N-doped graphene quantum dot-decorated N-TiO2/P-doped porous hollow g-C_(3)N_(4) nanotube composite photocatalysts for antibiotic photodegradation and H2 production

Exclusive responsiveness to ultraviolet light (~3.2 eV) and high photogenerated charge recombination rate are the two primary drawbacks of pure TiO_(2). We combined N-doped graphene quantum dots (N-GQDs), morphology regulation, and heterojunction construction strategies to synthesize N-GQD/N-doped TiO_(2)/P-doped porous hollow g-C_(3)N_(4) nanotube (PCN) composite photocatalysts (denoted as G-TPCN). The optimal sample (G-TPCN doped with 0.1wt% N-GQD, denoted as 0.1% G-TPCN) exhibits significantly enhanced photoabsorption, which is attributed to the change in bandgap caused by elemental doping (P and N), the improved light-harvesting resulting from the tube structure, and the upconversion effect of N-GQDs. In addition, the internal charge separation and transfer capability of0.1% G-TPCN are dramatically boosted, and its carrier concentration is 3.7, 2.3, and 1.9 times that of N-TiO_(2), PCN, and N-TiO_(2)/PCN(TPCN-1), respectively. This phenomenon is attributed to the formation of Z-scheme heterojunction between N-TiO_(2) and PCNs, the excellent electron conduction ability of N-GQDs, and the short transfer distance caused by the porous nanotube structure. Compared with those of N-TiO_(2), PCNs, and TPCN-1, the H2 production activity of 0.1%G-TPCN under visible light is enhanced by 12.4, 2.3, and 1.4times, respectively, and its ciprofloxacin (CIP) degradation rate is increased by 7.9, 5.7, and 2.9 times, respectively. The optimized performance benefits from excellent photoresponsiveness and improved carrier separation and migration efficiencies. Finally, the photocatalytic mechanism of 0.1% G-TPCN and five possible degradation pathways of CIP are proposed. This study clarifies the mechanism of multiple modification strategies to synergistically improve the photocatalytic performance of 0.1% G-TPCN and provides a potential strategy for rationally designing novel photocatalysts for environmental remediation and solar energy conversion.

Hollow tubes constructed by carbon nanotubes self-assembly for CO_(2) capture

Carbon nanotubes(CNTs)have garnered significant attention in the fields of science,engineering,and medicine due to their numerous advantages.The initial step towards harnessing the potential of CNTs involves their macroscopic assembly.The present study employed a gentle and direct self-assembly technique,wherein controlled growth of CNT sheaths occurred on the metal wire’s surface,followed by etching of the remaining metal to obtain the hollow tubes composed of CNTs.By controlling the growth time and temperature,it is possible to alter the thickness of the CNTs sheath.After immersing in a solution containing 1 g/L of CNTs at 60℃ for 24 h,the resulting CNTs layer achieved a thickness of up to 60μm.These hollow CNTs tubes with varying inner diameters were prepared through surface reinforcement using polymers and sacrificing metal wires,thereby exhibiting exceptional attributes such as robustness,flexibility,air tightness,and high adsorption capacity that effectively capture CO_(2) from the gas mixture.

Morphology Control of TiO_(2)Nanotubes towards High-Efficient Electrodes for Supercapacitor

This article studies the role of electrochemical parameters in controlling the morphology of oxidized TiO_(2)nanotubes and the electrochemical performance of modified TiO_(2)nanotubes.Humidity is a key factor for fabricating TiO_(2)nanotubes.When the relative humidity belows 70%,the TiO_(2)nanotubes can be successfully prepared.What's more,by changing the anodization voltage and time,the diameter and the length of TiO_(2)nanotubes can be adjusted.In addition,the TiO_(2)nanotubes are modified through electrochemical self-doping and loading Pt metal particles on the surface of the nanotubes,which promotes the performance of the supercapacitor.The sample anodized at 100 V for 3 h has a specific capacity of up to 2.576 mF/cm~2 at a scan rate of 100 mV/s after self-doping,and its capacity retention rate still remains at 89.55%after 5000 cycles,demonstrating excellent cycling stability.The Pt-modified sample has a specific capacity of up to 3.486 mF/cm~2 at the same scan rate,exhibiting more outstanding electrochemical performance.

