Unraveling the Mechanistic Origin of High N 2 Selectivity in Ammonia Selective Catalytic Oxidation on CuO-Based Catalyst.

NH 3 emissions from industrial sources and possibly future energy production constitute a threat to human health because of their toxicity and participation in PM 2.5 formation. Ammonia selective catalytic oxidation to N 2 (NH 3 -SCO) is a promising route for NH 3 emission control, but the mechanistic origin of achieving high N 2 selectivity remains elusive. Here we constructed a highly N 2 -selective CuO/TiO 2 catalyst and proposed a CuO x dimer active site based on the observation of a quadratic dependence of NH 3 -SCO reaction rate on CuO x loading, ac-STEM, and ab initio thermodynamic analysis. Combining this with the identification of a critical N 2 H 4 intermediate by in situ DRIFTS characterization, a comprehensive N 2 H 4 -mediated reaction pathway was proposed by DFT calculations. The high N 2 selectivity originated from the preference for NH 2 coupling to generate N 2 H 4 over NH 2 dehydrogenation on the CuO x dimer active site. This work could pave the way for the rational design of efficient NH 3 -SCO catalysts.