Hollow Mesoporous Carbon Spheres Research Articles

Fe-N hollow mesoporous carbon spheres with high oxidase-like activity for sensitive detection of alkaline phosphatase.

Due to the vital role of alkaline phosphatase (ALP) in clinical diagnoses and biomedical research, a sensitive and selective detection method for ALP activity is of considerable importance. Herein, a facile and sensitive colorimetric assay for the detection of ALP activity was developed based on Fe-N hollow mesoporous carbon spheres (Fe-N HMCS). Fe-N HMCS were synthesized by a practical one-pot method with aminophenol/formaldehyde (APF) resin as the carbon/nitrogen precursor, silica as the template and iron phthalocyanine (FePC) as the iron source. Thanks to the highly dispersed Fe-N active sites, Fe-N HMCS exhibited exceptional oxidase-like activity. In the presence of dissolved oxygen, Fe-N HMCS were able to effectively convert colorless 3,3',5,5'-tetramethylbenzidine (TMB) into oxidized TMB (oxTMB) with blue color, while the reducing agent of ascorbic acid (AA) inhibited the color reaction. Based on this fact, an indirect and sensitive colorimetric sensing method was developed to detect alkaline phosphatase (ALP) with the assistance of the substrate L-ascorbate 2-phosphate (AAP). This ALP biosensor exhibited a linear range of 1-30 U L-1 and a limit of detection (LOD) of 0.42 U L-1 in standard solutions. In addition, this method was applied to detect ALP activity in human serum with satisfactory results. This work offers a positive reference for the reasonable excavation of transition metal-N carbon compounds in ALP-extended sensing applications.

Anchored and confined Pt nanoparticles in radial mesoporous hollow carbon spheres enhancing oxygen reduction reaction stability

Pt particles were uniformly dispersed on N-doped mesoporous hollow carbon spheres through the synergism of nitrogen anchoring and pore confinement.

Ultra-thin MoO2 nanosheets loaded on hollow mesoporous carbon spheres promoting polysulfide adsorption and redox kinetics for lithium-sulfur batteries

Inhibiting polysulfide shuttle and improving cycling stability are crucial for the commercialization of lithium-sulfur batteries (LSBs). Developing multifunctional sulfur host materials that combine rational carbon structure with highly catalytic metal compounds is pivotal for LSBs. Herein, Ultra-thin MoO2 nanosheets loaded on hollow mesoporous carbon (HMC@MoO2) were rationally designed and synthesized. In this structure, the hollow mesoporous carbon provides sufficient space to store sulfur and buffer volume fluctuations, the mesoporous carbon shell and the MoO2 nanosheets on its surface can act as a double defensive system to effectively prevent polysulfide dissolution through physical and chemical trapping. Moreover, the ultra-thin MnO2 nanosheets with more exposed active sites facilitate the capture and catalytic conversion of LiPSs, thereby effectively suppressing the shuttle effect of polysulfide. Consequently, the HMC@MoO2-S cathode exhibits impressive cycling stability, maintaining 771 mAh g−1 after 500 cycles at 0.5 C with a very low capacity decay of 0.045% per cycle. In particular, the HMC@MoO2-S cathode with high areal sulfur loading of 5.0 mg cm−2 achieved initial areal capacities of 4.48 mAh cm−2 and retention capacities of 3.32 mAh cm−2 after 500 cycles at 0.1 C.

Engineered mesoporous hollow carbon spheres for pollutant degradation: Disclosing catalytic activity, matrix effect, transport, and aquatic ecotoxicity