Synergistic effect of carbon nanotube and encapsulated carbon layer enabling high-performance SnS_2-based anode for lithium storage

Tin disulfide(SnS_(2)),due to large interlayer spacing and high theoretical capacity,is regarded as a prospective anode material for lithium-ion batteries.Nevertheless,the poor electron conductivity of SnS_(2) and huge volumetric change during the lithiation/delithiation process lead to a rapid capacity decay of the battery,hindering its commercialization.To address these issues,herein,SnS_(2) is in-situ grown on the surface of carbon nanotubes(CNT)and then encapsulated with a layer of porous amorphous carbon(CNT/SnS_(2)@C)by simple solvothermal and further carbonization treatment.The synergistic effect of CNT and porous carbon layer not only enhances the electrical co nductivity of SnS_(2) but also limits the huge volumetric change to avoid the pulverization and detachment of SnS_(2).Density functional theo ry calculations show that CNT/SnS_(2)@C has high Li^(+)adsorption and lithium storage capacity achieving high reaction kinetics.Consequently,cells with the CNT/SnS_(2)@C anode exhibit a high lithium storage capacity of 837mAh/g after 100 cycles at 0.1 A/g and retaining a capacity of 529.8 mAh/g under 1.0 A/g after 1000 cycles.This study provides a fundamental understanding of the electrochemical processes and beneficial guidance to design high-performance SnS_(2)-based anodes for LIBs.

Two-Dimensional Co_(2)(OH)1,4-Benzenedicarboxylate-Halloysite Nanotube Nanocomposite-Epoxy Coating with High Corrosion Resistance

Introducing inorganic nanomaterials into a polymer matrix greatly improves the anticorrosion performance of epoxy coatings(EP);however,poor compatibility between the materials can limit the improvement in properties.In this work,based on the high interface compatibility of two-dimensional(2D)Co_(2)(OH)_(2)BDC(BDC=1,4-benzenedicarboxylate)in the epoxy coating that we reported in previous work,we fabricated a 2D Co_(2)(OH)_(2)BDC-halloysite nanotube(HNT)nanocomposite have a structure consisting of alternating of nanosheets and nanotube by in situ synthesis.The nanocomposite was characterized by Fourier transform infrared spectroscopy,X-ray diffraction,and scanning electron microscopy.The mechanical and anticorrosion performance of the 2D Co_(2)(OH)_(2)BDC-HNT/EP coating was evaluated by mechanical tests and electrochemical impedance spectroscopy spectra.Compared with a conventional unreinforced epoxy coating,the 2D Co_(2)(OH)_(2)BDC-HNT/EP coating had higher mechanical strength and toughness,and the low-frequency impedance modulus of 2D Co_(2)(OH)_(2)BDC-HNT/EP coating was increased by three orders of magnitude,demonstrating the high corrosion resistance of our reinforced coating.

Fabrication and Characterization of Lanthanide-TiO2 Nanotube Composites

Titanium dioxide (TiO2) doped with neodymium (Nd) and/or Gadolinium (Gd) rare-earth elements were fabricated into nanotubes via the hydrothermal method in a KOH solution and in-situ doping. Titanium dioxide nanotubes (TNTs) and in-situ Nd-doped and/or Gd-doped TNTs were characterized with transmission and scanning electron microscopy, energy-dispersive X-ray analysis, X-ray diffraction, Raman spectroscopy, and Fourier-transform infrared spectroscopy. Morphologies indicated a network of aggregated nanotubes. The phase and composition analyses revealed that the lanthanide TNTs had anatase phases with Nd and/or Gd nanoparticles in the TNT lattice. The nanoparticles were uniformly deposited on the surface because of hydroxyl groups on the TNT surfaces, resulting in a very high loading density. The outer diameter and the length of the TNTs increased with doping. The mechanisms for the formation of multiwall TNTs are discussed.

