Ruowen Fu

Design and Preparation of Porous Polymers

Dingcai Wu,*,† Fei Xu,† Bin Sun,† Ruowen Fu,† Hongkun He,‡ and Krzysztof Matyjaszewski*,‡ †Materials Science Institute, Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, Peoples Republic of China ‡Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, United States

Facile synthesis of ultrahigh-surface-area hollow carbon nanospheres for enhanced adsorption and energy storage

Exceptionally large surface area and well-defined nanostructure are both critical in the field of nanoporous carbons for challenging energy and environmental issues. The pursuit of ultrahigh surface area while maintaining definite nanostructure remains a formidable challenge because extensive creation of pores will undoubtedly give rise to the damage of nanostructures, especially below 100 nm. Here we report that high surface area of up to 3,022 m2 g−1 can be achieved for hollow carbon nanospheres with an outer diameter of 69 nm by a simple carbonization procedure with carefully selected carbon precursors and carbonization conditions. The tailor-made pore structure of hollow carbon nanospheres enables target-oriented applications, as exemplified by their enhanced adsorption capability towards organic vapours, and electrochemical performances as electrodes for supercapacitors and sulphur host materials for lithium–sulphur batteries. The facile approach may open the doors for preparation of highly porous carbons with desired nanostructure for numerous applications.

Mesoporous MnO2/carbon aerogel composites as promising electrode materials for high-performance supercapacitors.

MnO(2) as one of the most promising candidates for electrochemical supercapacitors has attracted much attention because of its superior electrochemical performance, low cost, and environmentally benign nature. In this Letter, we explored a novel route to prepare mesoporous MnO(2)/carbon aerogel composites by electrochemical deposition assisted by gas bubbles. The products were characterized by energy-dispersive spectrometry (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The MnO(2) deposits are found to have high purity and have a mesoporous structure that will optimize the electronic and ionic conductivity to minimize the total resistance of the system and thereby maximize the performance characteristics of this material for use in supercapacitor electrodes. The results of nitrogen adsorption-desorption experiments and electrochemical measurements showed that these obtained mesoporous MnO(2)/carbon aerogel composites had a large specific surface area (120 m(2)/g), uniform pore-size distribution (around 5 nm), high specific capacitance (515.5 F/g), and good stability over 1000 cycles, which give these composites potential application as high-performance supercapacitor electrode materials.

Fast ion transport and high capacitance of polystyrene-based hierarchical porous carbon electrode material for supercapacitors

In this paper, we report the electrochemical capacitive properties of polystyrene-based hierarchical porous carbon (PS-HPC) for supercapacitors. Compared to many porous carbons such as a commercially available activated carbon and an ordered mesoporous carbon, PS-HPC has a unique three-dimensionally (3D) interconnected micro-, meso- and macroporous network and thus exhibits faster ion transport behavior and a larger utilization of surface area in electric double layer capacitors. The 3D interconnected meso- and macroporous network originates respectively from the compact and loose aggregation of crosslinked polystyrene-based carbon nanoparticles, and is able to facilitate rapid ion transfer/diffusion rates. Furthermore, PS-HPCs micropores exist from the 3D interconnected network inside these crosslinked polystyrene-based carbon nanoparticles, thus giving an exceptional electrochemically accessible surface area for charge accumulation. As a result, the capacitance retention ratio and capacitance per surface area of PS-HPC at a high sweep rate of 200 mV s−1 are as high as 84% and 28.7 μF cm−2, respectively. These encouraging results demonstrate the promising application of PS-HPC for high performance supercapacitors.

Radical Covalent Organic Frameworks: A General Strategy to Immobilize Open‐Accessible Polyradicals for High‐Performance Capacitive Energy Storage

Ordered π-columns and open nanochannels found in covalent organic frameworks (COFs) could render them able to store electric energy. However, the synthetic difficulty in achieving redox-active skeletons has thus far restricted their potential for energy storage. A general strategy is presented for converting a conventional COF into an outstanding platform for energy storage through post-synthetic functionalization with organic radicals. The radical frameworks with openly accessible polyradicals immobilized on the pore walls undergo rapid and reversible redox reactions, leading to capacitive energy storage with high capacitance, high-rate kinetics, and robust cycle stability. The results suggest that channel-wall functional engineering with redox-active species will be a facile and versatile strategy to explore COFs for energy storage.

