Nitrogen-doped Hollow Carbon Spheres Research Articles

Curvature strain tunes electron transfer accelerates peroxymonosulfate activation to achieve high-efficiency advanced oxidation

The development of high performance and stable heterogeneous catalysts is conducive to promoting the advanced oxidation process (AOPs) to promote the degradation of organic pollutants efficiently, low-cost and environmentally friendly. Here nitrogen-doped hollow carbon spheres (NHCSs) and rigid organic molecule were used to create space confinement and complexation confinement conditions, respectively, and an advanced single-atom catalyst capable of strongly activating peroxymonosulfate (PMS) to degrade organic pollutants was finally constructed. The AOPs system driven by CoNC/NHCSs (20 mg) combined with PMS (20 mg) can degrade nearly 100 % of 20 mg/L (100 mL) bisphenol A (BPA, a microplastic) pollutant within 30 min, and the mineralization rate is up to 70.5 %. Face the complex water environment, such as sewage containing coexisting anions and cations, or acidic or alkaline sewage, the CoNC/NHCSs/PMS system still has high catalytic stability, and universality for other organic pollutants. The filter column with CoNC/NHCSs as the core also realizes the continuous purification of organic pollutants, which shortens the distance between laboratory research and practical application. Radical quenching and electron paramagnetic resonance techniques confirmed that CoNC/NHCSs activated PMS to SO4·−, ·OH, and 1O2, and these reactive oxygen species combined to eliminate organic pollutants. Density functional theory (DFT) calculations jointly confirm that the strong activation of PMS by CoNC/NHCSs is the key to achieving efficient degradation of organic pollutants, and the activity of CoNC/NHCSs is derived from high exposure rate of active sites and curvature effect caused by structural bending.

Surface crystallized supramolecular to achieve highly dispersed ultrafine nano-palladium in-situ deposition to promote thermal/electrocatalytic reduction

To promote the greening and economization of industrial production, the development of advanced catalyst manufacturing technology with high activity and low cost is an indispensable part. In this study, nitrogen-doped hollow carbon spheres (NHCSs) were used as anchors to construct a supramolecular coating formed by the self-assembly of boron clusters and β-cyclodextrin by surface crystallization strategy, with the help of the weak reducing agent characteristics of boron clusters, highly dispersed ultra-small nano-palladium particles were in-situ embedded on the surface of NHCSs. The deoxygenation hydrogenation of nitroaromatics and the reduction of nitrate to ammonia were used as the representatives of thermal catalytic reduction and electrocatalytic reduction respectively. The excellent properties of the constructed Pd/NHCSs were proved by the probe reaction. In the catalytic hydrogenation of nitroaromatics to aminoaromatics, the reaction kinetic rate and activation energy are at the leading level. At the same time, the constructed Pd/NHCSs can also electrocatalytically reduce nitrate to high value-added ammonia with high activity and selectivity, and the behavior of Pd/NHCSs high selectivity driving nitrate conversion was revealed by density functional theory and in situ attenuated total reflection Fourier transform infrared (ATRFTIR) technique. These results all reflect the feasibility and superiority of in-situ anchoring ultra-small nano-metals as catalysts by surface crystallization to build a supramolecular cladding with reducing properties, which is an effective way to construct high-activity and low-cost advanced catalysts.

Nitrogen-doped hollow carbon sphere composite Mn3O4 as an advanced host for lithium-sulfur battery

As the most promising advanced energy storage system, lithium-sulfur batteries (LSBs) are highly favored by the researchers because of their advantages of high energy density (2500 W h kg−1), low cost and non-pollution. However, the low conductivity, volume expansion of sulfur, and shuttle effect are still the great hindrance to the practical application of LSBs. Herein, the above problems can be addressed through the following strategies: (1) Hollow carbon microspheres with high specific surface area were constructed as sulfur hosts to increase sulfur loading while also being able to enhance the physical adsorption of polysulfides; (2) the loading of Mn3O4 particles on the basis of hollow carbon microspheres facilitates the capture and adsorption of polysulfides; (3) the hollow carbon sphere structure as a conductive network can provide more pathways for rapid electrical/ionic transport and also accelerate electrolyte wetting. Moreover, the thinner shell of hollow carbon microsphere is conducive to ion diffusion and speed up the reaction rate. Thus, the NHCS/Mn3O4/S composites exhibit a high discharge specific capacity of 1010.3 mAh g−1 at first and still maintained a reversible capacity of 269.2 mAh g−1 after 500 cycles. This work presents a facile sustainable and efficient synergistic strategy for the development of advanced LSBs.

