Yingying Lv

Two-Dimensional Mesoporous Carbon Nanosheets and Their Derived Graphene Nanosheets: Synthesis and Efficient Lithium Ion Storage

We report a new solution deposition method to synthesize an unprecedented type of two-dimensional ordered mesoporous carbon nanosheets via a controlled low-concentration monomicelle close-packing assembly approach. These obtained carbon nanosheets possess only one layer of ordered mesopores on the surface of a substrate, typically the inner walls of anodic aluminum oxide pore channels, and can be further converted into mesoporous graphene nanosheets by carbonization. The atomically flat graphene layers with mesopores provide high surface area for lithium ion adsorption and intercalation, while the ordered mesopores perpendicular to the graphene layer enable efficient ion transport as well as volume expansion flexibility, thus representing a unique orthogonal architecture for excellent lithium ion storage capacity and cycling performance. Lithium ion battery anodes made of the mesoporous graphene nanosheets have exhibited an excellent reversible capacity of 1040 mAh/g at 100 mA/g, and they can retain at 833 mAh/g even after numerous cycles at varied current densities. Even at a large current density of 5 A/g, the reversible capacity is retained around 255 mAh/g, larger than for most other porous carbon-based anodes previously reported, suggesting a remarkably promising candidate for energy storage.

A comprehensive study on KOH activation of ordered mesoporous carbons and their supercapacitor application

Activation of ordered mesoporous carbon orientates the development and application of new carbonaceous supercapacitor materials with high energy density and power density. Ordered mesoporous carbons FDU-15 are synthesized in large scale via a soft template method through evaporation induced self-assembly of mesostructure on the sacrificed polyurethane foam. Common activating agent potassium hydroxide (KOH) is utilized to improve the surface area and tailor the pore texture of the ordered mesoporous carbon by adjusting KOH/carbon mass ratio as well as activation time. At low KOH/carbon ratio, the generated micropores increase in volume and either connect to other micropores or eventually become mesopores. At high KOH/carbon ratio, an excess amount of micropores would be generated. Meanwhile, the continuous shrinkage of carbon framework is carried through as prolonged time at high activation temperature. Competition between KOH etching and shrinkage of mesopores is existed during the activation. The latter obviously preponderates over the former at low KOH/carbon ratio, which is reversed at high KOH/carbon ratio. Thus, an optimized micro-mesostructure is achieved under certain activation conditions: maintained ordered mesostructure, suitable microporosity, high surface area (1410 m2 g−1) and large pore volume (0.73 cm3 g−1). The activated sample exhibits improved electrochemical behavior with a gravimetric capacitance of 200 F/g, excellent rate performance and good cycling stability with capacitance retention of ∼98% over 300 cycles.

Free-Standing Mesoporous Carbon Thin Films with Highly Ordered Pore Architectures for Nanodevices

We report for the first time the synthesis of free-standing mesoporous carbon films with highly ordered pore architecture by a simple coating-etching approach, which have an intact morphology with variable sizes as large as several square centimeters and a controllable thickness of 90 nm to ∼3 μm. The mesoporous carbon films were first synthesized by coating a resol precursors/Pluronic copolymer solution on a preoxidized silicon wafer and forming highly ordered polymeric mesostructures based on organic-organic self-assembly, followed by carbonizing at 600 °C and finally etching of the native oxide layer between the carbon film and the silicon substrate. The mesostructure of this free-standing carbon film is confirmed to be an ordered face-centered orthorhombic Fmmm structure, distorted from the (110) oriented body-centered cubic Im3̅m symmetry. The mesoporosity of the carbon films has been evaluated by nitrogen sorption, which shows a high specific BET surface area of 700 m(2)/g and large uniform mesopores of ∼4.3 nm. Both mesostructures and pore sizes can be tuned by changing the block copolymer templates or the ratio of resol to template. These free-standing mesoporous carbon films with cracking-free uniform morphology can be transferred or bent on different surfaces, especially with the aid of the soft polymer layer transfer technique, thus allowing for a variety of potential applications in electrochemistry and biomolecule separation. As a proof of concept, an electrochemical supercapacitor device directly made by the mesoporous carbon thin films shows a capacitance of 136 F/g at 0.5 A/g. Moreover, a nanofilter based on the carbon films has shown an excellent size-selective filtration of cytochrome c and bovine serum albumin.

