Tailored Co₃O₄-Based Nanosystems: Toward Photocatalysts for Air Purification

The adverse effects of NO (NO + NO₂) gases on the environment and human health have triggered the development of sustainable photocatalysts for their efficient removal (De-NO). In this regard, the present work focuses on supported Co₃O₄-based nanomaterials fabricated via chemical vapor deposition (CVD), assessed for the first time as photocatalysts for sunlight-activated NO oxidation. A proof-of-principle investigation on the possibility of tailoring material performances by heterostructure formation is explored through deposition of SnO₂ or Fe₂O₃ onto Co₃O₄ by radio frequency (RF) sputtering. A comprehensive characterization by complementary analytical tools evidences the formation of high-purity columnar Co₃O₄ arrays with faceted pyramidal tips, conformally covered by very thin SnO₂ and Fe₂O₃ overlayers. Photocatalytic functional tests highlight an appreciable activity for bare Co₃O₄ systems, accompanied by a high selectivity in NO conversion to harmless nitrate species. A preliminary evaluation of De-NO performances for functionalized systems revealed a direct dependence of the system behavior on the chemical composition, SnO₂/Fe₂O₃ overlayer morphology, and charge transfer events between the single oxide constituents. Taken together, the present results can provide valuable guidelines for the eventual implementation of improved photocatalysts for air purification.