Ultrathin Mesoporous Nanosheets Research Articles

Synthesis of Flower-Like Cobalt–Molybdenum Mixed-Oxide Microspheres for Deep Aerobic Oxidative Desulfurization of Fuel

Flower-like cobalt–molybdenum mixed-oxide microspheres (CoMo-FMs) with hierarchical architecture were successfully synthesized via a hydrothermal process and subsequent calcination step. The characterization results show that CoMo-FMs were assembled from ultrathin mesoporous nanosheets with thicknesses of around 4.0 nm, providing the composite with a large pore volume and a massive surface area. The synthesized CoMo-FMs were employed as catalysts for the aerobic oxidative desulfurization (AODS) of fuel, and the reaction results show that the optimal catalyst (CoMo-FM-2) demonstrated an outstanding catalytic performance. Over CoMo-FM-2, various thiophenic sulfides could be effective removed at 80–110 °C under an atmospheric pressure, and a complete conversion of sulfides could be achieved in at least six consecutive cycles without a detectable change in chemical compositions. Further, the catalytic mechanism was explored by conducting systemic radical trapping and transformation experiments, and the excellent catalytic performance for CoMo-FMs should be mainly due to the synergistic effect of Mo and Co elements.

Construction of 2D C,N-co-doped ZnO/Co3O4 over Ni(OH)2 mesoporous ultrathin nanosheets on Ni foam as high-performance electrocatalysts for benzyl-alcohol oxidation and accelerating hydrogen evolution

The synthesis of 2D C,N-co-doped ZnO/Co3O4@Ni(OH)2/NF heterostructure mesoporous nanosheets which show high activity for benzyl alcohol oxidation (a benzoic acid yield of 99%, and a faradaic efficiency over 97%) is reported.

Nitrogen-doped graphene quantum dots-modified mesoporous SnO2 hierarchical hollow cubes for low temperature detection of nitrogen dioxide

Abstract The exploration of nitrogen dioxide (NO2) gas sensor with high response, fast response and recovery speed, and low working temperature is still an urgent challenge. In this work, a novel SnO2 hierarchical hollow cube composed of ultrathin mesoporous nanosheets was successfully prepared via a simple sulfidation-oxidation method, and nitrogen-doped graphene quantum dots (N-GQDs) were evenly modified on the surface of SnO2. The prepared N-GQDs modified SnO2 (NG/Snx) shows an improved response, and the optimal sample (NG/Sn1.5) response (Rg/Ra = 417) toward 1 ppm NO2 is approximately 2.2 times that of pure SnO2 at 130 °C. Moreover, the NG/Sn1.5 sensing material exhibits fast response and recovery speed, good selectivity, repeatability, and long-term stability. More attractively, the NG/Sn1.5 sensor has outstanding detection ability (Rg/Ra = 25.3) for low concentration NO2 (100 ppb). The significantly improved NO2 sensing performance of NG/Sn1.5 sensing material is mainly attributed to the zero-dimensional/three-dimensional (0D/3D) heterostructure construction and N doping, which increases the space charge modulation depth and NO2 adsorption active sites of the composite material. In addition, the mesoporous hierarchical cubic structure is beneficial to the improvement of NO2 sensing performance due to its stable gas diffusion channels, large specific surface area, and abundant nanoscale grain boundaries. The results obtained herein may provide new ideas for the preparation of high performance NO2 sensors at low temperatures.

Honeycombed-like nanosheet array composite NiCo2O4/rGO for efficient methanol electrooxidation and supercapacitors

