Li-Bing Lv

Nitrogen-doped graphene microtubes with opened inner voids: Highly efficient metal-free electrocatalysts for alkaline hydrogen evolution reaction

A facile method was developed to fabricate nitrogen-doped graphene microtubes (N-GMT) with ultra-thin walls of 1–4 nm and large inner voids of 1–2 μm. The successful introduction of nitrogen dopants afforded N-GMT more active sites for significantly enhanced hydrogen evolution reaction (HER) activity, achieving a current density of 10 mA·cm–2 at overpotentials of 0.464 and 0.426 V vs. RHE in 0.1 and 6 M KOH solution, respectively. This HER performance surpassed that of the best metal-free catalyst reported in basic solution, further illustrating the great potential of N-GMT as an efficient HER catalyst for real applications in water splitting and chlor-alkali processes.

Wrinkled Graphene Monoliths as Superabsorbing Building Blocks for Superhydrophobic and Superhydrophilic Surfaces

Superhydrophobic and superhydrophilic surfaces are of great interest because of a large range of applications, for example, as antifogging and self-cleaning coatings, as antibiofouling paints for boats, in metal refining, and for water-oil separation. An aqueous ink based on three-dimensional graphene monoliths (Gr) can be used for constructing both superhydrophobic and superhydrophilic surfaces on arbitrary substrates with different surficial structures from the meso- to the macroscale. The surface wettability of a Gr-coated surface mainly depends on which additional layers (air for a superhydrophobic surface and water for a superhydrophilic surface) are adsorbed on the surface of the graphene sheets. Switching a Gr-coated surface between being superhydrophobic and superhydrophilic can thus be easily achieved by drying and prewetting with ethanol. The Gr-based superhydrophobic membranes or films should have great potential as efficient separators for fast and gravity-driven oil-water separation.

Converting waste paper to multifunctional graphene-decorated carbon paper: from trash to treasure

Proper disposal of waste paper is an important waste-management concern. We developed a facile and inexpensive method to transform waste paper into graphene-tethered carbon fiber composite paper (GCCP). Urea was the only additive for the carbonization of the GCCP. The as-obtained GCCP exhibited high electrical conductivity, and GCCP/polydimethyl siloxane (GCCP/PDMS) composites showed good stretchability with great electromechanical stability. The surface of the GCCP membrane was observed to be superhydrophobic; this property apparently endowed the membrane with the ability to separate oil from water in our experiments, which makes GCCP a promising candidate material for cleanup of oil spills. The hierarchical structure, N doping feature and low decoration with Pt make GCCP a potential electrocatalyst for oxygen reduction, oxygen evolution and hydrogen evolution reactions with superior activity and high stability, and hence also a promising candidate for application as a direct working electrode in future energy systems.

Ultra-durable two-electrode Zn–air secondary batteries based on bifunctional titania nanocatalysts: a Co2+ dopant boosts the electrochemical activity

High energy density, low cost and ultra-stable bifunctional electrocatalysts that act simultaneously for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are important for commercializing the rechargeable Zn–air batteries. Co-doped TiO2 nanoparticles as an ultra-stable and cheap electrocatalyst exhibited excellent activity for both ORR and OER in alkaline media. A real air cathode made of the Co-doped TiO2 electrocatalyst further offered superior high energy density (778 mA h gZn−1 and 938.5 W h kgZn−1 at 5 mA cm−2, and 785.9 mA h gZn−1 and 911.3 W h kgZn−1 at 20 mA cm−2) and ultra-high stability (37 cycles for 750 h of operation at 20 mA cm−2 and 3150 cycles for 1050 h of operation at 5 mA cm−2) in two-electrode Zn–air batteries.

Programmable synthesis of mesoporous ZSM-5 nanocrystals as selective and stable catalysts for the methanol-to-propylene process

Mesoporous ZSM-5 nanocrystals with an optimized Si/Al ratio and mesoporosity were facilely synthesized without involving additional template in high yield, exhibiting high stability and high propylene selectivity for the methanol to propylene reaction. Kilogram-scale production of mesoporous ZSM-5 nanocrystals ensured their possible applications as catalysts in industry.