Repairable body-centered cubic Fe0 anchoring on porous hollow nitrogen-doped carbon spheres with adjusting electron distribution for efficient electrocatalytic ammonia synthesis

Electrocatalytic nitrogen reduction reaction (ENRR) is a promising and efficient method for ammonia production. However, ENRR is restricted by the adsorption and activation of N2. Herein, an efficient nitrogen reduction reaction (NRR) electrocatalyst loaded with zero valent iron (ZVI) particles onto porous nitrogen-doped carbon (NC) hollow spheres is reported. The optimal Fe@10N3C-950 exhibits excellent performance with high ammonia (NH3) yield (152.28 µg h−1 mgcat−1) and Faradaic efficiency (FE, 54.55 %) at − 0.3 V (versus reversible hydrogen electrode, vs. RHE). Bader charge shows that the adsorbed N2 acquires more electrons from Fe sites with body-centered cubic (BCC) structure to better activate N2. Moreover, i-t experiments are performed before electrocatalytic NH3 production to effectively eliminate the effect of oxidation on ZVI and thus, maintain high ENRR activity for Fe@10N3C-950. Theoretical calculations indicate that nitrogen doping not only reduces the Gibbs free energy of rate determining step (RDS), but the BCC-structured Fe can also decrease the energy barriers of N2 activation and RDS.

Hemp-ball-like structured Fe3O4-hollow carbon sphere nanozymes functionalized carbon fiber cathode for efficient flow-through electro-Fenton

Electro-Fenton (EF) technology has been recognized as a highly promising electrochemical advanced oxidation process. Promoting effective contact between active species and contaminant is crucial in electrocatalysis. Herein, we had innovatively designed a unique nanozymes in the form of hemp-ball-like structures, consist of the uniform growth of Fe3O4 nanoparticles on nitrogen-doped nano hollow carbon spheres (NHCS). This catalyst was employed in a flow-through EF system with carbon felt (CF) filters serving as the work electrode. The active sites were fully exposed through the ultradispersed Fe3O4 nanoparticles, and the NHCS facilitated efficient cycling of Fe3+/Fe2+. The results showed that the generation capacity of hydroxyl radicals (·OH) was enhanced, and the oxidation flux reached 370.080 mg h−1m−2 with low energy consumption. The superiority of the hollow carrier was proved by the degradation results and COMSOL calculation for various carbon carriers. Moreover, the active catalyst exhibited adaptability in complex water matrices. This study offers a new perspective to synergize nanomaterials, EF reactions and flow-type systems.

Hollow Nitrogen-Doped Carbon Spheres as Zincophilic Sites for Zn Flow Battery.

Severe dendrite growth on Zn anodes poses a significant challenge to the development of Zn-based batteries. An effective strategy for inhibiting the formation of Zn dendrites involves electrode modification. In this study, hollow nitrogen-doped carbon spheres (HNCS) are synthesized and used as electrodes to regulate Zn deposition in Zn-based flow batteries. The electrochemical performance of HNCS reveals that the pyrrole nitrogen of HNCS changes the electrode surface state. Therefore, HNCS can inhibit the hydrogen evolution reaction and achieve uniform Zn deposition. HNCS can effectively inhibit dendrite growth and improve the reversibility of the Zn plating/stripping process to regulate the reversibility of Zn-based batteries. The zinc-bromine redox flow battery assembled with HNCS significantly reduces the hydrogen evolution reaction and exhibits a coulombic efficiency of 90 % and energy efficiency of 73 % at a current density of 60 mA cm-2. Similarly, an alkaline zinc-iron flow battery can maintain high Coulombic efficiency and energy efficiency of 83 %.

