Electrochemical hydrogen evolution efficiently boosted by interfacial charge redistribution in Ru/MoSe_(2) embedded mesoporous hollow carbon spheres

The strong metal-support interaction inducing combined effect plays a crucial role in the catalysis reaction. Herein, we revealed that the combined advantages of MoSe_(2), Ru, and hollow carbon spheres in the form of Ru nanoparticles(NPs) anchored on a two-dimensionally ordered MoSe_(2) nanosheet-embedded mesoporous hollow carbon spheres surface(Ru/MoSe_(2)@MHCS) for the largely boosted hydrogen evolution reaction(HER) performance. The combined advantages from the conductive support, oxyphilic MoSe_(2), and Ru active sites imparted a strong synergistic effect and charge redistribution in the Ru periphery which induced high catalytic activity, stability, and kinetics for HER. Specifically, the obtained Ru/MoSe_(2)@MHCS required a small overpotential of 25.5 and 38.4 mV to drive the kinetic current density of 10 mA cm^(-2)both in acid and alkaline media, respectively, which was comparable to that of the Pt/C catalyst. Experimental and theoretical results demonstrated that the charge transfer from MoSe_(2) to Ru NPs enriched the electronic density of Ru sites and thus facilitated hydrogen adsorption and water dissociation. The current work showed the significant interfacial engineering in Ru-based catalysts development and catalysis promotion effect understanding via the metal-support interaction.

Fabrication of functional hollow carbon spheres with large hollow interior as active colloidal catalysts

In this study, we have established a facile method to synthesize functional hollow carbon spheres with large hollow interior, which can act as active colloidal catalysts. The method includes the following steps： first, hollow polymer spheres with large hollow interior were prepared using sodium oleate as the hollow core generator, and 2,4-dihydroxybenzoic acid and hexamethylene tetramine （HMT） as the polymer precursors under hydrothermal conditions; Fe3＋ or Ag＋ cations were then introduced into the as-prepared hollow polymer spheres through the carboxyl groups; finally, the hollow polymer spheres can be pseudomorphically converted to hollow carbon spheres during pyrolysis process, meanwhile iron or silver nanoparticles can also be formed in the carbon shell simultaneously. The structures of the obtained functional hollow carbon spheres were characterized by TEM, XRD, and TG. As an example, Ag-doped hollow carbon spheres were used as colloid catalysts which showed high catalytic activity in 4-nitrophenol reduction reaction.

Consecutive hybrid mechanism boosting Na+storage performance of dual-confined SnSe2 in N,Se-doping double-walled hollow carbon spheres

Rationally designed hierarchical structures and heteroatomic doping of carbon are effective strategies to enhance the stability and electrical conductivity of materials.Herein,SnSe_(2)flakes were generated in the double-walled hollow carbon spheres(DWHCSs),in which N and Se atoms were doped in the carbon walls,to construct SnSe_(2)@N,Se-DWHCSs by confined growth and in-situ derivatization.The N and Sedoped DWHCSs can effectively limit the size increase of SnSe_(2),promote ion diffusion kinetics,and buffer volume expansion,which can be proved by electron microscope observation and density functional theory calculation.Consequently,the SnSe_(2)@N,Se-DWHCSs as an anode material for sodium ion batteries(SIBs)demonstrated a distinguished reversible capacity of 322.8 mAh g^(-1)at 5 A g^(-1)after 1000 cycles and a superior rate ability of 235.3 m Ah g^(-1)at an ultrahigh rate of 15 A g^(-1).Furthermore,the structure evolution and electrochemical reaction processes of SnSe2@N,Se-DWHCSs in SIBs were analyzed by exsitu methods,which confirmed the consecutive hybrid mechanism and the phase transition process.

Core-shell mesoporous carbon hollow spheres as Se hosts for advanced Al-Se batteries

Incorporating a selenium(Se)positive electrode into aluminum(Al)-ion batteries is an effective strategy for improving the overall battery performance.However,the cycling stability of Se positive electrodes has challenges due to the dissolution of intermediate reaction products.In this work,we aim to harness the advantages of Se while reducing its limitations by preparing a core-shell mesoporous carbon hollow sphere with a titanium nitride(C@TiN)host to load 63.9wt%Se as the positive electrode material for Al-Se batteries.Using the physical and chemical confinement offered by the hollow mesoporous carbon and TiN,the obtained core-shell mesoporous carbon hollow spheres coated with Se(Se@C@TiN)display superior utilization of the active material and remarkable cycling stability.As a result,Al-Se batteries equipped with the as-prepared Se@C@TiN composite positive electrodes show an initial discharge specific capacity of 377 mAh·g^(-1)at a current density of 1000 mA·g^(-1)while maintaining a discharge specific capacity of 86.0 mAh·g^(-1)over 200 cycles.This improved cycling performance is ascribed to the high electrical conductivity of the core-shell mesoporous carbon hollow spheres and the unique three-dimensional hierarchical architecture of Se@C@TiN.

