Study of the effect of ceria on the activity and selectivity of Co and Ce co-doped birnessite manganese oxide for formaldehyde oxidation

Catalytic oxidation is a promising approach to eliminating formaldehyde (HCHO) to improve indoor air quality. Herein, CeO₂ was explored due to its remarkable properties for oxygen storage and oxygen transfer capability for co-doping δ-MnO₂ alongside cobalt for enhanced low-temperature oxidation of HCHO. Various characterization techniques were deployed to understand the morphology and physicochemical properties of the synthesized catalysts. The Co-Ce co-doped catalysts with low CeO₂ loading (0.05 and 0.1) showed higher catalytic activity for HCHO oxidation due to their higher concentration of surface-active oxygen species. Catalytic oxidation results showed that the presence of CeO₂ leads to the generation of methanol as a secondary hazardous pollutant. Methanol selectivity increases with increasing CeO₂ loading in the catalysts. The results from in-situ DRIFTS confirmed the formation of methoxy species in the presence of CeO₂, which are intermediates for methanol generation. Considering the recent interest in CeO₂ as a potential catalyst for practical abatement of HCHO from the indoor environment, this work has thus raised questions on the safety of using CeO₂ as a catalytic material for HCHO oxidation. It also provides insights into the surface reaction mechanism leading to the generation of methanol in the presence of CeO₂.