Single Mo atoms paired with neighbouring Ti atoms catalytically decompose ammonium bisulfate formed in low-temperature SCR

Selective catalytic reduction (SCR) of NOx with NH3 has been widely used for NOx emission control, but commercial catalysts inevitably suffer severe deactivation in SO2-containing stack gases at low temperatures because the ammonium bisulfate (NH4HSO4, ABS) formed in SCR blocks the surface active sites. We resolve this issue by developing a TiO2-supported single-atom Mo catalyst (Mo-1/TiO2) that decomposes ABS at similar to 225 degrees C, far lower than the dew point of ABS (similar to 260 degrees C). Single Mo atoms paired with the neighboring surface Ti atoms function as Mo-Ti acid-base dual sites, which respectively adsorb the NH4+ and HSO4- of ABS. After the oxidation of NH4+ by surface lattice oxygen on the Mo sites, electrons left behind on the dual sites are localized around the Fermi level, which allows them to transfer to the adsorbed HSO4- on the Ti sites, thus releasing SO2 at low temperatures. The Mo-1/TiO2 catalyst with Mo-Ti acid-base dual sites enables the decomposition of ABS at low temperatures, and thus this work provides a way to effectively control NOx emission particularly from industrial boilers.

Automated summary

The development of a novel catalyst Mo-1/TiO2 enables the decomposition of ABS at low temperatures, effectively addressing the issue of SO2 deactivation in SCR catalysts. This provides a new approach to controlling NOx emissions from industrial boilers.