Porous Nanoribbons Research Articles

Mn-doped CeO2 derived from Ce-MOF porous nanoribbons as highly active catalysts for the synthesis of dimethyl carbonate from CO2 and methanol.

It is desirable but challenging to develop highly-efficient catalysts for the direct synthesis of dimethyl carbonate (DMC) from methanol and CO2. The vacancy-mediated incorporation of heteroatom into surface reconstruction is an efficient method of defect engineering for enhancing the catalytic properties. In this work, manganese-doped cerium oxide porous nanoribbons (Mn/CeO2-BTC) were prepared derived from a Ce-BTC by a sacrificial template approach. It is found that the catalytic activity of Mn/CeO2-BTC catalysts can be readily controlled by varying the amount of Mn dopants and the as-synthesized 0.1-Mn/CeO2-BTC exhibited an outstanding activity for the synthesis of DMC from CO2 and methanol, which reached a high DMC yield (6.53 mmolDMC/gcat.) without any dehydrating agents. Based on characterization results, the enhanced performance may be attributed to the defective structures caused by Mn doping and the porous nanoribbons of the CeO2 crystals, which provide more surface oxygen vacancies and acidic-basic sites, favoring adsorption and activation of CO2 and methanol.

Morphology engineering and electronic structure remodeling of manganese-incorporated VN for boosting urea-assisted energy-saving hydrogen production

Urea-assisted water electrolysis offers a promising route to reduce energy consumption for hydrogen production and meanwhile treat urea-rich wastewater. Herein, we devised a shear force-involved polyoxometalate-organic supramolecular self-assembly strategy to fabricate 3D hierarchical porous nanoribbon assembly Mn-VN cardoons. A bimetallic polyoxovanadate (POV) with the inherent structural feature of Mn surrounded by [VO6] octahedrons was introduced to trigger precise Mn incorporation in VN lattice, thereby achieving simultaneous morphology engineering and electronic structure modulation. The lattice contraction of VN caused by Mn incorporation drives electron redistribution. The unique hierarchical architecture with modulated electronic structure that provides more exposed active sites, facilitates mass and charge transfer, and optimizes the associated adsorption behavior. Mn-VN exhibits excellent activity with low overpotentials of 86 mV and 1.346 V at 10 mA/cm2 for hydrogen evolution reaction (HER) and urea oxidation reaction (UOR), respectively. Accordingly, in the two-electrode urea-assisted water electrolyzer utilizing Mn-VN as a bifunctional catalyst, hydrogen production can occur at low voltage (1.456 V@10 mA/cm2), which has the advantages of energy saving and competitive durability over traditional water electrolysis. This work provides a simple and mild route to construct nanostructures and modulate electronic structure for designing high-efficiency electrocatalysts.

Flower-like carbon spheres formed by self-assembly of nitrogen-doped porous nanoribbons to boost SnS2 nanosheets for advanced lithium storage

SnS2 is a two-dimensional layered material with high theoretical capacity, but its further application in lithium-ion batteries is limited by problems such as low intrinsic conductivity and dramatic volume expansion during lithiation process. Therefore, SnS2 nanosheets were designed to anchor in the interlayer nanospaces of flower-like carbon spheres self-assembled from nitrogen-doped porous carbon nanoribbons (SnS2/N-FC). Nitrogen-doped porous nanoribbons facilitated the uniform distribution of SnS2 nanosheets in the interlayer nanospaces of the flower-like carbon spheres, establishing a face-to-face interaction with the nanoribbons and the SnS2 nanosheets. This composite structure enhances the transfer of electrons between the components. In addition, the integration of spherical flower-like electrodes with the reserved interlayer nanospaces provided a buffering space for volume expansion which ensured an even distribution of mechanical stress. As a result, SnS2/N-FC exhibited a high reversible specific capacity of 1322.3 mAh g−1 after 200 cycles at 0.1 A g−1, with the capacity kept growing to 1329.4 mAh g−1 after 1000 cycles at 1 A g−1. This study introduces a novel approach for the design of anode materials which demonstrate excellent lithium storage.

