ZrO2/C3N4 Nanocomposites: Green Solid-State Grinding Synthesis, Characterization, and Photocatalytic Degradation of MB Dye

ZrO 2 /carbon nitride (C 3 N 4 ) composite photocatalysts were prepared by solid-state grinding and subsequent calcination. They were characterized by X-ray diffraction, scanning electron microscopy, UV–Vis diffuse reflectance spectroscopy, and photoluminescence spectroscopy. Their photocatalytic activity was evaluated by the degradation of methylene blue (MB). Results showed that the grain size of the C 3 N 4 /ZrO 2 composite photocatalyst was relatively small at about 10 nm. HRTEM showed that a heterojunction was formed between ZrO 2 and g-C 3 N 4 . Under the assistance of H 2 O 2 , the visible-light degradation activity of MB by the composites was much higher than that by pure ZrO 2 . The 9%g-C 3 N 4 /ZrO 2 composite photocatalyst had the best photocatalytic performance, and it could degrade 99% of MB in 60 min. Adding a small amount of NaCl to the solution had a significant effect on the photocatalytic effect of the composite. Such addition could inhibit the photocatalytic activity of samples with high C 3 N 4 content and significantly improve the performance of photocatalysts with low C 3 N 4 content. The 1%g-C 3 N 4 /ZrO 2 composite (assisted by H 2 O 2 ) had the best photocatalytic effect on the MB solution containing salt. It could degrade MB solution containing 0.15, 0.3, and 0.6 g/L NaCl within 30, 40, and 45 min, respectively.