Exploiting Phase Transitions in Catalysis: Adsorption of CO on doped VO(2)‐Polymorphs

VO(2) is well known for its low‐temperature metal‐insulator transition between two phases with tetragonal rutile and monoclinic structure. The adsorption of CO on the two polymorphs of Mo‐doped VO(2) is calculated to investigate the effect of a substrate phase change on the adsorption energy. The system is investigated theoretically at density‐functional theory level using a hybrid functional with London dispersion correction. We establish a computational protocol applicable for the study of physisorption on open‐shell transition metal oxides. The main task is to control the spin state of open‐shell slab models used to model adsorption of closed‐shell molecules in order to obtain numerically stable adsorption energies and to reduce spin contamination within the broken‐symmetry unrestricted Kohn‐Sham approximation. Applying this procedure, it is possible to identify the most stable adsorption positions of CO on both phases of VO(2). CO adsorbs vertically with the C atom on a surface V atom in the monoclinic phase with an adsorption energy of −56 kJ/mol. The same adsorption position has an adsorption energy of only −46 kJ/mol on the rutile phase. Similar differences were obtained with multireference methods using an embedded cluster model. This effect may inspire experimental strategies exploiting the rutile [Formula: see text] monoclinic VO(2) phase transition in catalytic processes where CO is formed as product or as an intermediate.