Hollow Carbon Matrix Research Articles

Orbital Coupling of Dual-Atom Sites Boosts Electrocatalytic NO Oxidation and Dynamic Intracellular Response.

In situ measurement of nitric oxide (NO) in living tissue and single cells is highly important for achieving a profound comprehension of cellular functionalities and facilitating the precise diagnosis of critical diseases; however, the progress is greatly hindered by the weak affinity of ultratrace concentration NO in cellular environment toward electrocatalysts. Herein, a new strategy is reported for precisely constructing orbital coupled dual-atomic sites to enhance the affinity between the metal atomic sites and NO on a class of N-doped hollow carbon matrix dual-atomic sites Co─Ni (Co1Ni1-NC) for greatly boosting electrocatalytic NO performance. The as-synthesized Co1Ni1-NC demonstrates a substantially higher current density than Ni1-NC and Co1-NC, coupled with exceptional stability with a negligible degradation rate of 0.6 µA·cm-2·h-1, which is the best among the state-of-the-art electrocatalysts for NO oxidation. Experimental and theoretical investigations collectively reveal that the pivotal role of d-d orbit coupling between Co and Ni sites enables Ni to acquire additional electrons, leading to the occupation of Ni's 3dxy/yz within the 2π orbitals of NO, thus weakening the N≡O triple bond and concurrently accelerating NO adsorption kinetics. It is demonstrated that Co1Ni1-NC-coated nanoelectrode can achieve the in situ sensing of NO in living organs and single cells.

Synergistic effect of oxygen defects and calabash-like hollow carbon matrix enables VO2 as high-performance cathode for zinc ion battery

Vanadium dioxide (VO2) materials exhibit significant theoretical specific capacity, which is ascribed to multi-electron transfer reactions and unique tunneled structures. However, the low electronic conductivity and sluggish reaction kinetics of VO2 have impeded its further development. Hence, in this study, we employed a synergistic strategy of defect engineering and compositing with a calabash carbon matrix to reduce Zn2+ diffusion barriers and accelerate electron transfer. The VO2 cathode provided a high specific capacity at a low rate of 303 mA h g−1 at 0.1 A g−1 after 191 cycles, along with good rate performance (168 mA h g−1 at 10 A g−1) and satisfactory long-term stability (170 mA h g−1 at 1 A g−1 after 1100 cycles). The exhaustive structural analyses indicated that oxygen vacancies accelerated the Zn2+ diffusion rate, while a uniform calabash-like hollow carbon matrix improved electronic conductivity during cycling. Moreover, ex-situ measurements demonstrated that during discharge, the composite cathode transformed to layered Zn3+x(OH)2V2O7·2H2O, which then facilitated the subsequent intercalation of Zn2+. This cooperative strategy advances the practical application of aqueous zinc ion batteries by leveraging vanadium-based electrodes.

Engineering of active site coupling to facilitate interatomic charge transfer for bifunctional oxygen electrocatalysis

Interatomic charge transfer emerges as a robust technique for enhancing catalytic efficacy in key energy reactions, specifically the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Despite its potential, advancing simultaneous improvements in reversible oxygen catalysis pose considerable challenges. Herein, we detailed an active site coupling engineering method to create a CoCu@NSC bifunctional oxygen electrode. In this configuration, OER-active Cu sites were alloyed with ORR-active Co within a N/S-doping carbon nanobox. This arrangement yielded a half-wave potential of 0.924 V for ORR, alongside an overpotential of η10 = 356 mV for OER. The fabricated CoCu@NSC cathode yielded a discharge capacity of 768 mAh/gZn, a peak power density of 295 mW/cm2, and extensive cycling durability. Work function assessments indicated that the chemical integration of Co and Cu components at the atomic level promoted interfacial charge redistribution, effectively optimizing the adsorption-desorption dynamics of intermediates at the active sites, thereby substantially enhancing the catalytic performance for both OER and ORR. Additionally, doping with N/S species enhanced the conductivity of the hollow carbon matrix, facilitating more effective mass and charge transport pathways. These insights illuminate a compelling approach for the design and synthesis of effective bifunctional oxygen electrodes that is pivotal for advanced energy storage advice.

