Nanoplate Arrays Research Articles

Co/N-codoped carbon nanoplate array coated carbon fiber cathode for solar driven uranium extraction from complex radioactive wastewater

Organics bring great challenge on uranium reduction due to the formation of stubborn complexes between uranyl ions (UO22+) and organics. Herein, we developed an effective strategy to synchronously degrade organics and extract uranium from complicated radioactive wastewater, accompanied with electricity generation, by a novel self-driven photocatalytic fuel cell (NSPFC) system, in which a three-dimensional (3D) Co/N-doped carbon nanoplate array (Co-N-C/CF) decorated carbon fiber is employed as the cathode for highly efficient UO22+ reduction. Compared to pure CF, the optimized Co-N-C/CF cathode increases the rate constants (k) by 9 and 9.1 times for UO22+ and organic elimination, respectively, and improves electricity output by 2 times (Pmax, 1180 μW/cm2). This improvement should be ascribed to the 3D morphology of Co-N-C/CF that provided plenty of surface area for U(VI) reduction, and the doping of N and Co, which effectively increased the U(VI) adsorption sites and optimized the electron behavior on the cathode, respectively. These features endow the NSPFC system with excellent adaptability in treating complex radioactive wastewater with a wide range of pollutant concentration, pH, co-existed ions, pollutant organics and natural organic matters. Fascinating activity is also achieves in treating polluted seawater or under real sunlight illumination. This work not only provides a outstanding nanostructured cathode for uranium reduction but also suggests a charming system to resourcefully treatment of radioactive wastewater or polluted water bodies.

Surface S doping induced ladder-regulation of lattice oxygen on the vertical FeCoOOH for water oxidation

Reasonable design and manipulation of appropriately activated lattice oxygen on the catalytic surface is key to efficient oxygen evolution reaction (OER). Utilizing anionic regulation mechanism, partial and rapid sulfur (S) substitution for oxygen can provide optimal surface reconstruction of CoFe oxo/(hydroxo)ide materials during the OER process. S-doping can modulate the local electronic structure of CoFe oxo/(hydroxo)ide compounds, thereby reducing the oxygen vacancies formation energy. This is the first gradient to form more oxygen vacancies, thus activating lattice oxygen. In addition, the hybridization between Co/Fe 3d and O 2p is enhanced by the trace S doping on the surface of CoFe oxo/(hydroxo)ides, suggesting a faster rate of electronic transfer. Therefore, the electrochemical measurements show that the obtained electrocatalyst demonstrates an overpotential of 361.1 mV at 100 mA cm−2 and long-term stability. The characterizations after stability tests confirm that surface S was rapidly leached to form a second gradient high concentration oxygen vacancies. Moreover, the formation of uniformly dispersed vertical nanoplate arrays of FeCoOOH exposes a wealth of active sites. This work provides a promising ladder regulation strategy of lattice oxygen for the design of pre-catalysts for the development of large-scale water decomposition systems.

LDH/MXene Synergistic Carrier Separation Effects to Improve the Photoelectric Catalytic Activities of Bi2WO6 Nanosheet Arrays.

Photoelectric catalysis is a green and efficient way to degrade pollutants, which has been paid more and more attention by researchers. Among them, Bi2WO3 has been proved to have excellent photocatalytic oxidation activity on its {001} facets. In this study, {001}-oriented facets with high exposure were successfully integrated into Bi2WO6 nanoplate arrays (Bi2WO6 NAs) to create a photoelectrode. This structure was grown in situ on an indium tin oxide (ITO) substrate. To promote photogenerated carrier separation efficiency and reduce agglomeration of Bi2WO6 photocatalysts, the electrochemical deposition of NiFe-layered double hydroxide (NiFe-LDH) and Ti3C2 (MXene) were introduced in this research to synergistically catalyze pollutant degradation. Morphology, spectral characterization, and electrochemical analysis jointly confirmed that the outstanding performance of hole capture behavior with LDH and electron conduction properties with MXene were the main reasons for the improvement in catalytic activity of the photoelectrode. Taking bisphenol A (BPA) as the model pollutant, the rate constant k of the NiFe-LDH/Ti3C2/Bi2WO6 NAs photoelectrode reaches 0.00196 min-1 under photoelectrocatalytic (PEC) conditions, which is 4.5 times that of the pure Bi2WO6 NAs photoelectrode. This work provides a new way to improve the reaction kinetics of the PEC degradation of pollutants.

