Sintesis dan Uji Fotokatalitik Komposit ZnO/CuO Berbasis Ekstrak Daun Teh Hijau (Camellia sinensis) untuk Degradasi Methylen Blue (MB)

Abstract

In this study, the synthesis, characterization, and analysis of a ZnO/CuO composite photocatalyst based on green tea leaf extract were successfully carried out. The ZnO/CuO composite was synthesized using a green synthesis method. The synthesis process began with the mixing of Zn and Cu precursor solutions with green tea leaf extract, followed by stirring at 60 °C for 2 hours. After drying, the sample was calcined at 500 °C for 4 hours to obtain a composite powder that was then characterized. Characterization using SEM showed that the particle morphology was non-uniform and exhibited agglomeration. This agglomeration is likely caused by van der Waals forces between closely spaced particles. XRD analysis confirmed the formation of two distinct crystalline phases, ZnO (hexagonal structure) and CuO (monoclinic structure). The CuO peaks became more pronounced with increasing CuO content in the samples. The addition of CuO also led to an increase in crystallite size and degree of crystallinity. FTIR data showed absorption bands at 909 cm⁻¹ and 685 cm⁻¹, indicating the presence of Zn–O and Cu–O bonds, as well as an –OH group around 3400 cm⁻¹ attributed to biomolecules from the green tea extract. UV-Vis analysis showed that the maximum absorption wavelength of methylene blue was observed at 664 nm. The highest degradation efficiency was obtained in the ZnO:CuO = 8:2 sample, with a concentration reduction from 10 ppm to approximately 0.53 ppm, or about 94.32%. This high photocatalytic activity is presumed to result from the formation of a p–n heterojunction that enhances charge separation and boosts photocatalytic performance.