ProfessorJohnKilner

The Kilner Research Group

In the past my group has centered on fundamental studies of the mass transport in ceramic materials for clean energy production and storage technologies.  These are materials for lithium ion batteries and materials for  Intermediate Temperature Solid Oxide Fuel Cells (ITSOFC's) and  for Solid Oxide Electrolysers (SOEC's). These last two applications are very closely related in terms of the materials requirements. A schematic of an SOEC for the production of hydrogen from steam is shown below. The aim is to produce hydrogen from renewable sources for use as a fuel for electric vehicles and static electricity production.

Schematic of possible SOEC cells for the electrolysis of steam

Isotopic exchange and surface analysis

The majority of the fundamental researchin the group deals with the experimental study of oxygen transport in ceramics. Such studies are difficult in mixed conducting materials using electrical methods because of the high electronic conductivity and oxygen isotopic exchange methods must be used instead. Oxygen exchange data is particularly relevant to fuel cell cathode and oxygen separation membrane materials where the exchange of oxygen between the gas and the solid phase must be extremely rapid. ¹⁸O gas/solid exchange experiments, followed by SIMS analysis, provide a measurement of the kinetics of this step.  An example of an oxygen isotopic depth profile in a mixed conducting cathode material La_1-xSr_xCo_1-yFe_yO_3-δ(LSCF)obtained by SIMS is shown below.

A depth profile obtained from an isotopically exchanged ceramic sample of LSCF cathode material

Such depth profiles can be analysed to yield both the tracer diffusion coefficient and the surface exchange coefficient for oxygen.  There is some understanding of the atomistic mechanisms of oxygen transport in bulk materials but currently a key goal is to understand the atomistic mechanisms of isotopic exchange of oxygen across the surface of the ceramic.  To facilitate this research we have recently been succesful in obtaining a new SIMS LEIS instrument from ION-TOF GmbH, funded by the UK EPSRC, to study the chemical composition of the outermost atomic layers.

The new ION TOF SIMS-LEIS Instrument

The LEIS instrument detects ions scattered from the surface of a material when bombarded by ion beams of energy of a few keV.  This provides information about the masses of the ions sitting on the surface of the ceramic material and is very surface specific. A comparison of the concentration and depth sensitivity of the common surface analytical methods is shown below, where the ability of the LEIS to give information of the outermost monolayers of atoms is apparent.

The relative sensitivies of common surface analytical techniques

The SIMS instrument has a time of flight mass analyser, and as a consequence all masses are recorded for each data point in an analysis.  This gives the capability of reconstructing the analysed volume, post analysis, in 2 and 3 dimensions for any chosen mass.  An example of the capability of this instrument is shown below.  The example is of the analysis of a strained YSZ/CeO₂ epitaxial multilayer structure grown by PLD by our collaborators at the National Institute of Materials Research (NIMS) in Tsukuba Japan. The Image on the RHS is an image constructed using the  CeO ion and clearly shows the 9nm thick CeO₂ layers.

New Materials

The group also has an interest in the development of new materials for ITSOFC's and currently have projects  involving the characterisation and optimisation of electrolyte materials, cathode materials and anodes.  The techniques involve both experimental and theoretical investigations of oxygen transport in these materials.  Many of these materials have the perovskite or perovskite related structure and the group

has been instrumental in developing oxygen excess materials such as La₂NiO_{4 δ} and GdBaCo₂O_{5 δ} which show high rates of oxygen transport mediated by oxygen interstitials.  Recent results from MD simulations of Pr₂NiO_{4 δ}  (below) show the complex oxygen pathways involving the interstitial sites.

Recent results from MD simulations of the n=1 Ruddlesden Popper phase Pr₂NiO_{4 δ} showing the complex oxygen migration pathways involving the interstitial sites. On the LHS is the crystal structure including an oxygen interstitial (key O-red spheres, La blue spheres and Ni green spheres, the NiO₆ octahedra are shaded green) . On the RHS is a false colour image showing the oxygen nuclear density at 1100K for a δ value of 0.099 (Parfitt et al. Phys. Chem. Chem. Phys., 2010, 12, 6834–6836)

Collaborators

The group is currently collaborating with a number of groups in order to investigate these interesting problems including:

• Prof. Tatsumi Ishihara, Kyushu University Japan
• Prof Masatomo Yashima, Tokyo Institute of Technology Japan
• Prof. Rose Noel Vannier, The University of Lille, France 
• Dr. Jose Santiso CIN2,  Barcelona, Spain 
• Pro f. Bilge Yidiz and Prof. Harry Tuller, MIT, USA
• Prof. David McComb, Ohio State University, USA 
• Dr. Thomas Lippert, PSI, Zurich, Switzerland 
• Prof. Teo Rojo, UNPV, Bilbao, Spain
• Prof. Jean - Marc Bassat Institut de Chimie de la Matière Condensée de Bordeaux (I.C.M.C.B.)
• Prof. Truls Norby, University of Oslo, Norway

Visiting Positions

Prof. Kilner is a visiting researcher at the Basque Energy research centre in Vitoria, Spain (CIC Energigune)

He is also a Prinicpal Investigator in the International Institute for Carbon Neutral Energy Research (I2CNER) in Kyushu Japan, one of the Japanese World Premier Research institutes (WPI).

Spin Outs

Prof. Kilner is a founder, consultant and shareholder of CeresPower ltd. a spin out company formed at Imperial College to commercialise intermediate temperature fuel cell technology. Ceres is now an independent company operating from its own premises in Horsham and has a team of ~350 engineers.