Enhanced ionic conductivity in a novel composite electrolyte based on Gd-doped SnO_(2) nanotubes for ultra-long-life all-solid-state lithium metal batteries

All-solid-state electrolytes are exceedingly attractive because of the outstanding inherent safety and energy density compared to liquid electrolytes.Whereas,it is still formidable to simultaneously design solid electrolytes with favorable electrode/electrolyte interface compatibility and high ionic conductivity in a simple and scalable manner.Hence,the oxygen-vacancy-rich Gd-doped SnO_(2) nanotubes(GDS NTs)are innovatively prepared and applied to the electrolyte of all-solid-state lithium metal batteries for the first time.The addition of GDS NTs can validly construct long-range co ntinuous ion transport networks in the poly(ethylene oxide)(PEO)-based system and greatly improve the mechanical properties of the electrolyte.Compared to the PEO-based electrolyte,the composite electrolyte displays a higher lithium ion conductivity of 2.41×10^(-4) S cm^(-1) at 30℃,a higher lithium ion transference number up to 0.62 and a wider electrochemical window of 5 V at 50℃.In addition,the composite electrolyte manifests outstanding compatibility with high-voltage LiNi_(0.8)Mn_(0.1)Co_(0.1)O_(2)(NMC811)cathode,LiFePO4 cathode and lithium metal anode.The assembled Li/Li symmetric battery exhibits stable Li plating/stripping cycling performance,which can cycle steadily for 1500 h at a capacity of 0.3 mA h cm^(-2).And Li/LiFePO4 battery still maintains a high capacity of 131.54 mA h g^(-1) at 0.5C after 800 cycles,which has a superior capacity retention rate of 93.2%.The obtained novel composite electrolyte has promising application prospects in the field of all-solid-state lithium metal cells.

In-situ incorporation of halloysite nanotubes with 2D zeolitic imidazolate framework-L based membrane for dye/salt separation

Layered assembled membranes of 2D leaf-like zeolitic imidazolate frameworks(ZIF-L)nanosheets have received great attention in the field of water treatment due to the porous structure and excellent antibacterial ability,but the dense accumulation on the membrane surface and the low permeate flux greatly hinder their application.Herein,we synthesized m HNTs(modified halloysite nanotubes)/ZIF-L nanocomposites on modified m HNTs by in situ growth method.Interestingly,due to the different size of m HNTs and ZIF-L,m HNTs were packed in ZIF-L nanosheets.The hollow m HNTs provided additional transport channels for water molecules,and the accumulation of the ZIF-L nanosheets was decreased after assembling m HNTs/ZIF-L nanocomposites into membrane by filtration.The prepared m HNTs/ZIF-L membrane presented high permeate flux(59.6 L·m^(-2)·h^(-1)),which is 2-4 times of the ZIF-L membranes(14.8 L·m^(-2)·h^(-1)).Moreover,m HNTs/ZIF-L membranes are intrinsically antimicrobial,which exhibit extremely high bacterial resistance.We provide a controllable strategy to improve 2D ZIF-L assembles,and develops novel membranes using 2D package structure as building units.

Binary molten salt in situ synthesis of sandwich-structure hybrids of hollowβ-Mo2C nanotubes and N-doped carbon nanosheets for hydrogen evolution reaction

Focused exploration of earth-abundant and cost-efficient non-noble metal electrocatalysts with superior hydrogen evolution reaction(HER)performance is very important for large-scale and efficient electrolysis of water.Herein,a sandwich composite structure(designed as MS-Mo2C@NCNS)ofβ-Mo2C hollow nanotubes(HNT)and N-doped carbon nanosheets(NCNS)is designed and prepared using a binary NaCl–KCl molten salt(MS)strategy for HER.The temperature-dominant Kirkendall formation mechanism is tentatively proposed for such a three-dimensional hierarchical framework.Due to its attractive structure and componential synergism,MS-Mo2C@NCNS exposes more effective active sites,confers robust structural stability,and shows significant electrocatalytic activity/stability in HER,with a current density of 10 mA cm-2 and an overpotential of only 98 mV in 1 M KOH.Density functional theory calculations point to the synergistic effect of Mo2C HNT and NCNS,leading to enhanced electronic transport and suitable adsorption free energies of H*(ΔGH*)on the surface of electroactive Mo2C.More significantly,the MS-assisted synthetic methodology here provides an enormous perspective for the commercial development of highly active non-noble metal electrocatalysts toward efficient hydrogen evolution.