Efficient WO3 Nanoplate Arrays Photoanode Modified by ZnO Nanosheets for Enhanced Charge Separation and Transfer to Promote Photoelectrochemical Performances

AbstractA key factor in the photoelectrochemical (PEC) performance of photoelectrodes is the efficient separation and transfer of photogenerated charges. Herein, a novel photoanode comprising three‐dimensional (3D) WO3 nanoplate@ZnO nanosheet hierarchical type‐II heterojunction arrays (3D WO3@ZnO HHAs) is designed and constructed via modification of the WO3 nanoplate arrays with ZnO nanosheets. The synthesized materials are characterized viaX‐ray diffraction (XRD), ultraviolet and visible spectrophotometry (UV–vis), scanning electon microscopy (SEM), transmission electron microscopy (TEM), and X‐ray photoelectron spectroscopy (XPS) analyses. Photoelectrochemical (PEC) test results reveal that the synthesized 3D WO3@ZnO HHAs photoanode exhibits reduced charge transfer resistance, improved electron‐hole pair life, and enhanced photocurrent density (≈4.5 times increase in comparison to that of the bare WO3). The increased light capture and high surface area in contact with the electrolyte as well as the enhanced charge transfer through the synergy between morphology and band structures may be responsible for the improved PEC characteristics.

Electroactivated Modulation of Highly Aligned Manganese-Doped Cobalt Sulfide Nanoplate Arrays for High-Performance Hybrid Supercapacitors

Electroactivated Modulation of Highly Aligned Manganese-Doped Cobalt Sulfide Nanoplate Arrays for High-Performance Hybrid Supercapacitors

Efficient plasmonic water splitting by heteroepitaxial junction-induced faceting of gold nanoparticles on an anatase titanium(IV) oxide nanoplate array electrode.

Plasmonic photocatalysts represented by gold nanoparticle (NP)-loaded titanium(IV) oxide (Au/TiO2) can be promising solar-to-fuel converters by virtue of their response to visible-to-near infrared light. Hitherto, Au/rutile (R)-TiO2 has been recognized as exhibiting photocatalytic activity higher than that of Au/anatase (A)-TiO2. Herein, we demonstrate that the high potential of A-TiO2 as the Au NP support can be brought out through atomic level interface control. Faceting of Au NPs is induced by a heteroepitaxial junction on an A-TiO2(001) nanoplate array (Au/A-TiO2 NPLA). Photoexcitation towards the Au/A-TiO2 NPLA electrode generates current for the water oxidation reaction at λ < 900 nm with a maximum efficiency of 0.39% at λ = 600 nm, which is much larger than the values reported so far for the usual electrodes. The striking activity of the Au/A-TiO2 NPLA electrode was rationalized using a potential-dependent Fowler model. This study presented a novel approach for developing solar-driven electrodes for green and sustainable fuel production.

Highly-efficient uranium reduction, organic oxidation and electricity generation via a solar-driven wastewater resourceization system with a PANI/CF cathode

Co-existed organics bring great challenges for uranium recycling from water because of the formation of obstinate complexes with uranyl ions (UO22+), predominated species of uranium in water). Here, we proposed an effective strategy to simultaneously decompose organics and recycle uranium from complex radioactive wastewater, combined with electricity production, by a solar-driven wastewater resourcization system (SWRS), in which an electrodeposited polyaniline (PANI) decorated carbon fiber (CF-PANI) cathode was used for highly efficient UO22+ reduction based on the abundant –NH- groups and conductivity of PANI. Under sunlight illumination, a BiVO4 decorated WO3 nanoplate array (BVO/WNP) combined with a rear silicon cell (SC) was applied as the monolithic photoanode to generate oxidative holes and derived hydroxyl radicals for robust organic oxidation, and driven electrons to the CF-PANI cathode for uranium reduction and simultaneous electricity generation at external circuit. Compared to CF, the optimized CF-PANI improved the rate constants (k) by 6 and 6.7 times for UO22+ and organic removal, respectively, and enhanced power output by 2 times (Pmax, 1.12 mW/cm2). Additionally, near 100 % removal ratios for both UO22+ and organics accompanying with Pmax around 1 mW/cm2 were achieved by SWRS when treating model complex wastewater under wide conditions or even under real sunlight illumination. The fixed uranium on the CF-PANI cathode was mainly reduced into U(IV) species (95.8 %) and the repeated tests demonstrated the excellent stability of SWRS (without obvious decay after reusing 15 times). This work provides new insights on the resourceful treatment of radioactive wastewater and contaminated waters.

