Configurations of V4+ centers in the MoVO catalyst material. A systematic stability analysis of DFT results

Abstract

The reactivity of a catalyst is in part determined by its geometric and electronic structure. Here we present a model that is able to describe the energy trend of the important oxidation catalyst material MoVO, as obtained from hybrid density functional calculations for various V 4+ /V 5+ configurations. For an exemplary V/Mo occupancy, we systematically examined the universe of all V 4+ distributions. The distribution of these V 4+ centers, in combination with the induced lattice distortions, plays a key role in determining the stability of the material, entailing energy variations of up to ~140 kJ mol −1 per unit cell. Hence, for this kind of catalyst, it is crucial to account for the V 4+ distributions. To this end, we are proposing novel predictive models based on features like the number of Mo centers with two reduced neighbors V 4+ and the locations of potentially reducible centers V 5+ . For the V/Mo occupancy chosen, these models are able to describe the energy variation due to the V 4+ distribution with root mean square errors as low as 6 kJ mol −1 . Accordingly, catalytically selective sites featuring pentameric units with a single polaron center are among the most of stable configurations. Another aspect of this work is to understand energy contributions of polaron arrangements bracketing Mo centers.