Manipulating d-d orbital hybridization induced by Mo-doped Co_(9)S_(8) nanorod arrays for high-efficiency water electrolysis

Precisely refining the electronic structure of electrocatalysts represents a powerful approach to further optimize the electrocatalytic performance.Herein,we demonstrate an ingenious d-d orbital hybridization concept to construct Mo-doped Co_(9)S_(8) nanorod arrays aligned on carbon cloth(CC)substrate(abbreviated as Mo-Co_(9)S_(8)@CC hereafter)as a high-efficiency bifunctional electrocatalyst toward water electrolysis.It has experimentally and theoretically validated that the 4d-3d orbital coupling between Mo dopant and Co site can effectively optimize the H_(2)O activation energy and lower H^(*)adsorption energy barrier,thereby leading to enhanced hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)activities.Thanks to the unique electronic and geometrical advantages,the optimized Mo-Co_(9)S_(8)@CC with appropriate Mo content exhibits outstanding bifunctional performance in alkaline solution,with the overpotentials of 75 and 234 mV for the delivery of a current density of 10 mA cm^(-2),small Tafel slopes of 53.8 and 39.9 mV dec~(-1)and long-term stabilities for at least 32 and 30 h for HER and OER,respectively.More impressively,a water splitting electrolylzer assembled by the self-supported Mo-Co_(9)S_(8)@CC electrode requires a low cell voltage of 1.53 V at 10 mA cm^(-2)and shows excellent stability and splendid reversibility,demonstrating a huge potential for affordable and scalable electrochemical H_(2) production.The innovational orbital hybridization strategy for electronic regulation herein provides an inspirable avenue for developing progressive electrocatalysts toward new energy systems.

Hydrothermal growth of well-aligned TiO_2 nanorod arrays: Dependence of morphology upon hydrothermal reaction conditions

Well-aligned TiO2 nanorod arrays （TNAs） were prepared on pretreated quartz substrates via hydrothermal method.The effect of the different preparation conditions on the growth morphologies of TNAs was systematically investigated by X-ray diffraction （XRD） and field-emission scanning electron microscopy （FE-SEM）.The photocatalytic properties were tested by photodegradation of a methyl blue solution.It is demonstrated that the hydrothermal reaction conditions,such as precursor concentration,hydrothermal reaction temperature,and hydrothermal reaction times,can greatly affect the growth of TNAs.Controlling the preparation process,TNAs with 2 μm in length and 140-170 nm in diameter and well-aligned orientation have been successfully prepared.The photocatalytic experiment results indicate that TNAs have much better photocatalytic activity than TiO2 nanoparticles.

Fabrication of highly oriented ZnO nanorod arrays by galvanostatic deposition

Highly oriented ZnO nanorod arrays were successfully prepared on the indium tin oxide （ITO） substrate using a galvanostatic electrodeposition method. The ITO substrate was pretreated with ZnO nanoparticles via simple low-temperature solution route. The crystallinity, microstructure of surface, and optical properties of the obtained ZnO were characterized by X-ray diffraction, scanning electron microscope, and transmittance spectrum. The results indicate that the average diameter of ZnO nanorod arrays is about 30 nm, and the narrow size distribution ranges from 20 to 50 nm. The nanorod arrays are growing along wavelength of incident is over 380 nm, the ZnO nanorod arrays growth mechanism of the nanorod arrays was discussed. [001] direction with an orientation perpendicular to the substrate. When the show a high optical transmission of above 95%. Furthermore, the possible

Direct Z-scheme WO_(3-x) nanowire-bridged TiO_(2) nanorod arrays for highly efficient photoelectrochemical overall water splitting

