Suppression of Ammonia Slip by Smart Reductants in Selective Catalytic Reduction of Nitrogen Oxides

ABSTRACT Ammonia (NH 3 )‐based selective catalytic reduction (SCR) is a mainstream flue gas denitration technology for stationary and mobile sources, but NH 3 slip remains a critical challenge from mismatches between stoichiometric reaction requirements and fluctuating nitrogen oxides (NO x ) concentrations. Herein, we show organic amines (e.g., n ‐butylamine, n ‐B) act as smart reductants for SCR systems. Unlike NH 3 , n ‐B reacts stoichiometrically with NO x and undergoes NO‐accelerated self‐elimination when overdosed over TiO 2 ‐supported VO x catalysts. Mechanistic studies reveal Ti─OH sites on the catalyst facilitate n ‐B adsorption and activation, with the *NH 3 intermediate driving NO x reduction. *NH 2 from excess n ‐B oxidizes to nitrites and NO 2 under NO+O 2 , which further react with *NH 3 via an internal SCR pathway, avoiding free NH 3 formation and slip. We propose a hybrid reductants system (NH 3 + n ‐B) enabling efficient NH 3 slip suppression over a reductant/NO x molar ratio of 1.2, providing a promising strategy without modifying existing SCR hardware or structures.