Hierarchically grown CaMn₃O₆ nanorods by RF magnetron sputtering for enhanced visible-light-driven photocatalysis

CaMn₃O₆ films with hierarchical nanostructures were deposited for the first time on unheated quartz glass substrates by the radio frequency (RF) magnetron sputtering technique using a polycrystalline CaMnO₃ sample as sputtering target, and their photocatalytic activity was evaluated on the decolorization of Rhodamine 6G (Rh6G) aqueous solutions. The films scanning electron microscope (SEM) images evidence a growth of nanorods (NRs) arrays with planar endings and a narrow size distribution centered at about 30 nm in diameter. The CaMn₃O₆ films surface is uniform and presents a high density of nanorods (116 nanorods per μm²). The high surface area combined with the tunnels crystallographic structure, evidenced by X-ray diffraction (XRD), results in an effective photocatalyst for Rh6G degradation under visible light irradiation. Based on the photodegradation experiments, it is suggested that a process of dye self-sensitization can be one of the key factors of the superior photocatalytic performance of CaMn₃O₆ NRs. The kinetics of photocatalytic degradation of Rh6G follows a first-order reaction. Furthermore, XRD of the used films did not reveal additional phases indicating high photochemical stability, and the diffuse reflection infrared Fourier transform spectrum (DRIFT) does not show adsorbed organic species on the CaMn₃O₆ NRs surface. This work provides a potential route to develop high-performance immobilized nanostructures, and the achievements open up many possibilities to tailor visible light active materials for environmental applications.