All-solid-state Z-scheme photocatalysts for overall water splitting to evolve H_(2) is a promising strategy for efficient conversion of solar energy.However,most of these strategies require redox mediators.Herein,a direct Z-scheme photoelectrocatalytic electrode based on a WO_(3-x)nanowire-bridged TiO_(2)nanorod array heterojunction is constructed for overall water splitting,producing H_(2).The as-prepared WO_(3-x)/TiO_(2)nanorod array heterojunction shows photoelectrochemical(PEC)overall water splitting activity evolving both H_(2) and O_(2)under UV-vis light irradiation.An optimum PEC activity was achieved over a 1.67-WO_(3-x)/TiO_(2)photoelectrode yielding maximum H_(2) and O_(2)evolution rates roughly 11 times higher than that of pure TiO_(2)nanorods without any sacrificial agent or redox mediator.The role of oxygen vacancy in WO_(3-x)in affecting the H_(2) production rate was also comprehensively studied.The superior PEC activity of the WO_(3-x)/TiO_(2)electrode for overall water splitting can be ascribed to an efficient Z-scheme charge transfer pathway between the WO_(3-x)nanowires and TiO_(2)nanorods,the presence of oxygen vacancies in WO_(3-x),and a bias potential applied on the photoelectrode,resulting in effective spatial charge separation.This study provides a novel strategy for developing highly efficient PECs for overall water splitting.

Quantitative modeling, optimization, and verification of ^(63)Nipowered betavoltaic cells based on three-dimensional ZnO nanorod arrays

Betavoltaic cells(BCs)are promising self-generating power cells with long life and high power density.However,the low energy conversion efficiency(ECE)has limitations in practical engineering applications.Widebandgap semiconductors(WBGSs)with three-dimensional(3-D)nanostructures are ideal candidates for increasing the ECE of BCs.This paper proposes hydrothermally grown ZnO nanorod arrays(ZNRAs)for ^(63)Ni-powered BCs.A quantitative model was established for simulation using the parameter values of the dark characteristics,which were obtained from the experimental measurements for a simulated BC based on a Ni-incorporated ZNRAs structure.Monte Carlo(MC)modeling and simulation were conducted to obtain the values of the β energy deposited in ZNRAs with different nanorod spacings and heights.Through the simulation and optimization of the 3-D ZNRAs and 2-D ZnO bulk structures,the performance of the ^(63)Ni-powered BCs based on both structures was evaluated using a quantitative model.The BCs based on the 3-D ZNRAs structure and 2-D ZnO bulk structure achieved a maximum ECE of 10.1%and 4.69%,respectively,which indicates the significant superiority of 3-D nanostructured WBGSs in increasing the ECE of BCs.

Strain relaxation and optical properties of etched In_(0.19)Ga_(0.81) N nanorod arrays on the GaN template

InGaN/GaN epilayers, which are grown on sapphire substrates by the metal-organic chemical-vapour deposition （MOCVD） method, are formed into nanorod arrays using inductively coupled plasma etching via self-assembled Ni nanomasks. The formation of nanorod arrays eliminates the tilt of the InGaN （0002） crystallographic plane with respect to its GaN bulk layer. Photoluminescence results show an apparent S-shaped dependence on temperature. The light extraction efficiency and intensity of photoluminescence emission at low temperature of less than 30 K for the nanorod arrays are enhanced by the large surface area, which increases the quenching effect because of the high density of surface states for the temperature above 30 K. Additionally, a red-shift for the InGaN/GaN nanorod arrays is observed due to the strain relaxation, which is confirmed by reciprocal space mapping measurements.

Novel photoelectric material of perovskite-like(CH_(3))_(3)SPbI_(3) nanorod arrays with high stability

Organometallic halide perovskite materials make great achievements in optoelectronic fields,especially in solar cells,in which the organic cations contain amine components.However,the amine with NàH bonds is easily hydrolyzed with moisture in the air,weakening the perovskite materials stability.It is desirable to develop other non-amine stable perovskite materials.In this work,sulfur-based perovskite-like(CH_(3))_(3)SPbI_(3) nanorod arrays were fabricated by a solution-processed method,which can be indexed hexagonal crystal structure in the space group P63 mc.The binding force is exceptionally strong between the non-amine(CH_(3))_(3) S+and[PbI_(6)]_(4)-octahedral,leading to high stability of(CH_(3))_(3)SPbI_(3).The(CH_(3))_(3)SPbI_(3) nanorod arrays can keep the morphology and crystal structure in an ambient atmosphere over 60 days.In addition,the(CH_(3))_(3)SPbI_(3) nanorod arrays can offer direct charge transfer channels,which show excellent optoelectronic properties.The(CH_(3))_(3)SPbI_(3) nanorod arrays-based solar cells with VOx hole transfer layers achieved a power conversion efficiency of 2.07%with negligible hysteresis.And the(CH_(3))_(3)SPbI_(3) nanorod arrays were also effectively applied in photodetectors with interdigitated gold electrodes.This work demonstrates that sulfur-based perovskite-like(CH_(3))_(3)SPbI_(3) is a novel promising stable compound with great potential for practical optoelectronic applications.

