The sustainable management of wastewater and the production of clean fuel with a reduced carbon footprint require innovative methods, including photocatalytic degradation of pollutants and hydrogen generation. To achieve this, biosynthesized photocatalysts are necessary, with carbon quantum dots (CQDs) being a promising candidate for achieving this goal. In this study, CQDs were prepared from water caltrop peels and a composite of greenly synthesized CQDs with copper selenide (CuSe) was used for the photocatalytic degradation of pollutants and production of fuel. Thymol blue (TB) and Congo red (CR) were chosen as model dyes for degradation studies, with optimized reaction conditions being determined by varying the dose, pH, intensity, and concentration of dyes. The composite (CuSe@CQDs) showed a degradation rate of 99.4% and 97.8% for TB and CR, respectively, within 60 minutes, with a corresponding hydrogen production rate of 2360 and 1875 μmol g-1 h-1. The yield of hydrogen production using the composite was 35.7 and 29 times greater than that of CuSe alone for TB and CR, respectively. Spectroscopic techniques such as XRD, UV-Vis, FESEM, HRTEM, XPS, FTIR, BET, and TGA were used to characterize the composite, and the results revealed that the composite had superior degradation rates compared to CuSe alone, with the degradation rate being enhanced by about three times. GCMS analysis was used to investigate the intermediate and possible degradation pathways. Overall, this study highlights the potential of biosynthesized CQDs as effective photocatalysts for the sustainable management of wastewater and production of fuel.
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