Supramolecular nano-assemblies with tailorable surfaces: recyclable hard templates for engineering hollow nanocatalysts

Supramolecular assemblies are introduced here as new-concept hard templates for the synthesis of hollow nanostructures (exemplified with TiO2 hollow nanostructures in this work). Supramolecular templates with tunable morphology and rich surface functional groups facilitate the tight coating of other materials for the formation of hollow nanostructures. The weak interaction between the supramolecules or micromolecules benefits the facile removal of the templates for large-scale synthesis of hollow nanostructures and also affords excellent template reusability. This method allows for the incorporation of various metal dopants into the TiO2 lattice, as a typical example of nanocatalyst, by introducing the corresponding metal salt as a dopant source. High-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and UV-vis absorption spectroscopy investigations suggested substitution of Ti4+ sites by Co2+, which increased the activity of the catalytic sites in the doped materials, reducing the overpotential of TiO2 for the oxygen evolution reaction.摘要超分子自组装化合物具有可调控的形貌和丰富的表面官能团. 超分子或小分子单体之间的弱相互作用有利于除去模板, 作为硬模板合成空心纳米结构(以TiO2为例), 不仅能得到具有可调控形貌的空心纳米结构, 并且超分子模板可以回收和重复利用. 实验表明, 用三聚氰氨和三聚氰酸作为原料合成的超分子模板, 有利于在模板表面复合无机组分, 并且模板中的氢键在水中易断裂, 因此可以通过透析方法除去模板得到空心纳米结构. 这种超分子模板法也可以用于合成掺杂金属离子的空心结构纳米催化剂, 进一步调控电子结构增加析氧反应的活性位点, 降低超电势. 更重要的是, 此模板合成方法简单、 耗能低、 可重复利用, 可以用于合成大批量的空心结构纳米催化剂.

Polarized few-layer g-C3N4 as metal-free electrocatalyst for highly efficient reduction of CO2

The greenhouse effect and global warming are serious problems because the increasing global demand for fossil fuels has led to a rapid rise in greenhouse gas exhaust emissions in the atmosphere and disruptive changes in climate. As a major contributor, CO2 has attracted much attention from scientists, who have attempted to convert it into useful products by electrochemical or photoelectrochemical reduction methods. Facile design of efficient but inexpensive and abundant catalysts to convert CO2 into fuels or valuable chemical products is essential for materials chemistry and catalysis in addressing global climate change as well as the energy crisis. Herein, we show that two-dimensional fewlayer graphitic carbon nitride (g-C3N4) can function as an efficient metal-free electrocatalyst for selective reduction of CO2 to CO at low overpotentials with a high Faradaic efficiency of ~ 80%. The polarized surface of ultrathin g-C3N4 layers (thickness: ~ 1 nm), with a more reductive conduction band, yields excellent electrochemical activity for CO2 reduction.

High-permittivity and low-dielectric-loss polymer composites based on TiO 2 -nanorod functionalized carbon nanotubes

High permittivity polymer-based composites have attracted increasing attention because of their inherent advantages of being easy to process, flexible and light weight in electronic and electrical industry. However, the permittivity of common polymer is very low (<;10). Adding conductive fillers provides a promising route to significantly increase the permittivity of a polymer with a low loading. Nevertheless, polymer composites containing conductive fillers often exhibit very high dielectric loss due to their large electrical conduction or leakage currents. In this paper, we report a simple and effective way to synthesize TiO2-nanorod-decorated multi-walled carbon nanotubes (TD-CNTs). The resultant TD-CNT/polystyrene (PS) composites show high permittivity and low dielectric loss. The composites with 17.2 vol% TD-CNTs show a permittivity of 37 at 1 kHz, which is 13.7 fold higher than that of the pure PS, but the dielectric loss still shows a low level below 0.11.

Mesoporous H-ZSM-5 nanocrystals with programmable number of acid sites as “solid ligands” to activate Pd nanoparticles for C–C coupling reactions

In this work, we described a proof-of-concept method to promote the activity and selectivity of Pd nanoparticles for heterogeneous catalysis (exemplified by C–C coupling reactions) by using acid sites within a zeolite framework. The Pd nanoparticles were encapsulated inside the crystalline walls of mesoporous H-ZSM-5 leading to hybrid samples (denoted as Pd@mZ-x-H) with controlled number of acid sites. A linear relationship between the number of acid sites of the zeolite nanocrystals and the catalytic activities of the Pd nanoparticles in organic reactions was established. Moreover, the shape-dependent selectivity of Pd@mZ-x-H was not sacrificed when the final activity was enhanced.

Direct reduction of oxygen gas over dendritic carbons with hierarchical porosity: beyond the diffusion limitation

The direct activation of oxygen molecules in the gas phase at the interface of solid (catalyst), liquid (electrolyte) and gas (oxygen gas) is highly alluring for the oxygen reduction reaction (ORR) catalyst in a liquid-phase reactor. Such a multiphase pathway without the limitation of the diffusion rate of the dissolved oxygen molecules promises a much higher catalytic efficiency. However, a stable gas–liquid–solid interface can hardly be maintained due to the high surface tension of the aqueous solution to repel the gas phase on the surface of conventional ORR electrodes. Taking advantage of graphene layers with super-absorbing nature, we designed a dendritic carbon structure catalyst to stabilize oxygen bubbles in the nano-intervoids of the dendrites without loss of conductivity and structural integrity, achieving the direct reduction of oxygen gas in an aqueous electrolyte and an ultra-high ORR current density without a diffusion controlled plateau.