A self-powered ultraviolet photodetector with van der Waals Schottky junction based on TiO_(2) nanorod arrays/Au-modulated V2CTx MXene

A self-powered ultraviolet photodetector(UV PD)with van der Waals(vdW)Schottky junction based on TiO_(2) nanorod arrays/Au-modulated V2 CTx MXene is reported.The Schottky junction enables the device to operate in self-powered mode.The dangling bond-free surface of V2 CTx MXene reduces the charge recombination at the junction interface.Meanwhile,V2 CTx MXene,with the work function(WF)increasing to 5.35 eV,forms a hole transport layer by contacting with Au electrode,which facilitates the carrier extraction.The electron lifetime in the device has prolonged to 8.95μs.As a result,the responsivity and detectivity of the PD have achieved 28 mA/W and 1.2×10^(11) cm Hz1/2/W(340 nm,65 mW/cm2,0 V),respectively.In addition,the presence of the Au electrode prevents the vanadium from coming into contact with oxygen and oxidizing,preserving the properties of the V2 CTx films.After 180 days of exposure to the atmosphere,the device performance remained at a particularly high level,indicating enhanced durability.This work points out an effective approach to modulate the properties of V2 CTx to obtain the high performance and stability of the UV PD.

Free-standing ZnO nanorod arrays modified with single-walled carbon nanotubes for betavoltaics and photovoltaics

A full-duplex radiant energy converter based on both betavoltaic and photovoltaic effects in an easyto-implement way is an attractive alternative for the autonomous wireless sensor microsystem.Here,we report a novel beta/photovoltaic cell based on free-standing Zn O nanorod arrays(ZNRAs)modified with metallic single-walled carbon nanotubes(m-SWCNTs),using radioisotope63 Ni as beta-emitting source.The ZNRAs were grown on Al-doped Zn O(AZO)conductive glass using hydrothermal method.The optimum length and diameter of Zn O nanorods were determined by Monte Carlo simulation for beta energy deposition in ZNRAs.The m-SWCNTs were anchored into the ZNRAs to form a three-dimensional(3-D)Schottky junction structure for effectively separating the beta/photo-excited electron-hole pairs.Experimentally,the betavoltaic and photovoltaic effects were confirmed through the I-V measurements of beta/photovoltaic cells under beta/UV/Vis irradiations,respectively.It is suggested that the m-SWCNTs play key role for the enhancement of beta/photovoltaic performance through the formation of extensive3-D Schottky junction,the conductive network for hole transport,and the surface plasmon resonance exciton absorption for visible light.

In situ growth of single-crystal TiO2 nanorod arrays on Ti substrate： Controllable synthesis and photoelectro- chemical water splitting

Despite one-dimensional （1D） semiconductor nanostructure arrays attracting increasing attention due to their many advantages, highly ordered TiO2 nanorod arrays （TiO2 NR） are rarely grown in situ on Ti substrates. Herein, a feasible method to fabricate TiO2 NRs on Ti substrates by using a through-mask anodization process is reported. Self-ordered anodic aluminum oxide （AAO） overlaid on Ti substrate was used as a nanotemplate to induce the growth of TiO2 NRs. The NR length and diameter could be controlled by adjusting anodization parameters such as electrochemical anodization voltage, anodization time and temperature, and electrolyte composition. Furthermore, according to the proposed NR formation mechanism, the anodized Ti ions migrate and deposit in the AAO nanochannels to form Ti（OH）4 or amorphous TiO2 NRs under electric field, owing to the confinement effect of the template. Photoelectrochemical tests indicated that, after hydrogenation, the TiO2 NRs presented higher photocurrent density under simulated sunlight and visible light illuminations, suggesting their potential use in photoelectrochemical water splitting, photocatalysis, solar cells, and sensors.

