“Optimization of Synthesis Parameters for Enhanced Photocatalytic Degradation of Methylene Blue Dye Using g-C₃N₄/ZnO Nanocomposites: A Study on the Influence of Temperature and Time Interval”

Background: The synthesis temperature and duration were shown to impact the physicochemical properties and photocatalytic performance of the g-C₃N₄/ZnO (g-CN/ZnO) nanocomposites. Higher temperatures (≈400°C) and longer reaction times (≈ 2-4 hours) generally led to better crystallinity, surface area, and visible light absorption of the nanocomposites, resulting in improved photocatalytic degradation of MB dye compared to pure ZnO or pure g-CN.

Objective: The primary object of the present work is to synthesise g-CN/ZnO at different temperatures with different time intervals and then assess its photocatalytic activity against methylene blue dyes.

Methods: g-C₃N₄/ZnO nanocomposites will be synthesised with a certain weight of urea and zinc acetate through the thermolysis method by varying the temperature: 400⁰C for 1 hour (S1), t400⁰C for 2 hours (S2), 500⁰C for 3 hours (S3), and 550⁰C for 4 hours (S4). Properties like functional groups; particle size, shape, surface morphology, and surface area; porosity of the composite; phase purity; crystalline nature; and band gap were analysed using FTIR, SEM, TEM, BET, XRD, UV-visible, and DRS techniques. For Photocatalytic activity tests, 0.001 gram g-CN/ZnO was immersed in 100 mL of the MB solution, and then the solution was continuously stirred in the dark for 20 min to reach the equilibrium state of adsorption, followed by placing it in sunlight.

Results and Conclusion:

Fabricated nanocomposites have an appearance of light yellow (S1 and S2), whereas S3 and S4 have a creamy colour. The percentage yields of S1, S2, S3, and S4 are 26.1%, 25.39%, 12.12%, and 3.2%, respectively. The photocatalytic performance of MB dyes in sunlight is S1<S2<S3, and the results indicate that the temperature and duration of the g-CN/ZnO nanocomposites' synthesis play a key role in determining their structural, optical, and photocatalytic properties for the degradation of methylene blue dye under visible-light irradiation.