Unraveling the high catalytic activity of single atom Mo-doped TiO2 toward NH3-SCR: Synergetic roles of Mo as acid sites and oxygen vacancies as oxidation sites

Herein, the single-atom Mo doped TiO2 catalysts with abundant oxygen vacancies (OVs) were fabricated to get a deep insight into the roles of Mo species and OVs for selectivity catalytic reduction (SCR) of NOx. The single-atom Mo doping largely enhances the catalytic activity of TiO2 even with the presence of 5 vol% H2O. Surface Mo species remarkably enhance the strength of Brønsted acid sites on TiO2, which further facilitates the adsorption and activation of NH3 to –NH2. Meanwhile, the in-situ generated OVs largely increase the concentration of monatomic species (O-), which facilitate the oxidation of NO to NO2, thus promoting the catalytic activity below 350 °C. Additionally, the surface polymeric Mo would lead to the side reaction at high-temperature range above 350 °C. This work gives a new insight into the effect of Mo species, and the synergistic role of Mo and OVs in the SCR reaction over Mo-based catalysts.