers are also formed in the Nb2O5@NC microspheres. Notably, at a high mass loading of 12.8 mg cm-2, Nb2O5@NC can achieve a high specific capacity of 171.5 mAh g-1 and an areal capacity of 2.05 mAh cm-2, showing its high lithium storage capacity. The intercalation reaction mechanism with a small volume change during cycling at both crystal lattice and microsphere levels is confirmed by in situ X-ray diffraction and in situ high-resolution transmission electron microscopy. The elegant structure and the electrochemical reaction mechanism disclosed in the work is important for designing ultrafast-(dis)charge electrode materials.

Ni3Fe nanoparticles encapsulated by N-doped carbon derived from MOFs for oxygen evolution reaction

It has been a hot research topic to look for inexpensive alternative oxygen evolution reaction (OER) catalysts to replace noble metal-based materials due to their scarcity. Transition metals are ideal candidates because of their high abundance, impressive activities, and easy accessibility. However, a facile method leading to improved performance and stability is still needed. Herein, a highly efficient carbon-encapsulated bimetal catalyst derived from Ni-based metal-organic-frameworks (MOF) was successfully prepared through the low-temperature (350 ℃) pyrolysis of Prussian blue analogue (PBA) precursors under H 2 /Ar atmosphere. Cube-structured PBA as template and precursor，parameters during the pyrolysis process including temperature and calcination atmosphere can be tuned to control the structure and properties of the catalysts. Benefiting from the porous three-dimensional (3D) cubic structure and abundant defect-rich amorphous N-doped carbon shell, Ni 3 Fe@NC-350 exhibits excellent OER activity. The as-prepared catalysts exhibited excellent catalytic performance for OER in 1.0 M KOH with an overpotential of 237 mV to achieve 10 mA cm −2 . More importantly, the presented catalyst has an extremely good durability. • A simple low-temperature annealing method was developed to produce alloy encapsulated with N-doping carbon. • The NiFe PBA was employed as nitrogen and carbon source. • The increased activity of OER is due to the synergy of Ni 3 Fe alloy and N-doped carbon layer. • Theoretical calculations revealed that the synergistic effect of NiFe alloy nanoparticles and N-doped carbon layer.