Unveiling a remarkable enhancement role by designing a confined structure Ho-TNTs@Mn catalyst for low-temperature NH3-SCR reaction

MnOx-based catalysts are considered promising alternative catalysts for NH3-SCR to remove NOx at low temperature. However, their poor SO2 or H2O tolerance and unfavorable N-2 selectivity are still the main obstacles restraining their further practical application. Herein, we carefully confined the manganese oxide active species in Ho-modified titanium nanotubes to improve their SO2 resistance and N-2 selectivity. Ho-TNTs@Mn exhibits excellent catalytic activity, strong SO2 and H2O tolerance and superior N-2 selectivity, and more than 80% NO conversion can be achieved in the range 80-300 & DEG;C with 100% N-2 selectivity. The characterization results verify that the pore confinement effect of Ho-TNTs for Mn increases the dispersion of Mn to promote the interfacial effect between Mn and Ho. The electron synergistic effect between Mn and Ho improves the electron transformation of Mn and Ho, which inhibits electron transfer between SO2 and Mn to avoid poisoning from SO2. We also find that the interaction between Ho and Mn induces electron migration to restrain the production of Mn4+, contributing to the suitable redox capacity to decrease the creation of byproducts, which serves as the motivation for high N-2 selectivity. In situ DRIFTs analysis clarifies that Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms co-exist in the NH3-SCR reaction over Ho-TNTs@Mn, and the E-R reaction mechanism predominates We believe that Ho-TNTs@Mn with a well-designed nanotube structure will show preferable development and application prospects in the NH3-SCR reaction.

Automated summary

MnOx-based catalysts are promising alternatives for low-temperature NH3-SCR to remove NOx, but their poor tolerance to SO2 and H2O, as well as unfavorable N-2 selectivity, hinder their practical application. To overcome these limitations, the researchers confined manganese oxide active species in Ho-modified titanium nanotubes, resulting in enhanced SO2 resistance and N-2 selectivity. The Ho-TNTs@Mn catalyst exhibited excellent catalytic activity, strong tolerance to SO2 and H2O, and high N-2 selectivity. The study proposes that Ho-TNTs@Mn with a well-designed nanotube structure has great potential for NH3-SCR applications.