Modulating the Coordinatively Unsaturated Mo Species through Oxide-Support Interaction for Enhanced Reverse Water-Gas...

The coordinatively unsaturated metal species of metal oxides always play important roles in both constructing oxide-based catalysts and catalyzing some reactions. However, it is a challenge to tune its surface density and stability due to the uncontrolled reduction. Herein, we deposit MoO₃ onto different oxides via the simple dry combustion method and find that the host oxides affect formation of coordinatively unsaturated Mo species through the oxide-support interaction, thus strongly altering their reverse water-gas shift activity. The strong oxide-support interaction lowers the reduction temperature of the amorphous oligomeric MoO_x species on m-ZrO₂ and a-TiO₂ supports, generating high surface content of coordinatively unsaturated MoO_2-x species with high stability, compared with those on CeO₂, γ-Al₂O₃, and SiO₂ supports. Consequently, MoO₃/m-ZrO₂ displays the highest CO₂ reaction rate through the formate reaction pathway, i.e., 19.2 mmol_CO2·g_catal^-1·h^-1, followed by MoO₃/a-TiO₂ (12.8 mmol_CO2·g_catal^-1·h^-1), which are 21 and 14 times higher than that of MoO₃, respectively. Moreover, the MoO₃/m-ZrO₂ and MoO₃/a-TiO₂ catalysts also display good stability during the 60 h reaction due to the strong interface bonding. This work provides a way to mediate catalytic performance of metal oxide catalysts through the oxide-support interaction.