Preparation Of Cobalt Modified Mesoporous Graphitic Carbon Nitride And Its Visible-light Photocatalytic Activity

Mesoporous graphitic carbon nitride (mpg-C3N4) was synthesized using silica nanoparticles as the hard template, and cobalt modified mpg-C3N4were prepared via a facile impregnation method. The structure, morphology, specific surface area, and cobalt valence of mpg-C3N4and cobalt modified mpg-C3N4were characterized by XRD, FI-IR, HRTEM, N2adsorption-desorption analysis, and XPS. The light absorption and photocurrents were studied by UV-VIS DRS and photocurrents response measurement. Methylene Blue (MB) and bisphenol A (BPA) aqueous solution were selected as the target pollution to evaluate visible-light photocatalytic activity. The main conclusions are summarized as follows:The embedment of cobalt changed the crystal structure and chemical construction of mpg-C3N4slightly. The cobalt species deposited on mpg-C3N4was Co3O4. The interior possessed microporous structure and specific surface area of the catalysts were208.1m2/g. The embedded cobalt on the surface of mpg-C3N4not only enhanced the light absorbance in the range of visble region but also facilitated the separation of photogenerated holes and electrons pairs.The photodegradation activity of MB increased with the cobalt loading on the surface of mpg-C3N4and the maximum was achieved with3%cobalt and calcination temperature of200℃. It also displayed high photocatalytic activity after reuse for three times. Both hydroxyl radicals and photogenerated holes were responsible for the MB photodegradation in the cobalt-doped mpg-C3N4reaction system. The enhancement in performance should be assigned to the effective separation and transfer of photogenerated charges originating from the well-matched overlapping band-structures.The photodegradation efficiency of BPA using the cobalt-doped mpg-C3N4were significantly higher than that of pristine mpg-C3N4and an optimum content of cobalt doping in the mpg-C3N4was1.5%. The cobalt-doped mpg-C3N4exhibited very high efficient photocatalytic activity to BPA in a wide range of pH3.01～10.05. Mineralization ability was observed through TOC analysis and mineralization degree was80%.