Abstract
Major challenges encountered when developing manganese-based materials for ozone decomposition are related to the low stability and water inactivation. To solve these problems, a hierarchical structure consisted of graphene encapsulating α-MnO2 nanofiber was developed. The optimized catalyst exhibited a stable ozone conversion efficiency of 80% and excellent stability over 100 h under a relative humidity (RH) of 20%. Even though the RH increased to 50%, the ozone conversion also reached 70%, well beyond the performance of α-MnO2 nanofiber. Here, surface graphite carbon was activated by capturing the electron from inner unsaturated Mn atoms. The excellent stability originated from the moderate local work function, which compromised the reaction barriers in the adsorption of ozone molecule and the desorption of the intermediate oxygen species. The hydrophobic graphene shells hindered the chemisorption of water vapour, consequently enhanced its water resistance. This work offered insights for catalyst design and would promote the practical application of manganese-based catalysts in ozone decomposition.
Highlights
Major challenges encountered when developing manganese-based materials for ozone decomposition are related to the low stability and water inactivation
Graphene encapsulating Fe particles is synthesized in their group to balance O2 adsorption and OH− desorption in oxygen reduction reaction (ORR)[24]
These functional groups serving as anchoring sites enable to in situ form MnO6 octahedron units on the surface of graphene layer with the addition of KMnO4 solution[35], which is corresponding to amorphous MnO2 as shown in Fig. S1a, e
Summary
Major challenges encountered when developing manganese-based materials for ozone decomposition are related to the low stability and water inactivation. To solve these problems, a hierarchical structure consisted of graphene encapsulating α-MnO2 nanofiber was developed. The excellent stability originated from the moderate local work function, which compromised the reaction barriers in the adsorption of ozone molecule and the desorption of the intermediate oxygen species. Due to its small local work function, oxygen vacancy cannot capture electron from the intermediate oxygen species to release the active site, resulting in a depressed ozone-conversion efficiency[11,17]. The smaller thickness of the graphene is, the closer the work function of the encapsulated structure is to the inner metal[34]
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