Hollow Spheres Research Articles

Nitrogen-oxygen co-doped carbon@silica hollow spheres as encapsulated Pd nanoreactors for acetylene dialkoxycarbonylation

The introduction of heteroatoms into hollow carbon spheres is imperative for enhancing catalytic activity. Consequently, we investigated the utilization of nitrogen–oxygen(N/O) co-doped hollow carbon (C)/silica (SiO2) nanospheres (NxC@mSiO2), which have a large internal volume and a nano-constrained environment that limits metal aggregation and loss, making them a potential candidate. In this study, we demonstrate the synthesis of nitrogen–oxygen (N/O) co-doped hollow carbon spheres using resorcinol and formaldehyde as carbon precursors, covered with silica, and encapsulated with palladium nanoparticles (NPs) in situ. The N/O co-doping process introduced defects on the surface of the internal C structure, which acted as active sites and facilitated substrate adsorption. Subsequent treatment with hydrogen peroxide (H2O2) introduced numerous carboxyl groups onto the C structure, increasing the catalytic environment as acid auxiliaries. The carboxyl group is present in the carbon structure, as determined calculations based on by density functional theory, reduces the adsorption energy of acetylene, thereby promoting its adsorption and enrichment. Furthermore, H2O2-treatment enhanced the oxygen defects in the carbon structure, improving the dispersion of Pd NPs and defect structure. The Pd/NxC@mSiO2-H2O2 catalysts demonstrated outstanding performance in the acetylene dialkoxycarbonylation reaction, showcasing high selectivity towards 1,4-dicarboxylate (>93 %) and remarkable acetylene conversion (>92 %). Notably, the catalyst exhibited exceptional selectivity and durability throughout the reaction.

Hematite Hollow-Sphere-Array Photoanodes for Efficient Photoelectrochemical Water Splitting.

Constructing 3D nanophotonic structures is regarded as an effective method to realize efficient solar-to-hydrogen conversion. These photonic structures can enhance the absorbance of photoelectrodes by the light trapping effect, promote the charge separation by designable charge transport pathway and provide a high specific surface area for catalytic reaction. However, most 3D structures reported so far mainly focused on the influence of light absorption and lacked a systematic investigation of the overall water splitting process. Herein, hematite hollow-sphere-array photoanodes are fabricated through a facile hydrothermal method with polystyrene templates. Validating by simulations and experiments, the hollow sphere array is proved to enhance the efficiency of light harvesting, charge separation and surface reaction at the same time. With an additional annealing treatment in oxygen, a photocurrent density of 2.26mA cm-2 at 1.23V versus reversible hydrogen electrode can be obtained, which is 3.70 times larger than that with a planar structure in otherwise the same system. This work gains an insight into the photoelectrochemical water splitting process, which is valuable for the further design of advancing solar driven water splitting devices.

Core-shell nanoconfinement: Nanoreactors for directional electron migration in photothermal-assisted photocatalytic hydrogen production

Photothermal-assisted photocatalysis play crucial factors in solar to chemical/thermal energy conversion via the light–matter interaction. Herein, a photothermal nanoconfinement reactor comprised of a co-catalyst (Mo2C hollow spheres) as the core and a semiconductor photocatalyst (ZnIn2S4 nanosheets) as the shell was designed for achieving high-efficient photothermal-assisted photocatalytic H2 production. Remarkably, the optimal Mo2C@ZnIn2S4 core–shell nanoreactor attains an astonishing H2 evolution rate of 26.1 mmol g−1 h−1 under simulated sunlight irradiation and apparent quantum efficiencies (AQE, 420 nm) value of 19.4 %. The enhanced photocatalytic H2 production performance is attributed the unique core–shell structure can induce the directional migration of the photo-generated electrons excited by the shell (ZnIn2S4) to the nuclear region (Mo2C) with photothermal property, and effectively transport the electrons to the high-temperature zone through the nanoconfinement effect, thus ensuring the effective separation of the photogenerated carriers. This study provides an innovative design for high-efficient photothermal-assisted photocatalyst based on nanoconfinement effect.

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.