3D g-C3N4 porous nanoribbons pillared-MXene/ PVA nanocomposite: An architecture with high dielectric, breakdown strength, thermal conductivity, and mechanical strength characteristics

In polymer nanocomposites with conductive fillers, obtaining boosted dielectric constant, breakdown strength, lower dielectric loss concurrently, and mixing to build a homogeneous structure is challenging. In this work, 3D g-C3N4 porous nanoribbons pillared-MXene/PVA nanocomposite (MXene/CNNR/PVA) was fabricated. The solution casting method was utilized for embedding Mxene/CNNR into poly (vinyl alcohol) (PVA) to produce MXene/CNNR/PVA dielectric composites. The maximum observed electrical displacement is 10.95 μC/cm2 at (T = 25 °C and E = 400 MV/m). Furthermore, the obtained density of discharged energy is 18.11 J/cm3, much higher than that of pristine PVA (4.21 J/cm3 at E = 200 MV/m). The relative permittivity of 3.5 wt% ternary composites (MXene/CNNR/PVA) at 25 °C and 1000 Hz is 25.1, and the loss is just 0.03. Moreover, the combined use of MXene and CNNR results in a synergistic effect; the MXene/CNNR/PVA composite films exhibit more incredible mechanical characteristics compared to pure PVA nanocomposite modified by MXene alone, with notable increases in tensile strength and Young’s modulus while retaining the majority of its elasticity.

Multi-responsive fluorescent switches and iodine capture of porous hydrogen-bonded self-assemblies

Porous nanoribbons from gels may act as smart materials for applications in iodine absorption and fluorescence sensing for gaseous nitrobenzene, and could reversibly change its fluorescence color under shearing force and solvent annealing.

Constructing ultra-long life and super-rate rechargeable aqueous zinc-ion batteries by integrating Mn doped V6O13 nanoribbons with sulfur-nitrogen modified porous carbon

In this research, a hybrid structure composed of Mn doped V6O13 nanoribbons and N-S modified porous carbon structure (MnVO/(SN)-C) has been designed. Unidimensional porous nanoribbon structure can form Zn2+ diffusion channels and enable the abundant energy-storage sites, while the doping of Mn ion into V6O13 can optimize the electronic structure simultaneously. The rigid and conductive N-S modified carbon structure can not only protect the nanoribbons, but also boost the electron transport rate in the electrochemical reaction, and thus depress the huge volume expansion and ameliorate conductivity. Therefore, Zn2+ diffusion rate and electrochemical reaction kinetics are greatly promoted, resulting in excellent cycle stability and super-rate performance of this cathode material. At the current density of 0.5 A g−1, this electrode material can deliver favorable capacity of 414.2 mA h g−1, and can deliver 272.4 mA h g−1 at 10 A g−1 (67.37% retention from 1 to 10 A g−1). It also achieves long-term cycle stability (100.1% after 1000 cycles) at 10 A g−1. The rechargeable aqueous ZIBs with ultra-long life and ultra-high rate may be the most advantageous candidate for the next generation of energy storage facilities.

High‐performance counter electrode based on nitrogen‐doped porous carbon nanoribbons for quantum dot‐sensitized solar cells

Nitrogen-doped porous carbon nanoribbons (NPCNs) are facilely prepared by carbonization of polypyrrole (PPy) nanotubes followed by a chemical activation process. NPCN counter electrodes are subsequently fabricated by depositing NPCNs onto Ti mesh for quantum dot-sensitized solar cells (QDSCs). Electrochemical tests are carried out to evaluate the electrocatalytic performance of obtained NPCN electrode. The data of electrochemical tests suggest that the NPCN electrode has a superior electrocatalytic ability towards polysulfide (S22−/S2−) electrolyte regeneration reaction and displays a high stability in polysulfide electrolyte. The excellent electrocatalytic performance of NPCN electrode can be ascribed to their large surface area, 2D porous nanoribbon morphology, and nitrogen atom doping, which provides abundant electrocatalytic active sites and facilitates the electrolyte diffusion. Consequently, a power conversion efficiency of 3.27% is obtained by using NPCN electrode as the counter electrode for QDSC. This efficiency is close to the QDSC assembled with commonly used PbS electrode (4.0%).