Remediation of organic contaminants through advanced oxidation process hold great promise for both ground and surface water environments. Despite the fact, the treatment efficiency depends on multiple factors, i.e., catalyst dosage, persulfate/peroxymonosulfate activation capability, and catalyst toxicity to aquatic creatures. Herein, we aimed to demonstrate the potential of the mesoporous carbon hollow sphere (MCHS) catalyst in persulfate activation for advanced oxidation in pure and groundwater matrix by choosing tetracycline as a model compound. Surface properties of MCHS were examined using multiple characterization techniques and the data revealed that MCHS is benefited by high specific surface area, numerous mesopores, and an excellent degree of particle dispersion. The results of this study indicate that pH, catalyst dosage, and persulfate and tetracycline concentrations influence tetracycline’s degradation rate. Features like colloidal nature, high specific surface area (>1200 m2/g), and porosity of MCHS allow for very low catalyst dosage (10 mg L−1). Electron spin resonance (ESR) and scavenger studies showed that the TC degradation in persulfate/MCHS system is dominated by 1O2 rather than OH, and SO4– radical species. Electrochemical study confirmed that electrons are transferred from tetracycline to the persulfate/MCHS complex during oxidation reaction. Additionally, the tetracycline degradation performance in natural groundwater matrices outperforms the persulfate/MCHS pure water system. Ecotoxicity study revealed the survival rate of Daphnia magna neonates is >95% if MCHS is <12 mg L−1.

Mesoscale Mass Transport Enhancement on Well-Defined Porous Carbon Platform for Electrochemical H2O2 Synthesis.

Two-electron oxygen reduction toward hydrogen peroxide (H2O2) offers a promising alternative for H2O2 production, but its commercial utilization is still hindered by the difficulty of transferring lab-observed catalyst performance to the practical reactor. Here we report the investigation of the porosity engineering effect on catalytic performance inconsistency through a material platform consisting of a series of hollow mesoporous carbon sphere (HMCS) samples. The performance comparison of HMCS samples in rotating ring-disk electrode and Zn-air battery together with the simulation of diffusion behavior reveals that, in low current density conditions, large surface area is preferred, but the mass transport governs the performance in high current density regions. On account of the favorable porous structure, HMCS-8 nm delivers the most excellent practical performance (166 mW cm-2) and performs well in the bifunctional Zn-air battery for the wastewater purification (70% RhB degraded after 2 min and 99% after 32 min).

Inner wrinkled mesoporous hollow carbon spheres with nanopillars connected to double shells for excellent potassium storage

Carbon spheres are widely used in energy storage due to their adjustable particle size, controllable shape, and variable surface physical and chemical properties. However, there are still problems such as low specific surface area and unsatisfactory ion transport kinetics in K + storage. Although increasing the specific surface area of the active material can increase the K + storage sites, the contact area between the active material and the electrolyte also increases, aggravating the occurrence of side reactions and the consumption of the active materials. We developed an N-doped mesoporous hollow carbon sphere with a novel morphology-a smooth exterior and wrinkled interior structure with a carbon-supported pseudo-bilayer carbon structure (IW-MHCS). Its smooth outer structure sufficiently reduces the contact area with the electrolyte, and the wrinkled inner structure effectively increases the specific surface area. The obtained IW-MHCS exhibits superior rate performance (120.6 mAh g −1 at 5 A g −1 ) and sufficient capacity (202.7 mAh g −1 after 800 cycles at 1 A g −1 ) for K + storage. This study provides a new insight into the structural design and morphological control of high-energy-storage carbon-based materials. • A novel mesoporous hollow carbon spheres (HCSs) with pseudo-bilayer structure were synthesized. • The HCSs possess a smooth exterior surface and a wrinkled interior morphology. • The optimized sample exhibited excellent potassium storage performance. • The good electrochemical performance is ascribed to the unique microstructure of HCSs.

Biomimetic Synthesis of VOx@C Yolk‐Shell Nanospheres and Their Application in LiS Batteries

AbstractMany biological processes involve active transport where the desired substances can be transported against the concentration gradient with energy consumption. This feature is highly desirable for the synthesis of yolk‐shell structures using preformed capsules to efficiently encapsulate yolk materials. Here, the synthesis of VOx@C yolk‐shell nanospheres by biomimicking prey–predation of carnivorous Utricularia is reported. The high intrinsic frequency and superior mechanical properties of hollow mesoporous carbon spheres (HMCS) maintain their integrity during ultrasonication, making HMCS an ideal capsule. Numerical simulation elucidates that the encapsulation of the VOx nanoparticles is ascribed to the periodic change of pressure and the damping force generated from the relative motion between the mesoporous tunnel in the HMCS and VOx nanoparticles. The resulting VOx@C yolk‐shell nanospheres demonstrate promising application as a regenerative polysulfide‐scavenging layer (RSL) for high‐loading LiS batteries (≈5 mAh cm−2). As compared with the cells with a commercial Celgard polypropylene (PP) separator, those with a RSL present improved capacity retention from 467 to 860 mAh g−1 after 100 cycles, superior rate capability, and reduced impedance. This method provides an additional synthesis tool for yolk‐shell materials otherwise inaccessible by conventional methods with potential applications in energy storage and conversion devices.