Ordered Mesoporous Platinum@Graphitic Carbon Embedded Nanophase as a Highly Active, Stable, and Methanol-Tolerant Oxygen Reduction Electrocatalyst

Highly ordered mesoporous platinum@graphitic carbon (Pt@GC) composites with well-graphitized carbon frameworks and uniformly dispersed Pt nanoparticles embedded within the carbon pore walls have been rationally designed and synthesized. In this facile method, ordered mesoporous silica impregnated with a variable amount of Pt precursor is adopted as the hard template, followed by carbon deposition through a chemical vapor deposition (CVD) process with methane as a carbon precursor. During the CVD process, in situ reduction of Pt precursor, deposition of carbon, and graphitization can be integrated into a single step. The mesostructure, porosity and Pt content in the final mesoporous Pt@GC composites can be conveniently adjusted over a wide range by controlling the initial loading amount of Pt precursor and the CVD temperature and duration. The integration of high surface area, regular mesopores, graphitic nature of the carbon walls as well as highly dispersed and spatially embedded Pt nanoparticles in the mesoporous Pt@GC composites make them excellent as highly active, extremely stable, and methanol-tolerant electrocatalysts toward the oxygen reduction reaction (ORR). A systematic study by comparing the ORR performance among several carbon supported Pt electrocatalysts suggests the overwhelmingly better performance of the mesoporous Pt@GC composites. The structural, textural, and framework properties of the mesoporous Pt@GC composites are extensively studied and strongly related to their excellent ORR performance. These materials are highly promising for fuel cell applications and the synthesis method is quite applicable for constructing mesoporous graphitized carbon materials with various embedded nanophases.

Dual‐Pore Mesoporous Carbon@Silica Composite Core–Shell Nanospheres for Multidrug Delivery

Monodispersed mesoporous phenolic polymer nanospheres with uniform diameters were prepared and used as the core for the further growth of core-shell mesoporous nanorattles. The hierarchical mesoporous nanospheres have a uniform diameter of 200 nm and dual-ordered mesopores of 3.1 and 5.8 nm. The hierarchical mesostructure and amphiphilicity of the hydrophobic carbon cores and hydrophilic silica shells lead to distinct benefits in multidrug combination therapy with cisplatin and paclitaxel for the treatment of human ovarian cancer, even drug-resistant strains.

Synthesis of 2D-Mesoporous-Carbon/MoS2 Heterostructures with Well-Defined Interfaces for High-Performance Lithium-Ion Batteries

A sandwich-like 2D-mesoporous-carbon/MoS2 -nanosheet heterostructure is fabricated for the first time. The hybrid structure is composed of three well-stacked monolayers: an ordered-mesoporous-carbon monolayer, a MoS2 monolayer, and a further ordered-mesoporous-carbon monolayer. This unique heterostructure exhibits excellent electrochemical performance as an anode material for lithium-ion batteries.

Multi-layered mesoporous TiO2 thin films with large pores and highly crystalline frameworks for efficient photoelectrochemical conversion

Mesoporous thin films with various compositions are unique architectures for photoelectrochemical (PEC) solar cells. In this paper, we report the synthesis of highly ordered, multi-layered, continuous mesoporous TiO2 thin films with uniform large pores, crystalline walls and tunable film thickness, via a ligand-assisted evaporation induced self assembly (EISA) method. A Ti(acetylacetone) precursor and a diblock copolymer PEO-b-PS are employed for the controlled assembly of the TiO2/template mesostructure, followed by a two-step pyrolysis that generates carbon residue as an intermediate protection layer to support the TiO2 framework and mesostructures during the crystallization. Other transition metal ion dopants (such as Cr, Ni and Co) can be facilely incorporated into the TiO2 frameworks by co-assembly of these metal acetylacetone precursors during the EISA process. The obtained TiO2 thin film possesses an ordered monoclinic mesostructure distorted from a (110)-oriented primitive cubic structure, uniform and tunable large pores of 10–30 nm, a large surface area of ∼100 m2 g−1 and a high crystallinity anatase wall. The film thickness can be well controlled from 150 nm to several microns to tune the absorption, with the capability of generating free-standing film morphologies. Furthermore, this designed architecture allows for effective post-deposition of other small-bandgap semiconductor nanomaterials inside the large, open and interconnecting mesopores, leading to significantly improved solar absorption and photoconversion. As a proof-of-concept, we demonstrate that the photoanodes made of 4.75 μm thick mesoporous TiO2 film with deposited cadmium sulfide quantum dots exhibit excellent performance in PEC water splitting, with an optimized photocurrent density of 6.03 mA cm−2 and a photoconversion efficiency of 3.9%. These multi-layered mesoporous TiO2-based thin films can serve as a unique architecture for PEC and other solar energy conversion and utilization.