A nitrogen-doped hollow carbon nanospheres-based aptasensor for non-invasive salivary detection of progesterone

Developing an easy-to-use and non-invasive sensor for monitoring progesterone (P4) as a multi-functional hormone is highly demanded for point-of-care testing. In this study, an ultrasensitive electrochemical aptasensor is fabricated for monitoring P4 in human biofluids. The sensing interface was designed based on the porous nitrogen-doped hollow carbon spheres (N-HCSs). The N-HCSs covalently immobilized high-dense aptamer (Apt) sequences as the bioreceptor of P4. The electron transfer of the redox probe was hindered by incubating P4 on the aptasensor surface and forming the P4-Apt complexes. Meanwhile, the signaling was decreased under two wide linear dynamic ranges (LDRs) from 10 fM to 5.6 μM with a limit of detection (LOD) value of 3.33 fM. The aptasensor presented satisfactory selectivity in the presence of different off-target species with successful feasibility for P4 detection in some human urine and saliva samples. The aptasensor with high sensitivity, as an advantage for on-site and sensitive measurement of P4, can be considered a non-invasive tool for routine analysis of real-world clinical samples method.

Photoelectrothermocatalytic reduction of CO2 to glycol via CdIn2S4-N/C hollow heterostructure mimicking plant cell

A series of novel semiconductor composites of CdIn2S4-N/C, in which CdIn2S4 is grown on hollow nitrogen-doped carbon spheres to mimic plant cells, were designed and applied to photoelectrothermocatalytic reduction of CO2. Our results reveal that the unique hollow structure and photothermal properties of N/C contribute to excellent performance of catalyst in CO2 reduction. Specifically, the optimal catalyst of CdIn2S4-N/C-2–800 demonstrates an outstanding catalytic activity with a formation rate of 168.5 µM h−1 cm−2 for carbon-based products and an electron selectivity for C2 products of 66.9 %. DFT calculations demonstrate that pyridine N and pyrrole N can reduce the energy barrier during CO2 reduction. Two important species of *=C=O and OC-COH* were detected by operando IR spectra and suggested to be key intermediates to C2 products via a carbene (*=C=O) coupling mechanism. CdIn2S4-N/C provides thermoelectrons and active sites like in the membrane of plant to enhance the probability of C-C coupling.

Efficient PMS activation toward degradation of bisphenol A by metal-free nitrogen-doped hollow carbon spheres

Peroxymonosulfate (PMS) activation methods conventionally face challenges such as high energy consumption and the risk of metal leaching, limiting their practical application. Metal-free catalysts often face the problem of low catalytic activity. This study designed an in-situ nitrogen-doped hollow carbon catalyst (DNC-9), which offers balances efficient catalytic performance and metal-free catalysis. The results indicate that the DNC-9/PMS system effectively degrades bisphenol A, achieving complete degradation over a broad pH range (3.0–9.0). Through structure modification, the degradation efficiency of bisphenol A compared with SiO2@DNC-9/PMS system was improved by around 6 times and the degradation kinetic rate can reach 0.346 min−1. DNC-9 can activate PMS, resulting in a higher concentration of singlet oxygen without the generation of free radicals. Graphitic nitrogen in DNC-9 plays a crucial role in this activation, offering adsorption sites that facilitate decomposition of PMS and generating 1O2. In addition, graphitic nitrogen forms a transient active intermediate, DNC-9-PMS*, enhancing bisphenol A degradation. The catalyst recovers its high activity to complete bisphenol A removal with 15 min after thermal regeneration in cyclic experiments, demonstrating its potential as a practical solution for the efficient degradation of emerging contaminants.

Nitrogen-doped hollow carbon spheres decorated with NiCo alloy nanoparticles for high-performance supercapacitor electrode

Nitrogen-doped hollow carbon spheres (NHCSs) decorated with NiCo alloy nanoparticles (NPs) were prepared and examined for their prospective role as high-performance electrode materials. The NHCSs were synthesized through a silica-assisted synthesis method, followed by the decoration of NiCo alloy NPs onto the NHCSs using a simple wet impregnation method, employing a 1:1 M ratio of Co to Ni elements. The NiCo/NHCS-23, composed of NHCSs with 23 wt% of NiCo alloy NPs, exhibited a specific capacitance (Csp) of 536 F g−1 when tested in a 6 M KOH solution at a current density of 1 A g−1. This high Csp is attributed to the synergistic effect of the faradaic charge storage provided by NiCo alloy NPs and the N-doped hollow carbon structure. The N content of the NHCSs and NiCo/NHCS-23 was found to be 1.9 % and 2.2 %, respectively. Symmetric supercapacitor (SSC) devices were assembled using two NiCo/NHCS-23 electrodes and a 0.5 M tetraethylammonium tetrafluoroborate/propylene carbonate electrolyte. The resulting SSC device operated within a potential window of 3.5 V and exhibited an energy density of 16.1 Wh kg−1 at the power density of 250 W kg−1. The SSC device demonstrated impressive cycling stability, maintaining 90.0 % capacitance and 83.1 % Coulombic efficiency after 5000 cycles. These results suggest that NiCo/NHCS nanocomposites have significant potential for utilization in high-energy storage applications.