Uniform and reproducible plasmon-enhanced fluorescence substrate based on PMMA-coated, large-area Au@Ag nanorod arrays

Here we describe a plasmon-enhanced fluorescence substrate based on poly（methyl methacrylate） （PMMA）-coated, large-area Au@Ag nanorod arrays. The use of a PMMA medium enables precise control of the competition between enhancing and quenching processes as a function of the distance between Au@Ag nanorods and dye molecules. At the optimal PMMA layer thickness of 56 nm （for which the distance between nanopartides and dye molecules is 16 nm）, a maximum enhancement of fluorescence of up to N 27 times is measured. The competition mechanism between enhancing and quenching processes depends on the thickness of the PMMA layer, which has been confirmed by consistent experimental and theoretical modeling results. Notab136 the micropatterned metal-enhanced fluorescence （MEF） substrate exhibits high uniformity and reproducibility. The simple spin-coating process described herein provides an attractive, scalable, and low-cost strategy to produce uniform and reproducible large-area MEF substrates that can potentially be used in many fields, such as biochips, diagnostics, and photonics.

Effect of Substrate Pretreatment on Controllable Growth of TiO_2 Nanorod Arrays

Well-aligned TiO2 nanorod arrays （TNAs） were prepared on the pretreated quartz substrates. The effect of the pretreatment conditions on the growth of TNAs was systematically investigated by X-ray diffraction （XRD）, field-emission scanning electron microscopy （FE-SEM） and high-resolution transmission electron microscopy （HRTEM）. It is demonstrated that the pre-coating TiO2 crystal seeds on the substrates can greatly improve the growth orientation of TNAs. Rutile Ti02 crystal seeds induce the nucleation and growth of TNAs more preferably than the anatase TiO2 seeds. The growth density and diameter distribution of TNAs strongly depend on the TiO2 crystal seeds density. It is proved that TNAs with different morphologies can be controllably synthesized by using hydrothermal approach by pretreating substrates. The photocatalytic activity of TNAs was investigated by measuring the photodegradation rate of methyl blue aqueous solution under UV irradiation （254 nm）. And the results show that TNAs with large growth density and small diameter size exhibit relatively higher photocatalytic activity.

Enhancement of mass transfer efficiency and photoelectrochemical activity for TiO_(2)nanorod arrays by decorating Ni^(3+)-states functional NiO water oxidation cocatalyst

Photoelectrochemical(PEC)water splitting is a promising technology to use solar energy.However,current metal oxides photoanode face the problem of sluggish water oxidation kinetic.In this study,we propose that the sluggish water oxidation process will cause slow mass transfer efficiency,which are rarely considered previously,especially at large bias and strong illumination.Mass transfer refers to the migration of reactants(like H_(2)O and OH^(-))to the photoanode surface,reaction with holes and diffusion of products(like radical and O^(2))to the bulk of the electrode.If the migration and diffusion are not fast enough,the mass transfer will inhibit the increase of PEC activity.This problem will be more apparent for nanorod arrays(NRAs),where the space among the NRAs is related narrow.Herein,we solve this problem by decorating the surface of the photoanode by NiO clusters with Ni3+state as water oxidation cocatalysts.This work studies the PEC process from the viewpoint of mass transfer and firstly demonstrates that mass transfer in NRAs structure can be promoted by using Ni-based water oxidation cocatalyst.