Modulating Coordination of Iron Atom Clusters on N,P,S Triply‐Doped Hollow Carbon Support towards Enhanced Electrocatalytic Oxygen Reduction

AbstractConstructing atom‐clusters (ACs) with in situ modulation of coordination environment and simultaneously hollowing carbon support are critical yet challenging for improving electrocatalytic efficiency of atomically dispersed catalysts (ADCs). Herein, a general diffusion‐controlled strategy based on spatial confining and Kirkendall effect is proposed to construct metallic ACs in N,P,S triply‐doped hollow carbon matrix (MACs/NPS−HC, M=Mn, Fe, Co, Ni, Cu). Thereinto, FeACs/NPS−HC with the best catalytic activity for oxygen reduction reaction (ORR) is thoroughly investigated. Unlike the benchmark sample of symmetrical N‐surrounded iron single‐atoms in N‐doped carbon (FeSAs/N−C), FeACs/NPS−HC comprises bi‐/tri‐atomic Fe centers with engineered S/N coordination. Theoretical calculation reveals that proper Fe gathering and coordination modulation could mildly delocalize the electron distribution and optimize the free energy pathways of ORR. In addition, the triple doping and hollow structure of carbon matrix could further regulate the local environment and allow sufficient exposure of active sites, resulting in more enhanced ORR kinetics on FeACs/NPS−HC. The zinc‐air battery assembled with FeACs/NPS−HC as cathodic catalyst exhibits all‐round superiority to Pt/C and most Fe‐based ADCs. This work provides an exemplary method for establishing atomic‐cluster catalysts with engineered S‐dominated coordination and hollowed carbon matrix, which paves a new avenue for the fabrication and optimization of advanced ADCs.

Modulating Coordination of Iron Atom Clusters on N,P,S Triply-Doped Hollow Carbon Support towards Enhanced Electrocatalytic Oxygen Reduction.

Constructing atom-clusters (ACs) with in situ modulation of coordination environment and simultaneously hollowing carbon support are critical yet challenging for improving electrocatalytic efficiency of atomically dispersed catalysts (ADCs). Herein, a general diffusion-controlled strategy based on spatial confining and Kirkendall effect is proposed to construct metallic ACs in N,P,S triply-doped hollow carbon matrix (MACs /NPS-HC, M=Mn, Fe, Co, Ni, Cu). Thereinto, FeACs /NPS-HC with the best catalytic activity for oxygen reduction reaction (ORR) is thoroughly investigated. Unlike the benchmark sample of symmetrical N-surrounded iron single-atoms in N-doped carbon (FeSAs /N-C), FeACs /NPS-HC comprises bi-/tri-atomic Fe centers with engineered S/N coordination. Theoretical calculation reveals that proper Fe gathering and coordination modulation could mildly delocalize the electron distribution and optimize the free energy pathways of ORR. In addition, the triple doping and hollow structure of carbon matrix could further regulate the local environment and allow sufficient exposure of active sites, resulting in more enhanced ORR kinetics on FeACs /NPS-HC. The zinc-air battery assembled with FeACs /NPS-HC as cathodic catalyst exhibits all-round superiority to Pt/C and most Fe-based ADCs. This work provides an exemplary method for establishing atomic-cluster catalysts with engineered S-dominated coordination and hollowed carbon matrix, which paves a new avenue for the fabrication and optimization of advanced ADCs.

Atomic Engineering Modulates Oxygen Reduction of Hollow Carbon Matrix Confined Single Metal-Nitrogen Sites for Zinc-Air Batteries.

The systematical understanding of metal-dependent activity in electrocatalyzing oxygen reduction reaction (ORR), a vital reaction with sluggish kinetics for zinc-air batteries, remains quite unclear. An atomic and spatial engineering modulating ORR activity over hollow carbon quasi-sphere (HCS) confined in a series of single M-N (M = Cu, Mn, Ni) sites is reported here. Based on the theoretical prediction and experimental validation, Cu-N4 site with the lowest overpotential shows a better ORR kinetics than Mn-N4 and Ni-N4 . The ORR activity of single-atom Cu center can be further improved by decreasing the coordination number of N to two, namely Cu-N2 , due to the enhancement of electrons with lower coordination structure. Benefitting from the unique spatial confinement effect of the HCS structure in modulating electronic feature of active sites, the Cu-N2 site confined in HCS also delivers highly improved ORR kinetics and activity relative to that on planner graphene. Additionally, the best catalyst holds excellent promise in the application of zinc-air batteries. The findings will pave a new way to atomically and electronically tune active sites with high efficiency for other single-atom catalysts.