In-situ growth of VS4 nanorods on Ni-Fe sulfides nanoplate array towards achieving a highly efficient and bifunctional electrocatalyst for total water splitting

In-situ growth of VS4 nanorods on Ni-Fe sulfides nanoplate array towards achieving a highly efficient and bifunctional electrocatalyst for total water splitting

All-plasmonic-metal chiral nanostructures fabricated by circularly polarized light

Chiral plasmonic nanostructures, which would be applied to enantioselective sensors and metasurfaces, can be prepared in an enantioselective manner by irradiation with circularly polarized light (CPL). However, their resonance sites have been covered with non-plasmonic, dielectric moieties. Here, we prepared all-silver chiral plasmonic nanostructures on a glass plate in one-step by irradiating 380–450 nm right- or left-CPL to an aqueous solution containing Ag+ and citrate ions. Achiral or racemic Ag nanoparticles with anisotropic geometry are deposited on a glass plate by photochemical electron transfer from citrate to Ag+ in the initial phase. The deposited nanoparticles are grown into chiral structures under CPL via generation of an electric field with chiral distributions. An achiral Ag nanoplate array was also grown under 600–700 nm CPL into chiral nanostructure arrays on the basis of hot electron reduction of Ag+.

Photofabrication of Chiral Plasmonic Nanostructure Arrays

AbstractChiral plasmonic nanostructures can be potentially applied to chiroptical materials and devices, as well as sensors for chiral molecules. When those are applied to metasurfaces or metamaterials, those would be appropriately oriented and aligned. We therefore prepared arrays of chiral plasmonic nanostructures on the basis of bottom‐up, self‐assembling methods. A triangular Au nanoplate array as an achiral precursor was prepared on a TiO2‐coated substrate by nanosphere lithography. The array was irradiated with right‐ or left‐circularly polarized light (CPL) in a solution containing Pb2+ for site‐selective deposition of PbO2 in a chiral geometry by plasmon‐induced charge separation. The well‐aligned Au−PbO2 nanostructure array thus obtained exhibits circular dichroism, and the handedness of the array can be inverted by changing the rotation direction of the irradiated CPL.

Interface engineering of heterostructrured MoSe2/Co0.85Se nanoplate array as a highly efficient electrocatalyst for overall water splitting

Hollow nanoplate array of MoSe2/Co0.85Se heterostructure on nickel frame (MoSe2/Co0.85Se/NF) was prepared using metal-organic framework as a template via a process of dissolution–regrowth following by gas-phase selenization and annealing. 3D architecture of MoSe2/Co0.85Se heterostructure shows a significantly enhanced activity and durability as a bifunctional electrocatalyst for oxygen and hydrogen evolution reactions (OER and HER) in alkaline solution. A current density of 10 mA/cm2 can be delivered at an overpotential of 102 mV for HER and 229 mV for OER with a corresponding Tafel slope of only 35 mV/dec for HER and 48 mV/dec for OER, respectively. Density functional theory calculations revealed that MoSe2/Co0.85Se heterostructure will favor water dissociation, and the neutral adsorption energy of H∗ intermediate in MoSe2/Co0.85Se heterostructure can boost hydrogen evolution. OER measurements will cause surface reconstruction of MoSe2/Co0.85Se/NF and form a new heterostructure of CoO/Co2Mo3O8 in alkaline media. OER occurs at Co atoms on CoO/Co2Mo3O8 heterojunction interface, and the neighboring Mo atom will promote the formation of OOH∗ intermediate, leading to a fast OER kinetics. The superior HER and OER performance of MoSe2/Co0.85Se/NF can rival most of reported transition metal catalysts, holding great promise as advanced catalysts for water splitting in industrial scale.

