Boosted catalytic soot oxidation by hierarchical hollow cobalt oxide constructed from a Template-Sacrificial Method: Promoting Roles of morphologies and oxygen vacancies

Diesel engine soot, deemed harmful, is controlled by diesel particulate filters (DPFs). However, these filters need heat for regeneration, leading to energy use. An effective way to decompose soot at lower temperatures is sought. Co₃O₄ from metal organic frameworks (MOFs) has high catalytic activity for soot oxidation. Using cobalt glycerate (CG) as a precursor, zeolitic imidazolate framework (ZIF)-67 grows on CG's surface, forming ZIF-67-decorated CG (ZCG). Heat treatment turns ZCG into air-treated ZIF-derived Co₃O₄-decorated CG (AZCCG). AZCCG, with more oxygen vacancies and increased contact points, enhances active oxygen species, promoting spillover from catalysts to soot. It also exhibits superior NOx storage capacity and high H₂O tolerance with ignition temperature compared to ACG, AZC, and commercial Co₃O₄ (COM); as a result, the conversion temperature (T₅₀, 50 % soot was oxidized) was reduced by 248℃ with loose contact mode in 500 ppm NO + 10 %H₂O + 10 % O₂/N₂. This study proposes a simple method to create a cobalt oxide-based catalyst with a unique structure and abundant oxygen vacancies to boost soot oxidation. The catalyst developed through this method demonstrates hierarchical hollow morphology and a high specific surface area, distinguishing it from previously reported cobalt oxide catalysts. These features not only provide a greater abundance of active oxygen species but also offer increased opportunities for contact with soot, thereby improving its catalytic performance. As a result, AZCCG is highly promising for application in diesel particulate filters(DPFs).