On-Surface Synthesis of Porous Carbon Nanoribbons on Silver: Reaction Kinetics and the Influence of the Surface Structure.

We report on the influence of the surface structure and the reaction kinetics in the bottom‐up fabrication of porous nanoribbons on silver surfaces using low‐temperature scanning tunneling microscopy. The porous carbon nanoribbons are fabricated by the polymerization of 1,3,5‐tris(3‐bromophenyl)benzene directly on the Ag surface using an Ullmann‐type reaction in combination with dehydrogenative coupling reactions. We demonstrate the successful on‐surface synthesis of porous nanoribbons on Ag(111) and Ag(100) even though the self‐assemblies of the intermediate organometallic structures and covalently‐linked polymer chains are different on both surfaces. Furthermore, we present the formation of isolated porous nanoribbons by kinetic control. Our results give valuable insights into the role of substrate‐induced templating effects and the reaction kinetics in the on‐surface synthesis of conformationally flexible molecules.

Preparation of three-dimensional vanadium nitride porous nanoribbon/graphene composite as an efficient electrode material for supercapacitors

Three-dimensional vanadium nitride porous nanoribbons/graphene composite with hierarchical porosity was prepared and investigated as the electrode material for supercapacitors. Morphology characterization of vanadium nitride porous nanoribbons/graphene composite indicates that vanadium nitride porous nanoribbons incorporate with graphene nanosheets to from a stable three-dimensional architecture with hierarchical porosity. This unique three-dimensional architecture and the combining effect of vanadium nitride porous nanoribbons and graphene nanosheets network make vanadium nitride porous nanoribbons/graphene composite a high-performance electrode material for supercapacitors. At a current density of 0.3 A g−1, vanadium nitride porous nanoribbons/graphene electrode displays a specific capacitance of 164.4 F g−1, which is much higher than that of pure vanadium nitride electrode. In addition, vanadium nitride porous nanoribbons/graphene composite shows high capacitance retention rate (82% capacitance retention at the current density up to 10 A g−1) and good long-term cycling stability (97.5% capacitance retention over 2500 cycles).

Three-dimensional porous vanadium nitride nanoribbon aerogels as Pt-free counter electrode for high-performance dye-sensitized solar cells

Three-dimensional (3D) porous vanadium nitride nanoribbon aerogels (PVNNRAs) are prepared by hydrothermal synthesis and subsequent nitridation in ammonia/argon atmosphere and investigated as Pt-free counter electrode in dye-sensitized solar cells (DSCs). 3D porous nanoribbon aerogel can simultaneously offer more electrocatalytic active sites, a fast electron-transport pathway, and a favorable electrolyte diffusion channel, which endows the PVNNRA electrode with high electrocatalytic activity for the reduction of I3−. Under full-sun illumination (AM 1.5, 100mWcm−2), the DSC fabricated with PVNNRA counter electrode achieves a conversion efficiency of 7.05%, which is comparable to that of DSCs fabricated with Pt counter electrode. In addition, the PVNNRA electrode exhibits good stability in I−/I3− redox electrolyte. Thus, 3D PVNNRAs can be considered as a cost-effective alternative to Pt as the counter electrode of DSCs.

Porous vanadium nitride nanoribbon aerogel and its electrochemical properties

Porous vanadium nitride nanoribbon aerogel (PVNNRA) was prepared by hydrothermal reaction at 180°C and subsequent ammonia treatment at 550°C using NH4VO3 as the precursor. The electrochemical properties of PVNNRA were discussed. SEM and TEM images demonstrated that as-prepared vanadium nitride showed a porous nanoribbon morphology with the width of 100–400 nm and the pore size of 10–20 nm. The analysis of electrochemical impedance spectroscopy indicated that the charge-transfer resistance of PVNNRA electrode was 1.36 Ω cm2, indicating a high electrocatalytic activity for I3− reduction. The dye-sensitized solar cell fabricated with PVNNRA counter electrode achieved a conversion efficiency of 7.05%, which is closed to that of the cell fabricated with Pt counter electrode. The results of cyclic voltammetry and galvanostatic charge/discharge tests demonstrated that PVNNRA has a good capacitive performance. At the current density of 0.5 A/g, PVNNRA exhibited a specific capacitance of 292.2 F/g in 2 mol/L KOH aqueous solution. Therefore, as-prepared PVNNRA can be considered as an effective electrode material for application in dye-sensitized solar cells and supercapacitors