Ru complex and N,P-containing polymers confined within mesoporous hollow carbon spheres for hydrogenation of CO_(2)to formate

The development of reliable catalysts with both excellent activity and recyclability for carbon dioxide(CO_(2))hydrogenation is challenging.Herein,a ternary hybrid heterogeneous catalyst,involving mononuclear Ru complex,N,P-containing porous organic polymers(POPs),and mesoporous hollow carbon spheres(Ru^(3+)-POPs@MHCS)is reported for CO_(2)hydrogenation to formate.Based on comprehensive structural analyses,we demonstrated that Ru^(3+)-POPs were successfully immobilized within MHCS.The optimized Ru^(3+)-0.5POPs@MHCS catalyst,which was obtained with about 5 wt.%Ru^(3+)and 0.5 mmol POPs polymers confined into 0.3 g MHCS,exhibited high catalytic activity for CO_(2)hydrogenation to formate(turnover number(TON)>1,200 for 24 h under mild reaction conditions(4.0 MPa,120℃))and improved durability,compared to Ru^(3+)catalysts without POPs polymers(Ru^(3+)-MHCS)and unencapsulated MHCS(Ru^(3+)-0.5POPs)catalysts.The improved catalytic performance is attributed to the high surface area and large pore volume of MHCS which favors dispersion and stabilization of Ru^(3+)-POPs.Furthermore,the MHCS and POPs showed high CO_(2)adsorption ability.Ru^(3+)-POPs encapsulated into MHCS reduces the activation energy barrier for CO_(2)hydrogenation to formate.

A candy-like photocatalyst by wrapping Co, N-co-doped hollow carbon sphere with ultrathin mesoporous carbon nitride for boosted photocatalytic hydrogen evolution

Hierarchical carbon material is used as a star cocatalyst in the field of photocatalysis due to its excellent catalytic properties. In this work, mesoporous carbon nitride sheet(MCNS) photocatalyst introduced nitrogen-doped hollow carbon spheres assembled with cobalt nanoparticles(Co@NHC) is synthesized by electrostatic adsorption. A series of characterizations are analyzed to display the structures, morphologies and optical properties of as-prepared materials. The photocatalytic activity of Co@NHC/MCNS material is evaluated with hydrogen evolution under visible light irradiation. The results indicate that 5 wt%Co@NHC/MCNS material reveals higher photocatalytic activity of hydrogen evolution rate of 3675 μmol/g with 4 h reaction time, which is 159 times than that of pure MCNS material. The carbon material with excellent charge transport properties can effectively accelerate the charge transfer from ultrathin MCNS to cobalt nanoparticles. The goal of improving the photocatalytic performance of Co@NHC/MCNS material is achieved. As a result, it provides a feasible and promised approach for doping transition metals to enhance photocatalytic activity.

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℃） 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 doved HCSs is a potential candidate for an efficient electrode material for supercapacitors.

Fe atoms anchored on defective nitrogen doped hollow carbon spheres as efficient electrocatalysts for oxygen reduction reaction

Defective electrocatalysts,especially for intrinsic defective carbon,have aroused a wide concern owing to high spin and charge densities.However,the designated nitrogen species favorable for creating defects by the removal of nitrogen,and the influence of defects for the coordination structure of active site and oxygen reduction reaction(ORR)activity have not been elucidated.Herein,we designed and synthesized a pair of electrocatalysts,denoted as Fe-N/C and Fe-ND/C for coordination sites of atomic iron-nitrogen and iron-nitrogen/defect configuration embedded in hollow carbon spheres,respectively,through direct pyrolysis of their corresponding hollow carbon spheres adsorbed with Fe(acac)3.The nitrogen defects were fabricated via the evaporation of pyrrolic-N on nitrogen doped hollow carbon spheres.Results of comparative experiments between Fe-N/C and Fe-ND/C reveal that Fe-ND/C shows superior ORR activity with an onset potential of 30 mV higher than that of Fe-N/C.Fe-ND sites are more favorable for the enhancement of ORR activity.Density functional theory(DFT)calculation demonstrates that Fe-ND/C with proposed coordination structure of FeN_(4-x)(0<x<4)anchored by OH as axial ligand during ORR,weakens the strong binding of OH^(*)intermediate and promotes the desorption of OH^(*)as rate-determining step for ORR in alkaline electrolyte.Thus,Fe-ND/C electrocatalysts present much better ORR activity compared with that of Fe-N/C with proposed coordination structure of FeN_(4).