Spray Pyrolysis Regulated FeCo Alloy Anchoring on Nitrogen-Doped Carbon Hollow Spheres Boost the Performance of Zinc-Air Batteries.

Low-cost and high-efficiency non-precious metal-based oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) bifunctional catalysts are the key to promoting the commercial application of metal-air batteries. Herein, a highly efficient catalyst of Fe0.18Co0.82 alloy anchoring on the nitrogen-doped porous carbon hollow sphere (FexCo1-x/N-C) is intelligently designed by spray pyrolysis (SP). The zinc in the SP-derived metal oxides and metal-organic framework volatilize at high temperature to construct a hierarchical porous structure with abundant defects and fully exposes the FeCo nanoparticles which uniformly anchor on the carbon substrate. In this structure, the coexistence of Fe0.18Co0.82 alloy and binary metal active sites (Fe-Nx/Co-Nx) guarantees the Fe0.2Co0.8/N-C catalyst exhibiting an excellent half-wave potential (E1/2 ═ 0.84V) superior to 20% Pt/C for ORR and a suppressed overpotential (280mV) than RuO2 for OER. Assembled rechargeable Zn-air battery (RZAB) demonstrates a promising specific capacity of 807.02mAhg-1, peak power density of 159.08mWcm-2 and durability without electrolyte circulation (550h). This work proposes the design concept of utilizing an oxide core to in situ consume the porous carbon shell for anchoring metal active sites and construct defects, which benefits from spray pyrolysis in achieving precise control of the alloy structure and mass preparation.

Boosting sodium-ion batteries performance by N-doped carbon spheres featuring porous and hollow structures.

Carbon materials are considered among the most promosing candidates for sodium ion batteries because of their competitive performance. Nevertheless, they suffer from low initial coulombic efficiencies (ICEs) and limited electrochemical performance. Herein, nitrogen-doped hollow carbon spheres (NHCSs) with a distinct porous structure are developed by a template-assisted carbonization of dopamine, followed by a template removal procedure. This advanced structural design, coupled with the surface chemistry of carbonized polydopamine, leads to an impressive ICE of 89.18% and a reversible capacity stabilized at ∼700 mA h g-1 at 50 mA g-1 after 100 cycles. Compared to commercial hard carbon anodes, NHCSs demonstrate superior rate performance, delivering a capacity of ∼200 mA g h-1 at 5 A g-1 with minimal capacity fading of ∼0.057 mA h g-1 per cycle over 1000 cycles. These findings highlight the potential of NHCSs as a high-performance anode material for sodium-ion batteries, offering both high efficiency and excellent cycling stability.

Platinum-group-metal quaternary alloys with lattice defects for enhanced oxygen electrocatalysis.

We propose a facile coreduction method to synthesize a platinum-group-metal quaternary alloy anchored on nitrogen-doped hollow carbon spheres (PtPdRuIr/HCS) by using [MClx]y--1-butyl-3-methylimidazole (M = Pt, Pd, Ru, and Ir) ionic liquid. Owing to the steric hindrance of the imidazolium cations, Pt-group metal atoms of different sizes can be deposited at approximately the same pace for the growth of an alloy with lattice defects. The lattice-distorted PtPdRuIr/HCS exhibits enhanced activity toward oxygen electroreduction when benchmarked against Pt counterparts.

FeNi decorated nitrogen-doped hollow carbon spheres as ultra-stable bifunctional oxygen electrocatalyst for rechargeable zinc-air battery with 2.7% decay after 300 hours cycling.

