Exploiting phase transitions in catalysis: reaction of and on doped -polymorphs

Abstract

is well known for its reversible transition between two phases with tetragonal rutile and monoclinic structure. In a previous theoretical study (Stahl and Bredow 2022 ChemPhysChem 23 e202200131) we showed that the adsorption energy of CO is different on surfaces of the two Mo-stabilized polymorphs. This can be exploited to promote catalytic reactions by removing CO from the catalyst surface. As proof-of-principle, we investigated the hydrogenation reaction of . For this purpose, the adsorption energies of and possible intermediates and products , HCOOH, and CO were calculated. Significant differences were found for the reaction energies of the hydrogenation of to formic acid and formaldehyde on the two polymorphs. This shows that it is in principle possible to alter the reaction thermodynamics by applying reaction conditions which stabilize a particular polymorph. In order to investigate the influence of the polymorph on kinetic properties, the reactions barriers of a step-wise reaction of was calculated using the nudged elastic band method. was found to reduce the reaction barriers compared to the gas phase. Additionally, the minimum energy path of the bulk phase transition of undoped was calculated using the distinguished reaction coordinate method. A catalytic cycle exploiting the phase transition is proposed based on the theoretical results.