Influence of Ca-doped NaNbO3 and its heterojunction with g-C3N4 on the photoredox performance

Undoped, Ca-doped NaNbO3 and its heterostructure with g-C3N4 have been successfully prepared through chemical route followed by heat treatment. All the prepared samples were analysed using XRD, FESEM, TEM and XPS spectroscopy for various structural and surface features. Further, absorbance (UV-visible) and photo-luminescence (PL) spectroscopy revealed the bandgap narrowing and emission quenching, respectively as a result of doping and formation of heterojunction. Ca doped NaNbO3-C3N4 sample exhibited almost 100% photodegradation of methylene blue (MB) dye in 4 h. Here, the superoxide anion radical has been found as the active reactive oxidative species (ROS). Further, being a visible active catalyst, photocatalytic H-2 evolution has also been studied through water splitting under solar irradiations in which H-2 yield of 0.01, 0.03, 0.09 and 0.29 mmol (in 1 h) was observed using bare NaNbO3, Ca-NaNbO3, and their respective heterostructures, respectively. Modified oxygen vacancies and synergistic interracial interaction have induced such a noteworthy photocatalytic H-2 evolution ability of as-prepared heterostructure with 3.45 mmol H-2 yield 4 h of exposure.