Synthesis of porous TiO2/SiO2 monodisperse hollow spheres as a platform for phosphopeptide enrichment

Synthesis of porous TiO2/SiO2 monodisperse hollow spheres as a platform for phosphopeptide enrichment

Highly sensitive electrochemical sensing of norfloxacin by molecularly imprinted composite hollow spheres

Poly (3,4-ethylenedioxythiophene) (PEDOT)-based molecularly imprinted electrochemical sensors have attracted widespread attention for monitoring contaminants in food and the environment. However, there are still problems such as poor hydrophilicity, easy agglomeration, and low selectivity in its preparation. In this work, a novel molecularly imprinted composite hollow sphere was prepared by a molecular imprinting technique using nitrogen-doped hollow carbon spheres as matrix material, and PEDOT and poly(methacrylic acid) as monomers. The selective binding capabilities and mechanism of the material to norfloxacin (NOR) were systematically investigated. Then the material-based sensor was constructed, and its electrochemical detection performance toward NOR was thoroughly studied. The sensor exhibited a wide linear range (0.0005–31 μM), a low detection limit (0.061 nM), satisfactory immunity to interference and stability. Besides, the sensor displayed better sensitivity and reliability (spiked recoveries of 98.0–105.2%, relative standard deviation of 3.45–5.69%) for detecting NOR in lake water, honey, and milk than high-performance liquid chromatography. This work provides a new strategy for developing poly(3,4-ethylenedioxythiophene)-based molecularly imprinted electrochemical sensors.

Framework confinement of multi-metals within silica hollow spheres by one-pot synthesis process

ABSTRACT The control incorporation of metals in silica hollow spheres (SHSs) may bring new functions to silica mesoporous structures for applications including catalysis, sensing, molecular delivery, adsorption filtration, and storage. However, the strategies for incorporating metals, whether through pre-loading in the hollow interior or post-encapsulation in the mesoporous shell, still face challenges in achieving quantitative doping of various metals and preventing metal aggregation or channel blockage during usage. In this study, we explored the doping of different metals into silica hollow spheres based on the dissolution-regrowth process of silica. The process may promote the formation of more structural defects and functional silanol groups, which could facilitate the fixation of metals in the silica networks. With this simple and efficient approach, we successfully achieved the integration of ten diverse metal species into silica hollow sphere (SHS). Various single-metal, dual-metal, triple-metal, and quadruple-metal doped SHSs have been prepared, with the doped metals being stable and homogeneously dispersed in the structure. Based on the structural characterizations, we analyzed the influence of metal types on the morphology features of SHSs. The synergistic effects of multi-metals on the catalysis applications were also studied and compared.

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.

Cobalt hydroxide decorating N-doped hollow carbon sphere as a new sulfur host to improve long cycle stability in lithium–sulfur batteries

Cobalt hydroxide decorating N-doped hollow carbon sphere as a new sulfur host to improve long cycle stability in lithium–sulfur batteries

Capture of volatile iodine by novel conjugated microporous polymers hollow spheres containing N, S electro-rich groups

The radioactive iodine contained in nuclear waste is a major threat to the ecological environment, the safety of the public and human health. Herein, two novel CMPs containing electron-rich N and S were synthesized using the Sonogashira-Hagihara cross-coupling condensation reaction and modulated their micromorphology into hollow microspheres for the study of iodine adsorption. The two CMPs exhibit better iodine adsorption capacity, with 154.6 wt % and 182.4 wt % of adsorbent mass for iodine at 80 °C, respectively. More importantly, HCMP-1 and HCMP-2 show excellent selectivity for iodine adsorption, and the presence of water vapor and cyclohexane which hardly hindered iodine adsorption. On the contrary, the presence of water vapor induces the adsorption of iodine by HCMP-1 with 1.7 times of the initial adsorption value. The adsorption behavior of iodine by HCMPs is consistent with the quasi-secondary kinetic model and the Freundlich isothermal model. Our study may provide new ideas for the design and synthesis of functional CMPs containing electron-rich groups for the effective capture and reversible storage of radioiodine to efficiently solve environmental problems.

Hyphae‐mediated bioassembly of carbon fibers derivatives for advanced battery energy storage

AbstractIngenious design and fabrication of advanced carbon‐based sulfur cathodes are extremely important to the development of high‐energy lithium‐sulfur batteries, which hold promise as the next‐generation power source. Herein, for the first time, we report a novel versatile hyphae‐mediated biological assembly technology to achieve scale production of hyphae carbon fibers (HCFs) derivatives, in which different components including carbon, metal compounds, and semiconductors can be homogeneously assembled with HCFs to form composite networks. The mechanism of biological adsorption assembly is also proposed. As a representative, reduced graphene oxides (rGOs) decorated with hollow carbon spheres (HCSs) successfully co‐assemble with HCFs to form HCSs@rGOs/HCFs hosts for sulfur cathodes. In this unique architecture, not only large accommodation space for sulfur but also restrained volume expansion and fast charge transport paths are realized. Meanwhile, multiscale physical barriers plus chemisorption sites are simultaneously established to anchor soluble lithium polysulfides. Accordingly, the designed HCSs@rGOs/HCFs‐S cathodes deliver a high capacity (1189 mA h g−1 at 0.1 C) and good high‐rate capability (686 mA h g−1 at 5 C). Our work provides a new approach for the preparation of high‐performance carbon‐based electrodes for energy storage devices.