Constructing a hollow core-shell structure of RuO_(2) wrapped by hierarchical porous carbon shell with Ru NPs loading for supercapacitor

Hollow core-shell structure nanomaterials have been broadly used in energy storage, catalysis, reactor,and other fields due to their unique characteristics, including the synergy between different materials,a large specific surface area, small density, large charge carrying capacity and so on. However, their synthesis processes were mostly complicated, and few researches reported one-step encapsulation of different valence states of precious metals in carbon-based materials. Hence, a novel hollow core-shell nanostructure electrode material, RuO_(2)@Ru/HCs, with a lower mass of ruthenium to reduce costs was constructed by one-step hydrothermal method with hard template and co-assembled strategy, consisting of RuO_(2) core and ruthenium nanoparticles(Ru NPs) in carbon shell. The Ru NPs were uniformly assembled in the carbon layer, which not only improved the electronic conductivity but also provided more active centers to enhance the pseudocapacitance. The RuO_(2) core further enhanced the material’s energy storage capacity. Excellent capacitance storage(318.5 F·g^(-1)at 0.5 A·g^(-1)), rate performance(64.4%) from 0.5 A·g^(-1)to 20 A·g^(-1), and cycling stability(92.3% retention after 5000 cycles) were obtained by adjusting Ru loading to 0.92%(mass). It could be attributed to the wider pore size distribution in the micropores which increased the transfer of electrons and protons. The symmetrical supercapacitor device based on RuO_(2)@Ru/HCs could successfully light up the LED lamp. Therefore, our work verified that interfacial modification of RuO_(2) and carbon could bring attractive insights into energy density for nextgeneration supercapacitors.

Hierarchical porous nitrogen,oxygen,and phosphorus ternary doped hollow biomass carbon spheres for high-speed and long-life potassium storage

Limited lithium resources have promoted the exploration of new battery technologies.Among them,potassium-ion batteries are considered as promising alternatives.At present,commercial graphite and other carbon-based materials have shown good prospects as anodes for potassium-ion batteries.However,the volume expansion and structural collapse caused by periodic K+insertion/extraction have severely restricted further development and application of potassium-ion batteries.A hollow biomass carbon ball(NOP-PB)ternarily doped with N,O,and P was synthesized and used as the negative electrode of a potassium-ion battery.X-ray photoelectron spectroscopy,Fourier‐transform infrared spectroscopy,and transmission electron microscopy confirmed that the hollow biomass carbon spheres were successfully doped with N,O,and P.Further analysis proved that N,O,and P ternary doping expands the interlayer distance of the graphite surface and introduces more defect sites.DFT calculations simultaneously proved that the K adsorption energy of the doped structure is greatly improved.The solid hollow hierarchical porous structure buffers the volume expansion of the potassium insertion process,maintains the original structure after a long cycle and promotes the transfer of potassium ions and electrons.Therefore,the NOP‐PB negative electrode shows extremely enhanced electrochemical performance,including high specific capacity,excellent long‐term stability,and good rate stability.

ZnS nanolayer coated hollow carbon spheres with enhanced rate and cycling performance for Li-S batteries

Conductive carbon structure has been considered as a promising sulfur-hosting material as the cathode of lithium-sulfur batteries.However, the issue of polysulfide shuttling requires an additional component to help restrict and convert sulfur substances.Herein, in this work, hollow and porous carbon nanospheres(HCS) are synthesized by a template method and a high-temperature carbonization treatment. A thin layer of ZnS coating is then deposited on the HCS-based sulfur(ZnS@HCS/S) cathode with controlled thickness, and the overall electrochemical properties are systematically evaluated. Results show that with 30 nm-thick ZnS coating, the cathode reveals an improved capacity of 1411 m A h g^(-1), and higher capacities from 0.2 to 3 C rate compared with bare HCS/S cathode. Moreover, the ZnS coating also enhances the cycling stability of ZnS@HCS/S cathode over 280 cycles at 0.5 C, with only 0.2% capacity decay per cycle. This work demonstrates potential applications for high-performance lithiumsulfur batteries.

