Synthesis and NMR Studies of Electron and Proton Conducting Mesoporous Nb, Ta and Ti Oxide Composites for Alternative Energy Applications

The synthesis of materials with periodic porosity on the mesoscale (ie 20-500 Angstrom range) is one of the most active areas of current research. By varying the composition of the structure of the walls between the mesopores it is possible to tailor in an enormous variety of physical properties for various applications such as selective gas sorption or catalysis or unusual electronic, optical or magnetic, properties. By impregnating the pore structure of these materials with secondary guest phases that modify the properties of the mesoporous composite, it is possible to create cooperative effects not observed in the pure mesoporous solid. One of the most fundamental properties of any material is its charge transport behavior because moving electrons and protons through a solid is a key step in myriad catalytic or electronic applications. While countless examples of inorganic materials with a periodic mesostructure exist, very few of them possess high electron conductivity. This is because the walls of the mesostructure are often two thin to possess any degree of regular structure, which leads to localization of the electrons in traps, or that the synthesis conditions to fabricate the conducting mesostructure are not compatible with the conditions that lead to conducting properties in the inorganic phase. This is problematic because a high surface area porous material with high conductivity and variable oxidation states would be ideal for use in a Li battery or as a catalyst support material for reactions requiring electron mobility. Proton conductivity through a solid is also important, especially for fuel cell membranes which regulate the flow of charge from one side of the electrochemical cell to the other, but Nafion, a fluorinated polymer with proton conducting sulfonate groups that is the most commonly used fuel cell membrane materials, possess low stability to dehydration, which leads to a decrease in proton conductivity at temperatures over 120 C. Nafion is also vulnerable to alcohol diffusion through the structure, which is problematic since many fuel cells are designed to use alcohol as a feedstock. For this reason many researchers have turned to the exploration of mesoporous material/polymer composite membranes, which promise to overcome the problems with Nafion. The research in this proposal sets out to modify the structure of mesoporous Nb, Ta and Ti oxides, materials possessing variable oxidation states and high acidities/proton conductivity with various agents to create composites with high electronic conductivity or metallic behavior in the one instance, and high proton conductivity in the other, depending on the agent used. Hence, mesoporous Nb, Ta and Ti oxides will be treated with reagents to replace the surface oxides with S or Se, hence creating a conducting sulfide or selenide phase on the inner surface of the material which will allow electron transport to the metal oxide under layer. Impregnation of the pores with electron conducting polymer nanowires of polyaniline or polythiophene will also be carried out to try to exploit these single strand polymers as electron pathways to the metal oxide centers on the walls of the pore channels. These materials will then be tested for use as cathode materials in Li batteries, where it is anticipated that electron mobility through the pores will lead to superior charge and discharge kinetics, an area of performance that is often a problem with Li batteries. The second part of this proposal involves the impregnation of mesoporous Nb, Ta and Ti oxides with sulfonated polymers with high proton conductivity. Here it is anticipated that the mesoporous channels will help overcome dehydration problems of Nafion by holding onto moisture at performance temperatures, while also limiting alcohol diffusion through the membrane. Once synthesized these materials will be tested as fuel cell membranes in operating conditions.

The research in this proposal involves the synthesis and investigation of a new class of composites that will be either electron or proton conducting depending on the composition. The electron conducting composites have obvious application in the Li battery arena where materials with fast recharging kinetics are currently being sought. At this stage of battery development recharge times are one of the biggest issues and the materials in this proposal will be of great interest in this area. They will also benefit the catalysis sector as conducting support materials are rare in the engineering of industrially important reactions. The proton conducting composites will have direct impact on the fuel cell sphere, where membrane materials that perform at high temperature without losing conductivity due to dehydration are sought. Materials impermeable to alcohol diffusion are also a great asset in fuel cell membrane design, and this proposal aims to address this problem in an innovative way. More specifically, the beneficiaries of this research are listed below. The auto sector will benefit from this research in two ways. The development of novel materials with fast recharging kinetics will impact the design and development of battery cars and hybrids, where recharge times remain one of the biggest hurdles to large-scale use. They will also benefit from the development of superior fuel cell membrane materials which can be implemented into existing fuel cell vehicles. Currently there are many cities that use fuel cell buses for public transport, indicating that this is potentially a direct to market technology. Antonelli has numerous contacts with the auto industry in the US through Tarek Abdel Baset (Chrysler) and Scott Jorgensen (GM) who he has consulted with regularly concerning his hydrogen storage work. He is also developing contacts in Wales, including Nissan, who are being approached by the Welsh Assembly government on his behalf in order to spearhead a plan to get Nissan involved in the Welsh low carbon R and D landscape. Through the University of Glamorgan's Hydrogen Center in Baglan Antonelli will be able to hold regular meeting s to update the public, industrial and government sectors on the development of this work. Discussions with Iano Premier at Glamorgan, an expert in fuel cell design, will help ensure that the membrane materials in this proposal are compatible with commercial designs, while talks with Jon Williams, also at Glamorgan and designer of the UK's first tribrid vehicle will help in the implementation of the battery designs and fuel cell membranes into actual demonstration vehicles. Antonelli also has strong contacts at Hydro Quebec in Canada, the owner of some of the most innovative battery technology in the world, and also in-kind contributors to the current proposal. Through this contact he will be able to hone the materials in this proposal for eventual use in commercial battery designs. The public and government sectors in the UK and Wales will benefit as this research will attract interest from companies willing to invest in government plans towards a low carbon future, leading to new jobs in the UK and a cleaner environment to improve quality of life. Antonelli is a member of the Low Carbon Research Institute in Wales where regular meetings between government, academics and companies are held in order to spearhead initiatives to improve the quality of the environment through cleaner industrial practices. The University of Glamorgan has recently secured a 6.3 M grant on hydrogen research and the work in this proposal will compliment this initiative by the parallel development of battery and fuel cell designs. The work will also complement the public investment by Advantage West Midlands in funding infrastructure via the Science City initiative to encourage research in the areas of advanced materials and energy efficiency which are aligned with the regional strategy.