Synergistic Transition-Metal Selenide Heterostructure as a High-Performance Cathode for Rechargeable Aluminum Batteries.

We synthesize and characterize a rechargeable aluminum battery cathode material composed of heterostructured Co3Se4/ZnSe embedded in a hollow carbon matrix. This heterostructure is synthesized from a metal-organic framework composite, in which ZIF-8 is grown on the surface of ZIF-67 cube. Both experimental and theoretical studies indicate that the internal electric field across the heterostructure interface between Co3Se4 and ZnSe promotes the fast transport of electron and Al-ion diffusion. As a result, the heterostructured Co3Se4/ZnSe demonstrates superior specific capacity and cycle stability compared to the single-phase Co3Se4 and ZnSe cathode materials.

Hierarchical Porous Carbon Spheres Loaded CoOX (CoOx/HPCS) for Efficient Oxygen Reduction Reaction in Alkaline Media

AbstractThe development of efficient non‐noble metal catalysts for oxygen reduction reaction (ORR) in alkaline media is vital for wide application of numerous energy conversion devices. In this work, the CoOx/HPCS catalysts are demonstrated to show excellent activity toward ORR with more positive peak potential, initial potential, and half‐wave potential than pure HPCS. Moreover, the CoOx/HPCS exhibits a long‐term stability and a stronger methanol resistance compared to 20% Pt/C. The outstanding ORR activity for CoOx/HPCS is owing to its excellent characteristics, like: 1) a good conductivity of the carbon matrix to improve the electron transfer ability; 2) the rich hierarchical hollow carbon matrix and high surface area conducive to providing more accessible active sites and improving mass transportation; 3) the defect caused by oxygen vacancy beneficial for enhancing catalytic activity; 4) the synergistic effect between CoOx and HPCS support being crucial for ORR, thence enhancing the electrochemical performance of CoOx/HPCS.

Synergic adsorption and catalytic conversion of polysulfides based on polar Mo2C and pyridinic N for the enhanced electrochemical performance of Li–S batteries

As a most promising potential next-generation energy storage system, lithium-sulfur batteries (Li–S batteries) received great attention in recent years. However, how to effectively prevent the shuttling effect and accelerate the redox reaction kinetics of polysulfides are still a challenge. Herein, a strategy of using the soft template as a pore-forming agent was proposed to prepare Mo2C/nitrogen-doped carbon hollow microflowers (marked as H–Mo2C/NC MFs), which was used as an efficient absorbent and electrocatalyst of polysulfides for Li–S batteries. Due to the physical limitations of assembling the special nanosheet into a hollow carbon matrix in the shape of a microflower, the H–Mo2C/NC MFs can be used as an appropriate S loading substrate. With the synergistic chemisorption from pyridine N sites and high content polar Mo2C nanoparticles, the as-prepared H–Mo2C/NC MFs can provide enhancing adsorption and catalytic conversion for polysulfides. As a result, the H–Mo2C/NC/S MFs-based cathode provides a high initial discharge capacity of 1104.8mAh/g at 0.2C. Even at the high rate of 1.0C, the initial capacity of 705.2mAh/g still shows good electrochemical performance, and in 1000 cycles, the average capacity decay rate is only 0.016%, with supercycle stability. This article provided a new strategy for a novel viewpoint for the reasonable design of conductive and polar materials for efficient and durable Li–S batteries.