Influence of MnO_(x)deposition on TiO_(2)nanotube arrays for electrooxidation

TiO_(2)has demonstrated outstanding performance in electrochemical advanced oxidation processes(EAOPs)due to its structural stability and high oxygen overpotential.However,there is still much room for improving its electrochemical activity.Herein,narrow bandgap manganese oxide(MnO_(x))was composited with TiO_(2)nanotube arrays(TiO_(2)NTAs)that in-situ oxidized on porous Ti sponge,forming the MnO_(x)-TiO_(2)NTAs anode.XANES and XPS analysis further proved that the composition of MnO_(x)is Mn2O3.Electrochemical characterizations revealed that increasing the composited concentration of MnO_(x)can improve the conductivity and reduce oxygen evolution potential so as to improve the electrochemical activity of the composited MnO_(x)-TiO_(2)NTAs anode.Meanwhile,the optimal degradation rate of benzoic acid(BA)was achieved using MnO_(x)-TiO_(2)NTAs with a MnO_(x)concentration of 0.1 mmol L^(-1),and the role of MnO_(x)was proposed based on DFT calculation.Additionally,the required electrical energy(EE/O)to destroy BA was optimized by varying the composited concentration of MnO_(x)and the degradation voltage.These quantitative results are of great significance for the design and application of high-performance materials for EAOPs.

Fabrication and photodegradation properties of TiO_2 nanotubes on porous Ti by anodization

Both Ti foil and porous Ti were anodized in 0.5%HF and in ethylene glycol electrolyte containing 0.5%NH4F(mass fraction) separately. The results show that TiO2 nanotubes can be formed on Ti foil by both processes, whereas TiO2 nanotubes can be formed on porous Ti only in the second process. The overhigh current density led to the failure of the formation nanotubes on porous Ti in 0.5%HF electrolyte. TiO2 nanotubes were characterized by SEM and XRD. TiO2 nanotubes on porous Ti were thinner than those on Ti foil. Anatase was formed when TiO2 nanotubes were annealed at 400 °C and fully turned into rutile at 700 °C. To obtain good photodegradation, the optimal heat treatment temperature of TiO2 nanotubes was 450 °C. The porosity of the substrates influenced photodegradation properties. TiO2 nanotubes on porous Ti with 60% porosity had the best photodegradation.

Enhanced Photoelectrochemical Property of Zn Loaded TiO2 Nanotube Arrays Electrode

TiO2 nanotube arrays （TNTs） electrode loaded with Zn nanoparticles was prepared by anodization and the size of Zn nanoparticle loaded on TNTs electrode was controlled by chronoamperometry deposition time. Results of SEM and XRD analysis show that Zn nanoparticles had a diameter of about 15-25 nm when the deposition time was 3-5 s. The UV-Vis diffuse reflectance spectra show the Zn loaded harvest light with 480-780 nm more effectively than the unloaded sample. The photocurrent response of Zn loaded TNTs electrodes were studied, the results showed that TNTs electrodes loaded with Zn nanoparti-cles has 50% increased photocurrent response under high-pressure mercury lamp irradiation compared with unloaded TNTs electrode.