Hollow carbon spheres and their noble metal-free hybrids in catalysis

Hollow carbon spheres have garnered great interest owing to their high surface area,large surface-tovolume ratio and reduced transmission lengths.Herein,we overview hollow carbon sphere-based materials and their noble metal-free hybrids in catalysis.Firstly,we summarize the key fabrication techniques for various kinds of hollow carbon spheres,with a particular emphasis on controlling pore structure and surface morphology,and then heterogeneous doping as well as their metal-free/containing hybrids are presented;next,possible applications for non-noble metal/hollow carbon sphere hybrids in the area of energy-related catalysis,including oxygen reduction reaction,hydrogen evolution reaction,oxygen evolution reaction,water splitting,rechargeable Zn-air batteries and pollutant degradation are discussed;finally,we introduce the various challenges and opportunities offered by hollow carbon spheres from the perspective of synthesis and catalysis.

A Bi-layer Composite Film Based on TiO_2 Hollow Spheres, P25,and Multi-walled Carbon Nanotubes for Efficient Photoanode of Dye-sensitized Solar Cell

A bi-layer photoanode for dye-sensitized solar cell(DSSC) was fabricated, in which TiO_2 hollow spheres(THSs) were designed as a scattering layer and P25/multi-walled carbon nanotubes(MWNTs) as an under-layer. The THSs were synthesized by a sacrifice template method and showed good light scattering ability as an over-layer of the photoanode. MWNTs were mixed with P25 to form an under-layer of the photoanode to improve the electron transmission ability of the photoanode. The power conversion efficiency of this kind of DSSC with bi-layer was enhanced to 5.13 %,which is 14.25 % higher than that of pure P25 DSSC.Graphical Abstract A bi-layer composite photoanode based on P25/MWNTs-THSs with improved light scattering and electron transmission, which will provide a new insight into fabrication and structure design of highly efficient dyesensitized solar cells.

Catalytic oxidation of pentanethiol on basic nitrogen doped carbon hollow spheres derived from waste tires

A series of basic nitrogen doped carbon hollow spheres(p-N-C) catalysts derived from waste tires were prepared by a green, facile and environmental “leavening” strategy for the catalytic oxidation of pentanethiol. Compared to pristine carbon, the p-N-C has a higher surface curvature conducive to the enrichment of substrates, leading to an excellent catalytic performance. This increased surface curvature of p-N-C was fabricated on the synergistic effect of two foaming agents((NH4)2 C2 O4 and NaHCO3), and the released gas also endows the spherical shell of p-N-C with a hierarchical porous structure, promoting the accessibility of active sites with pentanethiol. Pyridine-like and pyrrolic-like nitrogen atoms were investigated as reactive sites on the p-N-C to accelerate the electron transfer from sulfur to active surface oxygen and enhance the adsorption/oxidation process. As a result, the optimal p-N-C catalyst exhibits superior adsorption and oxidation performance(99.9%) of pentanethiol, outperforming the “unleavened”catalyst(20.8%). This work offers a new avenue for the fabrication of highly efficient materials for the desulfurization of fuel.

自然光条件下光自芬顿/PMS协同体系处理新污染物的实验设计

为强化学生对新污染物处理理论和实验技能的掌握,设计了光自芬顿/过氧单硫酸盐(PMS)协同体系在自然光条件下对新污染物的强化降解实验。利用水热法和浸渍法制备改性氮化碳空心球MoS_(2)/TCN_(Cl-S)(P),以四环素(TC)作为新污染物代表,构建了光自芬顿/PMS协同体系,基于其耦合效应,提高在自然光条件下污染物的降解效率。结果表明,光自芬顿/PMS体系对TC在120min内的降解率可以达到80%,较不引入PMS的光自芬顿体系提高了30%。其原因在于光自芬顿反应中产生的H_(2)O_(2)与PMS发生协同作用,产生了更多的·O_(2)^(-)、SO_(4)^(-)·和^(1)O_(2)等活性自由基,从而提高了TC的降解效率。该实验设计体系有助于促进学生对高级氧化技术的掌握,为学生科研创新能力培养体系的构建提供参考。

