Co-doped Hollow Carbon Research Articles

Facile synthesis of nitrogen and sulfur co-doped hollow microsphere polymers from benzothiazole containing wastewater for water treatment

Advanced oxidation is a very efficient method in wastewater treatment, but it is a waste of resources to directly oxide the high concentration of valuable organics into carbon dioxide and water. In this paper, the combination of persulfate and wet air oxidation was developed to recover organics from high concentration of wastewater, along with high mineralization of the residual organics. Nitrogen and sulfur co-doped hollow spherical polymers with narrow size distribution was recovered from the simulated benzothialzole (BTH) wastewater in this facile way, along with chemical oxygen demand (COD) removal rate higher than 90%. The formation route of the polymers was intensively studied based on detailed analysis of different kinds of reaction intermediates. The polymers can be further carbonized into co-doped hollow carbon microsphere, which showed better performance in organic contaminants removal than a commercial activated carbon both in adsorption or catalytic persulfate oxidation. This proposed a new strategy to simultaneously combine oxidation and polymerization for resource recovery from wastewater with high concentration of heterocyclic compounds.

Well-dispersed pyrite-type RuS2 nanocrystals anchored on porous nitrogen and sulfur co-doped hollow carbon spheres for enhanced alkaline hydrogen evolution

The hydrogen evolution reaction (HER) activity in alkaline condition is generally suppressed due to sluggish water dissociation–related Volmer process. Consequently, developing new highly-active and cost-efficient electrocatalysts for the alkaline hydrogen production is greatly desirable for achieving sustainable water splitting in industrial plants. Pyrite-type RuS2 is a potential excellent electrocatalyst for alkaline HER but the related research is still in its infancy. Herein, well-dispersed crystalline RuS2 nanoparticles (c-RuS2 NPs) with ultrasmall particle size anchored on porous nitrogen and sulfur co-doped hollow carbon spheres (NSC) are synthesized for alkaline HER electrocatalysis. The conductive and porous hollow carbon spheres with nitrogen and sulfur doping is used as the effective support to provide abundant anchoring sites and modify the electronic structure of RuS2, beneficial to increasing the active sites and improving the intrinsic activity. Furthermore, the crystallinity modulation of ruthenium sulfide also has a significant impact on HER activity. In 1.0 M KOH solution, the proposed c-RuS2 NPs/NSC catalyst exhibits admirable activity for HER electrocatalysis with a low overpotential of 11 mV at a current density of 10 mA cm−2 and a small Tafel slope of 35.4 mV dec−1. With low Ru loading, superior hydrogen evolution in alkaline media is achieved for c-RuS2 NPs/NSC compared to the commercial Pt/C and the reported ruthenium-sulfide-based electrocatalysts.

Engineering hollow metal ion-phenolic capsules and metal-doped hollow mesoporous carbon spheres with “full green” style

Hollow metal ion-phenolic capsules (HMPCs) were synthesized through the combination of chelation with multiple hydrogen bonding that derive from the interaction of tannic acid (TA) and Pluronic F127. In this strategy, TA, a renewable and natural polyphenol, plays main role in the whole reaction process: a) create the “TA/F127 emulsion” driven by the multiple hydrogen bonding; b) construct the skeleton of HMPCs via the coordination with CuⅡ. Furthermore, we expanded this advanced concept into the fabrication of metal-doped hollow mesoporous carbon spheres (MHMCSs) elegantly and obtained Cu-Fe co-doped hollow mesoporous carbon spheres with 3.9 nm pore size and high specific surface area (365 m2/g). Compared to existing technology, the redundant treatments (e.g. hydrothermal treatment, sacrificial template removal and quite long reaction time) and toxic raw materials (e.g. formaldehyde, resorcinol) have been abandoned. Full green concept throughout the whole synthesis process presents an elegant paradigm for the preparation of HMPCs and MHMCSs.