A series of novel honeycombed-like composites NiCo2O4/rGO-T (rGO: reduced graphene oxide, T: 200, 250 and 300 °C) were obtained by a pre-adjusted pH value aq. phase coprecipitation strategy assisted by citric acid, followed annealing in N2 flow. The NiCo2O4/rGO-250 shows the most uniformly highly-ordered honeycombed-like nanosheet array morphology consisting of ultrathin mesoporous nanosheets (~110 nm × 12 nm) interdigitated vertically grown on the rGO surface in both sides with the highest crystallinity, higher surface area (145 m2 g−1), bimodal pore size distribution (3.4 and 12.5 nm) along with the highly open macroporous networks. The NiCo2O4/rGO-250 electrode exhibits the highest current density for methanol oxidation reaction of 90 A g−1 at 0.6 V, as well as high cycling stability (94% after 500 cycles, returned to 98% with fresh electrolyte), which is the best one so far among reported catalysts with similar compositions. Simultaneously, NiCo2O4/rGO-250 electrode exhibits considerable specific capacitance of 1380 F g−1 at 1 A g−1, high rate performance (10 A g−1, 967 F g−1), and good cycling stability which remains 90% at 5 A g−1 after 1000 charge–discharge cycles for supercapacitor. The excellent electrochemical performance of the NiCo2O4/rGO-250 electrode can be attributed to the highly-ordered honeycombed-like mesoporous nanosheet array along with the greatly increased specific surface area exposing more active sites, the highly open macroporous networks formed by adjacent ultrathin NiCo2O4 nanosheets providing more ion/electron diffusion paths and effective contact area of electrolyte, and the strong NiCo2O4– rGO synergy endowing excellent conductivity and structural robustness, thus greatly facilitate the transfer of electrons and ions in electrode and at the electrolyte/electrode interface.

Mesoporous NiCo2O4 network constructed from ultrathin-mesoporous nanosheets as high performance electrocatalyst in dye sensitized solar cell

Three-dimensional (3D) mesoporous network provides favorable structural features for ion diffusion, electroactive sites and contact with electrolyte, but fabricating the 3D networks of transition metal oxides is still challenging. Based upon template-free method, NiCo2O4 network constructed from ultrathin mesoporous nanosheets (NiCo2O4 MNN) was designed and synthesized. NiCo2O4 nanosheets (~5 nm of thickness, 2–5 nm of pore diameters) are highly interlaced with each other to form a 3D network and create porous nanostructure. Benefiting from the specific structural advantages, NiCo2O4 MNN delivers superior electrocatalytic performance as counter electrode (CE) in dye sensitized solar cell (DSSC), with a higher power conversion efficiency (PCE) of 8.05% than Pt electrode (7.32%). We believe that this research will open a new avenue for the design and development of efficient and cost-effective metal oxides electrocatalysts in DSSC.

Co0.85Se hollow spheres constructed of ultrathin 2D mesoporous nanosheets as a novel bifunctional-electrode for supercapacitor and water splitting

Hollow spheres of Co0.85Se constructed by two-dimensional (2D) mesoporous ultrathin nanosheets were synthesized via simple and cost effective approach. Their bifunctional electrocatalytic-supercapacitive properties were obtained simultaneously due to synergistic effects between macroscopic morphological features and microscopic atomic/electronic structure of Co0.85Se. The as-synthesized hollow spheres of Co0.85Se that are constructed by 2D mesoporous ultrathin nanosheets exhibit inspiring electrochemical performance for supercapacitor, presenting maximum energy density at high power density (54.66 Wh·kg−1 at 1.6 kW·kg−1) and long cycle stability (88% retention after 8,000 cycles). At the same time, the hollow spheres of Co0.85Se constructed by 2D mesoporous ultrathin nanosheets display excellent catalytic performance for oxygen evolution reaction (OER) due to special structure, high surface area and mesoporous nature of sheets, which achieve low overpotential (290 mV at 10 mA·g−1) and low Tafel slope (81 mV·dec−1) for long-term operation (only 7.8% decay in current density after 9 h). It could be envisioned that the proposed simple approach will pave a new way to synthesize other metal chalcogenides for energy conversion and storage technology.

Metallic and plasmonic MoO2 monocrystalline ultrathin mesoporous nanosheets for highly sensitive and stable surface-enhanced Raman spectroscopy.

Structure and size control are always considered as effective routes to enhance sensitive performance. Different from common polycrystalline porous nanosheets, herein, the general synthesis of monocrystalline ultrathin porous nanosheets (MUPNSs) by a facile decompressing decomposition (DPD) route is reported. Accompanied with the properties inherited from MUPNSs, i.e., high adsorption and strong plasma resonance, these MoO2 MUPNSs presented high sensitive activity as a surface enhanced Raman spectrum (SERS) substrate. The SERS sensitivity of MoO2 MUPNSs was about 1000 times higher than MoO2 polycrystalline ultrathin porous nanosheets (PUPNSs).

