Zhengjie Li

Self-Assembled 3D Graphene Monolith from Solution.

Three-dimensional (3D) graphene-assembled monoliths (GAs), especially ones prepared by self-assembly in the liquid phase, represent promising forms to realize the practical applications of graphene due to their high surface utilization and operability. However, the understanding of the assembly process and structure control of 3D GAs, as a new class of carbon materials, is quite inadequate. In this Perspective, we give a demonstration of the assembly process and discuss the key factors involved in the structure control of 3D GAs to pave the way for their future applications. It is shown that the assembly process starts with the phase separation, which is responsible for the formation of the 3D networked structure and liquid phase as the spacers avoid the parallel overlap of graphene layers and help form an interlinked pore system. Well-tailored graphene sheets and selected assembly media must be a precondition for a well-controlled assembly process and microstructure of a 3D GA. The potential applications in energy storage featuring high rate and high volumetric energy density demonstrate advantages of 3D GAs in real applications.

A three-dimensional graphene skeleton as a fast electron and ion transport network for electrochemical applications

This study presents a method to optimize the mass transport and electron transfer of metal oxides in electrochemical processes by using a three-dimensional (3D) porous graphene macroassembly (GM) as a framework. A simple method, pressurized infiltration, is reported to realize uniform dispersion of metal oxide nanoparticles on the graphene skeleton in the GM. The obtained GM–NiO hybrid shows significantly improved performance in electrochemical catalytic processes and energy storage applications. When used as the active material in nonenzymic sensors, it shows a low detection limit towards glucose while maintaining high sensitivity. It also shows a high capacitance of about 727 F g−1 and maintains high rate performance when used as the electrode material for supercapacitors. More importantly, this method may be sufficiently versatile for the hybridization of different kinds of noncarbon materials with GM to promote their practical applications.

High-performance ultrafiltration membranes based on polyethersulfone–graphene oxide composites

Graphene oxide nanosheets are employed as nanofillers to improve hydrophilicity and antifouling performance of a polymer-based membrane, resulting in high performance ultrafiltration membranes with substantially improved flux.

Graphene Emerges as a Versatile Template for Materials Preparation

Graphene and its derivatives are emerging as a class of novel but versatile templates for the controlled preparation and functionalization of materials. In this paper a conceptual review on graphene-based templates is given, highlighting their versatile roles in materials preparation. Graphene is capable of acting as a low-dimensional hard template, where its two-dimensional morphology directs the formation of novel nanostructures. Graphene oxide and other functionalized graphenes are amphiphilic and may be seen as soft templates for formatting the growth or inducing the controlled assembly of nanostructures. In addition, nanospaces in restacked graphene can be used for confining the growth of sheet-like nanostructures, and assemblies of interlinked graphenes can behave either as skeletons for the formation of composite materials or as sacrificial templates for novel materials with a controlled network structure. In summary, flexible graphene and its derivatives together with an increasing number of assembled structures show great potentials as templates for materials production. Many challenges remain, for example precise structural control of such novel templates and the removal of the non-functional remaining templates.

A wavy graphene/platinum hybrid with increased electroactivity for the methanol oxidation reaction

Two distinct graphene sheets, highly flat graphene and wavy graphene, were used as support materials for in situ nucleation and growth of platinum nanoparticles (Pt NPs) to synthesize graphene/Pt catalysts. The average size of Pt NPs on the wavy graphene sheets is around 2 nm and is smaller than those on the flat graphene sheets. The electrochemical activity of the two as-prepared catalysts towards methanol oxidation was investigated and compared with that of a commercial Pt/carbon black (Pt/C) catalyst, and electrochemical results showed that the wavy graphene/Pt catalyst possessed the best poison tolerance and comparable electrochemical surface area to the commercial Pt/C catalyst. The wavy microstructure is believed to be responsible for the stable dispensability of the as-prepared wavy graphene and the acquisition of small size Pt NPs, since the abundant ripples coming from the wavy microstructure effectively prevent the aggregation of the graphene sheets, and also act as barriers to prevent agglomeration of Pt NPs during their in situ nucleation and growth process. This work indicates that the microstructure of the supporting material plays a crucial role in the electrochemical performance of platinum-based catalysts.

A hollow spherical carbon derived from the spray drying of corncob lignin for high-rate-performance supercapacitors

Controlling the microstructure of biomass-derived carbon is of essential importance for directing its use. Herein, a hollow spherical carbon (HSC) was prepared from corncob lignin through spray drying and subsequent heat treatment. The HSC, which is characterized by its hierarchically porous structure, delivers high rate capability when it is directly used as electrode material for supercapacitors. This strategy that uses lignin as the precursor avoids the intrinsic difficulty in tuning the microstructure of the biomass-derived carbons and is suitable for mass production for practical use.