Growth of Cu₂O Spherical Superstructures on g-C₃N₄ as Efficient Visible-Light-Driven p–n Heterojunction Photocatalysts for Degrading Various Organic Pollutants

g-C₃N₄ has been demonstrated as an efficient photocatalyst. To further broaden its photoabsorption range and improve photocatalytic activity, we reported the growth of p-type Cu₂O spherical superstructures on n-type g-C₃N₄ as efficient and stable visible-light-driven photocatalysts. g-C₃N₄ nanosheets were prepared by calcination-exfoliation, and the growth of Cu₂O on g-C₃N₄ nanosheets was realized by hydrothermal method. Cu₂O on g-C₃N₄ nanosheets are spherical superstructures with diameters of ~350 nm, and these superstructures are built from nanoparticles with diameters about 3~5 nm. g-C₃N₄–Cu₂O heterojunctions exhibit a broad photoabsorption at ~525 nm, revealing an obvious red-shift compared with g-C₃N₄ (~460 nm). Under visible-light irradiation, g-C₃N₄–Cu₂O heterojunctions have stronger photocurrent (~7.2 μA/cm²) than pure g-C₃N₄ (~3.0 μA/cm²) or Cu₂O (~5.1 μA/cm²) Furthermore, g-C₃N₄–Cu₂O heterojunctions exhibit higher photocatalytic activity for degrading rhodamine B (RhB, 92%), tetracycline (TC, 90%) and 4-chlorophenol (4-CP, 82%) after 120 min, which is higher than those by pure Cu₂O (32% RhB, 29% TC, 28% 4-CP) and g-C₃N₄ (46% RhB, 50% TC, 49% 4-CP). The obvious improvement of photocurrent and photocatalytic activity from g-C₃N₄–Cu₂O should be attributed to the broad photoabsorption, the spherical superstructures and the construction of p–n heterojunctions.