Synthesis of Well-Defined Microporous Carbons by Molecular-Scale Templating with Polyhedral Oligomeric Silsesquioxane Moieties

Formation of a uniform interface between the carbon precursor and the selected template is critical for preparing high-quality nanoporous carbons. It can be accomplished by various templating procedures but still remains a challenge, especially for microporous carbons. A new strategy to fabricate well-defined microporous carbon nanosphere (MCNS) materials via molecular-scale interfacial engineering using an organic/inorganic hybrid molecule as the building block was designed. A commercially available octaphenyl polyhedral oligomeric silsesquioxane was selected as such a building block and transformed into the MCNS products via cross-linking of organic components, followed by carbonization, and subsequent removal of monodispersed silica domains, surrounded by molecular-scale carbon/silica interfaces. The obtained MCNS materials exhibit very large surface area (e.g., 2264 m(2)/g) and fast and selective sorption, and thus demonstrate excellent adsorption and supercapacitance properties. These findings could provide a new benchmark for preparing well-defined nanoporous carbons for various applications.

Electrochemically active, crystalline, mesoporous covalent organic frameworks on carbon nanotubes for synergistic lithium-ion battery energy storage

Organic batteries free of toxic metal species could lead to a new generation of consumer energy storage devices that are safe and environmentally benign. However, the conventional organic electrodes remain problematic because of their structural instability, slow ion-diffusion dynamics, and poor electrical conductivity. Here, we report on the development of a redox-active, crystalline, mesoporous covalent organic framework (COF) on carbon nanotubes for use as electrodes; the electrode stability is enhanced by the covalent network, the ion transport is facilitated by the open meso-channels, and the electron conductivity is boosted by the carbon nanotube wires. These effects work synergistically for the storage of energy and provide lithium-ion batteries with high efficiency, robust cycle stability, and high rate capability. Our results suggest that redox-active COFs on conducting carbons could serve as a unique platform for energy storage and may facilitate the design of new organic electrodes for high-performance and environmentally benign battery devices.

Carbon Microfibers with Hierarchical Porous Structure from Electrospun Fiber-Like Natural Biopolymer

Electrospinning offers a powerful route for building one-dimensional (1D) micro/nanostructures, but a common requirement for toxic or corrosive organic solvents during the preparation of precursor solution has limited their large scale synthesis and broad applications. Here we report a facile and low-cost way to prepare 1D porous carbon microfibers by using an electrospun fiber-like natural product, i.e., silk cocoon, as precursor. We surprisingly found that by utilizing a simple carbonization treatment, the cocoon microfiber can be directly transformed into 1D carbon microfiber of ca. 6 μm diameter with a unique three-dimensional porous network structure composed of interconnected carbon nanoparticles of 10~40 nm diameter. We further showed that the as-prepared carbon product presents superior electrochemical performance as binder-free electrodes of supercapacitors and good adsorption property toward organic vapor.

Preparation and Electrochemical Performance of Novel Ordered Mesoporous Carbon with an Interconnected Channel Structure

A novel ordered mesoporous carbon with an interconnected channel structure (OMC-IC) has been successfully fabricated by adding proper hydrophilic SiO(2) nanoparticles to the solution of triblock copolymer F127 and phenol-formaldehyde resol. Experimental results show that the presence of SiO(2) nanoparticles does not hamper the self-assembly of F127 and resol to form an ordered two-dimensional hexagonal mesostructure. The neighboring channels of the OMC-IC are interconnected after removing SiO(2) nanoparticles with a diameter larger than the thickness of the carbon wall. Such an interconnectivity of channels is beneficial in improving ion diffusion properties. The as-prepared OMC-IC exhibits much lower impedance to ion transport within both the channels and the micropores in the carbon wall, and thus has better electric double layer performance as compared to the conventional OMC with an unconnected channel structure.

Template-free fabrication of hierarchical porous carbon by constructing carbonyl crosslinking bridges between polystyrene chains

A simple and effective template-free method to fabricate hierarchical porous carbon (HPC) has been successfully developed by adopting linear polystyrene resin as raw material, anhydrous aluminium chloride as Friedel–Crafts catalyst, and carbon tetrachloride as crosslinker and solvent. Experimental results show that the as-constructed carbonyl (–CO–) crosslinking bridges between polystyrene chains provide simultaneously to its hierarchical porous polystyrene precursor, both a high crosslinking density and a proper amount of oxygen atoms, and thus achieve good framework carbonizability and nanostructure inheritability during carbonization. The as-prepared HPCs hierarchical porous structure exhibits interesting uniqueness: micropores (<2 nm) are from the network inside crosslinking polystyrene-based carbon nanoparticles of 10–30 nm in size, and mesopores (2–50 nm) and macropores (50–400 nm) result from the compact and loose aggregation of these network nanoparticles, respectively; and these micro-, meso- and macropores are three-dimensionally interconnected to each other. Its Brunauer–Emmett–Teller surface area and total pore volume are 679 m2g−1 and 0.66 cm3g−1, respectively.