Electrocatalytic Model for Control of Transport in Oxide Grain Boundaries

Research Project, 2014 – 2017

We develop a conceptual framework for rational improvement of materials´ durabilities by means of first principles modeling. Load bearing alloys constitute the vast majority of electricity producing plants and boilers today. These in turn often work at high temperatures and longevity as well as efficiency is ultimately decided by their corrosion resistance, which in turn is decided by the transport properties of the oxide skin. Oxides growing on metals display a polycrystalline texture. We utilize the grain boundaries for control of the resulting electronic and ionic transport by means of doping. Large band gap oxides, e.g. alumina, zirconia, and titania are of particular insterest owing to their technological importance. Interestingly, these materials allow for optimal control of resulting oxide properties by the aliovalent cations causing impurity states in the band gap, thus offering well defined percolating electron transport channels attenuated by coupling to the lattice, redox induced moblities of oxygen ions by cations acting transient electron sinks, and dopant dependent electrocatalytic properties owing to the proximity to the reducing metal/oxide interface. Modeling this electrochemistry is very much uncharted territory. Pilot studies by us include modelling of chroium steel corrosion, trends in electrocatalytic water oxidation, trends in hydrolysis on metal oxide bonds, and dopant dependent electrocatalytic hydrogen evolution in hydrated ZrO2/Zr grain boundaries.