PMo11V polyoxometalate encapsulated into hollow mesoporous carbon spheres: A highly efficient and ultra-stable catalyst for oxidative desulfurization

The synthesis of highly efficient and stable catalysts for oxidative desulfurization is still a challenging task. Herein, a composite material (PMo11V@HMCS) of vanadium-substituted polyoxometalate (PMo11V) encapsulated in the hollow mesoporous carbon spheres (HMCS) was prepared via an incipient wetness impregnation method. As-synthesized catalysts were systematically characterized by ICP-OES, Contact angle testing, FT-IR, XRD, SEM, TEM, BET and XPS. The oxidative desulfurization experiments showed that PMo11V@HMCS had higher conversion of dibenzothiophene (DBT) than PMo11V@AC and could completely remove DBT in the model fuel in 30 min. It is found that the hollow mesoporous structure can not only effectively promote the contact between substrate and catalytic active sites to provide sufficient internal space for the catalytic reaction, but also significantly improve diffusion and mass transfer. The amphiphilic catalyst with hydrophilicity and lipophilicity was in full contact with the reaction substrate and oxidant, which improved the catalytic performance. In addition, because the nanoscale pore size in HMCS can effectively confine and anchor the POM clusters and prevent the loss of catalytic active species, the catalyst also exhibited outstanding recyclability and stability. PMo11V@HMCS could be reused for at least twenty runs without an obvious decline in activity.

Superhydrophobic Ru Catalyst for Highly Efficient Hydrogenation of Phenol under Mild Aqueous Conditions

Selective hydrogenations of lignin-derived phenolic compounds represent essential processes in the chemical industry, especially for production of a multitude of fine chemicals. However, selective hydrogenation of phenolic compounds in water phase suffers from low conversion. Here we report a catalyst of well-dispersed Ru clusters fixed in N-doped mesoporous hollow carbon spheres (Ru@N-CS) for enhanced cyclohexanol productivity in phenol hydrogenation at mild aqueous condition. This superhydrophobicity carbon spheres appear to selectively allow diffusion of phenol and hydrogen molecules to the electron-rich coordination unsaturated Ru active sites, while confining the reactants there to enhance its reaction probability. The Ru@N-CS catalyst can selectively hydrogenate phenol at 80 °C and 0.5 MPa of H2 in 30 min in aqueous medium with phenol conversions of 100% and ~100% cyclohexanol selectivity, corresponding to cyclohexanol productivity up to 471 per g of Ru per minute. The TOF value is up to 9980 h−1, which 14 times more than Ru nanoparticles supported on N-doped carbon hollow spheres (Ru/N-CS). This work provides an important catalytic system for upgrading of bio-oil into value-added chemicals under mild aqueous-phase.

Morphology-Controlled Fabrication Strategy of Hollow Mesoporous Carbon Spheres@f-Fe2O3 for Microwave Absorption and Infrared Stealth.

The design and development of radar--infrared compatible stealth materials are challenging in the field of broadband absorption due to the contradiction of stealth requirements and mechanisms in different frequency bands. However, hollow structures show great promise for multispectral stealth because they can lengthen the attenuation path of electromagnetic waves (EMWs) for microwave absorption, interrupt the continuity of heat-transport channels, and lower the thermal conductivity to realize infrared stealth. Here, a new morphological fabrication strategy has been developed to efficiently prepare compatible stealth nanomaterials. In a specific hydrothermal process, the confined growth of flake α-Fe2O3 (f-Fe2O3) outside of hollow mesoporous carbon spheres (HMCS) is achieved using NH3·H2O as a shape-controlled reagent. The introduction of f-Fe2O3 helps to lower infrared emissivity and improve high-frequency impedance matching, which depends on the stable dielectric property of the specific flake shape. Moreover, the size of f-Fe2O3 can be regulated by changing the constituent proportion in the hydrothermal suspension to obtain excellent performance. The minimum reflection loss (RL) of the HMCS@f-Fe2O3-6 composite is -34.16 dB at 2.4 mm, and the effective absorption bandwidth (EAB) reaches 4.8 GHz. Furthermore, the lowest emissivities of the HMCS@f-Fe2O3-6-20 wt %/polyetherimide (PEI) film in the 3-5 and 8-14 μm infrared wavebands are 0.212 and 0.508, respectively. These discoveries may pave the way for the development of radar-infrared compatible stealth materials from the perspective of microstructural design.

