Advanced Multifunctional Catalysts for Emission Control in Hydrogen and Diesel Engines

As hydrogen internal combustion engines (H₂-ICE) gain traction, optimizing exhaust aftertreatment technologies for nitrogen oxide (NOx) control has become increasingly critical. While selective catalytic reduction (SCR) systems remain the primary approach for NOx mitigation, oxidation catalysts are also being explored to facilitate hydrogen oxidation and improve overall exhaust treatment efficiency. This work presents a multifunctional catalyst (MFC) concept that combines supported Pd and Cu-zeolite to enable simultaneous NOx reduction and hydrogen oxidation within a single catalytic unit. Preliminary results show that hydrogen oxidation on supported Pd occurs above 300 °C, while Cu-zeolite achieves nearly complete NOx conversion. Experiments on individual components indicate that supported Pd initiates ammonia oxidation only after hydrogen is depleted. In the presence of hydrogen, ammonia conversion remains below 20%, indicating that hydrogen availability suppresses ammonia oxidation, which is favorable for SCR operation. The MFC can be configured either on a substrate or as an on-filter catalyst (MFCoF), providing simultaneous chemical conversion and urea-derived particulate filtration. In addition to hydrogen engines, the MFCoF concept can be applied to diesel and biodiesel engines, enabling effective filtration of soot particles while maintaining NOx reduction performance along with hydrocarbon oxidation capability. By combining NOx reduction, hydrogen/hydrocarbon oxidation, and particulate filtration in one unit, the MFCoF approach provides a promising pathway for next-generation exhaust systems across diverse engine platforms.