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Carbon Nanomaterials for energy harvest, storage and conversion


    A method has been developed in the group to selectively control the graphene orientations towards the axis of the carbon nanofibers. The principle for rationally design the nanostructure of CNFs has been gained by the detailed kinetic study and characterization of resulted CNFs. Carbon nanotubes, herringbone nanofibers, platelet nanofibers, onions and graphene are examples among the carbon nanomaterials. They provide a platform for study effects of graphene orientations on the properties of different carbon nanomaterials in different applicators. Synthesis of aligned CNTs on metallic substrates and graphene are the main topics in the group with an aim of direct application as energy conversion and storage devices.


   CNFs have unique properties such as high cystallinity, tuneable surface structure and surface groups, making them promising directly as catalysts for oxidation or oxidative dehydrogenation. The research has been focused on effects of graphene orientations of CNFs on oxidative dehydrogenation of propane and ethyl benzene.



    The edge structures, which as governed by the graphene sheet orientations of CNFs, significantly influence the interaction between the metal nanoparticles and CNFs. This directly determinates the metal cluster shapes, and thus the bond length distribution and facets exposed to the reactants. The reactive force field molecular dynamic simulations is a powerful tool to understand the interaction between nanoclusters and CNFs. The CNFs with different graphene orientations have been developed as a platform for rational catalyst design to manipulate the interaction, electronic properties and particle shapes. The CNFs supported Ni, Co, Cu, Pd, Pt and Ru have been studied in both gas phase and liquid phase reactions.


There is an increasing demand for energy storage devices with high power ad energy density for applications in renewable energy production, electric or hybrid cars, etc.. Supercapacitors with hybrid electrodes will share an important role in energy storage market. An important development in energy storage is to move the boundary of energy density of supercapacitors towards to batteries, as shown in Ragona plot. Asymmetric hybrids combine Faradaic and non-Faradaic processes by coupling an carbon electrode with a pseudocapacitor electrode through redox reactions. In particular, the coupling of a CNT negative electrode with a conducting polymer positive electrode has received a great deal of attention.


The research has focused on increasing the power and energy density of the supercapacitors, which is closely linked to the following objectives: 1) Design 3-D pillar structure integrating CNT with conductive polymer to have high surface area of conductive polymer with tailored thickness and regular open structure, aiming at a better access of electrolyte. 2) Synthesis of CNT arrays on Al foils aiming at reducing the weight of electrode and reduced resistance. 3) Electrochemical in-situ polymerization of conductive polymers with tailored thickness. 4)  Fundamental study of the relationship among the conductive thickness, electric resistance, ionic transport, capacitance, stability, energy and power density. 5) Fundamental study of the interface properties between the electrode surfaces and different electrolytes to increase the energy density. Prototype supercapacitors have been fabricated. The supercapacitors presented a high energy density (almost 2 order of magnitudes higher than conventional carbon based capacitors) and high power density (1-2 order of magnitudes higher than batteries. Similar structure of electrodes with different electroactive materials are testing in Li-ion batteries.


High conductivity, high external surface, tuneable surface structure and properties make carbon nanofibers promising as fuel cell catalyst supports. Our research was a part of the national project on nanomaterials for hydrogen conversion supported by Norwegian Research Council. The objectives are to gain a better understanding of the following effects on the fuel cell catalyst properties: 1) Nano carbon structure, in particular the  greaphene orientations; 2) Interaction between CNF and Pt particles; 3) Pt particle sizes and shapes; 4) Surface oxygen groups


The structured CNFs, for examples, CNF/carbon felt and CNF/monoliths can be used to protein separation and waster water treatment. The adsorptive removal of phenol and reactive removal N containing pollutants in water are the research topics. An EU project is running on this topic.


Hierarchically structured CNFs on carbon felt, monolith, foils and foams can be used as microreactors to facilitate mass and heat transfer in the reactor, and achieve almost 100% effectiveness of nanoclusters in the reactor. The structured reactors are highly conductive, which is suitable for highly exothermic reactions such as CO oxidation and Fischer-Tropsch reactions. In addition, the structures reactor itself can be used as a heating element to rapid heat up the reactor.   Recent a study illustrated that the CNF/carbon felt composite can avoid running away and achieve uniform distribution of temperature in the reactor and achieve 100% effectiveness of Co nanoclusters.