Hollow mesoporous carbon nanospheres space-confining ultrathin nanosheets superstructures for efficient capacitive deionization

In this work, we propose a novel strategy to fabricate nickel silicate nanoflakes inside hollow mesoporous carbon spheres (Ni3Si2O5(OH)4/C). Hollow mesoporous carbon spheres (HMCSs) can well regulate and limit the growth of Ni3Si2O5(OH)4 nanosheets, which obviously enhance the structural stability and conductivity of the composites. The core-shell Ni3Si2O5(OH)4/C superstructure has been proven to possess an extremely excellent electrosorption capacity of 28.7 mg g−1 at 1.2 V under a NaCl concentration of 584 mg L−1 for capacitive deionization (CDI). This outstanding property can be attributed to the core-shell superstructure with ultrathin Ni3Si2O5(OH)4 nanosheets as the stable core and mesoporous carbon as the conductive shell. This work will provide a direction for the application of core-shell superstructure carbon-based nanomaterials as high-performance electrode materials for CDI.

Oxygen-containing surface functional groups, mesoporous structure and photothermal effect co-modulated highly-efficient H2O2 production and pollutant degradation

Carbon-based nanomaterials are well-recognized catalysts for H2O2 production though remain insufficient for practical applications, and their photothermal effect is usually ignored. Herein, two typical carbon nanomaterials, mesoporous carbon hollow spheres (MCHS) and carbon hollow spheres (CHS), are selectively synthesized to explore the influence of oxygen-containing surface functional groups, mesoporous structure and photothermal effect on their electrocatalytic and application ability. It was found that the abundant oxygen-containing surface functional groups in MCHS can optimize the adsorption energy of *OOH while the mesoporous structure of MCHS provides plenty of electrochemical active sites, both of which significantly enhance H2O2 production selectivity of the MCHS (96.0% versus 87.0% for the CHS counterpart). Furthermore, the notable photothermal effect of the MCHS can promote the generation of more ·OH radicals and accelerate related reaction kinetics (3.5 times higher than those without NIR light irradiation) under the in-situ electro-Fenton degradation of methyl orange. As a result, remarkable degradation efficiency of 98.1% was achieved for the MCHS under the illumination of near infrared (NIR) light, outperforming those without NIR light irradiation (70.1% for MCHS and 54.7% for CHS). By integrating oxygen-containing surface functional groups, mesoporous structure and photothermal effect, this work achieves remarkable H2O2 production ability and pollutant degradation application simultaneously, providing a new avenue for the design of advanced electrocatalysts and may promote their energy related applications.

Nanostructured Pt-Ru Catalyst Supported on Si-Containing Ordered Mesoporous Carbon Hollow Spheres for the Ethanol Oxidation Reaction

Pt-Ru nanoparticles were dispersed on N-doped Ordered Mesoporous Carbon Hollow Spheres containing Si (N-OMCHS-Si), to obtain the Pt-Ru/N-OMCHS-Si nanocatalyst. Its catalytic activity for the Ethanol Oxidation Reaction (EOR) was evaluated in acid media. Pt-Ru/N-OMCHS-Si showed a higher mass catalytic activity at more negative onset potential (Eonset) for the EOR than Pt-Ru/N-OMCHS (i.e., support without Si), Pt/C and Pt-Ru/C (where C is Vulcan XC-72). Pt-Ru/N-OMCHS-Si also demonstrated a high tolerance to CO, oxidizing the molecule at potentials of comparable negative values as Pt-Ru/C. Moreover, Pt-Ru/N-OMCHS-Si showed enhanced electrochemical stability after Accelerated Degradation Test (ADT) compared to Pt-Ru/C. The high performance of Pt-Ru/N-OMCHS-Si was ascribed to the formation of Pt-Ru alloyed phases and the presence of Si oxides at the hollow spheres.