Hierarchical flower-like conductive CoNiO2 microspheres constructed with ultrathin mesoporous nanosheets towards long-cycle-life hybrid supercapacitors

Highly conductive transitional metal oxides (TMOs) positive electrodes can well address intrinsic power mismatching issues between negative and positive electrodes for advanced asymmetric supercapacitors. Purposeful exploration and rational design of dynamical TMOs with favorable microstructures and high-rate pseudocapacitances are crucially desired for advanced hybrid devices. Herein, we report efficiently bottom-up synthesis of hierarchical flower-like conductive CoNiO2 microspheres (CNOMS) self-constructed with mesoporous (∼2.4 nm) ultrathin nanosheet subunits of approximately 3.5–4.8 nm in thickness. Our CNOMS appealingly promise a fast electron and ion transport, large electroactive surface and strong structure stability in one. As a virtue of the compositional/structural features, the obtained CNOMS electrode with a high loading of 5 mg cm−2 delivers large specific capacitances of ∼854.9 and ∼414.5 F g−1 at high current rates of 1 and 20 A g−1 in 2 M aqueous KOH electrolyte, much superior to those of monometallic nickel/cobalt oxides counterparts. Encouragingly, the CNOMS-based hybrid device exhibits high energy density of ∼36.2 Wh kg−1 at a power rate of 160.0 W kg−1, as well as ∼100.8% long-duration capacitance retention over 10000 consecutive charge/discharge cycles. More promisingly, our CNOMS specimen is substantially highlighted as competitive electrode for long-cycle-life hybrid supercapacitors.

Nature-Inspired 2D-Mosaic 3D-Gradient Mesoporous Framework: Bimetal Oxide Dual-Composite Strategy toward Ultrastable and High-Capacity Lithium Storage.

In allusion to traditional transition-metal oxide (TMO) anodes for lithium-ion batteries, which face severe volume variation and poor conductivity, herein a bimetal oxide dual-composite strategy based on two-dimensional (2D)-mosaic three-dimensional (3D)-gradient design is proposed. Inspired by natural mosaic dominance phenomena, Zn1-xCoxO/ZnCo2O4 2D-mosaic-hybrid mesoporous ultrathin nanosheets serve as building blocks to assemble into a 3D Zn-Co hierarchical framework. Moreover, a series of derivative frameworks with high evolution are controllably synthesized, based on which a facile one-pot synthesis process can be developed. From a component-composite perspective, both Zn1-xCoxO and ZnCo2O4 provide superior conductivity due to bimetal doping effect, which is verified by density functional theory calculations. From a structure-composite perspective, 2D-mosaic-hybrid mode gives rise to ladder-type buffering and electrochemical synergistic effect, thus realizing mutual stabilization and activation between the mosaic pair, especially for Zn1-xCoxO with higher capacity yet higher expansion. Moreover, the inside-out Zn-Co concentration gradient in 3D framework and rich oxygen vacancies further greatly enhance Li storage capability and stability. As a result, a high reversible capacity (1010 mA h g-1) and areal capacity (1.48 mA h cm-2) are attained, while ultrastable cyclability is obtained during high-rate and long-term cycles, rending great potential of our 2D-mosaic 3D-gradient design together with facile synthesis.

Controllable synthesis of hierarchical MgMoO4 nanosheet-arrays and nano-flowers assembled with mesoporous ultrathin nanosheets

Self-standing hierarchical mesoporous MgMoO4 nanosheet-arrays and nano-flowers have been built via the self-assembly of ultrathin mesoporous nanosheets. The arrays and flower nanostructures can be facilely controlled by tuning the surfactant dosage. The formation mechanism of such special nanostructures has also been proposed. The flower structure has larger surface area than the arrays, owing to the more mesoporous nature of the former. Additionally, the as-prepared MgMoO4 nanomaterials not doped by any other ion have important optical properties, that enable the generation of strong red light with excitation wavelengths of 369 and 534 nm and emission of bright green light under irradiation by blue light (423 and 451 nm), demonstrating their potential applications in blue phototherapy and fluorescence labeling.