A facile solution processed ZnO@ZnS core–shell nanorods arrays for high-efficiency perovskite solar cells with boosted stability

Zinc Oxide(ZnO)has been extensively applied as electron transport material(ETM)in perovskite solar cells(PSCs)since the emergence of PSCs.However,some chemisorbed oxygen species on the surface of ZnO can cause the degradation of CH3NH3+(MA^(+))based perovskite.To avoid the destructive effect of ZnO,a facile solution strategy was proposed to produce a ZnS shell around the ZnO nanorods arrays(ZnO-NRs),i.e.ZnO@ZnS core-shell nanorods(ZnO-NRs@ZnS).The ZnO-NRs@ZnS cascade structure can not only facilitate carrier transport,but also enhance the stability of ZnO based PSCs.A power conversion efficiency(PCE)of 20.6%was finally yielded,which is the-state-of-the-art efficiency for PSCs with one-dimensional(1 D)ZnO electron transport materials(ETMs).Moreover,over 90%of the initial efficiency was retained for the unencapsulated device with ZnO-NRs@ZnS ETMs at 85℃for 500 h,demonstrating excellent stability.This work provides a simple and efficient avenue to simultaneously enhance the photovoltaic(PV)performance and stability of 1 D ZnO nanostructure-based PSCs.

Design and tailoring of patterned ZnO nanostructures for perovskite light absorption modulation

Lithography is a pivotal micro/nanomanufacturing technique,facilitating performance enhancements in an extensive array of devices,encompassing sensors,transistors,and photovoltaic devices.The key to creating highly precise,multiscale-distributed patterned structures is the precise control of the lithography process.Herein,high-quality patterned ZnO nanostructures are constructed by systematically tuning the exposure and development times during lithography.By optimizing these parameters,ZnO nanorod arrays with line/hole arrangements are successfully prepared.Patterned ZnO nanostructures with highly controllable morphology and structure possess discrete three-dimensional space structure,enlarged surface area,and improved light capture ability,which achieve highly efficient energy conversion in perovskite solar cells.The lithography process management for these patterned ZnO nanostructures provides important guidance for the design and construction of complex nanostructures and devices with excellent performance.

Interpenetrating structure for efficient Sb_(2)Se_(3) nanorod array solar cells loaded with CuInSe_(2) QDs sensitizer

The strong anisotropic electrical properties of one-dimensional(1 D) nanostructure semiconductors,especially the anisotropic carrier transport, have a negative and significant influence on the performance of solar cells if the nanostructures have random orientation. Considering the advantages of nanorod solar cells in carrier transport, we have achieved growth of vertically aligned Sb_(2)Se_(3) nanorod array with highly(hk1) orientation on Cd S substrate, and constructed superstrate nanorod solar cells for the first time. The Sb_(2)Se_(3) nanorod array solar cells exhibit the more efficient and long-range carrier transport in vertical direction. Furthermore, in order to suppress interface recombination, a CuInSe_(2) quantum dots(QDs) sensitizer has been applied to fill the volume between the nanorods completely, thus forming an interpenetrating nanocomposite structure. The CuInSe_(2) QDs can harvest additional light by absorption of visible light and contribute photocurrent. Meantime, the QDs function as a hole transport material and thus reduce the dependence of lateral transport. Consequently, the interpenetrating nanocomposite CuInSe_(2) / Sb_(2)Se_(3) solar cells display a power conversion efficiency of 7.54% with significant enhancements in the short-circuit current density and open-circuit voltage over pure Sb_(2)Se_(3) nanorod cells. This is the highest efficiency for superstrate solar cells based on Sb_(2)Se_(3) nanorod arrays.

Core-shell TiO_(2)/ZnO nanorod array films on FTO:Two-step synthesis and improved ethanol sensing performance

In this work,highly regular TiO_(2)nanorod array films were synthesized in situ on FTO by a facile hydrothermal method,and then ZnO shell layers were grown on the surface of the nanorods to form a coreshell structure via an ion-layer adsorption-reaction way.Compared to the TiO_(2)nanorods,the prepared TiO_(2)/ZnO nanocomposites exhibited enhanced ethanol sensing performances,including a low working temperature,higher sensitivity,and faster response capability.The optimum sensor based on 2c-TiO_(2)/ZnO exhibited the maximum response value of 30.85 toward 50×10^(-6)C_(2)H_(5)OH at 340℃,which was almost 4.15 times higher than that of the TiO_(2)sensor.The improved ethanol sensing mechanism was discussed in relation to the unique nanorod array structure and the heterojunctions between TiO_(2)and ZnO.