Ultrasmall Mn3O4 nanocrystalline@three-dimensional macroporous honeycomb-like hollow carbon matrix for high-rate and long-lifetime zinc-ion storage

Low specific capacity and poor cycling performance are two main problems of Mn-based oxides that hinder their application in aqueous zinc-ion batteries (ZIBs). Herein, we design a facile sacrificial template method to construct a unique three-dimensional macroporous honeycomb-like hollow carbon matrix, and then grow ultrasmall Mn3O4 nanocrystalline with the diameter of 5 nm inside the hollow carbon matrix. The composite has large surface area (56.9 m2 g−1) and high Mn3O4 content (about 47.1%). When the composite is used as the cathode material of ZIBs, it exhibits extraordinary discharge capacity of 845 mAh g−1 at 1 A g−1, impressive rate capability with average discharge capacity of 46 mAh g−1 at 10 A g−1, and superior long-term cycling performance with discharge capacity of 123 mAh g−1 at 5 A g−1 after 800 cycles. Electrochemical kinetics measurements and ex-situ XRD, SEM and TEM further demonstrate that the macroporous honeycomb-like hollow carbon matrix significantly increases electronic conductivity and structural stability of Mn3O4. Besides, electrochemical activity and surface capacitive effect of Mn3O4 are also greatly enhanced by its ultrasmall size.

G-C3N4 templated synthesis of the tubular CoFe/N doped carbon composite as advanced bifunctional oxygen electrocatalysts for zinc-air batteries

Rational incorporating transition metal into porous heteroatom-doped carbon is intensively investigated as an effective strategy to achieve high-performance and bifunctional requirements. Herein, we fabricated the hollow composite that CoFe alloy nanoparticles decorated on the tubular N-doped carbon (denoted as T-CoFe/NC) by soft-templating strategy. In order to effectively incorporate the CoFe alloy into nitrogen doped hollow carbon matrix, g-C3N4 nanotubes were selected as the template to attain high contents of nitrogen doping for tubular carbon matrix. Meanwhile, the coordination effect between tannic acid and metal ions is utilized to limit the metal agglomeration in the process of pyrolysis. Consequently, the resultant catalyst shows an outstanding ORR activity with the half-wave potential of 0.86 V and outstanding stability with only a 2 mV decay after 10,000 cycles. T-CoFe/NC also displays comparable overpotential to the RuO2 at 10 mA cm−2. The high bifunctional electrocatalytic activity is attributed to the unique tubular structure and the combination of Co with Fe can optimize the interaction between the oxygenic species and metal surfaces, enhancing the catalytic activity. And T-CoFe/NC based zinc-air battery exhibits excellent power density, large capacity and good cycling stability.

Defect-rich CeO2 in a hollow carbon matrix engineered from a microporous organic platform: a hydroxide-assisted high performance pseudocapacitive material.

A microporous organic polymer (MOP) was utilized for the engineering of nanoparticulate CeO2 in a hollow carbon matrix (H-C/CeO2). After CeO2 nanoparticles were incorporated into a hollow MOP platform (H-MOP) through the decomposition of cerium acetate, successive carbonization produced H-C/CeO2. The redox feature of defective CeO2 in a conductive carbon matrix induced promising pseudocapacitive behavior. In particular, the H-C/CeO2 showed excellent electrochemical performance in an alkaline electrolyte (KOH), due to the hydroxide ion-assisted redox behavior of defective CeO2. H-C/CeO2-3 with an optimized amount of CeO2 showed specific capacitances of up to 527 (@0.5 A g-1) and 493 F g-1 (@1 A g-1). Even at high current densities of 10 and 20 A g-1, the H-C/CeO2-3 maintained high capacitances of 458 and 440 F g-1, respectively. After 10 000 cycling tests, the H-C/CeO2-3 retained the 94-95% capacitance of the first cycle.

PH-dependent hydrogen evolution using spatially confined ruthenium on hollow N-doped carbon nanocages as a Mott–Schottky catalyst

We demonstrate Ru nanoparticles confined on a N-doped hollow carbon matrix as a wide pH hydrogen evolution electrocatalyst. The formation of a Mott–Schottky heterojunction at the strongly coupled Ru/N-doped C interface enhances the catalysis.

Ultralow Ru-Induced Bimetal Electrocatalysts with a Ru-Enriched and Mixed-Valence Surface Anchored on a Hollow Carbon Matrix for Oxygen Reduction and Water Splitting.