In Situ Growth of Free-Standing All Metal Oxide Asymmetric Supercapacitor

Metal oxides have attracted renewed interest in applications as energy storage and conversion devices. Here, a new design is reported to acquire an asymmetric supercapacitor assembled by all free-standing metal oxides. The positive electrode is made of 3D NiO open porous nanoribbons network on nickel foam and the negative electrode is composed of SnO2/MnO2 nanoflakes grown on carbon cloth (CC) substrate. The combination of two metal oxide electrodes which replaced the traditional group of carbon materials together with metal oxide has achieved a higher energy density. The self-supported 3D NiO nanoribbons network demonstrates a high specific capacitance and better cycle performance without obvious mechanical deformation despite of undergoing harsh bulk redox reactions. The SnO2/MnO2 nanoflakes as the pseudocapacitive electrode exhibit a wide range of voltage window (-1 to 1 V), which is conducive to electrochemical energy storage. The (CC/SnO2/MnO2)(-)//(NiO/Ni foam)(+) asymmetric supercapacitor device delivers an energy density of 64.4 Wh kg-1 (at a power density of 250 W kg-1) and two devices in series are applied to light up 24 red LEDs for about 60 s. The outstanding electrochemical properties of the device hold great promise for long-life, high-energy, and high-power energy storage/conversion applications.

Quantum-interference-enhanced thermoelectricity in single molecules and molecular films

We provide a brief overview of recent measurements and predictions of thermoelectric properties of single-molecules and porous nanoribbons and discuss some principles underpinning strategies for enhancing their thermoelectric performance. The latter include (a) taking advantage of steep slopes in the electron transmission coefficient T ( E ) , (b) creating structures with delta-function-like transmission coefficients and (c) utilising step-like features in T ( E ) . To achieve high performance, we suggest that the latter may be the most fruitful, since it is less susceptible to inhomogeneous broadening. For the purpose of extrapolating thermoelectric properties of single or few molecules to monolayer molecular films, we also discuss the relevance of the conductance-weighted average Seebeck coefficient. Nous procédons à un bref survol des mesures et prédictions récentes concernant les propriétés thermoélectriques de molécules individuelles ou de nanorubans poreux, puis nous discutons quelques-uns des principes sous-jacents aux stratégies visant à augmenter leurs performances thermoélectriques. On relèvera parmi ces dernières (a) l'utilisation de pentes élevées du coefficient de transmission électronique T ( E ) , (b) la création de structures avec des pics de transmission et (c) l'exploitation de ces derniers. Pour atteindre de hautes performances, nous suggérons que cette dernière approche puisse être la plus fructueuse, puisqu'elle est moins susceptible de présenter des élargissements inhomogénes. Afin d'extrapoler les propriétés thermoélectriques d'une ou de quelques molécules à des films moléculaires monocouche, nous discutons aussi la pertinence de l'utilisation d'une moyenne du coefficient Seebeck pondérée par la conductance.

Hydrothermal synthesis of cobalt oxide porous nanoribbons anchored with reduced graphene oxide for hydrogen peroxide detection

A new Co3O4-reduced graphene oxide (Co3O4–rGO) nanostructure was successfully prepared by hydrothermal-synthesized Co3O4 porous nanoribbons with an approximate length of 6–17 μm, a width of 21–737 nm, and a thickness of 33–80 nm hybridizing with reduced graphene oxide. The electrochemical properties of the Co3O4–rGO-modified electrode were investigated by the cyclic voltammograms and amperometric current–time method. The modified electrode shows high electrochemical activity for the catalytic reduction and detection of H2O2 in alkaline medium. The nonenzymatic hydrogen peroxide sensor exhibits wide linear range of 1–18.5 mM (R = 0.99439), high adsorption amount about 3.24 × 10−6 mol/cm2, and a low detection limit of 5.35 × 10−7 M (S/N = 3). In addition, the sensor has a fast response (<5 s), good long-term stability, excellent repeatability (3.22 % relative standard deviation), and high selectivity. These outstanding properties of the sensor derive from their particular hybrid structure and synergistic effects between rGO and Co3O4.