Improving color rendering index of Mn-doped ZnO nanorods on silicon-based substrate

Porous silicon pillar array（PSPA） samples which are ideal substantial materials with dominant electronic and luminescence properties were prepared by surface etching method. ZnO nanorods with or without Mn doping grown uniformly and aligned onto PSPA regardless of lattice matching show various photoluminescence（PL）properties. The doped Mn ions in ZnO nanorods were directly observed by X-ray photoelectron spectroscopy（XPS）,and ZnO structures were detected by X-ray diffraction（XRD）. As the doping concentration increases,XRD peaks of ZnO nanorods shift to low angle. The influences of doping Mn ions on luminescence properties of ZnO nanorods were investigated. Except for the ultraviolet（UV） PL band, the broad PL band is observed at visible region. The band could be divided into three separate bands（orange, green and red） by Lorentzian deconvolution. The intensity of orange PL band firstly increases then decreases, and then gets the maximum at the doping Mn-to-Zn molar ratio of 2.0：100.0 which is the most effective doping concentration. The green PL band is attributed to zinc vacancy of ZnO, the orange PL band to Mn ions recombination of itself, and the red PL band to oxygen vacancy of ZnO, respectively. As the Mn-doped ZnO nanorods could emit yellow green luminescence excited by UV radiation, and doped Mn ions could improve the color rendering index of the luminescence, the nanorods could be used as promising white-light emitters in the future.

Hierarchical ferric-cobalt-nickel ternary oxide nanowire arrays supported on graphene fibers as high-performance electrodes for flexible asymmetric supercapacitors

Fiber-based supercapacitors （FSCs） are new members of the energy storage family. They present excellent flexibility and have promising applications in lightweight, flexible, and wearable devices. One of the existing challenges of FSCs is enhancing their energy density while retaining the flexibility. We developed a facile and cost-effective method to fabricate a highly capacitive positive electrode based on hierarchical ferric-cobalt-nickel ternary oxide nanowire arrays/graphene fibers and a negative electrode based on polyaniline-derived carbon nanorods/graphene fibers. The elegant microstructures and excellent electrochemical performances of both electrodes enabled us to construct a high- performance flexible asymmetric graphene fiber-based supercapacitor device with an operating voltage of 1.4 V, a specific capacitance up to 61.58 mF.cm-2, and an energy density reaching 16.76 μW·h·cm-2. Moreover, the optimal device presents an outstanding cycling stability with 87.5% initial capacitance retention after 8,000 cycles, and an excellent flexibility with a capacitance retention of 90.9% after 4,000 cycles of repetitive bending.

Constructed TiO_(2)/WO_(3)heterojunction with strengthened nano-trees structure for highly stable electrochromic energy storage device

Tungsten trioxide(WO_(3))has been widely regarded as a prospective bifunctional material due to its electrochromic and pseudocapacitive properties,while still facing the dilemma of inadequate cycle stability and trapping-induced degradation.Here,inspired by the trees-strengthening approach,a unique titanium dioxide(TiO_(2))nanorod arrays strengthened WO_(3)nano-trees(TWNTs)heterojunction was rationally designed and constructed.In sharp contrast to the transmittance modulation(ΔT)attenuation of primary WO_(3)nano-trees during cycling,the TWNTs film showed not only excellent electrochromic performance but also fascinating cycle stability(77.35%retention of the initialΔT after 10,000 cycles).Besides,the trapping-induced degradation could be easily rejuvenated by a potentiostatic de-trapping process.An electrochromic energy storage device(EESD)was further assembled based on the TWNTs film to deliver excellentΔT(up to 79.5%at 633 nm),fast switching speed(tc/tb=1.9 s/14.8 s),extremely high coloration efficiency value(443.4 cm^(2)·C^(−1)),and long-term cycle stability(over 10,000 charge/discharge cycles).This innovative study provided in-depth insights into the electrochromism nature and a significant step in the realization of stable electrochromic-energy storage application,paving the way for multifunctional smart windows as well as next-generation optoelectronic devices.