Nitrogen, Sulfur, and Phosphorus Codoped Hollow Carbon Microtubes Derived from Silver Willow Blossoms as a High-Performance Anode for Sodium-Ion Batteries

Hard carbon materials have been considered as one of the most promising candidates as the anode in sodium-ion batteries. However, scale application of state-of-the-art hard carbon anodes is still hampered on account of their complicated, toxic, and time-consuming preparation techniques. In the present paper, silver willow blossoms composed of natural micrometer-scale fibers are employed to construct N, S, and P codoped hollow carbon microtubes (HCMTs) by direct high-temperature carbonization. The HCMT has a nanoscale wall with several micrometer-sized hollow cavities, which is facilitated to optimize the sodium-ion transfer. In addition, the temperature-dependent, tailorable interlayer spacing coupled with doped heteroatoms is able to provide sufficient energy storage sites. By combining these unique structural advantages, the HCMT exhibits impressive sodium storage performance. The HCMT sample pyrolyzed under 1300 °C is able to deliver a highly reversible capacity of 302 mAh g–1, and after repeated charge/discharge for 100 times, the capacity retains 301 mAh g–1, indicating no visible degradation. Moreover, under a large current density up to 1 A g–1, a high capacity of 201 mAh g–1 is still achieved, demonstrating good rate capability.

In situ W/O Co-doped hollow carbon nitride tubular structures with enhanced visible-light-driven photocatalytic performance for hydrogen evolution

Heteroatom co-doping has been considered as an effective strategy to simultaneously overcome intrinsic shortcomings of g-C3N4 to achieve enhanced photocatalytic properties, in which the involved dopants could play its role in altering electronic structure, optical absorption and charge separation of the catalyst. Herein, W/O co-doped hollow g-C3N4 tubular structures are successfully obtained for the first time via a one-step thermal decomposition. By W/O co-doping, architecture of g-C3N4 is able to be modulated with enhanced optical absorption towards visible region. In addition, narrowed band gap and restrained charge recombination are conducive for the excitation of electron-hole pairs and transportation. Photocatalytic water splitting tests indicate that the co-doped hollow tubular g-C3N4 structures enable superior activity for generating hydrogen up to 403.57 μmol g−1 h−1 driven by visible light, nearly 2.5 times as high as that of pristine g-C3N4. This work presents a rational strategy to design co-doped g-C3N4 as an efficient visible-light-driven photocatalyst.

S/N Co-Doped Hollow Carbon Particles for Oxygen Reduction Electrocatalysts Prepared by Spontaneous Polymerization at Oil-Water Interfaces.

We herein report that sulfur and nitrogen co-doped hollow spherical carbon particles can be applied to oxygen reduction reaction (ORR) electrocatalysts prepared by calcination of polydopamine (PDA) hollow particles. The hollow structure of PDA was formed by auto-oxidative interfacial polymerization of dopamine at the oil and water interface of emulsion microdroplets. The PDA was used as the nitrogen source as well as a platform for sulfur-doping. The obtained sulfur and nitrogen co-doped hollow particles showed a higher catalytic activity than that of nonsulfur-doped particles and nonhollow particles. The high ORR activity of the calcined S-doped PDA hollow particles could be attributed to the combination of nitrogen and sulfur active sites and the large surface areas owing to a hollow spherical structure.

MnO2 nanosheets grown on N and P co-doped hollow carbon microspheres for high performance asymmetric supercapacitor

The rapid development of supercapacitors has led to an increasing demand for the exploitation of stable and excellent electroactive electrode materials. Herein, a novel hybrid material of N, P co-doped hollow carbon microspheres (N/P-HCS) and ultrathin MnO2 nanosheets was facilely constructed for the electrode material of supercapacitors through a two-step synthetic strategy including the preparation of N/P-HCS and subsequent growth of MnO2 nanosheets on N/P-HCS. The N/P-HCS@MnO2 hybrid possesses a N/P-HCS core and a porous shell composed of ultrathin MnO2 nanosheets. Moreover, the morphology and content of MnO2 in the hybrid can be controlled by designing the stoichiometric chemical reaction between N/P-HCS and KMnO4. The hybrid electrode exhibits excellent electron transport, fast electrolyte ions diffusion, rapid and reversible Faradaic reaction, and good rate performance. Additionally, a green asymmetric supercapacitor was manufactured using typical hybrid N/P-HCS@MnO2-30 as positive electrode and N/P-HCS as negative electrode, which displayed a high energy density of 32.21 Wh kg−1 at a power density of 449.8 W kg−1 and excellent cycling stability (capacitance retention of 94.5% after 3000 cycles). These results show that the N/P-HCS@MnO2 might be an attractive electrode material for practical application in advanced supercapacitor.