Effect of graphene thickness on the morphology evolution of hierarchical NiCoO2 architectures and their superior supercapacitance performance

The rational design of electrode materials with special hierarchical architectures which possess both high surface area and conductivity is significant to enhance the performance of supercapacitors. Herein, hierarchical NiCoO2 architectures assembled by ultrathin mesoporous nanosheets are in-situ grown on graphene@Ni foam (G@NF) by a template-free solvothermal route and subsequent annealing process, which is used as self-supported and binder-free supercapacitor electrodes. The effect of graphene thickness on morphology evolution of NiCoO2 is investigated. Benefiting from the synergistic effect between graphene with remarkable conductivity and hierarchical NiCoO2 architectures with high specific capacity, the NiCoO2/G@NF electrodes show greatly improved electrochemical performance compared to NiCoO2@NF and G@NF. The optimized NiCoO2/G@NF has a specific capacitance of 1220F/g at 1A/g. While the NiCoO2@NF and G@NF are only 565 and 151F/g, respectively. The optimized NiCoO2/G@NF remains 840F/g at 20A/g, revealing a remarkable rate performance (69% capacity retention from 1 to 20A/g). Moreover, an outstanding cyclic stability of 80% capacitance retention can be obtained after 5000 charge/discharge cycles at 10A/g, whereas the NiCoO2@NF is only 46.5%. These results suggest that the hierarchical NiCoO2 architectures/graphene hybrids are good candidates as effective electrode materials for supercapacitors.

Graphene foam supported multilevel network-like NiCo2S4 nanoarchitectures for robust lithium storage and efficient ORR catalysis

Interconnected mesoporous ultrathin nanosheets are assembled to form NiCo2S4 nanowall arrays, which are grown on 3D graphene foams to fabricate multilevel network-like composites.

From biomass chitin to mesoporous nanosheets assembled loofa sponge-like N-doped carbon/g-C3N4 3D network architectures as ultralow-cost bifunctional oxygen catalysts

To accelerate the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in the field of air-based energy technologies, efficient low-cost bifunctional catalysts are highly desired. In this paper, biomass chitin-derived N-doped carbon (C-Chitin)/graphitic C3N4 (g-C3N4) composites have been designed and fabricated via an ultralow-cost route including the low-temperature dissolution of biomass chitin and the subsequent carbonization. The C-Chitin/g-C3N4 composites exhibit well-designed loofa sponge-like three-dimensional (3D) network architectures assembled with massive interconnected ultrathin mesoporous nanosheets. Benefiting from the well-designed morphology and unique mesoporous structure with a high surface density of catalytic active sites, as well as the incorporation of N-doped carbon with g-C3N4, the C-Chitin/g-C3N4 composites exhibit pronounced ORR activity (4-electron pathway), superior OER activity (much lower onset potential and higher current density than Pt/C), excellent tolerance to methanol crossover and high durability toward both ORR and OER. Especially, the obtained C-Chitin/g-C3N4 composites with 20 wt % addition of g-C3N4 exhibit a potential gap of 0.90 V between the OER potential at a current density of 10 mA cm−2 and the ORR half wave potential, which is even higher than some highly active metal catalysts including noble-metals, thus holding great promise as low-cost metal-free bifunctional catalysts for efficient ORR and OER.

Self-assembly of ultrathin mesoporous CoMoO4 nanosheet networks on flexible carbon fabric as a binder-free anode for lithium-ion batteries

Novel hierarchical CoMoO4 networks assembled by ultrathin mesoporous nanosheets are directly grown on flexible carbon fabric as integrated anodes for highly efficient and reversible lithium storage.

Template-free synthesis of 3D hierarchical nanostructured NiCo2O4 mesoporous ultrathin nanosheet hollow microspheres for excellent methanol electrooxidation and supercapacitors

Novel 3D hierarchical NiCo2O4 mesoporous ultrathin nanosheets hollow microspheres upon a facile template-free solvothermal method followed air-annealing shows excellent methanol electrooxidation and supercapacitors performance.