Interface tension-induced synthesis of monodispersed mesoporous carbon hemispheres.

Here we report a novel interface tension-induced shrinkage approach to realize the synthesis of monodispersed asymmetrical mesoporous carbon nanohemispheres. We demonstrate that the products exhibit very uniform hemispherical morphology (130 × 60 nm) and are full of ordered mesopores, endowing them high surface areas and uniform pore sizes. These monodispersed mesoporous carbon hemispheres display excellent dispersibility in water for a long period without any aggregation. Moreover, a brand new feature of the mesoporous carbon materials has been observed for the first time: these monodispersed mesoporous carbon hemispheres show excellent thermal generation property under a NIR irradiation.

Ordered mesoporous carbons and their corresponding column for highly efficient removal of microcystin-LR

Highly effective removal of toxic pollutant microcystins from water sources is achieved by employing ordered mesoporous carbons prepared from the surfactant-templating method as adsorbents. For the first time, a systematic study into the static and dynamic adsorption behaviours of ordered mesoporous carbons towards microcystin-LR (MC-LR) is demonstrated. Firstly, by adopting different mesoporous carbons with various mesostructures, textures and surface chemical properties for batch adsorption, definite relationships between the adsorption performance of MC-LR and properties of adsorbents are established. Among all the samples, the mesoporous carbon (MCS/C) obtained from a mesoporous silica–carbon composite after removing the silica component exhibits an unprecedented adsorption capacity of ∼526 mg g−1, due to its unique bimodal mesopores of ∼2.8 and 5.8 nm, a high surface area of 1680 m2 g−1, a large pore volume of 1.67 cm3 g−1 and two-dimensional (2D) straight mesopore channels. A comprehensive understanding of dynamic adsorption behaviour shows that this mesoporous carbon possesses a 30-fold higher adsorption capacity compared with powdery activated carbon at a high flux of 120 L m−2 h−1. Finally, two pollutants, Rhodamine B and phenol, are mixed with MC-LR for competitive adsorption onto the mesoporous carbon MCS/C. It is found that the total amount of removal pollutants increases sharply to ∼700 mg g−1. Considering all the advantages, the ordered mesoporous carbon MCS/C shows a promising potential for practical waste water treatment, especially for large toxin microcystin removal.

Multiwall carbon nanotube@mesoporous carbon with core-shell configuration: a well-designed composite-structure toward electrochemical capacitor application

Based on the desired electrical conductivity and high specific-surface-area for carbon-based electrodes, herein, we have designed and synthesized uniform multiwall carbon nanotube@mesoporous carbon (MWNT@mesoC) composites with core-shell configuration by combining sol–gel methods and nanocasting. Pristine MWNTs after acid treatment were first coated with uniform mesostructured silica shells to obtain the MWNT@mesoporous silica (MWNT@mesoS) composite using cationic surfactant cetyltrimethyl ammonium bromide (CTAB) as a template. Then, furfural alcohol (carbon source) and oxalic acid (catalyst) were impregnated into the template-free MWNT@mesoS composite and followed by carbonization. The removal of silica led to the replacement of the mesoC shells decorated on the surface of MWNTs. The obtained composite materials retain the one-dimension (1-D) tubular structure and three-dimension (3-D) entangled framework as the original MWNTs. Micro/nanostructure exploration demonstrates that each MWNT is uniformly coated by the mesoC shell with short-pore-length (∼15 nm), which contributes above 300 m2 g−1 to specific surface areas purely from bimodal-mesopores (3.9/8.9 nm in diameter). The MWNT@mesoC composite shows greatly increased specific capacitance from 9.0 to 48.4 F g−1 and 6.8 to 60.2 F g−1 in 1.0 M (C2H5)4NBF4 and 6.0 M KOH, good rate performance with ∼60% maintenance of the initial capacitance at the current density of 20 A g−1 and high cyclability (94% after 1000 cycles).