Resolving the Activity–Selectivity Trade‐Off in NH ₃ Oxidation with an Intermetallic‐Oxide Dual‐Site Catalyst

ABSTRACT Selective catalytic oxidation of NH3 is limited by a fundamental activity‐selectivity trade‐off: catalysts that accelerate low‐temperature turnover often promote NH ₃ over‐oxidation to NO _x and N ₂ O at higher temperature. Here, we address this limitation with a bifunctional platinum‐copper catalyst that combines distinct intermetallic and oxide sites supported on γ‐Al ₂ O ₃ . The catalyst exhibits > 90% NH ₃ conversion at 140°C and sustains > 80% N ₂ selectivity up to 300°C. Atomic‐resolution microscopy and X‐ray absorption spectroscopy identify L1 ₀ ‐ordered PtCu intermetallic nanoparticles with Pt‐enriched surfaces, coexisting with CuO _x clusters that host isolated Pt single atoms (Pt ₁ CuO _x ). DRIFTS analysis determines an internal selective catalytic reduction sequence that converts in situ formed NO _x to N ₂ on the Pt ₁ CuO _x . Meanwhile, the enhanced low‐temperature activity of the PtCu intermetallic nanoparticles was explained through DFT calculations and microkinetic modeling: electron‐enrichment of Pt by alloying with Cu lowers the upper d‐band edge (ε _u ), which weakens *N adsorption and reduces the barrier of the rate‐determining step of N–N coupling. This work proposes a dual‐site design concept of intermetallic‐oxide hybrid catalysts, harnessing ε _u engineering of intermetallic sites for activity control, with tandem conversion of in situ formed by‐products on oxide sites for N ₂ selectivity control.