MXene Hollow Spheres Supported by a C–Co Exoskeleton Grow MWCNTs for Efficient Microwave Absorption

HighlightsA hollow core–shell structure was constructed with C–Co as the exoskeleton to support the MXene and multiwalled carbon nanotubes (MWCNTs) endoskeleton, with MWCNTs growing toward the center of the sphere.A reflection loss of − 70.70 dB and an effective absorption bandwidth of 5.67 GHz were obtained when the thickness was only 2.04 mm. The powder filler ratio was only 15 wt%.The unique hollow core–shell structure enhanced multiple reflection and scattering losses.

The hydrothermal synthesis of d-Ti3CN/V2O5 hollow spheres for enhanced supercapacitors applications

In this work, d-Ti3CN MXene was obtained by selective etching of Al from Ti3AlCN by hydrofluoric acid, and a hydrothermal method was employed to prepare d-Ti3CN/V2O5 hollow spheres. The prepared d-Ti3CN/V2O5 hollow spheres showed enhanced electrochemical properties. V2O5 hollow spheres expanded the distance between d-Ti3CN MXene sheets, leading to fast electron transport and improved electrochemical performance of d-Ti3CN/V2O5 hollow spheres. A specific capacitance of 340 F g−1 was achieved at 1 A g−1 current density, which is higher than that of d-Ti3CN MXene (321 F g−1) and V2O5 hollow sphere (155 F g−1). The initial capacitance retention is 89 % after 6000 cycles of constant current charge and discharge at the current density of 10 A g−1. In short, d-Ti3CN/V2O5 hollow spheres show excellent supercapacitor performance regarding specific capacitance and stability.

Recent Developments in Materials for Physical Hydrogen Storage: A Review.

The depletion of reliable energy sources and the environmental and climatic repercussions of polluting energy sources have become global challenges. Hence, many countries have adopted various renewable energy sources including hydrogen. Hydrogen is a future energy carrier in the global energy system and has the potential to produce zero carbon emissions. For the non-fossil energy sources, hydrogen and electricity are considered the dominant energy carriers for providing end-user services, because they can satisfy most of the consumer requirements. Hence, the development of both hydrogen production and storage is necessary to meet the standards of a "hydrogen economy". The physical and chemical absorption of hydrogen in solid storage materials is a promising hydrogen storage method because of the high storage and transportation performance. In this paper, physical hydrogen storage materials such as hollow spheres, carbon-based materials, zeolites, and metal-organic frameworks are reviewed. We summarize and discuss the properties, hydrogen storage densities at different temperatures and pressures, and the fabrication and modification methods of these materials. The challenges associated with these physical hydrogen storage materials are also discussed.

High-Performance Lithium-Ion Batteries with High Stability Derived from Titanium-Oxide- and Sulfur-Loaded Carbon Spherogels.

This study presents a novel approach to developing high-performance lithium-ion battery electrodes by loading titania-carbon hybrid spherogels with sulfur. The resulting hybrid materials combine high charge storage capacity, electrical conductivity, and core-shell morphology, enabling the development of next-generation battery electrodes. We obtained homogeneous carbon spheres caging crystalline titania particles and sulfur using a template-assisted sol-gel route and carefully treated the titania-loaded carbon spherogels with hydrogen sulfide. The carbon shells maintain their microporous hollow sphere morphology, allowing for efficient sulfur deposition while protecting the titania crystals. By adjusting the sulfur impregnation of the carbon sphere and varying the titania loading, we achieved excellent lithium storage properties by successfully cycling encapsulated sulfur in the sphere while benefiting from the lithiation of titania particles. Without adding a conductive component, the optimized material provided after 150 cycles at a specific current of 250 mA g-1 a specific capacity of 825 mAh g-1 with a Coulombic efficiency of 98%.

Remarkable SO2 and H2S Resistant Ability on CO Oxidation by Unique Pd/WO3 3D Hollow Sphere Nanocatalyst: Correlating Structure–Activity Relationships on SO2 Exposure

Remarkable SO₂ and H₂S Resistant Ability on CO Oxidation by Unique Pd/WO₃ 3D Hollow Sphere Nanocatalyst: Correlating Structure–Activity Relationships on SO₂ Exposure

Micro-nano hierarchical urchin-like ZnO/Ag hollow sphere for SERS detection and photodegradation of antibiotics

Abstract Hollow urchin-like substrates have been widely interested in the field of surface-enhanced Raman scattering (SERS) and photocatalysis. However, most reported studies are simple nanoscale urchin-like substrate with limited light trapping range and complicated preparation process. In this paper, a simple and effective controllable synthesis strategy based on micro-nano hierarchical urchin-like ZnO/Ag hollow spheres was prepared. Compared with the 2D structure and solid spheres, the 3D urchin-like ZnO/Ag hollow sphere has higher laser utilization and more exposed specific surface area due to its special hollow structure, which resulted in excellent SERS and photocatalytic performance, and successfully realize the detection and photodegradation of antibiotics. The limited of detection of metronidazole can reach as low as 10−9 M, and degradation rate achieve 89 % within 120 min. The experimental and theoretical results confirm that the ZnO/Ag hollow spheres can be used in the development of ZnO heterostructure for the detection and degradation of antibiotics, which open new avenues for the development of novel ZnO-based substrate in SERS sensing and catalytic application to address environmental challenges.

