Carbon Nitrides: Metal-free Materials for Energy Applications

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Our project aims to develop and optimise a new class of metal-free electroactive graphitic carbon nitride materials (gCNMs) as lithium ion battery (LIB) electrodes, supercapacitors (SC) and fuel cell catalyst supports. These are important energy-related applications. gCNMs are based on layers of sp2-bonded carbon and nitrogen atoms similar to C-graphite or graphene, but they contain voids or channels within and between the layers giving a 3-dimensional character that we will develop here for reversible Li+ intercalation and LIB applications. During proof-of-concept studies supported by a 12-month award from UCL Enterprise we found that the Li+ storage capacity of gCNMs could be competitive with C-graphite (patent application 1311742.9, filed 1/7/13). In this project we will apply a systematic approach combining synthetic chemistry, ab initio theoretical prediction, advanced characterisation and electrochemical testing to control and optimise the potential of gCNMs as LIB electrode materials.The gCNM layers are built from triazine (C3N3) or heptazine (C6N7) units linked by -N= or -NH- groups. Fully condensed structures have composition C3N4: the number of -NH- linkages increases for incomplete polymerisation and this controls the electronic properties as well as voids and channels within and between layers. Non-bonded electron pairs and exchangeable H atoms attached to nitrogen provide charge storage capabilities for metal-free supercapacitors. A second area of our project will optimise gCNMs for SC applications.We will systematically tune the synthesis and processing to control the layer condensation and void arrangements optimised for each application. We will use templates to produce hierarchical structures with controlled porosity and incorporate the materials in electrochemical test devices. We will also build on our observation that gCNMs show promise as catalyst support materials for fuel cell applications. We will optimise the microstructure, surface chemistry and electronic properties to produce a new family of robust and efficient support materials that remain stable over many hundreds of cycles.Our project combines chemistry and chemical engineering approaches leading to design and construction of demonstrator devices. We will work with industrial partners to test and optimise the materials and devices under realistic operating conditions to provide a rapid route to commercialisation. Our gCNMs are physically and chemically compatible with C-based materials in current use and so are compatible with present-day technology. However because of their superior performance they will represent a major step forward in terms of application potential. Our project is designed so that there is constant feedback between prediction-synthesis-testing components of the research to permit efficient and informed identification and optimisation of key materials and properties targets for each application.Our team of researchers is at the forefront of synthesis, characterisation and electrochemical testing of gCNMs and they have patented the first result showing superior performance over C-graphite as LIB electrode materials. They have also observed excellent stability of gCNMs as Pt catalyst support materials for methanol oxidation fuel cells and predicted their action as metal-free supercapacitors. We wish to take advantage of this unique opportunity to build the UK lead in this new area of developing gCNMs for electrochemical applications. The PIs work closely together on several projects that integrate fundamental to applied science and are involved in commercialising products and devices for energy-related applications.