Heterostructured Mn-doped NiSx/NiO/Ni3N nanoplate arrays as bifunctional electrocatalysts for energy-saving hydrogen production and urea degradation

Urea oxidation reaction (UOR) instead of sluggish oxygen evolution reaction (OER) is a desirable approach to hydrogen production with reduced energy consumption, but developing an efficient bifunctional electrocatalyst for both HER and UOR is still a challenge. Here we report a Mn-doped NiSx/NiO/Ni3N nanosheets arrays loaded on nickel foam (denoted by Mn-NiSx/NiO/Ni3N@NF) catalyst through a simple hydrothermal and thiourea-assisted solid reaction. Benefitting from the densely interlaced network structure and plentiful heterojunctions induced by Mn dopant, Mn-NiSx/NiO/Ni3N@NF displays a superior HER and UOR activity. In the alkaline urea electrolyte, a low potential of 93 mV (for HER) and 1.31 V (for UOR) are needed to achieve 10 mA cm−2. Assembled in a symmetrical two-electrode electrolyzer, Mn-NiSx/NiO/Ni3N@NF can require a cell voltage of 1.70 V to deliver 100 mA cm−2 in alkaline urea medium, reducing by 200 and 239 mV in contrast with the commercial Pt/C@NF||RuO2@NF couple and the conventional water splitting, respectively. Furthermore, Mn-NiSx/NiO/Ni3N@NF as UOR electrode can impel urea removal rate reach up 56% after a successive operation for 32 h. The work provides a green and sustainable strategy from sewage treatment to recycling accompanied by energy-saving hydrogen production and urea-rich wastewater degradation.

Highly active and stable CuAlOx/WO3 photoanode for simultaneous pollutant degradation, hydrogen and electricity generation

An unassisted solar water-energy nexus system (SWENS) based on an ultra-thin CuAlOx overlayer coated WO3 nanoplate array (CuAlOx/WO3) photoanode, a rear silicon solar cell and a Pt-black/Pt cathode was proposed to efficiently degrade refractory organic pollutants and simultaneously produce hydrogen and electricity. The formed p-n junction between p-type CuAlOx and n-type WO3 effectively facilitated the charge separation in the CuAlOx/WO3 photoanode. Moreover, the CuAlOx overlayer enhanced the capture of photogenerated holes and isolated WO3 from the solution, thereby improving the charge transfer and inhibiting the photocorrosion of WO3. Therefore, the optimized CuAlOx/WO3 photoanode showed a significantly enhanced and stable photocurrent density of ∼2.82 mA cm−2 at 1.0 V vs. Ag/AgCl, which was ∼4 times higher than that of the pristine WO3. Based on this outstanding photoelectrocatalytic performance, the assembled SWENS showed a degradation efficiency of nearly 100% for tetracycline, a hydrogen generation rate of ∼26.8 μmol·h−1·cm−2 and a power density of ∼593 μW cm−2 under simulated solar light illumination. Our SWENS also exhibited outstanding universality in degrading various refractory organic pollutants for green energy production.

Microstructure and Formation Mechanisms of Nanowires and Nanoplates ZrO&lt;sub&gt;2&lt;/sub&gt; during the ZrB&lt;sub&gt;2&lt;/sub&gt; Deposition Process

Preparation of boride by chemical vapor deposition (CVD) is sensitive to oxygen, subtle changes in oxygen concentration during the deposition of ZrB2 can induce the formation of Zirconium dioxide (ZrO2) with a novel nanoplate-stacked structure and nanowire structure. The ZrO2 nanostructure changed with - oxygen concentration. Nanowires with uniform size of 50-100 nm in diameter and over 100 μm in length were obtained at high oxygen concentration, while highly-ordered nanoplate arrays were obtained at low oxygen concentration. Both of these nanostructures were grown in situ on the surface of ZrB2-coating. In this paper, the preparation method of novelty ZrO2 nano-structures grown in situ was provided, the morphologies and compositions of the nano-structural ZrO2 were characterized and the formation mechanism was proposed, which also provides experimental basis for the industrial morphology control of ZrB2 deposited by CVD method.

