effect of biochar on the photocatalytic activity of nitrogen-doped titanium dioxide nanocomposite in the removal of aqueous organic pollutants under visible light illumination

Biochar, as a low-cost carbon obtained from barley straw, was used for the simple sol–gel synthesis of visible-light photocatalysts comprising n-doped tio2/biochar nanocomposite (n-tio2/c) and thermally treated n-tio2/c. the nanocomposites were characterized by sem, edx, tem, xrd, bet, ftir, drs uv-vis, and pl measurements. the doped tio2 catalyzed the photodegradation of rhodamine b (rhb) in aqueous dispersion under visible-light illumination where the n-tio2/c nanocomposite with a band-gap of 2.96 ev and large surface area (206 m^2 g^-1) demonstrated the highest photocatalytic activity and degrading 99% of rhb under visible light of a 40-watt white led lamp within 105 min. photoluminescence (pl) spectroscopy experiments revealed the effective separation of charge carriers by the n-doped tio2 materials. the presence of carbon enhances the photocatalytic activity of n-tio2 material by decreasing the band gap, enhancing the visible light absorption, reducing the reflection of light, enhancing the adsorption of rhb and intermediates on the n-tio2 surface, thus prolonging the separation electrons (e-) and valence band hole (h^+).