Rational design of trifunctional electrocatalysts with robust efficiency used for oxygen reduction, oxygen evolution, and hydrogen evolution reactions (ORR, OER, and HER) is of significance to renewable energy conversion techniques, which remains a challenging issue. This study integrates dominant Co/Co3O4 with a small fraction of RuO2 and the CoRu alloy anchored on a hollow carbon matrix, originating from the novel Ru-doped hollow metal-organic framework (MOF) precursor, which is synthesized via tannic etching and ion exchange. Notably, the introduced ultralow Ru (1.28 wt %) not only generates new Ru-based species but also induces a Ru-enriched surface with abundant oxygen vacancies. Moreover, a suitable balance among different valencies of Co or Ru can be tuned by oxidation time, resulting in preferable Co2+ and Ru4+ species. Triggered by these unparalleled surface properties along with good conductivity, hollow structure, and the synergistic effect of multiple active sites, the resulting CoRu-O/A@hollow nitrogen-doped carbon (HNC) shows robust catalytic performance for ORR/OER/HER in an alkaline electrolyte. Typically, it exhibits a potential gap of 0.662 V for OER/ORR and enables an alkaline water electrolyzer with a cell voltage of 1.558 V at 10 mA cm-2. This work would serve as guidance for well construction of transition-metal-based trifunctional electrocatalysts by the MOF-assisted strategy or the modulation effects of low-content Ru.

Enhancing potassium-ion battery performance by MoS2 coated nitrogen-doped hollow carbon matrix

As an important alternative to lithium-ion batteries (LIBs), potassium-ion batteries (PIBs) have attracted much attention due to the abundance and low cost of potassium, however, it is still a great challenge to select suitable anode materials to accommodate the large-size of K-ion. Herein, MoS2 nanosheets were coated on the porous carbon polyhedron derived from zeolite imidazole framework-8 (designated as PCP@MoS2) and employed as the anode materials for PIBs. Benefiting from the high electrical conductivity, strong structure stability of the nitrogen-doped carbon polyhedron and the layered crystal structure of MoS2, the reversible capacity can be maintained at 375 mA h g−1 after 100 cycles at 100 mA g−1, 200 mA h g−1 after 200 cycles at 500 mA g−1 as well as excellent rate property. The excellent electrochemical performance can be attributed to the unique hybrid structures and the synergistic effects between MoS2 and N doped porous carbon polyhedron, which could enhance the electronic conductivity, shorten the K-ion diffusion distance, mitigate the agglomeration of the MoS2 nanosheets, relieve the volume variation, and provide plenty of active sites for K ion accomodation.

Dispersed Nickel Cobalt Oxyphosphide Nanoparticles Confined in Multichannel Hollow Carbon Fibers for Photocatalytic CO2 Reduction

AbstractMaterials for high‐efficiency photocatalytic CO2 reduction are desirable for solar‐to‐carbon fuel conversion. Herein, highly dispersed nickel cobalt oxyphosphide nanoparticles (NiCoOP NPs) were confined in multichannel hollow carbon fibers (MHCFs) to construct the NiCoOP‐NPs@MHCFs catalysts for efficient CO2 photoreduction. The synthesis involves electrospinning, phosphidation, and carbonization steps and permits facile tuning of chemical composition. In the catalyst, the mixed metal oxyphosphide NPs with ultrasmall size and high dispersion offer abundant catalytically active sites for redox reactions. At the same time, the multichannel hollow carbon matrix with high conductivity and open ends will effectively promote mass/charge transfer, improve CO2 adsorption, and prevent the metal oxyphosphide NPs from aggregation. The optimized hetero‐metal oxyphosphide catalyst exhibits considerable activity for photosensitized CO2 reduction, affording a high CO evolution rate of 16.6 μmol h−1 (per 0.1 mg of catalyst).

Dispersed Nickel Cobalt Oxyphosphide Nanoparticles Confined in Multichannel Hollow Carbon Fibers for Photocatalytic CO2 Reduction.

