Speaker : Prof. Jun Hee Lee (School of Energy and Chemical Engineering, UNIST)

Ideal catalytic surfaces should adapt their reactivity to rapidly changing charge states of reactant molecules in chemical reactions. Bare polar surfaces are less effective since strong, exposed, built-in dipoles cause unintentional surface reconstructions and adsorption of compensating charged species which interfere with the target reaction. As an alternative, we propose a heterostructure (catalysts/high-K) as an ideal catalyst adapting to the rapidly changing charge states of reactant molecules. Using first principles, we explore the reactivity of heterostructures of TiO2 anatase grown on high-K SrTiO3 focusing on the oxygen evolution reaction (OER), the bottleneck to water-splitting. Since high-K SrTiO3 has a large dielectric constant, it assists the supported TiO2 layer to exhibit transient dipoles to dynamically respond to the change of the reactant charges and lowers the thermodynamic energy barriers in OER reaction. As a result, the (photo-)chemical reactivity of the TiO2 surface is timely activated by the induced transient dipoles during the intermediate steps while initial and final steps in reaction remain unaffected and neutral [1]. Compared to the OER on unsupported TiO2, the interplay of the dynamically induced dipoles and epitaxial strain [2] eliminates rate-limiting thermodynamic barriers and significantly improves the efficiency of the reaction on the strained TiO2/SrTiO3 thin-film heterostructure.

Reference:
[1] J. H. Lee and A. Selloni, Physical Review Letters 112, 196102 (2014)