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 Bronsted 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 degrees C. Additionally, the surface polymeric Mo would lead to the side reaction at high-temperature range above 350 degrees 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.

Automated summary

Herein, single-atom Mo doped TiO2 catalysts with abundant oxygen vacancies (OVs) were fabricated to investigate the roles of Mo species and OVs in selective catalytic reduction (SCR) of NOx. The presence of single-atom Mo doping greatly enhances the catalytic activity of TiO2, even in the presence of 5 vol% H2O. Surface Mo species enhance the strength of Bronsted acid sites on TiO2 and promote the adsorption and activation of NH3 to -NH2. Additionally, in-situ generated OVs increase the concentration of monatomic species (O-) and promote the oxidation of NO to NO2, thereby enhancing catalytic activity below 350 degrees C. However, the presence of surface polymeric Mo leads to side reactions at temperatures above 350 degrees C.