Lattice-confined Ce-O-Mn pairs in anatase TiO₂ for superior N₂ selectivity during photo-assisted NH₃-SCR deNO_x

The atomic dispersion of Mn has been increasingly recognized as a critical factor governing N₂ selectivity in NH₃-SCR deNO_x. However, supported single-atom and diatomic Mn-based catalysts are prone to aggregation during long-term operation in the presence of O₂, leading to deteriorated selectivity. Herein, stable Ce-O-Mn metal pairs were constructed in anatase TiO₂ through a stress-compensation effect. The catalyst with 4.80% Ce and 1.20% Mn achieves ∼100% NO_x conversion and maintains N₂ selectivity > 84.0% in 150-300°C under illumination (WHSV = 60000 mL·g^-1·h^-1). Compared with Mn-doped TiO₂, the introduction of Ce significantly increases N₂ selectivity from 37.1% to 88.5% at 250°C. In situ DRIFTS spectra and DFT calculations reveal that the oxygen coordinated to Ce or Mn is responsible for NO activation, initiating the SCR cycle. The introduction of Ce weakens the proton affinity of the bridging oxygen in Ce-O-Mn structures, driving the conversion of NH₂NO to N₂ instead of N₂O. On the other hand, the lattice-confined Ce-O-Mn configurations promotes the dispersion of Mn sites, also suppressing N₂O formation. This work provides a rational strategy for designing Mn-based catalysts with superior N₂ selectivity.