Materials for high-efficiency photocatalytic CO2 reduction are desirable for solar-to-carbon fuel conversion. Herein, highly dispersed nickel cobalt oxyphosphide nanoparticles (NiCoOP NPs) were confined in multichannel hollow carbon fibers (MHCFs) to construct the NiCoOP-NPs@MHCFs catalysts for efficient CO2 photoreduction. The synthesis involves electrospinning, phosphidation, and carbonization steps and permits facile tuning of chemical composition. In the catalyst, the mixed metal oxyphosphide NPs with ultrasmall size and high dispersion offer abundant catalytically active sites for redox reactions. At the same time, the multichannel hollow carbon matrix with high conductivity and open ends will effectively promote mass/charge transfer, improve CO2 adsorption, and prevent the metal oxyphosphide NPs from aggregation. The optimized hetero-metal oxyphosphide catalyst exhibits considerable activity for photosensitized CO2 reduction, affording a high CO evolution rate of 16.6 μmol h-1 (per 0.1 mg of catalyst).

Unveiling the Activity Origin of Electrocatalytic Oxygen Evolution over Isolated Ni Atoms Supported on a N-Doped Carbon Matrix.

Exploring highly efficient electrocatalysts for the oxygen evolution reaction (OER) and unveiling their activity origin are pivotal for energy conversion technologies. Herein, atomically distributed Ni sites over a N-doped hollow carbon matrix are reported as a promising electrocatalyst for OER in alkaline conditions. Significantly boosted activity is observed after the decoration of the active Ni sites with well-controlled coordination geometry. Results of X-ray absorption spectroscopy investigation and density functional theory (DFT) calculation reveal that the effective electronic coupling via the Ni-N coordination can move down the Fermi level and lower the adsorption energy of intermediates, thus resulting in the facilitated OER kinetics.

Programmed degradation of a hierarchical nanoparticle with redox and light responsivity for self-activated photo-chemical enhanced chemodynamic therapy

Chemodynamic therapy (CDT) has recently emerged as a promising treatment for cancer due to the high specificity of CDT towards tumor microenvironment (TME). However, the low efficiency of reactive oxygen species (ROS) generation and the robust ROS defensive mechanisms in cancer cells remain critical hurdles for current CDT. Addressing both challenges in a single platform, we developed a novel redox and light-responsive (RLR) nanoparticle with a core-shell structure. Remarkably, our hierarchical RLR nanoparticle is composed of an ultrasmall Fe3O4 nanoparticle engineered framework of hollow carbon matrix core and a nanoflower-like MnO2 shell. Under the abundant overexpressed glutathione (GSH) and acidic nature in TME, the RLR nanoparticle was programmed to degrade and self-activate CDT-induced cancer-killing by accelerating ROS generation via overcoming the ROS defensive mechanisms based on the depletion of intracellular GSH, the sequential production of theranostic ion species (e.g., Mn2+ and Fe2+), a spatiotemporal controllable photothermal hyperthermia and a redox triggered chemotherapeutic drug release. Additionally, the carbon framework of RLR nanoparticle could collapse by leaching of iron ions. An excellent selective and near-complete tumor suppression based on the RLR nanoparticles through a strong synergy between CDT, PTT and anti-cancer drugs was demonstrated via in vitro and in vivo anti-tumoral assays.

Fabrication of molybdenum and tungsten oxide, sulfide, phosphide (MoxW1-xO2/MoxW1-xS2/MoxW1-xP) porous hollow nano-octahedrons from metal-organic frameworks templates as efficient hydrogen evolution reaction electrocatalysts

A metal-organic frameworks-derived sulfuration and phosphorization method is developed for constructing a hydrogen evolution reaction (HER) electrocatalyst (MoWOSP@C), which is composed of MoxW1-xO2 nanoparticles, MoxW1-xS2 nanosheets, and MoxW1-xP nanoparticles coated with a porous hollow carbon matrix. The three-dimensional MoWOSP@C nano-octahedron shows excellent catalytic activity with a low overpotential of −118 mV at a current density of −10 mA cm−2 and a small Tafel slope of 74.1 mV dec−1, which are all higher than those of the single phase components. The outstanding performance of the MoWOSP@C is due to the highly exposed active sites and synergistic effects of the MoxW1-xS2 and MoxW1-xP, carbon conductive matrix and mesoporous hollow structures.