Influence of TiO2 conjunct with different g–C3N4 mass ratios on photocatalytic activity: visible and UV degradation of organic pollutant

In recent years, heterojunction photocatalytic materials have received more and more attention. Ball milling and microwave–assisted heating were used in this work to prepare the g–C 3 N 4 /TiO 2 heterojunction photocatalytic nanocomposites with different g–C 3 N 4 /TiO 2 mass ratios (0.5:1, 1:1, 2.5:1, 5:1, 10:1, 20:1, 30:1, and 40:1, labeled as TCN–1, TCN–2, TCN–3, TCN–4, TCN–5, TCN–6, TCN–7, and TCN–8, respectively). The crystal structure, morphology, and optical properties of the samples were characterized by various analytical techniques. The photocatalytic activity was evaluated by the degradation efficiency of Rhodamine B (RhB) and methylene blue (MB) under visible light and UV irradiation. After 120 min at visible light illumination, TCN–7 had the best degradation efficiency with 99.41% for RhB and 91.75% for MB, whereas after 120 min at UV light illumination, TCN–7 exhibited the best degradation effect, and the efficiency reached at 48.66% for RhB and 71.64% for MB, respectively. The analysis of crystal structure of the as–prepared TCN samples confirmed that TCN–7 has a good crystallinity, which is facilitated for photocatalytic activity. In photocatalytic reactions, superoxide radical (·O 2 − ), hydroxyl radical (·OH), and hole (h + ) are recognized as the main active groups, and ·O 2 – plays the main role for TCN–7 in the photocatalytic reaction system for the degradation of RhB.