Catalytic Mo2C decorated hollow mesoporous carbon spheres as sulfur host for lithium-sulfur batteries with high sulfur loading

Hybrid structures as sulfur host materials have been proven to be an effective way to improve the electrochemical property of lithium-sulfur (Li–S) batteries. However, how to construct hybrid nanomaterials with reasonable structure and composition remains a challenge. Herein, the Mo2C nanoparticles grown on the surface of hollow mesoporous carbon spheres (HMCS@Mo2C) are synthesized as an effective sulfur host for Li–S batteries with high sulfur loading. In this hybrid structure, the HMCS can guarantee high sulfur loading, high-speed electron/ion transport, and sufficient buffer for volume change, and the Mo2C nanoparticles as effective catalysts significantly accelerate the conversion of polysulfides. Consequently, the as-prepared HMCS@Mo2C–S cathode demonstrates superb cyclic stability with a capacity decay rate of 0.065% for 500 cycles at 1 ​C. Impressively, HMCS@Mo2C–S cathode with high areal sulfur loading of 5.4 ​mg ​cm−2 can deliver a high specific capacity of 451.2 mAh g−1 after 500 cycles at 0.5 ​C. In addition, the preparation of HMCS@Mo2C is simple, feasible, and low cost. It is hoped that this work will provide new insight into the rational design of sulfur host materials integrating reasonable structure with an effective catalyst for Li–S batteries with high sulfur loading.

N and P dual heteroatom doped mesoporous hollow carbon as an efficient oxygen reduction reaction catalyst in alkaline electrolyte

Heteroatom is doped in hollow carbon materials could be an excellent approach for enhancing sluggish cathodic oxygen reduction reaction (ORR) in fuel cells. Herein, we proposed a facile one step synthesis of N and P dual heteroatom doped hollow mesoporous carbon sphere (NPHS) derived from dopamine hydrochloride (DA) and phytic acid (PA) precursors is inspected for the same. By altering PA addition time interval and its loading concentration we achieved NPHS with high surface area and excellent sphere morphology. We established that the addition of 0.4 g PA at an interval of 30 h into DA mixture found to be optimum condition for the formation of NPHS-0.4. Such conditions favored formation of high surface area (1120 m2 g−1), better shell thickness (31 nm), enriched pyridinic N, P–C and P–N sites thereby resulted to an exceptional ORR activity. Moreover, electrochemical studies proved that NPHS-0.4 material possess a moderate carrier concentration (2.3 × 1015 cm−3) and flat band potential (0.56 V vs RHE) leads to a positive onset potential (0.97 V), limiting current density (4.7 mA cm−2) by adopting a close to four electron ORR pathway. In addition, it shows a remarkable electrochemical stability and excellent methanol oxidation tolerance than the Pt/C catalyst. Thus, this interesting outcome absolutely provides a platform to develop a new type of active dual doped mesoporous carbon materials for various energy storage/conversion applications.

Atomically dispersed Ru(III) on N-doped mesoporous carbon hollow spheres as catalysts for CO2 hydrogenation to formate

Atomically dispersed Ru(III) catalysts on hierarchical and porous supports show great potential for application in the catalysis of the hydrogenation of CO2 to formate due to their high catalytic activity and stability. In this study, heterogeneous Ru(III) catalysts on N-doped mesoporous carbon hollow spheres (N-MCHS) were synthesized through a SiO2-templated resorcinol–formaldehyde polymer pyrolysis at different temperatures. At low pyrolysis temperatures (700–800 °C), the dominant N species on the catalysts were found to be pyrrolic and pyridinic N (Npyrrolic and Npyridinic). However, the dominant N species on the samples produced from 900 to 1000 °C was graphitic N (Ngraphitic). The highest catalytic activities on the batch hydrogenation experiments were recorded on the catalysts with the predominant Ru–Ngraphitic active sites. Using the Ru/N-MCHS-900 catalyst, the turn-over number (TON) was as high as 7550 after the hydrogenation for 2 h at 120 °C and 8 MPa. On the other hand, the Ru/N-MCHS-700 catalyst exhibited excellent stability in both batch and continuous reactors. No noticeable deactivation was observed even after 72 h of continuous hydrogenation, which can be attributed to the strong binding energy between the Ru(III) species, and the Npyridinic and Npyrrolic sites on the N-MCHS supports. This study provided significant insights for the development of novel heterogeneous catalyst systems for the hydrogenation of CO2 to formate.

