Toward gasoline vehicles with zero harmful emissions by storing NO at Pd nanoparticle–CeO₂ interface during the cold-start period

A significant amount of NO is emitted from advanced gasoline vehicles during preheating three-way catalysts (TWCs) to operating temperature (>150°C). Pd nanoparticles (NPs) loaded on CeO₂ are studied as a NO abatement material to mitigate NO emissions during the cold-start period. The air-fuel equivalence ratio is systematically switched from high to low while increasing temperature to promote NO storage below the operating temperature of TWCs and NO reduction at high temperature. Combined experimental and theoretical studies indicate that the Pd-NP–CeO₂ interface modified by oxygen vacancies (V_Os) plays an important role in converting NO∗ to NO₂. NO₂ is captured by V_Os formed on the CeO₂ surface, enabling the use of Pd/CeO₂ as a NO storage material. Consequently, NO emission decreases by 67.6% during the cold-start period under practical conditions, which has been unattainable with conventional TWCs, thus bringing us a step closer to zero harmful emissions.