Metal Substitution in Rutile TiO2: Segregation Energy and Conductivity

Abstract

State-of-the-art acidic oxygen evolution reaction catalysts are mainly based on mixed oxides of titanium and iridium or ruthenium. Because of its high chemical corrosion resistance and stability in acid, $${\hbox {TiO}_2}$$ is a promising support material, yet with poor electrical conductivity. We herein theoretically examined the stability and the electronic properties of substituted rutile-phase titania, in which Ti is partly replaced by elements of the fourth, fifth and sixth period. For negative values of the calculated segregation energy, we conclude that the heteroelement M forms a solid solution for 25% or 50% substitution. For these heteroelements, we calculate the electrical conductivity. Since it is known that the electronic structure of transition metal oxides strongly depends on the applied theoretical method, we performed self-consistent optimizations of the Hartree-Fock contribution to the exchange functional in a hybrid functional for every compound. Experimentally, two favorable and two unfavorable elements were synthesized with 25% foreign metal concentration. The most promising candidates to improve the electronic properties of titania are Ta and Nb.