BTA@HMCs/PANI微胶囊的制备及环氧涂层防腐性能

以硬模板法合成的中空介孔碳球(HMCs)为微容器,通过真空浸渍及原位聚合法成功制得负载缓蚀剂苯并三氮唑(BTA)的BTA@HMCs/PANI微胶囊。制备的微胶囊呈规则球形,平均粒径约为270nm,壁厚(50±10)nm,微胶囊芯材质量分数为31.0%。添加质量分数5%BTA@HMCs/PANI微胶囊的自修复环氧涂层具有最佳的防腐性能,盐水浸泡实验表明环氧复合涂层浸泡30d后无明显腐蚀现象,电化学阻抗实验表明,环氧复合涂层低频区的阻抗模量值较纯环氧涂层高2~3个数量级。文中同时揭示了微胶囊芯材腐蚀抑制剂BTA和微胶囊壁材聚苯胺(PANI)协同防腐机理。

以酚醛树脂为前驱体合成氮掺杂中空碳球及其类酶活性研究

以间苯二酚甲醛树脂为前驱体,三聚氰胺为氮源,球形碳酸钙为模板剂,氢氧化钾为扩孔剂,通过硬模板法合成了氮掺杂中空碳球(NHCSs),通过扫描电子显微镜、场发射透射电子显微镜、X射线光电子能谱仪对NHCSs的微观形貌、表面元素组成及化学价态进行了表征,探究了NHCSs过氧化物模拟酶活性及反应体系中产生的活性氧中间体。结果表明:在弱酸性和H_(2)O_(2)存在的条件下,NHCSs可以快速地催化氧化3,3′,5,5′-四甲基联苯胺(TMB)生成蓝色产物;经过氢氧化钾扩孔处理后的NHCS-1对TMB和H_(2)O_(2)具有良好的亲和力;超氧自由基·O_(2)^(-)和羟基自由基·OH是主要的活性物种。采用简单快速的比色法检测H_(2)O_(2),线性范围为8~1000μmol/L,检测限为4.97μmol/L。

Controllable assembling of highly-doped linked carbon bubbles on graphene microfolds

Carbon-based microassemblies(CMs) have attracted significant attention in numerous applications due to their unique hierarchical structures and delicate building blocks,especially when hollow carbon spheres(HCSs) are reasonably introduced into the construction.Herein,a new design for novel HCSscombined CMs is proposed.Remarkably,the HCSs are linear carbon bubbles linked one-by-one, arranging into necklaces decorating on the graphene microfolds.Detailed thermal analysis confirm that high temperatures straighten the linked carbon bubbles into bamboo-like carbon nanofibers,evidently due to the attenuation of doping degree.Benefiting from the abundant active sites of carbon bubbles,the obtained CMs exhibit satisfactory electrocatalytic activity for oxygen reduction reactions.This work establishes a bridge to precisely control the synthesis of carbon-based hierarchical architectures.

2H-MoS_(2)Modified Nitrogen-Doped Hollow Mesoporous Carbon Spheres as the Efficient Catalytic Cathode Catalyst for Aprotic Lithium-Oxygen Batteries

Developing excellent cathode catalysts with superior catalytic activities is essential for the practical application of aprotic lithium-oxygen batteries(LOBs).Herein,we successfully synthesized nitrogen-doped hollow mesoporous carbon spheres encapsulated with molybdenum disulfide(MoS_(2))nanosheets as the cathode catalyst for rechargeable LOBs,and the relationship between the battery performance and structural characteristics was intensively researched.We found that the synergistic effect of the nitrogen-doped mesoporous carbon and MoS_(2)nanosheets endows superior electrocatalytic activities to the composite catalyst.On the one hand,the nitrogen-doped mesoporous carbon could enable fast charge transfer and effectively accommodate more discharging products in the composite skeleton.On the other hand,the thin MoS_(2)nanosheets could promote mass transportation to facilitate the revisable formation and decomposition of the Li2O2 during oxygen reduction reaction and oxygen evolution reaction,and the side reactions were also prevented,apparently due to their full coverage on the composite surfaces.As a result,the catalytic cathode loaded with 2H-MoS_(2)-modified nitrogen-doped hollow mesoporous carbon spheres exhibited excellent electrochemical performance in terms of large discharge-/charge-specific capacities with low overpotentials and extended cycling life,and they hold great promise for acting as the cathode catalyst for high-performance LOBs.