Catalytic role of Cu(I) species in Cu_2O/CuI supported on MWCNTs in the oxidative amidation of aryl aldehydes with 2-aminopyridines

Cu2O and Cul were supported on multiwalled carbon nanotubes （MWCNTs） using a wet impregna- tion method, and the resulting materials were fully characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy, transmission electron microscopy, and temperature-programmed desorption with ammonia analysis. The results of these experiments revealed that Cu2O and CuI were deposited on the MWCNTs in the cubic and γ phases, respectively. These results also showed that the Cu-containing MWCNTs exhibited weak to strong electron-accepting （Lewis acidic） properties. The catalytic activities of these materials were studied for the synthesis of biologically significant N-（pyridin-2-yl）benzamides via the oxidative amidation of aryl aldehydes with 2-aminopyridines. The yields of the products were in the range 50%-95% with 100% selectivity. Notably, the CuI/MWCNT catalyst was much more effective than the Cu2O/MWCNT catalyst with respect to the isolated yield of the product, although the latter of these two catalysts exhibited much better recyclability. A preferential interaction was observed between the polar nature of the acid-activated MWCNTs and the ionic Cu2O compared with covalent CuL The differences in these interactions had a significant impact on the rate of the nucleophilic attack of the amino group of 2-aminopyridine substrate on the carbonyl group of the aryl aldehyde.

Crack initiation,propagation and saturation of TiO_2 nanotube film

Vertically orientated TiO2 nanotube array with diameters ranging from 60 up to 80 nm and length of 4 μm was grown on titanium by anodization.Crack initiation,propagation and saturation were studied using the substrate straining test.The results show that annealing obviously modifies the interfaces.With the increase of tensile strain,cracks in TiO2 nanotube films propagate rapidly and reach the saturation within a narrow strain gap.Interfacial shear strengths of TiO2 nanotube films without annealing,with 250 ℃ annealing and with 400 ℃ annealing can be estimated as 163.3,370.2 and 684.5 MPa,respectively.The critical energy release rates of TiO2 nanotube films are calculated as 49.6,102.6 and 392.7 J/m2,respectively.The fracture toughnesses of TiO2 nanotube films are estimated as 0.996,1.433 and 2.803 MPa-m1/2,respectively.The interfacial bonding mechanism of TiO2 nanotube film is chemical bonding.

Buckling pattern of TiO_2 nanotube film

Substrate straining test was carried out to study the buckling pattern of TiO2 nanotube film. The results show that the tensile strains of buckling occurrence of TiO2 nanotube films without annealing, with 250 ℃ annealing and with 400 ℃ annealing are 2.5%, 8.9% and 7.8%, respectively, which indicates the modifying effects of temperature annealing. Through the SEM observation, the critical buckling stresses of TiO2 nanotube films without annealing, with 250 ℃ annealing and with 400 ℃ annealing can be estimated as 180.4, 410.2 and 619.5 MPa, respectively. The critical buckling stress of TiO2 nanotube films with 250 ℃ annealing from AFM observation is estimated as 470.2 MPa, which indicates good agreement with the critical buckling stress from SEM observation. The true stress and the critical energy release rate of TiO2 nanotube film with 250 ℃ annealing are given as 840.3 MPa and 77.2 J/m2, respectively. Excellent agreement of the critical energy release rate of TiO2 nanotube film with 250 ℃ annealing in terms of buckling perspective and crack perspective is obtained.

Formation Mechanistism Study of TiO2 Film Comprising Nanotubes and Nanoparticles

A novel titanium dioxide （TiO2） film comprising both nanotubes and nanopaticles was fabricated by an anodization process of the modified titanium. The local electric field at the anodized surface was simulated and its influence on the morphology of the TiO2 film was discussed. The results show that the electric field strength is enhanced by the covering. The growth rate of TiO2 increases with the assist of the local electric field. However, TiO2 dissolution is hindered since the local electric field prevents [TiF6]6- from diffusing. It means that the balance condition for the formation of nanotubes is broken, and TiO2 nanoparticles are formed. Moreover, the crystal structure of the TiO2 film was confirmed using X-ray diffraction and Raman analysis. The anatase is a main phase for the proposed film.