Embedding Co2P nanoparticles into co-doped carbon hollow polyhedron as a bifunctional electrocatalyst for efficient overall water splitting

The reasonable design and construction of non-precious metal electrocatalysts with low cost and high performance is critical for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, a facile polymerization-pyrolysis method is proposed to encapsulate Co2P nanoparticles in co-doped hollow carbon shell by using ZIF-67 and P-containing polymers as precursor. The unique construction not only effectively prevents nanoparticles from detaching, showing good stability after long-term testing, but also provides abundant active sites, large surface areas and large pore volumes, enabling the electrolyte and electrode material to full contact. As expected, the Co2P/NPSC-800 performs superior HER performance with low overpotential of 173 mV at 10 mA cm−2 and excellent stability of 88% retention for 35 h and OER performance with low overpotential of 320 mV at 10 mA cm−2, which endows Co2P/NPSC-800 with good catalytic activity in overall water splitting. Furthermore, density functional theory (DFT) calculations reveal that the metallic property and the decreased reaction barriers of Co2P can promote the catalytic reactions. This work offers an effective route in synthesizing other transition metal phosphides with high catalytic properties.

Construction of Bimetallic Selenides Encapsulated in Nitrogen/Sulfur Co-Doped Hollow Carbon Nanospheres for High-Performance Sodium/Potassium-Ion Half/Full Batteries.

Metallic selenides have been widely investigated as promising electrode materials for metal-ion batteries based on their relatively high theoretical capacity. However, rapid capacity decay and structural collapse resulting from the larger-sized Na+ /K+ greatly hamper their application. Herein, a bimetallic selenide (MoSe2 /CoSe2 ) encapsulated in nitrogen, sulfur-codoped hollow carbon nanospheres interconnected reduced graphene oxide nanosheets (rGO@MCSe) are successfully designed as advanced anode materials for Na/K-ion batteries. As expected, the significant pseudocapacitive charge storage behavior substantially contributes to superior rate capability. Specifically, it achieves a high reversible specific capacity of 311 mAh g-1 at 10 A g-1 in NIBs and 310 mAh g-1 at 5 A g-1 in KIBs. A combination of ex situ X-ray diffraction, Raman spectroscopy, and transmission electron microscopy tests reveals the phase transition of rGO@MCSe in NIBs/KIBs. Unexpectedly, they show quite different Na+ /K+ insertion/extraction reaction mechanisms for both cells, maybe due to more sluggish K+ diffusion kinetics than that of Na+ . More significantly, it shows excellent energy storage properties in Na/K-ion full cells when coupled with Na3 V2 (PO4 )2 O2 F and PTCDA@450 °C cathodes. This work offers an advanced electrode construction guidance for the development of high-performance energy storage devices.

Synthesis and electrochemical performance of core-shell NiCo2S4@nitrogen, sulfur dual-doped carbon composites via confined sulfidation strategy in a polydopamine nanoreactor

Abstract Nickel cobalt binary sulfides (NiCo2S4 ) have attracted huge attention as a promising anode material for lithium-ion batteries (LIBs). Herein, a polydopamine (PDA) shell with a controlled thickness was in-situ polymerized on a nanohorn-shaped Ni-Co precursor (Ni-Co-Pre), thus obtaining a core-shell Ni-Co-Pre@PDA, and then a high-temperature sulfidation was utilized to convert the Ni-Co-Pre@PDA into the NiCo 2S4 confined in nitrogen, sulfur co-doped hollow carbon nanohorns (NiCo2S4@NS-HCN) using cheap and environmental-friendly sulfur powder as sulfur sources. During the sulfidation, the Ni-Co-Pre core was converted into the NiCo2S4 , while the PDA shell as a nanoreactor was carbonized into the NS-HCN with simultaneous co-doping of nitrogen and sulfur. Benefitting from high-efficiency redox reactions of NiCo 2S4 and efficient structural protections of conductive carbon shells, the NiCo2S4 @NS-HCN electrodes showed significantly enhanced electrochemical properties including high reversible specific capacity of 1235 mA h g -1 at 0.1 A g-1 and excellent rate/cycling capability (69% capacity retention after 100 cycles). This study thus provides a simple and efficient confined sulfidation strategy for construction of binary transition-metal sulfides for LIB anode materials.

