Carbon Nitrides: Metal-free Materials for Energy Applications

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.

Our project will have an impact on:
1) The UK and the global economy. We will create and optimise the functional properties of graphitic carbon nitrides (gCNM) and test them in devices of direct relevance to several industries with multi-billion £ annual turnovers. gCNMs have demonstrated or prospective value as key functional materials in electrochemical devices related to storage, production and use of energy including Li-ion batteries, supercapacitors and methanol oxidation fuel cells. The IP generated in our work will enable high-tech applications suitable for uptake not only by large multinationals but also by SMEs and academic spin-out companies that will increase the UK competitiveness.

2) UK society and the general public. Our research addresses topics with far reaching societal impact including low carbon energy, energy security and management. The discovery and production of new materials and devices for more efficient and sustainable use, storage and production of energy will improve quality of life; the materials developed here will contribute to commercialising high performance, durable electrochemical devices which can be applied across a range of applications (from consumer electronics, to transport to grid scale storage) with significant societal impact.

3) Policy makers, legislators and the public sector. With ever more stringent legislation in place to guarantee international agreements to reduce CO2 and other greenhouse gases to acceptable levels, viable routes to reduce or remove our reliance on fossil fuels are clearly of prime importance to policy makers and legislators. We will endeavour to contribute our expertise towards the formulation of relevant white papers and road maps to shape future policies for national and international agreements.

4) Commercial output. The application areas of devices based on gCNMs are much closer to market than those of other materials being researched to improve upon currently used C-graphite components. This is because the gCNMs are chemically and physically compatible with C-graphite while providing superior performance in applications ranging from Li-ion battery electrodes to fuel cell catalyst supports. The result is that they can enter the marketplace rapidly using existing processing technology. We will undertake device integration and scale-up activities for each application area in collaboration with industrial partners (see letters of support, including Sharp, AFC Energy, ITM Power plc, PV3 Technologies Ltd, etc.), so that any lead materials can be rapidly assessed, and fast-track the translation from the laboratory to the market. We estimate that
commercial products will emerge within or soon after the 3 year grant. The diversity of applications investigated mitigates risks; success in even one of the potential applications will generate sufficient outcome to repay the EPSRC investment. IP from the research will be developed according to procedures established at UCL that has a strong record for commercialising materials and
results of scientific research through its wholly owned subsidiary UCL Business plc.

5) Students and emerging scientists. Through our extensive public engagement activities the investigators will disseminate research findings to a wide audience including the general publica as well as schools audiences. Through our training of postodoctoral and PhD students in a multidisciplinary environment that links fundamental and applied sciences and extends to commercialisation of results we will contribute to formation of the next generation of scientists, engineers and entrepreneurs.