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

The atomic dispersion of Mn has been increasingly recognized as a critical factor governing N2 selectivity in NH3-SCR deNOx. 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% NOx 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.