A Versatile Nanozyme-Based NADH Circulating Oxidation Reactor for Tumor Therapy through Triple Cellular Metabolism Disruption.

Nanozyme-based metabolic regulation triggered by tumor-specific endogenous stimuli has emerged as a promising therapeutic strategy for tumors. The current efficacy, however, is constrained by the limited concentration of endogenous substrates and the metabolic plasticity of tumors. Consequently, the implementation of efficient metabolic regulation in tumor therapy is urgently needed. Herein, a versatile nanozyme-based nicotinamide adenine dinucleotide (NADH) circulating oxidation nanoreactor is reported. First, the synthesized cobalt-doped hollow carbon spheres (Co-HCS) possess NADH oxidase (NOX)-mimicking activity for the NADH oxidation to disrupt oxidative phosphorylation (OXPHOS) pathway of tumor cells. Second, the substrate-cycle manner of Co-HCS can be used for NADH circulating oxidation to overcome the limitation of substrate deficiency. Finally, 2-Deoxy-D-glucose (2-DG) and 6-aminonicotinamide (6-AN) are introduced to block glycolysis and pentose phosphate pathway (PPP), thus creating a versatile nanozyme-based NADH circulating oxidation nanoreactor (Co-HCS/D/A) for tumor therapy through triple cellular metabolism disruption. In vitro and in vivo results demonstrate that the designed nanoreactor not only enhances the catalytic efficiency but also disrupts the tumor metabolic homeostasis, leading to efficient therapy outcome. This study develops a novel NADH circulating oxidation nanoreactor for tumor therapy through triple cellular metabolism disruption, which addresses the limitations of current nanozyme-based metabolism regulation for tumor therapy.

Manganese doped hollow cobalt oxide catalysts for highly efficient oxygen evolution in wide pH range

Heteroatomic substitution of spinel oxides can theoretically optimize oxygen evolution reaction (OER) via redistribution of charges and modification of d-band center. However, the wide pH range of electrocatalysis and catalytic mechanism are still great challenges. Herein, we successfully construct heteroatom Mn-substituted spinel Co3O4 (Mn-Co3O4) with porous hollow sphere structure for highly efficient and wide pH range OER. Benefiting from the atomic Mn-substitution and charge transfer, the Co site in Mn-Co3O4 displays an increased ratio of Co3+/Co2+. Electrochemical measurements demonstrate that Mn-Co3O4 exhibited superior OER activities with small overpotentials of only 305, 520 and 460 mV to afford a current density of 10 mA cm−2 in alkaline, neutral and acidic media, respectively. Meanwhile, Mn-Co3O4 also possesses favorable long-term stability in wide-pH electrolyte. The improved reaction kinetics of Mn-Co3O4 are mainly attributed to the unique hollow sphere structure with high specific surface area, and the increased high valency of Co, which can introduce the d-band center modification of Mn-Co3O4, and reduce the adsorption energy of oxygen intermediates in rate-determining step (RDS).

P-bridged Fe-X-Co coupled sites in hollow carbon spheres for efficient hydrogen generation

Non-precious metals have shown attractive catalytic prospects in hydrogen production from ammonia borane hydrolysis. However, the sluggish reaction kinetics in the hydrolysis process remains a challenge. Herein, P-bridged Fe-X-Co coupled sites in hollow carbon spheres (Fe-CoP@C) has been synthesized through in situ template solvothermal and subsequent surface-phosphorization. Benefiting from the optimized electronic structure induced by Fe doping to enhance the specific activity of Co sites, bimetallic synergy and hollow structure, the as-prepared Fe-CoP@C exhibits superior performances with a turnover frequency (TOF) of 183.5 min−1, and stability of over 5 cycles for ammonia borane hydrolysis, comparable to noble metal catalysts. Theoretical calculations reveal that the P-bridged Fe-X-Co coupled sites on the Fe-CoP@C catalyst surfaces is beneficial to adsorb reactant molecules and reduce their reaction barrier. This strategy of constructing hollow P-bridged bimetallic coupled sites may open new avenues for non-precious metal catalysis.