Current research status, core challenges, and future development trends of exhaust gas catalytic purification technology for ammonia-fueled engines

Driven by energy transition and environmental governance demands, efficient and sustainable ammonia-fuel utilization has become a research priority, with precise catalytic aftertreatment central to mitigating engine emissions. This review summarizes advances and challenges in ammonia-engine exhaust post-treatment, focusing on NOx, N2O, and unburned NH3. For NOx control, NH3-SCR catalysts (vanadium-based systems, Mn–CeOx, Cu/Fe-exchanged zeolites) are assessed for activity and low-temperature optimization: Mn–CeOx achieves >90.0% NOx conversion at 125–225 °C, while Cu-zeolites reach nearly 100.0% conversion at 150–300 °C under fast-SCR conditions. For N2O abatement, direct catalytic decomposition and selective catalytic reduction (SCR) routes are compared, highlighting ion-exchange zeolites, Fe-zeolites and layered double hydroxides; direct decomposition exceeds 99.0% conversion, and Fe-zeolites enable coupled N2O/NO removal with 100.0% conversion at 400–600 °C. For unburned NH3, progress in adsorption and catalytic oxidation is reviewed across activated carbon, alkaline earth metal chlorides, metal oxides and zeolites. Future research should prioritize four directions: 1) practical translation of cost-efficient emerging materials (single-atom catalysts, MOF-based architectures); 2) integrated aftertreatment systems for simultaneous abatement of NH3 slip, NOx and N2O under dynamic real-world conditions; 3) ML-aided catalyst design via a closed DFT–ML–experiment loop to accelerate screening, widen temperature windows, boost N2 selectivity and improve durability; 4) optimization of exhaust-adapted catalyst arrangements to enhance long-term stability.