Tailored CoO-Based Nanosystems: Toward Photocatalysts for Air Purification.

The adverse effects of NO (NO + NO) 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 CoO-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 SnO or FeO onto CoO by radio frequency (RF) sputtering. A comprehensive characterization by complementary analytical tools evidences the formation of high-purity columnar CoO arrays with faceted pyramidal tips, conformally covered by very thin SnO and FeO overlayers. Photocatalytic functional tests highlight an appreciable activity for bare CoO 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, SnO/FeO 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.