Electrocatalytic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid via metal-organic framework-structured hierarchical Co3O4 nanoplate arrays

Electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) was examined as an alternative to thermocatalytic methods in which two-dimensional (2D) cobalt-metal–organic framework (Co-MOF, ZIF-L-Co) nanoplate arrays were prepared on nickel foam (NF) and then transformed into hierarchical porous Co3O4 nanostructures by chemical etching and low temperature annealing to form electrode materials. Hierarchical porous nanoarrays formed during synthesis enlarged the surface area of the as-prepared catalysts introduced a large number of defects and exposed active sites leading to reduced charge diffusion, improved mass transfer and efficient HMF oxidation. Co3O4/NF electrode materials were able to achieve a current density of 10 mA·cm−2 at an overpotential of 105 mV in 1 M KOH with 10 mM HMF, which was reduced by 175 mV compared with water oxidation. Electrocatalytic oxidation experiments afforded 100 % HMF conversion and 96.7 % FDCA yields with a minimum 96.5 % faradaic efficiency at 1.43 V vs RHE. The proposed MOF-structured synthesis method fundamentally reduces charge diffusion, improves mass transfer of electrodes and is generally applicable to fabrication of hierarchical porous nanostructured materials.

Facile preparation of CuO nanoplate arrays film on Si substrate and their photoelectric characteristics

• A large scale CuO film is prepared on Si substrate tightly by ozone etching and annealing. • The film consists of a dense polycrystalline nanoplate array. • The film is fabricated into a schottky contacted diode with Al electrodes. • The diode performs a large rectifying ratio and a highly sensitive. Schottky contacted sensors are of promising photoelectric devices due to the intrinsic high selectivity and high sensitivity properties. However, it is still a challenge to construct a stable contacted semiconductor material in Schottky sensors. In this work, a CuO film was prepared by an ozone etching and annealing on a silicon wafer substrate. Material characteristic investigation shows that the film composed of a highly dense polycrystalline nanoplate arrays film. The film is also used to fabricate a schottky diode with aluminum electrode to test its photoelectric performance. The test results indicate that the diode has a large rectifying ratio and a highly sensitive photoreponse effect. This work provides a new facile CuO nano arrays material process for Schottky contacted sensor application.

Manipulating the charge separation via piezoelectric field and heterojunction to enhance the photoelectrochemical water splitting ability of Bi2WO6/BiOBr photoanode

The unsatisfactory separation efficiency of photogenerated charge is one of the significant problems restricting the application of photoelectrochemical water splitting. Herein, we successfully prepared a Bi2WO6/BiOBr nanoplate arrays structure with the heterostructure for efficient piezoelectric photoelectric water splitting. A charge transfer path is formed by constructing a heterojunction to accelerate the spatial separation of photogenerated charges. The Bi2WO6/BiOBr shows the better photoelectrochemical performance with high photocurrent density of 0.068 mA/cm2 at 1.23 V vs. RHE which is 1.8 times higher than simple Bi2WO6. In addition, after the introduction of piezoelectric polarization, the carrier separation efficiency is further enhanced under the synergistic action of the piezoelectric polarization and the heterojunction, and the photocurrent of Bi2WO6/BiOBr photoanode is increased to 0.088 mA/cm2 at 1.23 V vs. RHE. By comparing the photoelectrocatalytic performance of the samples before and after the introduction of piezoelectric field, it further explains the role of piezoelectric built-in electric field in promoting carrier separation. This work provides a new method to improve the carrier separation efficiency by combining heterojunction and piezoelectric polarization.