Research on non-noble metal bifunctional electrocatalysts with high efficiency and long-lasting stability is crucial for many energy storage devices such as zinc-air batteries. In this report, nitrogen-doped porous hollow carbon spheres with a size of about 300 nm were fabricated using a modified Stöber method and decorated with an FeNi alloy through a pyrolytic reduction process, resulting in a promising bifunctional electrocatalyst for both the oxygen evolution reaction and oxygen reduction reaction. The as-prepared FeNi@NHCS electrocatalyst exhibits excellent bifunctional activity in KOH electrolyte, attributed to its mesoporous structure, large specific surface area, and the strong coupling between the FeNi nanoalloy and nitrogen-doped carbon carriers. The electrocatalyst demonstrates excellent ORR performance with E1/2 = 0.828 V and OER activity with Ej=10 mA = 1.51 V. A zinc-air battery using FeNi@NHCS as the air electrode achieves an open-circuit voltage of 1.432 V and a maximum power density of 181.8 mW cm-2. After 300 h of galvanostatic charge-discharge cycles, the charge-discharge voltage gap (ΔU) of the battery had only decayed by 2.7%, demonstrating superior cycling stability.

Poly (3, 4-propylenedioxythiophene)/Hollow carbon sphere composites supported Pt NPs to facilitate methanol oxidation reactions

Direct methanol fuel cells (DMFCs) are thought of as portable, sustainable, and non-polluting energy devices. The exploration of efficient and affordable catalysts for the methanol oxidation reaction (MOR) is significant for the industrial application of DMFCs. In this study, nitrogen-doped hollow carbon spheres (HCS) derived from polydopamine were proposed for the catalyst support for platinum nanoparticles (Pt NPs) for serving as the anode catalyst for DMFCs, and a composite support material was fabricated by in-situ oxidation of 3,4-ethylenedioxythiophene (ProDOT) with HCS to get core-shell structured poly(3,4-propylenedioxythiophene) (PProDOT)-embellished hollow carbon spheres (HCS) (PProDOT/HCS) for further improving the catalytic activity for supported catalyst. The results indicated that the platinum (Pt) on the surface of HCS was well dispersed, and the Pt became smaller and more evenly distributed with the introduction of PProDOT. Simultaneously, the Schottky junction formed between PProDOT and Pt NPs contributes to enhanced charge transfer and catalytic activity of the catalyst. Notably, the core-shell structure of the ternary catalyst, its excellent charge transfer capability, and the interaction between platinum and the support contribute to its high electrocatalytic activity. Electrochemical tests demonstrated that the PProDOT/HCS/Pt catalyst exhibited a mass activity of 1169.6 mA mg−1Pt for methanol oxidation in acidic electrolytes, surpassing the activity of the HCS/Pt catalyst (472.4 mA mg−1Pt) and commercial Pt/C (281.0 mA mg−1Pt).

Synergistic effect between Ni single atoms and Ni nanoparticles for effectively boosting sustainable co-electrolysis of CO2 and hydrazine

The intrinsic performance of single atom catalysts (SACs) to electrochemical CO2 reduction reaction (ECRR) is limited due to the absence of synergistic active sites. Herein, Ni single atom (NiSAs) and Ni nanoparticles (NiNPs) are co-loaded on nitrogen-doped hollow carbon spheres (N-HCSs) by a one-step calcination method, which exhibits high CO selectivity in H-type cell with aqueous solution or an ionic liquid as electrolyte. Particularly, NiSAs-NPs-N-HCSs demonstrate a CO selectivity of 98.98%, yielding an industrial level CO current density of 152.7 mA cm−2 in flow cell. In situ Raman spectroscopy and in situ infrared characterization technology confirm that *COOH and *CO are important intermediates in the ECRR process. Theoretical computations suggest that coexisting NiNPs can reduce the energy barrier of *COOH, thereby improving the ECRR performance, indicating the synergistic effect between NiSAs and NiNPs in the ECRR process. Moreover, NiSAs-NPs-N-HCSs is applied to the membrane electrode assembly system coupling the hydrazine oxidation reaction (HzOR), which can significantly reduce the voltage about 836 mV at 100 mA cm−2.

