Progress in methanol engine exhaust aftertreatment catalysts: Activity sources and synergistic mechanisms from precious metals to transition metal oxides

As a promising low-carbon alternative fuel, methanol demonstrates considerable potential for decarbonizing the transport sector when utilized in conventional combustion engines. However, methanol engine exhaust exhibits characteristics such as low exhaust temperature, high water content, and the presence of unburned methanol and highly toxic intermediate products like formaldehyde, posing severe challenges to the aftertreatment catalysts. This review provides recent advancements of the latest research progress in catalytic materials and reaction mechanisms for methanol engine exhaust purification in recent years. The opening discussion centers on the emission profile of methanol engines, particularly the levels of unburned methanol and formaldehyde in current exhaust outputs. Subsequently, the review then examines Pt-based and Pd-based precious metal catalysts for methanol deep oxidation, providing a detailed analysis of how metal dispersion influences their performance, valence state regulation, and support interaction on methanol deep oxidation. Secondly, it focuses on non-precious metal oxide catalysts such as Mn and Ce, revealing their key role in lattice oxygen migration characteristics in oxidation reactions dominated, as well as the support effect. Finally, based on this, it outlines the challenges and optimization directions that future methanol engine-specific catalysts need to face. This review provides valuable insights into methanol deep oxidation catalysts and the clean combustion of methanol.