Evaluation of density functionals for elementary steps of selective oxidation reactions

Aiming at redox reactions involving metal oxides, we evaluated various approaches of Density Functional Theory regarding the energetics of 8 processes consisting of at least 3 elementary steps: 1 GGA functional, 1 meta-GGA functional, 6 GGA-based hybrid functionals, 3 hybrid meta-GGA functionals, as well as 1 double-hybrid functional. The tested reactions included hydrogenation processes of metal oxides, epoxidation and oxidative dehydrogenation of organic adsorbates at metal-oxo groups. The metal oxides were modeled by single-center oxidic complexes of V, Mo, and Bi. Using energies obtained at the CCSD(T) level as reference, we characterized the energetics of these processes by (i) absolute energies of intermediates, relative to the initial state of the process, and (ii) reaction energies of elementary steps. According to criterion (i), the results obtained with the hybrid functionals TPSSh, M06, and B3LYP, agree best with the reference; overall mean absolute deviations (OMAD) are 17–21 kJ mol⁻¹. An empirical correction for the dispersion interaction slightly improves the average energetics of TPSSh and B3LYP for adsorption and desorption processes. The meta-GGA functional M06L does quite well, OMAD = 25 kJ mol⁻¹, especially compared to the GGA functional PBE, OMAD = 37 kJ mol⁻¹, often used for processes at surfaces.