Preparation of the monolith of hierarchical macro-/mesoporous calcium silicate ultrathin nanosheets with low thermal conductivity by means of ambient-pressure drying.

Calcium silicate monolith was prepared by the hydrothermal reaction of a slurry of SiO2 , calcium hydroxide, and surfactant (OP-10) obtained by high-energy ball milling, followed by drying at ambient pressure. By using this strategy, the shrinkage due to the collapse of pores during the drying of porous materials, which is a commonly observed phenomena, was successfully avoided. It has a unique microstructure of hierarchical macro-/mesoporous ultrathin calcium silicate nanosheets with a layered gyrolite crystalline structure. Very interestingly, the calcium silicate nanosheets can be peeled off to give a single-layer nanosheet (1.23 nm) of gyrolite by ultrasonication. The monolith has a low apparent density (0.073 g cm(-3) ) and low thermal conductivity (0.0399 W K(-1) m(-1) ). The reasons behind why the formation of the unique hierarchical macro-/mesoporous ultrathin nanosheets avoids shrinkage during the hydrothermal reaction and drying, and considerably decreases the thermal conductivity, is discussed.

Integration of network-like porous NiMoO4 nanoarchitectures assembled with ultrathin mesoporous nanosheets on three-dimensional graphene foam for highly reversible lithium storage

Interconnected ultrathin mesoporous NiMoO4 nanosheets with a network-like porous structure supported on a 3D graphene network for highly reversible lithium storage.

One-step synthesis of the nickel foam supported network-like ZnO nanoarchitectures assembled with ultrathin mesoporous nanosheets with improved lithium storage performance

Novel network-like ZnO nanoarchitectures are supported on nickel foam as binder-free anodes for high-performance lithium-ion batteries.

Microwave-assisted synthesis of nanosphere-like NiCo2O4 consisting of porous nanosheets and its application in electro-catalytic oxidation of methanol

A fast microwave-assisted synthesis method followed by a post-calcining process is used to prepare three-dimensional (3D) nanosphere-like NiCo2O4 nanostructure. The 3D NiCo2O4 nanospheres are constructed by intertwined two-dimensional (2D) ultrathin mesoporous nanosheets. The nanosphere-like NiCo2O4 has a large specific surface area (SSA, 146.5 m2 g−1) and is successfully applied to electro-catalytic oxidation of methanol. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and chronoamperometry (CA) measurements are used to investigate electro-catalytic performance of the as-prepared NiCo2O4. The current density of NiCo2O4/Ni foam (NiCo2O4/NF) electrode in 1 M KOH with 0.5 M methanol is up to 40.9 A g−1. And the current density can be returned to 97% of the original value by replacing new 1 M KOH electrolyte with 0.5 M methanol after a long-term CV cycle (500 cycles). These results show that our prepared NiCo2O4 possesses high electro-catalytic activity and good long-term stability for methanol oxidation. This may be benefit from the unique porous nanosphere-like structure and large SSA.

Enhanced performance of supercapacitors with ultrathin mesoporous NiMoO4 nanosheets

Both NiMoO4 nanowires (NWs) and NiMoO4 ultrathin mesoporous nanosheets (NSs) are successfully synthesized on Ni foam via simple hydrothermal methods. Benefiting from the ultrathin and mesoporous features, the NiMoO4 NSs with high electrical conductivity exhibit an enhanced electrochemical performance compared with the NiMoO4 NWs. The NiMoO4 NS electrode exhibits a high specific capacitance (2840 F g−1 at 10mAcm−2), good rate capability, electrochemical reversibility (the Coulombic efficiency is nearly 100%) and cycling stability (86.7% capacitance retention after 2000 cycles at a high current density of 15mAcm−2). Impressively, the energy density can reach ∼12.5×10−5 Wh cm−2 at 5mAcm−2. These excellent electrochemical performances indicate such NiMoO4 NSs-Ni foam electrodes could provide great potential for supercapacitor applications.