A high-energy sodium-ion capacitor enabled by a nitrogen/sulfur co-doped hollow carbon nanofiber anode and an activated carbon cathode.

Nonaqueous Na-ion capacitors (NICs) have been recently regarded as potential sustainable power devices due to their high specific energy/power and the abundant distribution of sodium resources on the Earth. However, the power performance of current NICs is usually restricted by the kinetics imbalance between sodium deintercalation/intercalation in the anode and surface ion adsorption/desorption in the cathode. Herein, we demonstrate superior sodium-ion storage properties of nitrogen/sulfur co-doped hierarchical hollow carbon nanofibers (N/S-HCNFs) for their application as an ideal anode material for NICs. The N/S-HCNFs are fabricated through in situ gas sulfuration of a hollow polyaniline nanofiber precursor, which is obtained with the aid of citric acid templates. Benefiting from the positive synergistic effects of both N and S co-doping in carbon and the hierarchical hollow one-dimensional structure, the sodium-storage performance of N/S-HCNFs half-cell versus Na/Na+ exhibits a high capacity (∼447 mA h g−1 at 50 mA g−1), excellent rate capability (∼185 mA h g−1 at 10 A g−1), and outstanding cycling stability (no capacity decay after 3000 cycles at 5 A g−1), which is among the best sodium-ion storage performances of carbonaceous Na-storage anodes. Furthermore, a dual-carbon NIC device is constructed with N/S-HCNFs as an anode and activated carbon (AC) as a cathode, and it has a large energy density of 116.4 W h kg−1, a high power density of 20 kW kg−1 (at 48.2 W h kg−1) and a long cycle life of 3000 cycles, which is superior to most reported AC-based NICs.

Enhanced oxygen reduction with single-atomic-site iron catalysts for a zinc-air battery and hydrogen-air fuel cell

Efficient, durable and inexpensive electrocatalysts that accelerate sluggish oxygen reduction reaction kinetics and achieve high-performance are highly desirable. Here we develop a strategy to fabricate a catalyst comprised of single iron atomic sites supported on a nitrogen, phosphorus and sulfur co-doped hollow carbon polyhedron from a metal-organic framework@polymer composite. The polymer-based coating facilitates the construction of a hollow structure via the Kirkendall effect and electronic modulation of an active metal center by long-range interaction with sulfur and phosphorus. Benefiting from structure functionalities and electronic control of a single-atom iron active center, the catalyst shows a remarkable performance with enhanced kinetics and activity for oxygen reduction in both alkaline and acid media. Moreover, the catalyst shows promise for substitution of expensive platinum to drive the cathodic oxygen reduction reaction in zinc-air batteries and hydrogen-air fuel cells.

Tannic acid-mediated synthesis of dual-heteroatom-doped hollow carbon from a metal-organic framework for efficient oxygen reduction reaction.

Herein, we report an original strategy to fabricate N/B co-doped hollow carbon (denoted as NB-HC) with the assistance of tannic acid. Inspired by its inherent porous structures, we used ZIF-8 as a structural template and a N-doping source. Tannic acid (TA) as a secondary material is uniformly coated on the surface of ZIF-8 to obtain ZIF-8@TA core-shell composites. The TA-modified shell mediates the post-formation of boron acid-polyol bond, where 1,4-benzene diboronic acid (BDBA) is used as a boron-containing reactant and doping source. After carbonization, the composite successfully turns into hollow N/B co-doped carbon with a high surface area of 936 m2 g-1. It exhibits a pronounced ORR reactivity with an onset potential of -0.12 V (vs. Ag/AgCl) along with superb methanol cross-over tolerance and long-term stability. The first-principles calculation proves that the synergistic effect arising from N and B dopants can create active sites; therefore, the value of free energy change in the rate-determining step decreases. This elucidates that the homogeneously synergistic coupling of B and N in the carbon structure and hierarchical porous structures endow the as-prepared NB-HC with enhanced ORR parameters.

Deflagration synthesis of nitrogen/fluorine co-doped hollow carbon nanoparticles with excellent oxygen reduction performance

NaN3/C5F5N deflagration is developed to synthesize hollow carbon nanospheres with high N/F doping level, graphitization degree and specific surface area in one step, which exhibit excellent ORR performance.

