Reactive adsorption of NO<sub>2</sub> over the NaCoO<sub>2</sub>-Co<sub>3</sub>O<sub>4</sub> nanocomposite: experimental study and first-principles calculations

Abstract

We have fabricated a NaCoO2-Co3O4 nanocomposite through high-temperature calcination of a Na,Co-MOF precursor. The resulting nanocomposite features Co3O4 polyhedral nanoparticles decorated over NaCoO2 nanosheets. The composite possessed a surface area of 21.0 m2 g(-1), surpassing that of the MOF. The composite was studied for its capacity to adsorb NO2 gas (100 ppm) in ambient conditions, demonstrating a substantial capacity of 68.1 mg g-1. However, this adsorption capacity was influenced negatively by factors such as moisture, increased gas flow rate, and reduced bed loading. Spectroscopic analysis and theoretical calculations revealed that NO2 exhibited a higher tendency to adsorb onto the NaCoO2 component than Co3O4. Apart from NO evolution, the adsorbed NO2 molecules underwent redox reactions on the composite's surface, yielding nitrite and nitrate species. Thus, for the first time, we have confirmed that Na-Co oxide effectively cleans lean sources.