Nitrogen-doped hollow carbon spheres as efficient metal-free peroxymonosulfate activator for degradation of organic pollutant

Developing effective metal-free catalytic materials via constructing copious surface-exposed active sites to promote peroxymonosulfate (PMS) activating for degradation of hazardous organics is highly desirable toward practical application. In this study, we report the utilization of N-functionalized hollow carbon spheres (N-HCS) as efficient PMS activator for Rhodamine B (RhB) degradation. Results indicate that N-doping of hollow carbon spheres can introduce an abundance of pyridinic N and CO sites, which serve as catalytically active sites for PMS activation toward RhB degradation. The fabricated catalyst exhibits excellent performances with a degradation efficiency of 100 % and a rate constant of 0.0566 min−1 for RhB degradation under optimal conditions. Besides, the developed N-HCS catalyst displays a good reusability, maintaining a high degradation efficiency after the 5th run. Quenching tests and electron spin resonance characterization results reveal the coexistence of radical and non-radical degradation pathways, and SO4− and 1O2 are demonstrated as the dominant reactive oxygen species. This architecture integrated surface microenvironment engineering strategy can be extended to regulate the degradation performance of carbon-based materials for PMS activation toward removing other organic pollutants.

Hollow Nitrogen-Doped Carbon Spheres with Presiding Graphitic Nitrogen for Oxygen Reduction Reaction

Hollow nitrogen-doped carbons, a class of metal free electrocatalysts, offer a wide range of modifications due to their tunable diameter and carbon wall thickness. Herein, hollow nitrogen-doped carbon spheres (HNCS-1000) with numerous structural defects, thin carbon wall of about 8 nm, high (sp2-sp3)/sp3 bond ratio of 3.11 and graphitic-N proportion of 71.4% are prepared using a double pyrolysis strategy. When employed as ORR catalyst in O2-saturated 0.1 M KOH solution, HNCS-1000 retains high onset and halfwave potentials of 1.03 V and 0.88 V, respectively. In addition, it also demonstrates excellent stability/durability with 90.25% current density retention after 84000 s continuous chronoamperometric operation and only 33 mV loss in halfwave potential after 7000 CV cycles. Overall, the ORR performance of HNCS-1000 surpasses most of the previously reported nitrogen-doped carbon catalysts, and it is among the best catalysts for ORR in alkaline environment.

Electrocatalytic response of nitrogen-doped hollow carbon spheres modified glassy carbon electrode for sulphite detection in water

In this work, the glassy carbon electrode (GCE) surface was modified with nitrogen-doped hollow carbon spheres (N-HCSs) to achieve a new electrochemical sulphite sensor (N-HCSs/GCE) in water samples. The N-HCSs were explored for electrocatalytic behavior through voltammetric approaches using a routine three-electrode system. The findings revealed an admirable efficiency for modified electrodes towards sulphite oxidation, highlighting the effectiveness of our as-produced sulphite sensor. The differential pulse voltammetry was utilized under obtained optimal circumstances to study the as-developed sensor, the results of which underlined linear electrochemical current in relation to sulphite concentration, with dynamic range as wide as 1.0-100.0 μM and limit of detection as narrow as 0.35 μM. Moreover, N-HCSs/GCE had commendable practical applicability for sensing sulphite present in real specimens with voltammetric techniques.

Nitrogen-doped hollow mesoporous carbon spheres for efficient oxygen reduction

Extensive investigations have been devoted to nitrogen-doped carbon materials as catalysts for the oxygen reduction reaction (ORR) in various conversion technologies. In this study, we introduce nitrogen-doped carbon materials with hollow spherical structures. These materials demonstrate significant potential in ORR activity within alkaline media, showing a half-wave potential of 0.87 V versus the reversible hydrogen electrode (RHE). Nitrogen-doped hollow carbon spheres (N-CHS) exhibit unique characteristics such as a thin carbon shell layer, hollow structure, large surface area, and distinct pore features. These features collectively create an optimal environment for facilitating the diffusion of reactants, thereby enhancing the exposure of active sites and improving catalytic performance. Building upon the promising qualities of N-CHS as a catalyst support, we employ heme chloride (1 wt%) as the source of iron for Fe doping. Through the carbonization process, Fe-N active sites are effectively formed, displaying a half-wave potential of 0.9 V versus RHE. Notably, when implemented as a cathode catalyst in zinc-air batteries, this catalyst exhibits an impressive power density of 162.6 mW cm−2.