Debonding phenomenon of TiO_2 nanotube film

Curvature method was used to measure the residual stress and substrate straining tensile test was carried out to study the debonding behavior of TiO2 nanotube film. The results indicate that the internal residual stress is -54 MPa. The strains of debonding initiation of TiO2 nanotube films without annealing, with 250 °C annealing and with 400 °C annealing are 2.6%, 5.1% and 8.6%, respectively, and the average radii of the debonding patches with debonding initiation are 27.5, 17.1 and 19.4 μm, respectively. The true critical debonding stresses of TiO2 nanotube films without annealing, with 250 °C annealing and with 400 °C annealing can be estimated as 220.4, 394.5 and 627.9 MPa, respectively. Interfacial shear lag model is modified and polynomial fitting equation of the interfacial shear strength of TiO2 nanotube film is demonstrated under debonding conditions. The modification and polynomial fitting are reliable since good agreement of the interfacial shear strengths after fitting is obtained compared with those results from the crack density analysis.

Three-dimensional Porous Networks of Ultra-long Electrospun SnO_2 Nanotubes with High Photocatalytic Performance

Recent progress in nanoscience and nanotechnology creates new opportunities in the design of novel SnO2 nanomaterials for photocatalysis and photoelectrochemical. Herein, we firstly highlight a facile method to prepare threedimensional porous networks of ultra-long SnO2 nanotubes through the single capillary electrospinning technique.Compared with the traditional SnO2 nanofibers, the as-obtained three-dimensional porous networks show enhancement of photocurrent and photocatalytic activity, which could be ascribed to its improved light-harvesting efficiency and high separation efficiency of photogenerated electron–hole pairs. Besides, the synthesis route delivered three-dimensional sheets on the basis of interwoven nanofibrous networks, which can be readily recycled for the desirable circular application of a potent photocatalyst system.

Two-dimensional ultrathin MoS2-modified black Ti^3+-TiO2 nanotubes for enhanced photocatalytic water splitting hydrogen production

Two-dimensional (2D) ultrathin MoS2-modified black Ti^3+-TiO2 nanotubes were fabricated using an electrospinning-hydrothermal treatment-reduction method.Bare TiO2 nanotubes were fabricated via electrospinning.Then,2D MoS2 lamellae were grown on the surface of the nanotubes and Ti^3+/Ov ions were introduced by reduction.The photocatalytic performance of the 2D MoS2/Ti^3+-TiO2 nanotubes was^15 times better than that of TiO2.The HER enhancement of the MoS2/Ti^3+-TiO2 nanotubes can be attributed to the Pt-like behavior of 2D MoS2 and the presence of Ti^3+-ions,which facilitated the quick diffusion of the photogenerated electrons to water,reducing the H2 activation barrier.The presence of Ov ions in the nanotubes and their hollow structure increased their solar utilization.

Electrochemical oxidation of rhodamine B by PbO_2/Sb-SnO_2/TiO_2 nanotube arrays electrode

A PbO2/Sb-SnO2/TiO2 nanotube array composite electrode was successfully synthesized and its electrochemical oxidation properties were investigated.Field-emission scanning electron microscopy(FE-SEM)and X-ray diffraction(XRD)results showed that the PbO2 coating was composed of anα-PbO2 inner layer and aβ-PbO2 outer layer.Accelerated life measurement indicated that the composite electrode had a lifetime of 815 h.Rhodamine B(RhB)was employed as a model pollutant to analyze the electrocatalytic activity of the electrode.The effects of initial RhB concentration,current density,initial pH,temperature,and chloride ion concentration on the electrochemical oxidation were investigated in detail.Inductively coupled plasma atomic emission spectroscopy(ICP-AES)results suggested that the concentration of leached Pb^2+in the electrolyte during the electrocatalytic oxidation process can be neglected.Finally,the degradation mechanism during the electrocatalytic oxidation process was proposed based on the results of solid-phase micro-extraction-gas chromatography-mass spectrometry(SPME-GC-MS).The high electrocatalytic performance of the composite electrode makes it a promising anode for the treatment of organic pollutants in aqueous solution.