Pt-porous ZnO nanoribbon hybrid materials with enhanced catalytic performances

With the help of bio-molecule l-lysine, a seeded growth method has been developed and Pt–ZnO porous nanoribbons have been successfully obtained. For the catalytic applications of CO oxidation and the photocatalytic degradation of MO, the hybrid nanomaterial exhibits remarkably enhanced catalytic properties.

Nanoconfinement of Ni clusters towards a high sintering resistance of steam methane reforming catalysts

This study reports an improvement of the stability of steam reforming catalysts at relatively low temperatures, such as for pre-reforming, and reforming of biomass derived compounds, by enhanced stabilization of Ni nanoparticles through spatial confinement in a mixed oxides matrix. We revealed a simple approach of three dimensional engineering of Ni particles by means of self-assembly of Ni atoms inside the nanoribbon of hydrotalcite-derived mixed oxides. Taking advantage of Transmission Electron Microscopy (TEM), together with electron tomography, the three dimensional (3D) structure of the catalyst was investigated at a nanometer scale, including the Ni particle size, shape, location and spatial distribution, as well as pore size and morphology of the mixed oxides. Porous nano-ribbons were formed by high temperature treatment, adopting the layer structure of the hydrotalcite-like materials. Ni particles formed by selective reduction of mixed oxides embedded in the nano-ribbons with connected pore channels, allowing good access for the reactants. These spatially confined and well distributed Ni particles increased catalyst stability significantly compared to the Ni particles supported on the support surfaces in a commercial catalyst during the steam methane reforming.

Synthesis of CuO nanowalnuts and nanoribbons from aqueous solution and their catalytic and electrochemical properties

One dimensional copper hydroxide nanostrands, two dimensional Cu(2)(OH)(3)NO(3) nanoribbons and three dimensional CuO nanowalnuts were synthesized from the same diluted copper nitrate solution with ethanolamine at room temperature and 10 °C, respectively. The Cu(2)(OH)(3)NO(3) nanoribbons were formed by slowly hydrolyzing ethanolamine at low temperature. The CuO nanowalnuts were formed through dehydration of copper hydroxide nanostrands in aqueous solution at room temperature. Although their average size is about 500 nm, the specific surface area of the CuO nanowalnuts can be as large as 61.24 m(2) g(-1), due to their particular morphology with assembling of 8 nm grains. The Cu(2)(OH)(3)NO(3) nanoribbons were converted to CuO porous nanoribbons, keeping the shape. The catalytic performance of the CuO nanowalnuts for CO oxidation is 160 mL h(-1) g(cat)(-1) which is 23 times higher than those of the CuO porous nanoribbons and 40 nm commercial CuO nanoparticles, respectively. The electrochemical properties of the CuO nanowalnuts were also examined in a lithium-ion battery. After 30 cycles, the capacity of the as-prepared CuO nanowalnuts could sustain 67.1% (407 mA h g(-1)) of the second cycle (607 mA h g(-1)) at a rate of 0.1 C.

Growth and characterization of ZnS porous nanoribbon array constructed by connected nanocrystallities

Well-aligned ZnS porous nanoribbon array has been prepared with a simple one-step solvothermal approach. X-Ray diffraction, energy dispersive X-ray spectrometry and scanning electron microscopy indicate the formation of ZnS nanoribbon array. Transmission electron microscope measurements reveal that the porous nanoribbons are composed of a large amount of connected nanocrystallites with sizes of about 2–5 nm as the building blocks. These ZnS nanocrystallites are all found to adopt the same crystallographic direction. Uniform separated nanopores exist among these nanopraticles. A possible formation mechanism of the nanoribbon array and a porous structure are proposed. The room-temperature luminescence property of the as-prepared ZnS porous nanoribbon array is also studied.