Simultaneous detection of dihydroxybenzene isomers in the environment by a free-standing flexible ZnCo2O4 nanoplate arrays/carbon fiber cloth electrode

The simultaneous determination of dihydroxybenzene isomers is highly valuable for early environmental monitoring, but it is still a challenge. In this work, a free-standing flexible electrode was prepared for the simultaneous detection of hydroquinone (HQ), catechol (CC), and resorcinol (RC). The bimetallic zinc/cobalt zeolitic imidazolate frameworks nanoplate arrays (Zn/Co-ZIF NPAs) grown in situ on the carbon fiber cloth (CFC) was fabricated by a facile static synthesis method, and the porous ternary ZnCo2O4 NPAs derived from Zn/Co-ZIF NPAs were formed by annealing in air. Due to the fast electron transmission, abundant active sites and excellent electrocatalytic properties with enzyme-like kinetic performance of the ZnCo2O4/CFC electrode, the as-proposed sensor showed a wilder linear response (2–500 μM), a lower detection limits (0.03 μM HQ, 0.06 μM CC and 0.15 μM RC) and a higher sensitivity (23.58 μA μM−1 cm−2 HQ, 17.72 μA μM−1 cm−2 CC, and 15.18 μA μM−1 cm−2 RC), respectively. More importantly, the proposed electrochemical sensor exhibited excellent detection performance in complex water samples, providing a strategy for the detection of other toxic substances in the ecological environment.

Engineering hierarchical quaternary superstructure of an integrated MOF-derived electrode for boosting urea electrooxidation assisted water electrolysis

Controllable design of the catalytic electrodes with hierarchical superstructures is expected to improve their electrochemical performance. Herein, a self-supported integrated electrode (NiCo-ZLDH/NF) with a unique hierarchical quaternary superstructure was fabricated through a self-sacrificing template strategy from the metal–organic framework (Co-ZIF-67) nanoplate arrays, which features an intriguing well-defined hierarchy when taking the unit cells of the NiCo-based layered double hydroxide (NiCo-LDH) as the primary structure, the ultrathin LDH nanoneedles as the secondary structure, the mesoscale hollow plates of the LDH nanoneedle arrays as the tertiary structure, and the macroscale three-dimensional frames of the plate arrays as the quaternary structure. Notably, the distinctive structure of NiCo-ZLDH/NF can not only accelerate both mass and charge transfer, but also expose plentiful accessible active sites with high intrinsic activity, endowing it with an excellent electrochemical performance for urea oxidation reaction (UOR). Specially, it only required the low potentials of 1.335, 1.368 and 1.388 V to deliver the current densities of 10, 100 and 200 mA cm−2, respectively, much superior to those for typical NiCo-LDH. Employing NiCo-ZLDH/NF as the bifunctional electrode for both anodic UOR and cathodic HER, an energy-saving electrolysis system was further explored which can greatly reduce the needed voltage of 213 mV to deliver the current density of 100 mA cm−2, as compared to the conventional water electrolysis system composed of OER. This work manifests that it is prospective to explore the hierarchically nanostructured electrodes and the innovative electrolytic technologies for high-efficiency electrocatalysis.

Single-Step Solid-State Scalable Transformation of Ni-Based Substrates to High-Oxidation State Nickel Sulfide Nanoplate Arrays as Exceptional Bifunctional Electrocatalyst for Overall Water Splitting.

Hydrogen, undoubtedly the next-generation fuel for supplying the world's energy demands, needs economically scalable bifunctional electrocatalysts for its sustainable production. Non-noble transition metal-based electrocatalysts are considered an economic solution for water splitting applications. A single-step solid-state approach for the economically scalable transformation of Ni-based substrates into single-crystalline nickel sulfide nanoplate arrays is developed. X-ray diffraction and transmission electron microscopy measurements reveal the influence of the transformation temperature on the crystal growth direction, which in turn can manipulate the chemical state at the catalyst surface. Ni-based sulfide formed at 450°C exhibits an enhanced concentration of electrocatalytically-active Ni3+ at their surface and a reduced electron density around sulfur atoms, optimal for efficient H2 production. The Ni-based sulfide electrocatalysts display exceptional electrocatalytic performance for both oxygen and hydrogen evolution, with overpotentials of 170 and 90 mV respectively. Remarkably, the two-electrode cell for overall electrolysis of alkaline water demonstrates an ultra-low cell potential of 1.46 V at 10 mA cm-2 and 1.69 V at 100 mA cm-2 . In addition to the exceptionally low water-splitting cell voltage, this self-standing electrocatalyst is of binderfree nature, with the electrode preparation being a low-cost and single-step process, easily scalable to industrial scales.