Sandwich‐Shell Structured CoMn2O4/C Hollow Nanospheres for Performance‐Enhanced Sodium‐Ion Hybrid Supercapacitor

AbstractSodium hybrid supercapacitors (Na‐HSCs) are regarded as one promising electrochemical energy storage device, because of the low price of sodium, prolonged life cycle, and high‐energy/power density. Nonetheless, the imparity between the fast capacitive reactions at cathode and the sluggish Faradaic reactions at the anode leads to an imbalance in the electrochemical reaction kinetics, limiting the development of Na‐HSCs. Therefore, it is urgent to develop suitable anode materials for performance‐enhanced Na‐HSCs. Herein, sandwich‐shell‐structured CoMn2O4/C hollow spheres are synthesized by a facile hydrothermal reaction and subsequent calcination, where mesoporous carbon hollow spheres (CHSs) serve as nonsacrificial hard templates. CHSs with numerous mesoporous channels are beneficial for the penetration of reactant ions. Therefore, CoMn2O4 nanosheets are successfully deposited on the inner and outer surfaces of CHSs, generating sandwich‐shell‐structured CoMn2O4/C hollow spheres. Benefiting from the unique design, CoMn2O4/C HSs exhibit excellent sodium storage performance, including a high‐specific capacity of 290 mAh g–1 at 0.1 A g–1 and prolonged cycling durability. A Na‐HSC assembled by CoMn2O4/C HSs anode and activated carbon cathode exhibits a high‐energy density (265 Wh kg–1) and a wide‐operating voltage range (0.01–4.0 V).

Protecting the state of Cu clusters and nanoconfinement engineering over hollow mesoporous carbon spheres for electrocatalytical C-C coupling

Copper-based catalysts are widely used to adjust the activity and selectivity of CO2 electroreduction reactions (CO2RR). In this article, we choose to use hollow mesoporous carbon spheres (HMCS) to confine and protect Cu clusters to achieve high C2 selectivity. The electrocatalytic results show that when the amount of Cu clusters confined by HMCS reaches 20% (Cu/HMCS5-20%), the selectivity of C2 products reach 88.7% at − 1.0 V vs. RHE. In situ Fourier transform infrared spectroscopy (FTIRS) shows that Cu clusters confined and protected by HMCS is beneficial to the conversion of *CO to *CHO, while the nanocavities formed by HMCS can effectively confine the in situ formed *CHO carbon intermediates, which facilitates the C-C bond coupling to form C2H4 and C2H5OH. We proposes a method to improve the C2 selectivity of CO2RR and reduce the amount of Cu in CO2RR by using the confinement effect of HMCS.

Ultrasensitive catechin electrochemical sensor based on uniform ordered mesoporous carbon hollow spheres (MCHSs) advanced carbon-based conductive materials.

Catechin is one of the flavonoids with antioxidant activity and has attracted great interest. A rapid and accurate detection of catechin is of great significance. Herein, an ultrasensitive catechin electrochemical sensor based on uniform ordered mesoporous carbon hollow spheres (MCHSs) advanced carbon-based conductive material modified glass carbon electrode was constructed. The MCHSs were synthesized by pyrolysis using nitrogen protection and template removal methods, and they exhibited excellent electrochemical detection for catechin owing to their high conductivity and uniform and small spheres with a large specific surface area and hollow structure. Under optimal conditions for the detection of catechin, the MCHSs/GCE showed a wider linear range (10 -1400 nM) and lower detection limit (LOD, 2.82 nM, (S/N = 3)). Furthermore, the electrochemical reaction sites and redox mechanisms of catechin were revealed by electrochemical behavior and density flooding theory. Moreover, the sensor we constructed exhibited good accuracy and stability for the detection of catechin in actual sample detections.

Mo3S13]2−as bidirectional cluster catalysts for high-performance Li–S batteries

[Mo3S13]2−bidirectional cluster catalysts combined with mesoporous carbon hollow spheres (MCHS) as a sulfur host material can improve the performance of Li–S batteries.