Our primary interest is in gas-solid reactions.  In particular we are interested in ion-conducting solids and their interaction with the gas phase.  Materials that conduct a single ionic species (e.g. oxygen ions or protons) can be used as solid electrolytes for devices such as Solid Oxide Fuel Cells (SOFCs). If two charge carriers are present in the solid phase we can construct highly selective gas permeable membranes (highly selective because solid state diffusion is very selective).  So oxygen ion and electron conductivity can be used for oxygen permeable membranes, proton and electron conductivity can be used for hydrogen permeable membranes and oxygen-ion and proton conductivity can be used for water permeable membranes. Dual phase membranes conducting oxygen ions, in the solid phase, and carbonate ions, within a molten salt in the pores of the solid, could be used to develop carbon dioxide permeable membranes.  Membrane transport requires a gas-solid reaction followed by transport of the charge carriers within the membrane.  The very same processes are critical to the operation of a chemical looping cycle.  We are using our knowledge of such processes to develop new materials for e.g. chemical looping hydrogen production.

At lower temperatures an ion-conducting solid may interact with a catalyst supported on that solid through the supply of promoting ions to the catalyst surface. The supply of promoting species can be achieved via electrical or chemical overpotential application across the ion-conducting membrane. This holds the catalyst in a modified state that would not be accessible even through conventional promotion (much in the way an active membrane modifies the properties of its own surface through the membrane flux). This phenomenon, known as Electrochemical Promotion of Catalysis (EPOC) can be fully reversible upon removal of the applied overpotential.

Our interest in gas-solid reaction has led us to become involved in the investigation of the redox mechanism through the use of pulsed isotopic oxygen exchange.  This technique can also be applied by us for the in-situ investigation of e.g. cathodic processes in a solid oxide fuel cell. Our work in SOFCs also looks at meterials with dual oxygen ion and protonic conductivity, i.e. water permeable membranes. In this case water permeability takes place across a membrane that remains an electrolyte and can be used in a solid oxide fuel cell.  This could potentially lead to some very interesting fuel cell reforming technologies.  We also work on hydrogen storage through the use of liquid organic hydrides (LOHs), attractive because of their high hydrogen storage capacity and their ease of distribution. 



Ceramic Membrane



Chemical Looping





SOFCs and H2 Storage