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.