Rh4 cluster supported on the In2O3(111) surface for enhancing the turnover frequency of CO2 hydrogenation to methanol: The application of energetic span model.

[Display omitted] • The supported Rh 4 cluster promotes the CO 2 adsorption and H 2 dissociation. • Rh 4 cluster and H 2 reduction are conducive to the formation of oxygen vacancy. • The TOF value for CH 3 OH formation on Rh 4 /In 2 O 3 (1 1 1)_D v1 is 3.02 × 10−5 s−1. The turnover frequency of CO 2 hydrogenation to methanol on the surface of Rh 4 cluster supported In 2 O 3 (1 1 1) is investigated using the first-principles calculation. The Rh 4 cluster and H 2 promote oxygen vacancy formation, which facilitates the interaction between the Rh 4 cluster and the In 2 O 3 (1 1 1) carrier and improves the stability of catalyst. The adsorption behavior of CO 2 and H 2 on catalyst is predicted by electrostatic potential and Fukui(−) index. The loading of Rh 4 cluster promotes the adsorption of CO 2 and allows easier dissociation of H 2 compared to the In 2 O 3 (1 1 1)_D surface. Afterwards, Gibbs free energy diagrams of three hydrogenation pathways are established and the turnover frequencies of all possible routes are calculated based on the energetic span model. The results reveal that the HCOO pathway is regarded as the optimum hydrogenation mechanism due to its greatest turnover frequency (3.02 × 10−5 s−1), higher than that of In 2 O 3 (1 1 1)_D and other reported catalysts. The specific process is CO 2 (g) + 6H → HCOO* + 5H → HCOOH* + 4H → H 2 COOH* + 3H → H 2 CO* + 2H + H 2 O(g) → H 2 COH* + H + H 2 O(g) → CH 3 OH(g) + H 2 O(g), while the RWGS pathway and by-products are effectively inhibited, thus enhancing the selectivity of methanol. The improvement in catalytic activity may result from the loaded Rh 4 cluster facilitating the adsorption of CO 2 and the dissociation of H 2. [ABSTRACT FROM AUTHOR]