Fabrication of nitrogen and sulfur co-doped hollow cellular carbon nanocapsules as efficient electrode materials for energy storage

Hierarchical hollow carbon materials are attracting considerable attention because of their unique structural characteristics, extraordinary electrical and thermal properties. Here, we present the fabrication of N and S co-doped hollow cellular carbon nanocapsules with high surface area and pore volume from a metal–organic framework composite by a facile external template-free method. The unique nanocapsules feature large internal hollow cores, hierarchical porous cellular shells with ultrathin walls of a few nanometers thickness, and uniform N and S co-doping, which enable an efficient supercapacitor behavior by enhancing the diffusion of electrolyte ions and providing large accessible active surface. The combination of the optimal pore structure and surface functionality of the resulting materials affords an excellent capacitive performance with high specific capacitances and energy densities in both aqueous and non-aqueous media.

Nitrogen–phosphorus co-doped hollow carbon microspheres with hierarchical micro–meso–macroporous shells as efficient electrodes for supercapacitors

Nitrogen–phosphorus co-doped hollow carbon microspheres with hierarchical micro–meso–macroporous shells were fabricated through co-assembly of SiO2nanospheres and melamine–formaldehyde resin.

Nitrogen and sulfur co-doped hollow carbon nanofibers decorated with sulfur doped anatase TiO2 with superior sodium and lithium storage properties

Nitrogen and sulfur co-doped hollow carbon nanofibers decorated with sulfur-doped anatase TiO2 (NSHCNF@STiO2) has been synthesized through a simple hydrothermal reaction process followed by a calcination treatment, in which uniform sulfur-doped anatase TiO2 nanoparticles are firmly attached to the nitrogen and sulfur co-doped HCNF matrix. When the as-designed NSHCNF@STiO2 composite is utilized as anode material for sodium and lithium storage, it delivers an enhanced electrochemical performance, which can be attributed to three synergic effects: (1) the core–shell and stable 3D network-like structures woven by nitrogen and sulfur co-doped HCNF in the NSHCNF@STiO2 composite can accommodate stress from cycling and provide a beneficial conductive environment; (2) the doping of sulfur can lower the electronic resistance of TiO2 and increase the interlayer distance of carbon; (3) the uniform sulfur-doped anatase TiO2 attachment can further shorten the electron and ion pathways during electrochemical cycling. These findings indicate that the NSHCNF@STiO2 composite has a great potential as TiO2-anode materials for sodium and lithium storage.

Nitrogen, Phosphorus, and Sulfur Co-Doped Hollow Carbon Shell as Superior Metal-Free Catalyst for Selective Oxidation of Aromatic Alkanes.

Metal-free heteroatom-doped carbocatalysts with a high surface area are desirable for catalytic reactions. In this study, we found an efficient strategy to prepare nitrogen, phosphorus, and sulfur co-doped hollow carbon shells (denote as NPS-HCS) with a surface area of 1020 m(2) g(-1). Using a poly(cyclotriphosphazene-co-4,4'-sulfonyldiphenol) (PZS) shell as carbon source and N, P, S-doping source, and the ZIF-67 core as structural template as well as extra N-doping source, NPS-HCS were obtained with a high surface area and superhydrophilicity. All these features render the prepared NPS-HCS a superior metal-free carbocatalyst for the selective oxidation of aromatic alkanes in aqueous solution. This study provides a reliable and facile route to prepare doped carbocatalysts with enhanced catalytic properties.

Supercapacitor performance of hollow carbon spheres by direct pyrolysis of melamine-formaldehyde resin spheres

The nitrogen and oxygen co-doped hollow carbon spheres(HCSs) were prepared via a simple pyrolysis of solid melamine-formaldhyde resin spheres. The carbonization temperature has an important influence on the specific surface area, pore-size distribution and heteroatom contents of HCSs. The synergistic effects of those physical and chemical properties on supercapacitor performance were systematically investigated. Among the HCSs obtained at different temperatures, HCSs-800(co-doped HCSs at 800 °C) exhibits the best reversible specific capacitance in 2 mol/L H2SO4 electrolyte and meanwhile maintains a high-class capacitance retention capability. The nitrogen heteroatoms were confirmed to play a crucial role in improving capacitance in an acid medium. This kind of nitrogen doped HCSs is a potential candidate for an efficient electrode material for supercapacitors.