MnO2–Graphene-oxide-scroll–TiO2 composite catalyst for low-temperature NH3-SCR of NO with good steam and SO2 resistance obtained by low-temperature carbon-coating and selective atomic layer deposition

The improvement of the steam and SO2 resistance of low-temperature selective catalytic reduction of NOx by an NH3 (NH3-SCR) reaction catalyst requires two steps: first, carbon-coating at low temperature and then the stabilization of the carbon layer. A low-temperature carbon-coating method was established and illustrated by using graphene oxide (GO) sheets to crimp and wind around the outer surface of MnO2 nanowires. The TiO2 was selectively deposited on the oxygen-containing functional groups of GO by atomic layer deposition to provide a method for protecting the carbon layer. The morphology (TEM) and element analysis (STEM) results revealed that the scrolling of GO on the outside of MnO2 and then the deposition of TiO2 on GO had led to the formation of MnO2–graphene-oxide-scroll–TiO2 composites (MnO2–GOS–TiO2). Coupling H2-TPR, DRIFT and activity test results with DFT, it was discovered that the electron-induced effect between the GO, MnO2 and TiO2 neutralizes the enhanced activity after the combination of GO and MnO2 and the decreased activity after the combination of TiO2 and MnO2, which gives the composited structure a conversion of more than 84% to N2 in the range of 150 °C to 280 °C. Meanwhile, the GOS–TiO2 layer was shown to boost the catalytic stability remarkably in an environment containing steam and SO2 due to a shielding effect from SO2 and delayed oxidation. The synergistic effect of GO and TiO2 thus improved the steam and SO2 resistance of the manganese-based catalyst at low temperature.